Comparison of Kuqa foreland basin with Persian Gulf Basin in salt tectonics

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森林里的蘑菇对比英语作文

森林里的蘑菇对比英语作文The Enchanting Fungi of the Forest: A Comparative Analysis.Within the verdant embrace of the forest, wherenature's artistry unfolds in its myriad forms, there exists a realm of wonder and intrigue: the realm of fungi. These enigmatic organisms, neither plant nor animal, have captivated human imagination for centuries, inspiring both awe and curiosity. Two such fungi, the solitary Fly Agaric and the communal Honey Mushroom, offer a fascinating case study of the diversity and ecological importance of this remarkable kingdom.Fly Agaric: The Solitary Sentinel.Amanita muscaria, commonly known as the Fly Agaric, stands out as a solitary beacon of beauty amidst theforest's mosaic of life. Its brilliant red cap, adorned with distinctive white spots, serves as a vibrant warningto potential predators. Beneath the cap lies a pure white stem, which rises majestically from the forest floor.Fly Agaric is a mycorrhizal fungus, forming symbiotic relationships with the roots of trees, particularly thoseof birch. This mutually beneficial partnership allows the exchange of nutrients between the two organisms. In return for sugars provided by the tree, the fungus aids in the absorption of water and minerals from the soil, enhancing the tree's overall health and resilience.Despite its alluring appearance, Fly Agaric is a potent hallucinogen, containing psychoactive compounds that have been used for shamanic and medicinal purposes for centuries. Its effects range from euphoria to visual hallucinations, but its consumption can also be dangerous, causing nausea, vomiting, and even organ failure.Honey Mushroom: The Communal Empire.In contrast to the solitary nature of Fly Agaric, Honey Mushrooms, belonging to the genus Armillaria, form vastunderground networks that connect individual mushrooms across extensive distances. These networks, known as mycelia, spread through the soil in search of nutrients, colonizing tree roots and forming the foundation of complex underground ecosystems.Honey Mushrooms are saprobic fungi, deriving their sustenance from decomposing organic matter. Their presence accelerates the decomposition process, releasing nutrients back into the soil and contributing to the forest's ecological balance. They favor moist, shady environments, often congregating in large clusters around the base of trees.The Honey Mushroom's communal nature has significant ecological implications. By sharing resources and coordinating their activities, the network can efficiently exploit available food sources and withstand environmental stresses. This cooperation also allows them to spread rapidly through the forest, effectively colonizing new areas and establishing new colonies.Ecological Significance of Fungi.Both Fly Agaric and Honey Mushrooms play crucial roles in the delicate equilibrium of the forest ecosystem. Their mycorrhizal and saprobic activities contribute to nutrient cycling, soil health, and the decomposition of organic matter. By creating and maintaining underground networks, fungi facilitate communication and nutrient exchange among plants and other organisms, fostering interconnectedness and resilience within the forest community.Moreover, fungi provide a valuable food source for various animals, including insects, rodents, and larger mammals. Their role in nutrient cycling also impacts the availability of food for other organisms in the food chain, including herbivores and predators. The intricate web of relationships between fungi and other forest inhabitants further emphasizes the interconnectedness and interdependence of life within the ecosystem.Conclusion.The Fly Agaric and Honey Mushroom, though vastly different in their solitary and communal lifestyles, exemplify the remarkable diversity and ecological importance of fungi in the forest. Their unique adaptations and interactions with other organisms contribute significantly to the intricate balance and resilience of this vibrant ecosystem.As we delve deeper into the realm of fungi, we uncover a hidden world of complexity and beauty. From the mesmerizing colors of Fly Agaric to the subterranean empires of Honey Mushrooms, these enigmatic organisms remind us of the interconnectedness of life and the vital role that each species plays in the symphony of nature.。

ComparisonoftheCold_r_省略_ourLigustrumCul

Comparison of the Cold-resistance Capabilities of Four Ligustrum CultivarsHAO Ming-zhuo ，HAN Ming-hui ，PENG Fang-ren *，LIANG You-wangCollege of Forest Resources and Environment ，Nanjing Forestry University ，Nanjing ，Jiangsu 210037，ChinaAbstract ［Objective ］To compare the cold-resistance capabilities of four Ligustrum cultivars．［Method ］Based on semilethal low temperature testand low temperature stress test in phytotron ，cold-resistance capabilities of two-year-old seedlings of 4Ligustrum cultivars were compared at leaf-ex-pansion and shoot-growing stage．［Result ］At leaf-expansion and shoot-growing stage ，the semilethal low temperatures of Ligustrum ˑVicaryi Hort．，Ligustrum lucidum Ait．，Ligustrum japonicum Thunb．‘Howardii ’and Ligustrum lucidum Ait．‘Excelsum Superbum ’were －6．34，－5．69，－4．55and －3．27ħ，respectively．SOD activity ，soluble protein content ，soluble sugar content and MDA content in leaves under low temperature stress were all higher than those under normal temperature．As the low temperature stress enhanced ，soluble protein content in leaves firstly en-hanced and then decreased．Among the 4cultivars ，soluble sugar content in 3cultivars firstly increased and then decreased ；and MDA content con-tinuously enhanced．［Conclusion ］The cold-resistance capabilities of Ligustrum ˑVicaryi Hort．and Ligustrum lucidum Ait．were higher than other cultivars ；Ligustrum japonicum Thunb．‘Howardii ’was middling ；and Ligustrum lucidum Ait．‘Excelsum Superbum ’was the worst．Key words Ligustrum ；Cultivars ；Cold-resistance capability ；Semilethal low temperatureReceived ：August 24，2012Accepted ：December 20，2012Supported by the Science and Technology Support Project of Jiangsu Province （BE2010311），and the Science and Technology Develop-ment Program of Northern Jiangsu Province （SBN200910136，SBE200870251）．*Corresponding author．E-mail ：frpeng@njfu．com．cnPlants of genus Ligustrum in family Oleaceae have been widely applied in landscape greening and the production of Kuding tea．Researches have shown that the roots ，leaves and fruits of most Ligustrum plants have the functions of clearing heat ，detoxification ，analgesia ，hemostasis ，relieving cough ，bacteriostasis and so on．More and more attention has been paid to its medicinal value and health function ［1－2］．In recent years ，new Ligustrum cultivars have been introduced in China ，such as Ligustrum japonicum Thunb．‘Howardii ’，Ligustrum ˑVicaryi Hort．，and Ligustrum lucidum Ait．‘Excelsum Super-bum ’．These cultivars are very popular and their cultivation ar-ea and range have increased each year．At present ，they have been introduced into northern Jiangsu and Anhui Prov-inces ［3－5］．However ，some new varieties of Ligustrum are ex-tended relatively late ，so the growth habitat and cold resistance mechanism are still unclear．Some reports are found on the cold resistance of Ligustrum vicaryi ，Ligustrum quihoui and so on at home and abroad ［6－13］．But few are about the cold resist-ance mechanism of Ligustrum japonicum ‘Howardii ’and Ligus-trum lucidum ‘Excelsum Superbum ’．Plant freeze injury is commonly seen in winter and spring．When the there is late spring cold and other natural disasters in plant germination stage ，leaf-expansion and shoot-growing stage ，freeze injury ofplant often becomes more serious．This phenomenon also cause the attention of many experts and scholars ［14－16］．In thisresearch ，cold-resistance capabilities of Ligustrum japonicum Thunb．‘Howardii ’，Ligustrum ˑVicaryi Hort．，Ligustrum lucid-um Ait．，and Ligustrum lucidum Ait．‘Excelsum Superbum ’were compared ，aiming at providing references for the cultiva-tion management and regionalized extension of new Ligustrum cultivars．1Materials and methods1．1Materials1．1．1Plant materials．Two-year-old cutting seedlings of Ligu-strum japonicum Thunb．‘Howardii ’，Ligustrum ˑVicaryi Hort．，and Ligustrum lucidum Ait．‘Excelsum Superbum ’were introduced from Hangzhou Base of Zhejiang Senhe Group inMarch 2011；and two-year-old seedlings of Ligustrum lucidum Ait．were introduced from Tangquan Town of Nanjing City．1．2Methods1．2．1Pretreatment of plant materials．Test site was located in Nanjing Forestry University．After seedling introduction ，they were planted in the round plastic pots ，which were 28cm in di-ameter and 32cm in height．There was a small hole in the pot bottom with 10kg soil in each pot．Soil used was the mixture of organic matter under forest and yellowish-brown loam soil．Itsphysicochemical properties were as follows ：1．883ˑ106mg /kg organic matter ，0．27ˑ106mg /kg total nitrogen ，921mg /kg to-tal phosphorus ，1．34ˑ106mg /kg total potassium ，134．8mmol /kg CEC ，and pH 5．5．After 30d of transplantation ，seedlings at leaf-expansion stage were put in phytotron at 5ħfor 7d．The condition was as follows ：12h illumination eachday ，30μmol /（m 2·s ）light intensity ，and 75%－80%relative humidity．Proper irrigation should be ensured during the cultiva-tion in order to maintain the soil moisture in pot．1．2．2Imitated freeze injury test in phytotron under low tem-perature stress treatment．As for each Ligustrum cultivar ，healthy plants in 6pots were put in phytotron at 0，－7and －14ħand the greenhouse at 25ħ．After treated by 48h ，Medicinal Plant 2012，3（12）：111－115Germplasm Resources and Cultivationmorphological appearance of plants with freeze injury was ob-served．Then，50g leaves of each Ligustrum cultivar were ran-domly collected and immediately stored in ultra low temperature refrigerator at－75ħ．The soluble sugar content，soluble pro-tein content，SOD activity，MDA content in leaves were detec-ted［17－18］．1．2．3Determination of semilethal low temperature［19－20］．Based on pre-cooling test，10standard plants were selected for each Ligustrum cultivar．10－15normal leaves were collected randomly from each standard plant．After well mixed，the leav-es were divided into6groups and stored in refrigerators at the designed temperature for1h．After thawing for24h，the rela-tive conductivity was detected．According to the Logistic equa-tion，semilethal low temperatures of four Ligustrum cultivars were calculated．The designed temperatures were0，－5，－10，－15，－20and－25ħ．2Results and analyses2．1Morphological appearance of Ligustrum cultivars with freeze injury Table1reported that Ligustrum lucidum Ait．and LigustrumˑVicaryi Hort．had relatively good cold-resistance capability．Their freeze injury was relatively not severe；their growth status was relatively good；and their survival rate under low temperature stress at－14ħwas relatively high．Ligustrum japonicum Thunb．‘Howardii’showed middle cold-resistance capability and grew relatively good at25and0ħtreatments．However，plants of Ligustrum japonicum Thunb．‘Howardii’had slight freeze injury at－7and－14ħtreat-ments；some leaves turned yellow and crimped and some even died．Ligustrum japonicum Thunb．‘Howardii’had the poorest cold-resistance capability under low temperature treatment．Leaves began to be withered under the environment of0ħ；and survival rate of plants was extremely low under low temper-ature stress of－14ħ．2．2Changes of nutritional component contents in leaves of different Ligustrum cultivars under low temperature stress The soluble protein content in plant is closely related to the cold re-sistance．Under normal conditions，soluble protein content en-hances in the plants under low temperature stress，which ad-justs the cold resistance of plant［21］．Fig．1illustrated that un-der normal temperature，Ligustrum lucidum Ait．‘Excelsum Su-perbum’had higher content of soluble protein than other three cultivars．As the temperature fell，soluble protein contents in leaves of different cultivars firstly enhanced and then reduced．Among them，soluble protein content in Ligustrum lucidum Ait．‘Excelsum Superbum’began to fall at－7ħ，while those in the rest three cultivars began to fall at－14ħ．Under low tem-perature stress，the increasing extent of soluble protein content in leaves varied；and they were in the order of Ligustrum lucid-um Ait．（96．2%）＞LigustrumˑVicaryi Hort．（69．4%）＞Li-gustrum japonicum Thunb．‘Howardii’（55．0%）＞Ligustrum lucidum Ait．‘Excelsum Superbum’（13．7%）．Table1Morphological appearance of Ligustrum cultivars under low temperature stressPlant name Tempera-ture∥ħSurvivalrate∥%FreezinggradeGrowth statusLigustrum lucidum Ait．25100．01Normal，deep green leaves0100．01Normal，deep green leaves－7100．01Normal，relatively small amount of leaves，blackish green leaves－1483．32Relatively poor，relatively small amount of leaves，dry leaf edge LigustrumˑVicaryi25100．01Normal，many leaves，deep green leaves，relatively few yellow leaves Hort．0100．01Normal，many leaves，deep green leaves，relatively few yellow leaves －7100．01Normal，many leaves，deep green leaves，30%of yellow leaves－1483．32Relatively poor，curled leaves，light green leaves，half yellow leaves Ligustrum lucidum Ait．25100．01Normal，many leaves，deep green leaves‘Excelsum Superbum’083．32Relatively poor，curled leaves，slight yellow leaves，wilting－766．73Drying，withered leaves，rare，slight yellow leaves，wilting－1416．74slight yellow and dry leaves，mostly dyingLigustrum japonicum25100．01Normal，many leaves，deep green old leaves，golden yellow new leaves Thunb．‘Howardii’0100．01Normal，many leaves，more golden yellow leaves－7100．02Relatively poor，curled leaves，dry and withered leaves，deep yellow leaves－1466．72Relatively poor，curled leaves，dry and withered leaves，wiltingNote：Freezing grade1indicated no freeze injury；2was slight freeze injury；3was middle freeze injury；and4was severe freeze injury．The soluble sugar content could enhance the osmotic con-centration of plant cells，reduce the water potential，increase the water retention capacity，decrease the freezing point，and protect the cell cytoplasm colloids from solidification．Soluble sugar content showed positive correlation with the cold resist-ance of most plants．When under cold environment，plants en-hanced their soluble sugar content to defense against the cold［15］．Fig．2indicated that with the decrease of temperature，soluble sugar content in Ligustrum lucidum Ait．leaves en-hanced，and those in LigustrumˑVicaryi Hort．，Ligustrum luci-dum Ait．‘Excelsum Superbum’and Ligustrum japonicumThunb．‘Howardii’enhanced firstly and then reduced．Soluble sugar content in leaved under－14ħcold temperature treat-ment was significantly lower than that in－7ħtreatment．The decreasing extents of both Ligustrum japonicum Thunb．‘Howardii’and Ligustrum lucidum Ait．‘Excelsum Superbum’were significantly higher than that of LigustrumˑVicaryi Hort．；the three decreasing extents were all higher than those at25ħtreatment．2．3Changes of SOD activity and MDA content in Ligustrum cultivars under low temperature stress SOD has close correla-tion with the stress resistance of plants．Under low temperature211Medicinal Plant2012Fig．1Changes of soluble protein content in Ligustrum culti-vars under low temperaturestressFig．2Changes of soluble sugar content in Ligustrum cultivars under low temperature stressstress ，SOD has super oxidation disproportionation reaction with oxygen and free radicals in order to ensure the stability of membrane ［21］．Fig．3illustrated that with the decrease of tem-perature ，SOD activities in the leaves of Ligustrum lucidum Ait．and Ligustrum japonicum Thunb．‘Howardii ’firstly enhanced and then maintained stable ；SOD activity in Ligustrum lucidum Ait．‘Excelsum Superbum ’enhanced firstly and then reduced．Under normal temperature ，SOD activity of Ligustrum lucidum Ait．‘Excelsum Superbum ’was significantly lower than those of the rest three cultivars ；but it increased by 59．7%from 25ħto －7ħ，and reduced by 21．2%from －7ħto －14ħ，which was obviously different from other cultivars．Besides ，SOD activities of all the Ligustrum cultivars at －7and －14ħtreatments were higher than those in 25ħtreatment．MDA is a product of membrane lipid peroxidation induced by free radicals ，which has certain inhibitory effects on SOD ac-tivity．MDA content also has close correlation with the cold re-sistance of plants ［22］．Fig．4indicated that as the treatment temperature fell ，MDA contents in Ligustrum lucidum Ait．，Ligustrum lucidum Ait．‘Excelsum Superbum ’and Ligustrum japonicum Thunb．‘Howardii ’enhanced by 88．7%，70．9%and 74．0%，respectively．MDA content in Ligustrum ˑVicaryi Hort．firstly enhanced and then decreased ；and it enhanced by 94．4%from 25ħto －7ħ，but reduced by 5．3%from －7to－14ħ．Under normal temperature ，MDA contents in Ligus-trum lucidum Ait．，Ligustrum ˑVicaryi Hort．and Ligustrum ja-ponicum Thunb．‘Howardii ’were higher than that in Ligustrum lucidum Ait．‘Excelsum Superbum ’．Fig．3Changes of SOD activity in Ligustrum cultivars underlow temperaturestressFig．4Changes of MDA content in Ligustrum cultivars underlow temperaturestressFig．5Change laws of relative conductivity of the leaves of Li-gustrum cultivars under low temperature stress311HAO Ming-zhuo et al．Comparison of the Cold-resistance Capabilities of Four Ligustrum Cultivars2．4Determination of semilethal low temperature Relative conductivity of leaves is an important physiological index com-monly used to evaluate the injury degree of plants under low temperature stress．Low temperature stress enhances the per-meability of cell membrane．Plants have poor coldness resist-ance show a rapid increase of membrane permeability，which is expressed in the sharp rising of conductivity［21］．Fig．5indica-ted that from0to－10ħtreatments，the four Ligustrum culti-vars showed slowly increasing of relative conductivity；from －10and－15ħtreatments，relative conductivity enhanced sharply；from－15to－25ħtreatments，relative conductivity enhanced gradually by100%，showing a slowly increasing tendency．The relative conductivity of the leaves of four Ligus-trum cultivars showed the change of"S"curve with the de-crease of treatment temperature．At the same time，the testshowed that the relative conductivity of Ligustrum lucidum Ait．‘Excelsum Superbum’was significantly higher than other culti-vates between0and－10ħ．Research results showed that under low temperature stress treatment，Logistic equation could better reflect the changes of plant organs with temperature［20］．According to the results of equation and test，coefficients K，A and B were ob-tained．Thus，the conductivity-derived Logistic equations of Li-gustrum lucidum Ait．，LigustrumˑVicaryi Hort．，Ligustrum lu-cidum Ait．‘Excelsum Superbum’and Ligustrum japonicum Thunb．‘Howardii’were obtained under low temperature stress［20］．According to the equation coefficients，the semilethal low temperatures of the four cultivars were－6．34，－5．69，－4．55and－3．27ħ，respectively．Table2Logistic equation analyses of semilethal low temperatures of different Ligustrum cultivarsCultivars Coefficient A Coefficient B Coefficient KLT50Semilethallow temperature∥ħF value test P value testLigustrum lucidum Ait．3．44123355960．2171396．9－5．6935．340．0040 LigustrumˑVicaryi Hort．3．76836040110．2091198．0－6．3432．180．0048 Ligustrum japonicum2．72298852610．2203293．9－4．5527．010．0065 Thunb．‘Howardii’Ligustrum lucidum Ait．1．86468101330．1906594．0－3．2754．390．0018‘Excelsum Superbum’Note：Logistic equation was Y=K/（1+Ae－BX），where Y was conductivity，X was temperature，K，A and B were the equation coefficients．3Conclusions and discussionsUnder low temperature stress，the soluble protein content，soluble sugar content，SOD activity，MDA content and relative conductivity in leaves of Ligustrum cultivars were researched．Ac-cording to the morphological appearance of plants，Ligustrum luci-dum Ait．and LigustrumˑVicaryi Hort．showed relatively strong cold-resistance capability，followed with Ligustrum japonicum Thunb．‘Howardii’．And Ligustrum lucidum Ait．‘Excelsum Su-perbum’had the poorest cold-resistance capability．Xiang Yan-jun et al．［21］found out that with the decrease of temperature from9to－7ħ，soluble protein contents in the leaves of5types of vine plants showed an ascendant trend．However，results of this research indicated that with the de-crease of temperature，soluble protein contents in the leaves of 4Ligustrum cultivars firstly enhanced and then decreased，which was similar to the research results of Feng Xian-bin et al．［23］．Results also showed that under low temperature stress，the increasing extent of soluble protein content in plant leaves was closely related to the cold-resistance capability．Li-gustrum cultivars with relatively great increasing extent had strong physiological adjustment ability under low temperature stress，and had relatively strong cold-resistance capability．Be-sides，with the decrease of temperature，decrease of soluble protein content in plant in early stage would lead to poor cold-resistance capability．In this research，Ligustrum lucidum Ait．‘Excelsum Superbum’had the poorest cold-resistance capa-bility and its soluble protein content decreased greatly at －7ħ；while the soluble protein contents in other3cultivars started at－14ħ．This preliminarily proved this conclusion．Research results showed that under low temperaturestress，soluble sugar contents in Ligustrum cultivars enhanced significantly．However，with the further decrease of tempera-ture，soluble sugar content sometimes reduced．Gao Wen-fang et al．［11］researched on the cold tolerance mechanism of5 types of colorful vegetations；research results showed that the soluble sugar content in Ligustrum vicaryi leaves firstly en-hanced and then reduced，which was consistent with the results of LigustrumˑVicaryi Hort．，Ligustrum lucidum Ait．‘Excelsum Superbum’，and Ligustrum japonicum Thunb．‘Howardii’in this research．Reduction of soluble sugar content might be caused by the following reason：leaf chlorophyll was destroyed under low temperature；photosynthesis mechanism was re-stricted；and synthesis of soluble sugar content was greatly af-fected［24］．Besides，as the temperature decreased，soluble sugar content in plant reduced in early stage and the reduction extent was great，which indicated that the cold-resistance capa-bility of this plant was poor．Xie Xiao-jin et al．argued that the decreasing extent of soluble sugar content was closely related to the cold-resistance capability under low temperature treat-ment［25］．Results showed that the SOD activity in plant firstly en-hanced and then reduced as the temperature fell［23］．Change of SOD activity was complex under low temperature stress．Some reduced firstly and then enhanced；some enhanced and then maintained stable；and some increased and then decreased．It was noteworthy that SOD activity of Ligustrum lucidum Ait．‘Excelsum Superbum’was relatively low under normal temper-ature，but enhanced under low temperature，showing the in-crease and decrease with relatively great extent．SOD activity of Ligustrum lucidum Ait．‘Excelsum Superbum’was quite411Medicinal Plant2012sensitive to temperature change，which might be one manifes-tation of its poor cold-resistance capability．Under adversity stress，plant cells produced a large amount of free radicals，induced or accelerated the cell mem-brane lipid peroxidation，and further destroyed the cell mem-brane．As the final product of membrane lipid peroxidation，MDA was an important index reflecting the damage degree of cell membrane［21］．Research results showed that MDA content in plant leaves enhanced as the low temperature stress in-creased［11］．Test results showed that as the temperature de-creased，MDA content in the leaves of4Ligustrum cultivars was not always increasing．For instance，LigustrumˑVicaryi Hort．firstly enhanced and then reduced，which might because that plant could not stand extreme low temperature，so that cell death appeared；cell membrane was completely destroyed；membrane lipid oxidation reaction basically stopped；cell inclu-sion flew away；and MDA content reduced［26］．Research results also indicated that there were differences in the semilethal low temperature of plants in different seasons．Xie Xiao-jin and Hao Ri-min researched on the cold resistance of12types of evergreen broad-leaved trees；and the semilethal low temperature was detected in different months［27］．Results showed that the semilethal low temperatures of12trees from October2005to March2006were all higher than－10ħ，those from December2005to January2006were mostly lower than－10ħ；and there were significant differences in the cold-resistance capability of seedlings in different phenophases．An-alyses of Logistic equation showed that at leaf-expansion and shoot-growing stage，the semilethal low temperatures of Ligus-trumˑVicaryi Hort．，Ligustrum lucidum Ait．，Ligustrum japoni-cum Thunb．‘Howardii’and Ligustrum lucidum Ait．‘Excelsum Superbum’were－6．34，－5．69，－4．55and－3．27ħ，re-spectively，indicating that the cold-resistance capabilities of4 Ligustrum cultivars were poor and introduction should be care-fully considered．References［1］LI XM，LI XQ，ZHAG DZ．Chemical composition，pharmacological action and clinical application research situation of Ligustrum［J］．Academic Journal of Guangdong College of Pharmacy，1997，13（2）：44－47．（in Chinese）．［2］TU YH，GAO NN．Survey in study on chemical constituents and pharmacologic action of Ligustrum［J］．Lishizhen Medicine and Ma-teria Medica Research，2007，18（5）：1228－1230．（in Chinese）．［3］PAN XD．The characteristics and landscape application of Ligustrum quihoui［J］．Green China，2008（9）：45．（in Chinese）．［4］DU YJ，LIU XQ．Gardening application and rapid propagation tech-nology of Ligustrum japonicum［J］．Forest By-Product and Speciality in China，2010，107（4）：42－43．（in Chinese）．［5］SUN YX，SUN XY．Difference and application of Ligustrum japoni-cum and Ligustrum vicaryi in garden greening［J］．Shanghai Agricul-tural Science and Technology，2009（3）：106，104．（in Chinese）．［6］GAJIC G，MITROVIC M，PAVLOVIC P，et al．An assessment of the tolerance of Ligustrum ovalifolium Hassk．to traffic-generated Pb using physiological and biochemical markers［J］．Ecotoxicology and Environmental Safety，2009，72（4）：1090－1101．［7］ZHANG LC，ZANG DK，HAN RC．Effects of shading treatment on the growth and photosynthesis characteristic of Ligustrum japonicum‘Howardii’［J］．Northern Horticulture，2010（19）：108－111．（in Chi-nese）．［8］WANG LX，ZHANG G，XUE M，et al．Response of Ligustrum vicaryi seedling to freezing temperature and duration during dehardening ［J］．Northern Horticulture，2008（1）：112－114．（in Chinese）．［9］YANG XL，GUO SH，QI YL，et al．Comparison of some stress-re-sistant physiological indexes of three kinds of privet leave［J］．Non-wood Forest Research，2009，27（3）：94－97．（in Chinese）．［10］ZHANG DS，LIU HQ，CHEN YM．Cold resistance of eight ever-green broadleaved tree species［J］．Acta Horticulturae Sinica，1994，21（3）：283－287．（in Chinese）．［11］GAO WF．Study on the cold-resistant mechanism of five species of color-leafed cover plants［J］．Journal of Anhui Agricultural Sci-ences，2007，35（15）：4430－4431．（in Chinese）．［12］LI YH，SU SH，JI HF，et al．Effect of low temperature stress on lip-id peroxidation and activity of cell defense enzymes of Ligustrum lu-cidum Ait［J］．Hebei Journal of Forestry and Orchard Research，2007，22（1）：84－86．（in Chinese）．［13］LIU H，ZHANG G．The influence of short-day on the frost hardiness and electrical impedance spectroscopy parameters in stems of Ligu-strum vicaryi during hardening［J］．Acta Agriculturae Boreali-Sini-ca，2008，23（2）：173－179．（in Chinese）．［14］GUO YL．Warning of late spring coldness in2005：Considerate of trees introduction［N］．China Flower＆Gardening News，2005－03－22（002）．（in Chinese）．［15］SHEN M，WANG MX．Research progress of plant cold resistance mechanism［J］．Chinese Bulletin of Botany，1997，14（2）：1－8．（in Chinese）．［16］LOYONS JM．Chilling injury in plants［J］．Plant Physical，1997，24（3）：445－446．［17］ZHANG ZL．Plant physiology experiment guidance［M］．Beijing：Higher Education Press，1990：154－155．（in Chinese）．［18］LI HS．Principle and technology of plant physiological and biochemi-cal experiment［M］．Beijing：Higher Education Press，2000：20－30．（in Chinese）．［19］FAN GB．A method to estimating the parameters of logistic model and application［J］．Mathematics in Economics，2010，27（1）：105－110．（in Chinese）．［20］ZHU GH，LIU ZQ，ZHU PH．A method to estimating the parame-ters of logistic model and application［J］．Mathematics in Econom-ics，2010，27（1）：105－110．（in Chinese）．［21］XIANG YJ，LI XZ，WANG XD．Preliminary study on cold resistance of five different lianas［J］．Journal of Zhejiang University：Agricul-ture＆Life Sciences，2011，37（4）：421－424．（in Chinese）．［22］HE KY．Influence of cold stress on soluble sugar and malondialde-hyde content in Fujian cypress［J］．Journal of Jiangsu Forestry Sci-ence＆Technology，2000，27（6）：6－8．（in Chinese）．［23］FENG XB，DONG Q，WANG J，et al．Effects of low temperature on cold resistance of Pistacia chinensis［J］．Chinese Agricultural Science Bulletin，2011，27（8）：23－26．（in Chinese）．［24］XU DX，ZHUANG BL，XUE JH，et al．Evaluation on cold resistance of five evergreen broad-leaved ornamental tree species in the area of Nanjing［J］．Journal of Nanjing Forestry University：Natural Sci-ences Edition，2010，34（3）：72－76．（in Chinese）．［25］XIE XJ，HAO RM，ZHANG JL，et al．Low-temperature tolerance characteristic and ecological evaluation of broad-leaved evergreen tree species［J］．Acta Ecologica Sinica，2004，24（11）：2671－2677．（in Chinese）．［26］ZHENG GH，ZHANG HY，ZHONG XR．Changes in cell ultra-struc-ture，membrane permeability and protective enzyme activity in Erio-botrya japonica Lindl．leaves under cold stress［J］．Chinese Jour-nal of Eco-Agriculture，2009，17（4）：739－745．（in Chinese）．［27］XIE XJ，HAO RM．Dynamic changes of cold hardiness in winter in twelve evergreen broad-leaved species from Nanjing［J］．Acta Eco-logica Sinica，2009，29（4）：2149－2154．（in Chinese）．511HAO Ming-zhuo et al．Comparison of the Cold-resistance Capabilities of Four Ligustrum Cultivars。

tpo32三篇托福阅读TOEFL原文译文题目答案译文背景知识

tpo32三篇托福阅读TOEFL原文译文题目答案译文背景知识阅读-1 (2)原文 (2)译文 (5)题目 (7)答案 (16)背景知识 (16)阅读-2 (25)原文 (25)译文 (28)题目 (31)答案 (40)背景知识 (41)阅读-3 (49)原文 (49)译文 (53)题目 (55)答案 (63)背景知识 (64)阅读-1原文Plant Colonization①Colonization is one way in which plants can change the ecology of a site.Colonization is a process with two components:invasion and survival.The rate at which a site is colonized by plants depends on both the rate at which individual organisms(seeds,spores,immature or mature individuals)arrive at the site and their success at becoming established and surviving.Success in colonization depends to a great extent on there being a site available for colonization–a safe site where disturbance by fire or by cutting down of trees has either removed competing species or reduced levels of competition and other negative interactions to a level at which the invading species can become established.For a given rate of invasion,colonization of a moist,fertile site is likely to be much more rapid than that of a dry, infertile site because of poor survival on the latter.A fertile,plowed field is rapidly invaded by a large variety of weeds,whereas a neighboring construction site from which the soil has been compacted or removed to expose a coarse,infertile parent material may remain virtually free of vegetation for many months or even years despite receiving the same input of seeds as the plowed field.②Both the rate of invasion and the rate of extinction vary greatly among different plant species.Pioneer species-those that occur only in the earliest stages of colonization-tend to have high rates of invasion because they produce very large numbers of reproductive propagules(seeds,spores,and so on)and because they have an efficient means of dispersal(normally,wind).③If colonizers produce short-lived reproductive propagules,they must produce very large numbers unless they have an efficient means of dispersal to suitable new habitats.Many plants depend on wind for dispersal and produce abundant quantities of small,relatively short-lived seeds to compensate for the fact that wind is not always a reliable means If reaching the appropriate type of habitat.Alternative strategies have evolved in some plants,such as those that produce fewer but larger seeds that are dispersed to suitable sites by birds or small mammals or those that produce long-lived seeds.Many forest plants seem to exhibit the latter adaptation,and viable seeds of pioneer species can be found in large numbers on some forest floors. For example,as many as1,125viable seeds per square meter were found in a100-year-old Douglas fir/western hemlock forest in coastal British Columbia.Nearly all the seeds that had germinated from this seed bank were from pioneer species.The rapid colonization of such sites after disturbance is undoubtedly in part a reflection of the largeseed band on the forest floor.④An adaptation that is well developed in colonizing species is a high degree of variation in germination(the beginning of a seed’s growth). Seeds of a given species exhibit a wide range of germination dates, increasing the probability that at least some of the seeds will germinate during a period of favorable environmental conditions.This is particularly important for species that colonize an environment where there is no existing vegetation to ameliorate climatic extremes and in which there may be great climatic diversity.⑤Species succession in plant communities,i.e.,the temporal sequence of appearance and disappearance of species is dependent on events occurring at different stages in the life history of a species. Variation in rates of invasion and growth plays an important role in determining patterns of succession,especially secondary succession. The species that are first to colonize a site are those that produce abundant seed that is distributed successfully to new sites.Such species generally grow rapidly and quickly dominate new sites, excluding other species with lower invasion and growth rates.The first community that occupies a disturbed area therefore may be composed of specie with the highest rate of invasion,whereas the community of the subsequent stage may consist of plants with similar survival ratesbut lower invasion rates.译文植物定居①定居是植物改变一个地点生态环境的一种方式。

invading algae托福阅读

invading algae托福阅读侵袭性海藻是一种常见的生物现象，它对海洋生态系统产生了深远的影响。

这种海藻的快速扩张和繁殖能力，给海洋生物和人类社会带来了许多问题和挑战。

侵袭性海藻对海洋生态系统造成了严重的破坏。

它们通过吸收大量的养分和光能，抑制了其他海洋生物的生长和繁殖。

这导致了海洋生物多样性的减少和生态系统的不稳定。

例如，一些重要的渔业资源，如鱼类和贝类，因为缺乏足够的食物和栖息环境而减少了数量。

这对渔民的生计和人类的食物安全带来了威胁。

侵袭性海藻对海滩和海岸线的生态系统也造成了严重的影响。

它们在海滩和海岸线上形成了厚厚的覆盖层，阻碍了海洋生物的繁殖和孵化。

这不仅破坏了海滩的自然景观，也对沿海旅游业产生了负面影响。

许多海滩和度假胜地因为侵袭性海藻的存在而失去了吸引力，游客数量大幅减少，从而影响了当地经济的发展。

侵袭性海藻还对海洋污染和水质产生了负面影响。

它们在大量繁殖时会释放出有毒物质，污染海水。

这不仅危害了海洋生物的健康，也对人类的健康构成了威胁。

当人们在污染的海域游泳或捕鱼时，可能会受到有害物质的损害。

因此，侵袭性海藻的存在需要我们加强海洋环境保护和治理，保护海洋生态系统和人类的健康。

为了解决侵袭性海藻问题，我们需要采取一系列的措施。

首先，加强监测和预警系统，及时发现和控制海藻的扩散。

其次，加强海洋环境保护，控制污染源的排放，减少养分的输入，防止海藻过度生长。

此外，可以采取物理和化学方法，如清除和灭杀海藻，来控制其数量和分布。

在面对侵袭性海藻的挑战时，我们需要全球合作和共同努力。

只有通过各国的合作和协调，才能有效地解决侵袭性海藻问题，保护海洋生态系统和人类的福祉。

让我们携起手来，保护海洋，共建美丽的蓝色星球。

古生物大小对比中文翻译

古生物大小对比中文翻译古生物大小对比（Comparisons of Prehistoric Creature Sizes）古生物大小对比是一种常见的科普方式，通过将古生物的大小与现代物种进行对比，帮助人们更好地理解古代生物的巨大体型。

下面是一些常见的古生物大小对比及其中英文对照例句：1. 悉尼海螺（Sydney Opera House）与巨型恐龙（Gigantic Dinosaur）- "The Sydney Opera House, with its iconic sail-like structures, is dwarfed in size when compared to a gigantic dinosaur like the Argentinosaurus."（悉尼歌剧院的标志性帆状结构在与像阿根廷龙这样的巨型恐龙进行对比时显得微不足道。

）2. 摩天大楼（Skyscraper）与巨大海洋生物（Enormous Marine Creature）- "Even the tallest skyscrapers pale in comparison to the immense size of prehistoric marine creatures such as the Megalodon."（即使是最高的摩天大楼也在与史前巨大海洋生物如巨齿鲨进行对比时黯然失色。

）3. 大象（Elephant）与远古哺乳动物（Ancient Mammal）- "Although elephants are considered the largest land mammals today, they are significantly smaller than ancientmammals like the Indricotherium."（尽管大象被认为是当今最大的陆地哺乳动物，但它们与象骨兽这样的古代哺乳动物相比要小得多。

塔里木盆地主要前陆冲断带差异构造变形

塔里木盆地主要前陆冲断带差异构造变形汤良杰;李萌;杨勇;陈刚;周鑫【摘要】According to field investigation,based on typical profiles of Kuqa,southwestern Tarim and southeastern Tarim areas,the characteristics of structural deformation for the three foreland thrust belts were contrasted, and the main controlling factors of differential structural deformation were discussed.The differences of structural deformation of foreland basin around Tarim Basin are layered difference in vertical domain and segmentation and zonation differences in horizontal domain. Four detachment layers develop in Kuqa foreland thrust belt, and the differences of deep,middle and shallow tectonic styles in vertical domain are significant;three detachment layers develop in southwestern Tarim foreland thrust belt, and the layered characteristics of structure are significant;two detachment layers develop in southeastern Tarim foreland thrust belt, and contrasted with the above foreland thrust belts, the layered characteristics of structure is relatively simple. The regional tectonic stress field and basin boundary control the segmentation and zonation differences of deformation style of foreland tectonic belts.The strike of Kuqa foreland thrust belt,which is consistent with that of Tianshan tectonic belt, has obvious structural zonation;there is a certain segmentation in partial stress accommodation zones.Because of the different angles intersecting with the compression of Kunlun Mountains,the southwestern Tarim foreland thrust belt has obviousstructural segmentation along the strike,and there is zonation in each segment. The southeastern Tarim foreland thrust belt is characterized by structural segmentation,which is mainly controlled by West Kunlun Mountains and Altun Tagh Mountains respectively;zonation towards the basin is not obvious.%利用库车、塔西南和塔东南地区典型剖面等基础资料，结合野外地质调查，对比分析三大前陆冲断带构造变形特征，进一步探讨控制前陆冲断带差异变形特征的主要因素。

海绵英语作文

海绵英语作文Sponges are fascinating creatures that have been around for millions of years. They are simple yet highly efficient organisms that play a crucial role in marine ecosystems. In this essay we will explore the characteristics of sponges their habitat and their importance to the environment.Characteristics of SpongesSponges belonging to the phylum Porifera are multicellular organisms that lack true tissues and organs. They are composed of cells that are organized into a few distinct cell types but these cells are not separated by specialized tissues. The most notable features of sponges include1. Porosity Sponges have a porous structure that allows water to flow through their bodies. This is crucial for their filterfeeding mechanism.2. Chambered Body The body of a sponge is made up of a series of chambers connected by a network of canals.3. Lack of Nervous System Unlike more complex animals sponges do not have a nervous system brain or even a true digestive system.4. Reproduction Sponges reproduce both asexually and sexually. They can regenerate from small fragments which is a form of asexual reproduction.Habitat of SpongesSponges can be found in a variety of aquatic environments predominantly in marine settings. They are known to inhabit1. Shallow Waters Many species prefer shallow waters where sunlight is abundant aiding in the photosynthesis of their symbiotic algae.2. Deep Sea Some sponges can survive in the deep sea where they adapt to the high pressure and lack of light.3. Coral Reefs Sponges are often found in coral reefs where they contribute to the biodiversity and provide habitats for other marine creatures.4. Polar Regions Surprisingly some sponges can be found in the cold waters of polar regions demonstrating their adaptability.Importance of SpongesSponges are vital to the health of marine ecosystems for several reasons1. Filter Feeders By filtering water sponges help remove excess nutrients and pollutants thus contributing to water purification.2. Biodiversity As a part of the coral reef ecosystem sponges provide habitats and food for a variety of marine species.3. Bioindicators Sponges are sensitive to environmental changes and can serve as bioindicators of water quality.4. Sponge Products Some species of sponges have been used by humans for various purposes including as cleaning tools and in the medical field for their unique properties. In conclusion sponges are not just simple organisms they are complex and integral parts of marine ecosystems. Their ability to thrive in diverse environments and their contributions to the marine food web and water quality make them an essential component of our planets biodiversity. Understanding and protecting sponges is crucial for maintaining the health of our oceans.。

(完整版)托福TPOextra答案解析和原文翻译

TPO 34阅读解析第一篇Population and Climate【P1】地球人口的增长已经对大气和生态环境产生了影响。

化石燃料的燃烧，毁林，城市化，种植大米，养殖家畜，生产作为助推燃料和制冷剂的CFC增加了空气中CO2，甲烷，二氧化氮，二氧化硫灰尘和CFOs 的含量。

约70%的太阳能量穿过大气直射地球表面。

太阳射线提高了土地和海洋表面的温度，随后土地和海洋表面将红外射线反射会太空中。

这能使地球避免温度过高。

但是并不是所有的红外射线被返回会太空中，一些被大气中的气体吸收，然后再次反射回地球表面。

温室气体就是其中吸收了红外射线的一种气体，然后再次反射一些红外线到地球。

二氧化碳，CFC，甲烷和二氧化氮都是温室气体。

大气中温室效应形成和建立的很自然。

事实上，大气中如果没有温室气体，科学家预测地球温度比当前的能够低33度。

【P2】大气中当前二氧化碳浓度是360ppm。

人类活动正在对大气中二氧化碳浓度的增加有着重要的影响，二氧化碳浓度正在快速增长，目前预估在未来50-100年内，浓度将是目前的一倍。

IPCC在1992中做出一份报告，在该份报告中大多数大气科学家中观点一致，预测二氧化碳浓度翻倍可能会将全球气温提高1.4-4.5度。

IPCC在2001年的报告中做出的预测是气温几乎将会提高2倍。

可能发生的气温升高比在冰河时期发生的变化要大很多。

这种温度的升高也不会是一直的，在赤道周围变化最小，而在极点周围的变化则是2-3倍。

这些全球变化的本地化影响很难预测，但是大家一致认为可能会影响洋流的改变，在北半球的一些区域可能增加在冬天发洪水的可能性，在一些区域夏天发生干旱的概率提高，还有海平面的升高也可能会淹没位置较低的国家。

【P3】科学家积极参与地球气候系统中物理，化学和生物成分的调查，为了对温室气体的增加对未来全球气候的影响做出准确预测。

全球环流模型在这个过程中是重要的工具。

这些模型体现包含了当前对大气环流模式，洋流，大陆影响和类似东西所掌握的知识，在变化的环境下预测气候。

Raymond_2009_The contribution of agricultural and urban activities

This article appeared in a journal published by Elsevier.The attached copy is furnished to the author for internal non-commercial research and education use,including for instruction at the authors institutionand sharing with colleagues.Other uses,including reproduction and distribution,or selling or licensing copies,or posting to personal,institutional or third partywebsites are prohibited.In most cases authors are permitted to post their version of thearticle(e.g.in Word or Tex form)to their personal website orinstitutional repository.Authors requiring further informationregarding Elsevier’s archiving and manuscript policies areencouraged to visit:/copyrightThe contribution of agricultural and urban activities to inorganic carbon ﬂuxes within temperate watershedsRebecca T.Barnes ⁎,Peter A.RaymondYale University,School of Forestry &Environmental Studies,205Prospect St,New Haven,CT 06511,USAa b s t r a c ta r t i c l e i n f o Article history:Received 7October 2008Received in revised form 19June 2009Accepted 22June 2009Editor:D.RickardKeywords:Dissolved inorganic carbon δ13CLand use change Watersheds Weathering Nitri ﬁcation Riverine ﬂuxThe lateral transport of bicarbonate as dissolved inorganic carbon (DIC)to the oceans is an integral component of the global carbon budget and can represent the sequestration of CO 2from the atmosphere.Recently studies have implicated land use change,in particular agricultural development,as an accelerator of bicarbonate export.However,due to the co-variation of land use,bedrock and sur ﬁcial geologies,and the relationship between bicarbonate export and climate,the impact of anthropogenic activities on DIC export remains an important research question.In order to examine the land use controls on DIC export from small temperate watersheds we sampled 19streams draining catchments of varying land uses with similar bedrock and sur ﬁcial geologies.In addition to an agricultural effect,there was a strong correlation between the percent of watershed in urban development and DIC concentrations and DIC yields.Urban watersheds exported 7.8times more DIC than their nearby forested counterparts and 2.0times more DIC than nearby agricultural catchments.Isotopic data suggest that excess DIC export from altered systems results from increased chemical weathering,enhanced CO 2production within urban green spaces,and as a result of organic matter loading from septic systems and leaky sewer lines.Furthermore,we found that nitrogen additions (e.g.fertilizers and manure)are aiding in the dissolution of lime,increasing the total export of DIC from agricultural watersheds.Calculated anthropogenic loading rates ranged from 0.43to 0.86mol C m −2yr −1.These loading rates suggest that a signi ﬁcant portion of global DIC export might be attributable to human activities,although the impacts on CO 2sequestration are dif ﬁcult to determine.Published by Elsevier B.V.1.IntroductionRivers serve as a major conduit for the lateral transfer of carbon from continents to the oceans,providing an important link in the global carbon (C)cycle (Likens et al.,1981;Meybeck,1987).Globally,riverine transfers of C are estimated between 0.8and 1.6Pg yr −1(Ludwig et al.,1996;Suchet et al.,2003),with dissolved inorganic and organic C ﬂuxes to the ocean constituting approximately 0.4Pg yr −1each of this total C ﬂux (Richey,2004).Dissolved inorganic carbon (DIC)is produced in part via the weathering of carbonate and silicate rocks and is believed to be a major control on atmospheric carbon dioxide (CO 2)concentrations over geologic time (Berner et al.,1983).Riverine C ﬂuxes are very sensitive to regional and global change due to fact that riverine ﬂuxes re ﬂect physical,biotic and anthropogenic processes (Meybeck and Vorosmarty,1999;Raymond et al.,2008;White and Blum,1995).Researchers have therefore used spatial and temporal trends of C export to assess the impact of human activities on the carbon cycle.Watershed export of DIC is a re ﬂection of both terrestrial and in-stream processes.This includes the addition of bicarbonate from theweathering of carbonate and silicate rocks and the transport of CO 2produced via soil respiration.Both weathering and transport are strongly controlled by regional hydrology,geology,land use,soils,and climate (Markewitz et al.,2001;Meybeck,1987;Meybeck,1993;Nezat et al.,2004;White and Blum,1995).In-stream processes such as photosynthesis and respiration can also alter DIC through the utilization and production of CO 2(Neal et al.,1998a;Neal et al.,1998b;Raymond et al.,1997;Richey et al.,2002),although the fate of this DIC is generally exchange with the atmosphere (Dawson et al.,1995;Quay et al.,1992).The in-stream metabolism of organic C is often greater than primary production,resulting in the supersaturated CO 2(aq)conditions in streams and rivers,making them a source of CO 2to the atmosphere (Cole and Caraco,2001;Raymond et al.,1997).Collectively these processes control the alkalinity and pH of the water,thereby determining the partitioning of DIC into bicarbonate (HCO 3−),carbonate (CO 32−),and dissolved CO 2.Recently increases in the inorganic carbon ﬂux have been linked to agricultural activities (Oh and Raymond,2006;Perrin et al.,2008),sprawl (Interlandi and Crockett,2003),and urban activities (Baker et al.,2008).Land use change can affect both the production and transport of DIC by altering hydrologic ﬂow paths,increasing soil CO 2production,enhancing respiration through organic matter loading,through the application of lime (de ﬁned here as CaCO 3or CaMgChemical Geology 266(2009)327–336⁎Corresponding author.Present address:US Geological Survey,3215Marine Street,Suite E127,Boulder,CO 80303,USA.Tel.:+13035413026;fax:+13035413084.E-mail address:becca.barnes@ (R.T.Barnes).0009-2541/$–see front matter.Published by Elsevier B.V.doi:10.1016/j.chemgeo.2009.06.018Contents lists available at ScienceDirectChemical Geologyj o u r n a l h o me pa g e :w w w.e l s ev i e r.c o m/l o c a t e /c h e mg e o(CO3)2),and by increasing the availability of weatherable materials. However,as several researchers have noted it is often difﬁcult to tease apart human impacts on riverine constituents and ecology due to the highly correlated nature of land use,geology,soils and climate(Allan, 2004;King et al.,2005).We investigated watersheds of varying land use within a small area with minimal differences in watershed mineralogy and surﬁcial materials in the southern portion of the Connecticut River watershed. Throughout the study region quartz rich bedrock dominates and carbonate lithologies are not present within the headwater stream watersheds.Here we present the results of inorganic carbon concentration and isotopic analyses from nineteen watersheds of varying sizes and land uses.We also measured base cations and anions and analyzed spatial data sets describing the lithology,surﬁcial materials,land cover,and land use to provide ancillary information related to the inorganic carbon dynamics of these systems.Our two main objectives were to determine how urban and agricultural development affects DIC export and to examine how anthropogenic nitrogen inputs inﬂuence the sources and magnitude of DIC yields.By comparing the chemical and isotopic measurements between sites and through time we found large differences in inorganic carbon dynamics related to land cover and human activities.2.Methods2.1.Spatial analysisWatersheds were delineated using ArcHydro tools in ArcMap9.1 (ESRI,Redlands,CA)using NHDPlus data(available at:http://www. /nhdplus/data.php)which include hydrography and digital elevation information for the region.Spatial data were compiled from several federal and state agencies'websites:land use/ land cover data(MRLC,2005),surﬁcial materials and bedrock geology data(Robinson and Kapo,2003;Rodgers,1985;Stone et al.,1992),and data on sewered areas within Connecticut(CTDEP,1998).These data were then analyzed using spatial analysis tools in ArcMap9.1to determine land use/land cover,surﬁcial materials,bedrock geology, and sewage service of each watershed.2.2.Water chemistry sample collection and analysisSampling of nineteen stream sites occurred bimonthly over 14months,June2005to August2006.Streamwater was collected in acid-washed,stream-rinsed HDPE bottles andﬁltered in theﬁeld(0.7μm pre-combusted GF/Fﬁlters).Theﬁltrant was stored in acid-washed, stream-rinsed HDPE bottles on ice and theﬁlters were folded in half, wrapped in pre-combusted foil,placed in a sealed bag,and stored on ice. Upon returning to the lab all water andﬁlter samples were placed in the freezer.The same protocol was followed at the six wastewater treatment plant(WWTP)sites from December2005through August2006.At the time of sample collection,stream discharge for theﬁfteen small watersheds was estimated by measuring stream velocity and depth using a Marsh-McBirney electromagnetic current meter and wading rod at regular intervals across the stream.Discharge for the large tributaries was obtained from the USGS NWIS website(http:// /nwis/sw).Inﬁeld measurements of conductivity, temperature,and pH were made using an YSI Model85Dissolved Oxygen and Conductivity Meter(Yellow Springs,OH).Sample pH was also measured upon returning to the lab,using an Accumet Research AR15pH meter(Fisher Scientiﬁc).Cations(Na+,K+,Ca2+,Mg2+)were analyzed on a Perkin-Elmer Optima3000inductively coupled plasma atomic emission spectrom-eter(ICP-AES),Cl−and SO42−were measured on a Dionex ion chro-matograph,and NO3−was measured on an Astoria2Flow Analyzer in the Analytical Lab at Yale's School of Forestry and Environmental Studies.Sample replication was good between runs,with standard deviations of0.10mg L−1,0.07mg L−1,0.07mg L−1,0.09mg L−1, 0.01mg L−1,0.12mg L−1,and0.08mg L−1for K+,Ca2+,Mg2+,Na+, NO3−,Cl−,and SO42−,respectively.2.3.DIC sample collection and analysesHeliumﬂushed glass exetainers with0.05mL concentrated UHP H3PO4were injected with0.5mL ofﬁltered stream water in theﬁeld. Before injection the syringe was rinsed with2mL ofﬁltered stream water and care was taken to remove all gas bubbles prior to injection. The acid-water reaction begins immediately upon injection and all DIC present in the sample evolves to CO2(g)due to the rapid drawn down of pH.All samples were collected in duplicate and exetainers were stored on ice until returning to the lab and placed in the freezer prior to analysis;analyses were done within one week of sampling.Isotope analysis was performed using the GasBench in conjunction with a ThermoFinnigan Delta PLUS Advantage stable isotope mass spectrometer at Earth Systems Center for Stable Isotope Studies (ESCSIS)at Yale Institute for Biospheric Studies.All stable isotope values are reported in the standard per mill(‰)notation relative to VPDB.Standards and samples were loaded into the GasBench and the sampled headspace gas(CO2)was evaluated in relation to the prepared standards to calculate the amount and isotopic composition of DIC in stream water.Standards encompassed a range of concentra-tions(0µM to2500µM)and isotopic values(−3‰and−37.4‰). Replication indicates good precision for isotopic measurements and DIC concentrations,with standard deviations of0.21‰and28µM, respectively,across all runs.For both concentration and isotopic composition replication was relatively poor for samples with DIC concentrations b100µM.Concentrations this low did not occur often, however the majority of samples from the highﬂow event in October 2005had concentrations that fell below this threshold,therefore care should be taken in their interpretation.2.4.Soil and POM collection and analysesSoil samples were taken twice(July2006and October2006)at38 sites throughout14of the small watersheds,sampling did not occur in the Salmon Brook watershed(HSB)due to a lack of access.Sites were selected based on land use and surﬁcial material information,each site representing a permutation(i.e.forested-till)comprising at least10% of a watershed.When present,leaf litter was removed and three soil cores(2.1cm×20.3cm)were taken and combined in a sealable plastic bag.The composite samples were allowed to air dry for approximately one week,at which point sticks and stones were removed.Soil sub-samples were dried in pre-combusted aluminum weigh boats in a60°C oven for24h.The dried soil was homogenized with a Spex/CentriPrep6750freezer mill.A portion of each homogenized soil sample was exposed to concentrated HCl in a desiccator for24h to remove inorganic carbon.After exposure to HCl,samples were again dried in a60°C oven for24h.The13C/12C content of soil organic matter was determined using a Costech Elemental Analyzer and Finnigan Delta Advantage mass spectrometer in the ESCSIS.Both the acidiﬁed and non-acidiﬁed soil samples were run;comparison of results shows a strong agreement between the two with slopes only slightly less than1 (avg=0.96)and y-intercepts between−0.97and−1.25,indicating low amounts of inorganic carbon.However because the values did vary systematically between the two preparation techniques,the isotopic measurements reported here are from the acidiﬁed set of samples.These analyses were standardized to an in-house cocoa standard(δ13C=−28.23‰,48.7%C)which had a standard deviation of0.15‰across all runs.Duplicate sample measurements were made on10%of the samples and indicate good precision,with an average standard deviation between duplicate samples of1.2‰.Particulate organic matter(POM)was measured using theﬁlters collected in theﬁeld.Half of eachﬁlter was dried in a60°C oven for at328R.T.Barnes,P.A.Raymond/Chemical Geology266(2009)327–336least 24h in a pre-baked aluminum weigh boat.Particulate organic matter 12C/13C content was measured on the Costech Elemental Analyzer and Finnigan Delta Advantage mass spectrometer in the ESCSIS.These analyses were standardized to an in-house cocoa standard (δ13C=−28.23‰,48.7%C)which had a standard deviation of 0.23‰across all runs.Duplicate sample measurements were made on 5%of the samples,on average the standard deviation between duplicate samples was 0.35‰.2.5.Carbon constituent calculationsIn order to quantify the amount of DIC as bicarbonate,carbonate,and dissolved CO 2we used the CO2SYS program (Lewis and Wallace,1998)in conjunction with our DIC,pH,and temperature measure-ments.Due to lack of reliable pH values for some samples we could not calculate some sample's DIC constituents,the majority of these samples occurred in August 2005.2.6.Statistical methodsAnalysis of variance (ANOVA)was used to compare concentra-tions,yields and isotopic compositions between watersheds ofdifferent predominant land use,utilizing Tukey's method of pairwise comparison (family error rate of 5%).Paired t -tests were used to determine the statistical signi ﬁcance of seasonal variability among streams draining similar land uses.Linear correlations assumed independence between sampling dates at the same stream given the bimonthly nature of sampling;when comparing concentrations,yields,or isotopic compositions to land use variables samples were binned by site and averages were used to insure independence.All statistical analyses were conducted using Minitab and an αlevel of 0.05was used to determine signi ﬁcance.3.Study regionThe sampled watersheds are located in the southern portions of the Connecticut River watershed in southwestern Massachusetts and northern and central Connecticut.The headwater catchments are nested within four larger catchments (49to 1492km 2),the Farmington River,Still River,Hockanum River,and Broad Brook watersheds (Fig.1).The Still River watershed makes up approxi-mately 15%of the Farmington River drainage and the Farmington River,Hockanum River,and Broad Brook are tributaries to the ConnecticutRiver.Fig.1.Sampling locations.The urban sites are labeled with squares:Folly Brook (FB),Bigelow Brook (BB),Ogen Brook (OB),Thompson Brook (TB)&Chudsey Brook (CBu);the forested sites are indicated with circles:Charters Brook (CBf),Headwaters of the West Branch Farmington River (HWFR),Riiska Brook (RB),Sandy Brook (SB),&Headwaters of the Still River (HSR);and the agricultural sites are labeled with the diamonds:Headwaters of Broad Brook (HBB),Creamery Brook (CBa),Muddy Brook (MB),Headwaters of the East Branch of Salmon Brook (HSB),&Kendall Brook (KB).Sampled wastewater treatment plants and large tributary sampling locations are indicated with stars and asterisks,respectively.329R.T.Barnes,P.A.Raymond /Chemical Geology 266(2009)327–336Theﬁfteen headwater catchments(1.9to35.9km2)are character-ized by a dominant land use:forested,agricultural or urban.Theﬁve forested watersheds range in size from1.9to35.9km2,with mixed deciduous and coniferous stands covering80–98%of the catchment (Table1).The large majority(N95%)of agricultural and urban lands within the forested watersheds are classiﬁed as pasture or open space, respectively.Corn(maize)and hay are the principal crops within the agricultural watersheds(C.Clark&T.Morris,written communication) and along with dairy production occupy32–46%of the watershed area (Table1).Urbanized watersheds consist primarily(43–83%)of residential,industrial and commercial areas,encompassing a range of development densities,with light to medium density residential development dominating Thompson Brook(TB)and Chudsey Brook (CB u)and denser residential and commercial development character-izing Bigelow Brook(BB,Table1).The headwater catchments are dominated by quartz rich geologies, on average Mesozoic sedimentary rocks make up85%and74%of the agricultural and urban lithologies,respectively;in contrast,the forested watersheds are dominated(87%)by granitoids and quartz rich metamorphics(Table1).Glacial till is a dominant surﬁcial material in13out of the15small watersheds(Table1).There is a systematic difference in bedrock lithology between developed and undeveloped watersheds,though the mineralogy is similar and there are no calcareous lithologies present(Rodgers,1985);furthermore the surﬁcial materials are similar across the region due to the same glaciation history.It should be noted that calcite is ubiquitously present within granites(White et al.,1995);thus despite the absence of carbonates in the bedrock and surﬁcial materials the preferential weathering of calcite could have a disproportionate effect on stream chemistry.The larger tributary watersheds have similar bedrock geology and surﬁcial materials as their nested headwater catchments (Table1).The majority of Broad Brook and Hockanum River water-sheds as well as eastern portions of the Farmington River watershed are underlain by highly transmissive stratiﬁed drift aquifers,domi-nated by sand and gravel(Grady,1994).According to Grady(1994) residence times in these aquifers can range from less than a year to greater than20years resulting in low amounts of dissolved solids (b300mg/L)in the groundwater.The four large tributaries sampled are inﬂuenced not only by the catchment characteristics(Table1)but also by the presence of waste water treatment plants(WWTP),with the exception of Broad Brook.The average discharge of these plants during sampling ranged from 0.5to8MGD.At the time of sampling all of the WWTP engaged in secondary treatment processes.Precipitation in the region is distributed almost evenly through-out the year with an average annual budget of1140mm(Miller et al.,2002).Daily precipitation records for the duration of the study were obtained from the National Climatic Data Center for the weather station at Bradley International Airport,which lies north-west of Hartford Connecticut,at41°56′19″N72°40′57″W(NCDC, 2007).4.Results4.1.Dissolved inorganic carbonDissolved inorganic carbon concentrations varied signiﬁcantly between land uses,with DIC concentrations in urban streams4.7 times greater than nearby forest streams(1116±720µmol C L−1and 240±170µmol C L−1,respectively).Agricultural stream water DIC concentrations were3.3times greater than forest streams(800±538µmol C L−1),with the larger rivers(watershed areas N40km2) having intermediate concentrations,564±417µmol C L−1).Tukey's pairwise comparisons showed that DIC concentrations varied sig-niﬁcantly throughout the year(Fig.2a).Watershed yields of DIC followed similar patterns with urban,agricultural,and large river systems exporting6.0times,2.6times,and1.9times more DIC than forested watersheds(Fig.2b).The wastewater treatment plants' efﬂuent had the highest concentrations of DIC,averaging1508±772µmol C L−1.Bicarbonate(HCO3−)was the dominant constituent of DIC in all of the streams;making up87%,83%,80%,and79%of stream DIC in large tributaries,urban streams,agricultural streams,and forested streams,respectively.Dissolved CO2made up13–23%of total DIC. Carbonate(CO32−)rarely contributed signiﬁcant portions of DIC to the streams(b1%).Seventy-nine percent of the samples had CO2concen-trations that were supersaturated with respect to the atmosphere.The majority of stream CO2concentrations less than380µatm occurred in October2005and August2005.The October2005concentrations coincided with the highestﬂow event and lowest DIC concentrations measured.Given the lack of reliable pH values in August2005the pCO2 values for these dates were not interpreted.Table1Watershed characteristics for all sampling locations:the percent of watershed area covered by a given land use,impervious cover,and sewer service.Site Size(ha)%of watershed area BedrocktypeSurﬁcialmaterial Type Wetland Forest Urban Ag Impervious surface Sewer serviceHBB1587ag 2.049.615.931.9 2.5 4.0M T MB304ag0.641.910.745.8 1.40.0S T CBa290ag0.736.5 6.951.80.50.0S T KB356ag 4.230.822.238.1 3.5 1.0S T&SG HSB256ag 4.446.3 4.144.80.40.0S SG WBFR3593forest 4.880.77.9 1.3 1.00.0M&I T CBf749forest11.479.9 4.2 4.20.30.0I T RB414forest 4.987.8 1.1 4.80.20.0M T SB1116forest7.388.6 1.60.90.20.0M T HSR191forest0.197.8 1.30.80.10.0M T TB744urban 2.447.243.2 6.79.6 4.0S T&SG CBu465urban 2.543.849.2 3.710.9 3.0S T BB761urban0.214.282.7 2.136.485.0S SG FB332urban0.131.445.018.616.147.0S T OB315urban 1.324.762.610.618.099.0I T Broad Brook4941tributary 2.137.314.742.8 2.9 4.0S T&SG Farmington River149193tributary371.913.8 6.8 3.1 6.3M T Hockanum River19003tributary 3.140.338.913.813.232.5S&I T&SG Still River22534tributary 4.677.39.8 5.1 1.7 2.9M&I TBedrock types and surﬁcial materials were grouped into classes,metamorphic(M),sedimentary(S),igneous(I)and till(T),sand/gravel(SG),swamps(S),respectively.Only the dominant(N60%of the watershed area)is listed except for the cases where one type did not constitute a majority of the watershed.For more information on bedrock and surﬁcial material distribution please see Table S1.330R.T.Barnes,P.A.Raymond/Chemical Geology266(2009)327–3364.2.δ13C of dissolved inorganic carbonOverall the δ13C-DIC was most enriched in streams draining forested watersheds,averaging −10.4‰±3.3‰and most depleted in urban streams (−14.7‰±2.0‰).Agricultural streams were slightly enriched (−13.2‰±2.9‰)as compared to the urban streams.Temporal variation of δ13C-DIC in the small watersheds was similar across land use types with the most enriched values occurring between December 2005and April 2006(Fig.3).4.3.Soil and particulate organic carbon δ13CThe δ13C of individual soil samples from each small watershed were area-weighted based on land use and sur ﬁcial material information in order to approximate an average δ13C of soil for a given watershed.The range in area-weighted samples for the watersheds was small (−27.3‰to −24.6‰)as compared to the range for individual soil samples (−28.1‰to −20.2‰).The isotopic composition of soil samples did not vary appreciably between sampling dates and therefore samples were grouped for statistical analyses.Two-sample t -tests (Tukey family error rate of 5%)illustrated that individual soil sample δ13C varied signi ﬁcantly (p b 0.05)between land use types;agricultural soils had the most enriched values of δ13C (−23.6‰±2.0‰,n =12)as compared to urban (−25.3‰±1.7‰,n =24)and forested soils (−26.7‰±0.7‰,n =40).The δ13C of particulate organic matter (POM)in streams did not show signi ﬁcant variation between land uses or with sampling date.Streams draining urban,forested,and agricultural areas had similar average δ13C-POM values of −28.2‰±1.4‰,−28.7‰±1.6‰,and −27.8‰±2.0‰,respectively.4.4.Ancillary cations and anionsCations (K +,Mg +,Na 2+,Ca 2+)and anions (Cl −,NO 3−,and SO 42−)varied signi ﬁcantly between land uses (Fig.4).Tukey pairwise comparisons demonstrate signi ﬁcant differences for K +,Ca 2+,NO 3−,and SO 42−concentrations in streams draining developed watersheds incomparison to those in forested areas.Magnesium,NO 3−,and SO 42−concentrations were greatest in agricultural streams and lowest inforested streams,with urban streams having similar SO 42−levels and signi ﬁcantly lower Mg 2+and NO 3−concentrations compared to the agricultural sites (Fig.4).Agricultural streams also had signi ﬁcantly elevated K +concentrations relative to undeveloped watersheds,while urban streams had signi ﬁcantly higher Na +,Cl −,and Ca 2+concentra-tions than either the agricultural or forested streams (Fig.4).For a more complete description of how stream chemistry varied between sites please see Table S2in the Supplemental Information .5.Discussion5.1.DIC export and land useComparisons between watersheds of different land use type illustrates that both urban and agricultural areas export signi ﬁcantly more DIC than their forested counterparts (Fig.2b).MultiplestudiesFig.3.The average δ13C of DIC across watersheds of similar land use.The error bars represent the standard error across watersheds of the same type,i.e.between sitevariation.Fig.4.Average cation and anion concentrations (in mM)of watersheds of similar land use type.Error bars represent the standard error of measurements both through time and across watersheds of the same land use type.Letters above bars indicate signi ﬁcantly different groups.For a more complete look at the water chemistry at each site,pleases see TableS2.Fig.2.The average DIC concentration (a)and yield (b)across watersheds of similar land use types.The error bars represent the standard error across watersheds of the same type,i.e.the between site variation.331R.T.Barnes,P.A.Raymond /Chemical Geology 266(2009)327–336have shown that the spatial variation in DIC export is linked to differences in lithology and surface materials of the watershed,in particular the amount of carbonate minerals available to weathering (e.g.Meybeck,1987).Unfortunately,decoupling land cover and land use from lithology and sur ﬁcial materials is dif ﬁcult.Results from our cation and HCO 3−analyses suggest that silicates are the dominant source of weathering products within all of our systems,as indicated by the comparison of normalized molar ratios ofriverine Ca 2+/Na +,Mg +/Na +,and HCO 3−/Na+to literature de ﬁned end members (Gaillardet et al.,1999).Though it should be noted that these comparisons are not de ﬁnitive given the perturbed nature and size of the streams in this study as compared to those examined by Gaillardet et al.(1999).The lithological characteristics of each watershed,as determined by spatial analyses,also indicate that silicate weathering should dominate as the bedrock is characterized by sedimentary silt and sandstones,granites,and quartz rich meta-morphics (Table 1).The dominance of silicate weathering and similarlithological characteristics across land cover groups argue for land use controls on DIC export.Within this study,while the bedrock mineralogical characteristics are similar,the type of rock does vary somewhat systematically between land use types.Igneous and metamorphic rocks dominate the forested watersheds while sedimentary rocks underlay most of the urban and agricultural systems.Thus it is possible that weathering rates also vary systematically.For example sedimentary rocks'greater permeability likely leads to higher amounts of exposed mineral surfaces and faster weathering rates in comparision to the meta-morphic rocks.Secondly,despite the lack of calcareous lithologies,carbonate inclusions could vary with rock type and in ﬂuence stream chemistry (White et al.,1995).However,it is important to note that one agricultural (HBB)and one urban (OB)watershed have bedrock similar to the forested watersheds (Table 1).In the case of HBB,DIC concentrations and yields were higher than the other agricultural watersheds within this study;while in OB,DIC concentrations and yields fell on the lower end of the observed range for urban streams though both concentration and yield were still signi ﬁcantly higher than those measured in forested systems (Table S2).Past work done within the region's shallow aquifers (Grady,1994)argues that increased DIC concentrations and yields within the developed areas are due to anthropogenic activities.Streams within this study are dominated by groundwater inputs from strati ﬁed drift aquifers and work by Grady (1994)showed that aquifer DIC concentrations varied signi ﬁcantly with land use;urban and agricul-tural systems had concentrations at least two times higher than their undeveloped counterparts despite similar aquifer properties.Thus we argue that land use changes are responsible for the observed differences in DIC concentration and yield.Comparisons of the relationship between water yield and DIC yield in watersheds of different land use indicates that urban and agricultural areas export more DIC for every unit of water throughput relative to undisturbed systems (Fig.5).Oh and Raymond (2006)found that watersheds dominated by agriculture (N 79%)exported 3.4times more HCO 3−on average than watersheds which had less than 5%cropland cover within the Ohio River watershed;similarly our results indicate that agricultural watersheds are exporting approximately four times more DIC per unit of water throughput than undisturbed systems (Fig.5).The percent of watershed in urban development was strongly correlated with DIC concentration (R 2=0.61,p b 0.0001)and DIC yield (Fig.6,R 2=0.54,p =0.003).In fact,urban watersheds exported 7.8times more DIC per unit of water yield than nearby forested systems and nearly 2times more DIC thanagriculturalFig.5.The relationship between water yield and DIC yield from headwater catchments dominated by different land uses.The slopes of the linear regressions are 0.136,0.540,and 1.056for forested,agricultural,and urban watersheds,respectively.The outlier within the urban plot was excluded from the regression,if included the slope and R 2increase to 1.466and 0.55,respectively.Fig.6.The amount of a watershed in urban and suburban development was signi ﬁcantly related to the yield of DIC from watersheds.This relationship existed across all watershed sizes sampled (1.9to 1492km 2).332R.T.Barnes,P.A.Raymond /Chemical Geology 266(2009)327–336。

2011复原草抗旱机制9.2

LARGE-SCALE BIOLOGY ARTICLEA Sister Group Contrast Using Untargeted Global Metabolomic Analysis Delineates the BiochemicalRegulation Underlying Desiccation Tolerance inSporobolus stapﬁanus C W OAMelvin J.Oliver,a,1,2Lining Guo,b,1Danny C.Alexander,b John A.Ryals,b Bernard W.M.Wone,cand John C.Cushman da U.S.Department of Agriculture-Agricultural Research Service,Plant Genetic Research Unit,University of Missouri,Columbia, Missouri65211b Metabolon Inc.,Durham,North Carolina27713c Department of Biological Sciences,University of Nevada,Reno,Nevada89557-0314d Department of Biochemistry and Molecular Biology,University of Nevada,Reno,Nevada89557-0200Understanding how plants tolerate dehydration is a prerequisite for developing novel strategies for improving drought tolerance.The desiccation-tolerant(DT)Sporobolus stapﬁanus and the desiccation-sensitive(DS)Sporobolus pyramidalis formed a sister group contrast to reveal adaptive metabolic responses to dehydration using untargeted global metabolomic analysis.Young leaves from both grasses at full hydration or at60%relative water content(RWC)and from S.stapﬁanus at lower RWCs were analyzed using liquid and gas chromatography linked to mass spectrometry or tandem mass parison of the two species in the fully hydrated state revealed intrinsic differences between the two metabolomes. S.stapﬁanus had higher concentrations of osmolytes,lower concentrations of metabolites associated with energy metabolism,and higher concentrations of nitrogen metabolites,suggesting that it is primed metabolically for dehydration stress.Further reduction of the leaf RWC to60%instigated a metabolic shift in S.stapﬁanus toward the production of protective compounds,whereas S.pyramidalis responded differently.The metabolomes of S.stapﬁanus leaves below40% RWC were strongly directed toward antioxidant production,nitrogen remobilization,ammonia detoxiﬁcation,and soluble sugar production.Collectively,the metabolic proﬁles obtained uncovered a cascade of biochemical regulation strategies critical to the survival of S.stapﬁanus under desiccation.INTRODUCTIONThe impact of drought on crop production is of continuous and growing concern as the world struggles to meet food production targets for an increasing global population.The predicted and emerging changes in global climate patterns generally forecast an increase in the number and severity of drought events that will negatively impact the production and stability of food supplies (Schmidhuber and Tubiello,2007).Drought usually implies a composite stress condition that includes soil water deﬁcits, increased daytime temperatures,and reduced nutrient availabil-ity,but,occasionally,also increased salinity in the soil.However, the most important factor limiting growth and impairing plant productivity is the drop in water availability to the plant.For example,Arabidopsis thaliana seedlings exposed to mild water deﬁcits cease shoot and root growth at water potentials of only 21and20.6megapascal(MPa),respectively,in controlled conditions(van der Weele et al.,2000).More severe water deﬁcits that send leaf osmotic potentials to22.6860.46MPa result in a95%lethality rate for mature Arabidopsis plants (Columbia ecotype;Yang et al.2005).In general,most crop species are very sensitive to soil water potential and only rarely survive soil water deﬁcits that drive leaf water potentials to24 MPa(Proctor and Pence,2002).Thus,Arabidopsis and other models are not appropriate for studies aimed at elucidating mechanisms of dehydration tolerance.Cellular responses to water deﬁcits include growth inhibition, stomatal closure,limited transpiration,and reduced photosyn-thesis,and those responses that enhance cellular dehydration tolerance(Mullet and Whitsitt,1996).Understanding which re-sponses are critical and adaptive for maintaining plant growth and productivity is essential for developing strategies that1These authors contributed equally to this work.2Address correspondence to mel.oliver@.The author responsible for distribution of materials integral to theﬁndings presented in this article in accordance with the policy describedin the Instructions for Authors()is:Mel Oliver(mel.oliver@).C Someﬁgures in this article are displayed in color online but in blackand white in the print edition.W Online version contains Web-only data.OA Open Access articles can be viewed online without a subscription./cgi/doi/10.1105/tpc.110.082800The Plant Cell,Vol.23:1231–1248,April2011,ã2011American Society of Plant Biologistsimprove drought tolerance of all major crops.Work with the major archetypal species,both crop(e.g.,maize)and noncrop (e.g.,Arabidopsis),has established a wealth of information and a substantial catalog of cellular responses to water deﬁcits.How-ever,most studies of water deﬁcit responses in plants do not attempt to reach water potentials that would generate signiﬁcant cellular dehydration,and many remain in the range where os-motic adjustment can prevent signiﬁcant dehydration of the cellular environment.This is because most present-day angio-sperms cannot survive dehydration of their vegetative tissues to 20to30%of full turgor(RWC),which translates to between25 and210MPa(Proctor and Pence,2002).The lowest reported water potential reached for an angiosperm that is not DT is212.1 MPa for Larrea divaricata,a desert shrub(Cunningham and Burk, 1973).Despite the array of data characterizing water deﬁcit responses that may relate to dehydration tolerance,there is still little understanding as to which responses,whether at the gene or cellular level,are actually adaptive in nature and truly critical for or central to tolerance(Bray,2002).Much of what we know of dehydration tolerance in vegetative tissues of plants comes from studies involving the so-called DT or resurrection plants that can tolerate water deﬁcits so severe that the plants loose all available free water from their tissues. The increased interest in drought tolerance and the accelerating search for novel genetic components and strategies for improv-ing or maintaining crop production under soil water deﬁcits has renewed interest in DT plants(Moore et al.,2009;Oliver et al., 2010).Several species have been studied in depth with a view toward understanding the genes that control the underlying mechanisms and processes involved in desiccation tolerance. These include a bryophyte Tortula ruralis;the clubmosses Se-laginella lepidophylla and Selaginella tamariscina;the dicots Craterostigma plantagineum,Craterostigma wilmsii,Boea hy-grometrica,and Myrothamnusﬂabellifolia;and the monocots Xerophyta viscosa,Xerophyta humalis,and S.stapﬁanus(re-viewed in Ingram and Bartels,1996;Alpert and Oliver,2002; Moore et al.,2009;Cushman and Oliver,2010;Oliver et al., 2010).Many studies using resurrection species are now focusing on gene discovery,large-scale transcriptome proﬁling of dehy-dration responses(Rodriguez et al.,2010),signaling pathways, and functional roles of individual genes in the desiccation re-sponse(reviewed in Cushman and Oliver,2010;Oliver et al., 2010).Proteomic-level investigations have also been under-taken,and novel insights into the dehydration response of several DT species have enriched our understanding of the cellular protection mechanisms that underpin desiccation toler-ance(Alamillo and Bartels,2001;Georgieva et al.,2009;re-viewed in Cushman and Oliver,2010).Perhaps some of the more revealing insights come from small-scale but in-depth analyses of metabolic processes that emerge or respond during the systemic loss of water from resurrection plants(reviewed in Cushman and Oliver,2010).Soluble sugars accumulate,and associated enzyme activities increase,in all DT tissues studied to date,sometimes in combination with oligo-saccharides(Vertucci and Farrant,1995;Whittaker et al.,2001; Phillips et al.,2002;Illing et al.,2005;Farrant,2007;Peters et al., 2007;Iturriaga et al.,2009).The disaccharide Suc is the most common soluble sugar associated with desiccation tolerance in resurrection plants and accumulates during drying(Smirnoff, 1992;Ghasempour et al.,1998).Amino acids such as Arg and Asn,perhaps derived from the breakdown of damaged proteins, accumulate in large amounts during the later stages of dehydra-tion in some resurrection species,as observed in S.stapﬁanus (Whittaker et al.,2007),and may,in addition to their roles as osmolytes,provide nitrogen and carbon for the return of growth and metabolism upon rehydration(Martinelli et al.,2007a).In addition to metabolites associated with cellular protection, other metabolites are thought to play important roles in protect-ing cellular constituents from reactive oxygen species(ROS)that build up during dehydration and in the desiccated state,partic-ularly under high light conditions.Anthocyanins,which may act as photoprotectants by masking photosynthetic pigments and by quenching free radicals,typically increase during dehydra-tion in resurrection angiosperms(Sherwin and Farrant,1998; Hoekstra et al.,2001).Antioxidants and their attending enzymes also appear central to the desiccation response in DT plants and tissues(Sherwin and Farrant,1998;Illing et al.,2005;Kranner and Birtic,2005;Berjak,2006;Farrant,2007).For example, ascorbate-glutathione cycle metabolites are often elevated during drying to combat ROS activity in resurrection plants (Navari-Izzo et al.,1997;Jiang et al.,2007).In fact,the length of time a resurrection plant can survive the dried state has been correlated to the level of antioxidants in its tissue(Kranner et al., 2002).Lastly,polyphenol oxidase,which catalyzes the oxidation of mono-and o-diphenols to o-diquinones,showed increased protein abundance and enzyme activity in the dehydrating leaves of several resurrection species(Jiang et al.,2007;Veljovic-Jovanovic et al.,2008).Polyphenols are powerful detoxiﬁers of toxic ROS and may function as antioxidants during theﬁrst few hours of rehydration(Veljovic-Jovanovic et al.,2008).Although we begin to grasp how resurrection plants respond to desicca-tion or rehydration,without a relevant comparison between the responses of sensitive and tolerant tissues,any insight into the adaptive processes remains simply speculative.Martinelli et al. (2007a)compared the metabolic response of older DS leaves of S.stapﬁanus to that of younger DT leaves.Although there are signiﬁcant and seemingly important differences in the desicca-tion response of these two leaf types,it remains unclear whether they result only from a change in leaf maturity or if they do indeed relate to a loss in DT.What might cause more mature leaves (cellular or otherwise)to lose their desiccation tolerance remains unknown.Another metabolic comparison performed by Farrant et al.(2009)in the fern Mohria caffrorum,which is DT during the dry season and DS during the wet season,led to clear differ-ences between the DT and DS fronds in terms of response to dehydration,but was limited to only a few metabolites.In this study,we have taken advantage of a natural experiment, comparing the metabolomic responses of closely related spe-cies(sister group contrast)that differ in their sensitivity or tolerance to desiccation.We compared the metabolome of young leaves from the DT grass S.stapﬁanus with that of young leaves from the DS species S.pyramidalis.By contrasting two closely related species that differ primarily in their abilities to tolerate dehydration of their vegetative tissues,we hope to better infer not only which processes or components relate directly to desiccation tolerance in these angiosperms,but also the1232The Plant Cellmetabolic mechanisms by which desiccation tolerance is ac-quired.We compared167metabolites in S.stapﬁanus and S. pyramidalis at full hydration and at various RWC levels during dehydration,and,in the case of S.stapﬁanus,all the way to the desiccated state.The data demonstrate that S.stapﬁanus is metabolically primed for a desiccation event and responds quickly as water is lost from the plant.In contrast,S.pyramidalis fails to respond in a measurable way to dehydration to60%RWC and is metabolically focused on energy metabolism,presumably for growth.The data also point to the strong involvement of the glutathione biosynthesis pathway,other antioxidant processes, and sugars in the desiccation tolerance phenotype of S.stapﬁa-nus.A novel plant compound also appears to be associated with the response of S.stapﬁanus to desiccation:ophthalmate,which is also linked to the glutathione biosynthesis pathway.These ﬁndings not only enable us to better understand how plants withstand desiccation of their vegetative tissues,but also to make inferences as to the processes and genetic components of adaptive value to the evolution of this important plant phenotype. RESULTSPhenotypic Responses to DehydrationThe two species exhibited similar drying curves(Figure1a),but S.stapﬁanus displayed an initially lower absolute water content and throughout the drying process(Figure1b).Both species initially lose water at a rate that is consistent withﬁeld observa-tions for S.stapﬁanus(Gaff et al.,2009).S.pyramidalis loses water faster once the overall water contents decline around d16 or17.The leaves of S.stapﬁanus curl as dehydration progresses after the cessation of irrigation,and,under our conditions, appear to curl to particular degrees at speciﬁc RWCs;leaves are halfway curled at68%RWC and fully curled(leaf margins touching)at44%RWC,as described previously(Gaff et al., 2009).Leaves of S.pyramidalis also begin to curl,but only when RWCs are between80and60%.At60%RWC,the leaves of S. pyramidalis are fully wilted and curled,but have not yet begun to visibly lose chlorophyll.At RWCs below60%,the leaves of S. pyramidalis start to yellow,and between40and30%RWC,they start to senesce and turn brown.Under our drying regimen,if the plants are allowed to dry beyond40%,all of the extant leaves loose viability.Based on this phenological data,we chose60% as our dehydration level for comparisons between the two species—a level at which S.pyramidalis is severely stressed (beyond the wilting point,but not to the point where chlorophyll islost or senescence is initiated).A RWC of60%for S.pyramidalis is the equivalent to a leaf water potential of23to23.5MPa,a water potential that results in leaf senescence in maize(Boyer, 1976).Metabolomic Proﬁles and Statistical AnalysisThe metabolomic proﬁling approach used in this study was a nonbiased,global analysis technology based on ultrahigh-per-formance liquid chromatography/tandem mass spectrometry (UHLC/MS/MS2)and gas chromatography/mass spectrometry (GC/MS).In short,the leaf samples were extracted,analyzed on the three MS platforms,ion peaks were matched to standards in a reference library,and their relative levels were quantiﬁed.A total of167metabolites that matched biochemicals with known structures was detected in the samples(see Supplemental Data Set1online).The metabolites were mapped onto general bio-chemical pathways,as illustrated in the Kyoto Encyclopedia of Genes and Genomes(http://www.genome.jp/kegg/)and the Plant Metabolic Network(/).As illus-trated in Figure2,interspecies comparisons were performed at each dehydration level,where possible.Within each species,the Figure1.Drying Curve and the Relationship of RWC to Water Content on a Gram Dry Weight Basis for Both S.stapﬁanus(s)and S.pyramidalis (d).Each point in the drying curve(A)is an average of a minimum of four samples from individual plants;the vertical lines through each point represents the standard deviation from the mean.Each point in the RWC to water content plot(B)is an individual sample taken from individual plants from multiple drying experiments(solid line,S.pyramidalis;dashed line,S.stapﬁanus).Metabolic Responses to Desiccation1233metabolomic data for each dehydration level were compared with its fully hydrated control.The full statistical table generated from this analysis is presented in Supplemental Data Set 2online.Metabolomic Differences between S.stapﬁanus and S.pyramidalis under Fully Hydrated ConditionsFrom 167metabolites detected,a number of them had missing values (not detected)in certain experimental samples.This was likely due to biological variations.To build a robust model using partial least squares-discriminant analysis (PLS-DA),we ex-cluded metabolites with missing values in either species and metabolites lacking more than 66%of sample replicates (four or more of six replicates missing),resulting in n =105for the hydration state comparisons within S .stapﬁanus ,and for the comparisons between S .stapﬁanus and S.pyramidalis at 100and 60%RWC.PLS-DA with three components produced discrete clustering of 100and 60%RWC treatments for both species (Figure 3;R 2=0.65,Q 2=0.61).Different metabolites are clearly responsible for the differences observed in the model,suggesting an obvious metabolic predisposition to water deﬁcit stress at 100%RWC that also persists at 60%RWC.PLS-DA was also performed on S.stapﬁanus at all hydration states tested,and also revealed clear differentiation among the treat-ments (see Supplemental Figure 1online).The supervised clas-siﬁcation method produced a slightly less robust model,with three components separating the treatments (R 2=0.68,Q 2=0.31).In the comparison of the metabolomic proﬁles for fully hy-drated S.stapﬁanus and S.pyramidalis ,a total of 70metabolites with signiﬁcantly altered concentrations (P <0.05)was identiﬁed;36had higher concentrations in S.stapﬁanus and 34had higher concentrations in S.pyramidalis .From these signiﬁcant differ-ences,two clear clusters of metabolism emerged that involve 34of the 70metabolites:amino acid biosynthesis and energy production (Figure 4).Amino acid biosynthesis in the hydrated state is remarkably different between the two species (Figure 4;see Supplemental Data Set 2online).To some degree,with the exception of Trp,all amino acids had accumulated to higher concentrations in S.stapﬁanus .Among the 18amino acids detected,nine (Ala,Arg,Asn,Asp,Glu,Gln,Ser,Thr,and Val)exhibited signiﬁcantly higher concentrations (from three-to 451-fold increase)in S.stapﬁanus than in S.pyramidalis .In fully hydrated plants,Asn exhibited the largest difference in concentration between the two species,a 451-fold higher level in S.stapﬁanus than in S.pyramidalis (Figure 4).In many plants,Asn is the major metabolite for nitrogen storage and transportation,along with allantoin and Gln (Schubert,1986),which are also in greater abundance,eight-and sixfold,respectively,in S.stap-ﬁanus than in S.pyramidalis (Figure 5;see Supplemental Data Set 2).Amino acids are often associated with osmoregulation (Morgan,1984),and in concordance with this possible role,other osmolytic metabolites also exhibit relatively higher con-centrations in S.stapﬁanus than S.pyramidalis ,including a threefold difference in arabitol,erythritol,and mannitol concen-trations,although the concentration of galactinol was much lower in S.stapﬁanus (Figure 6;see Supplemental Data Set 2online).The concentration of glycerophosphorylcholine,a well-recognized osmolyte in mammalian cells (Neuhofer and Beck,2005)only sparsely described in plants,also markedly differed between the two species,with an 11-fold greater accumulation in S.stapﬁanus than in S.pyramidalis (Figure 6).In energy metabolism,differences in the glycolytic pathway between the two species were observed.Both fructose-6-P and glucose-6-P levels were signiﬁcantly lower in S.stapﬁanus ,as were the concentrations of Suc,maltotetraose,and malto-pentaose,which are key metabolites in starch synthesis.ByFigure 2.Statistical Comparison Design.Statistical comparisons of samples from each species,indicated by arrows,were conducted between hydrated (Hyd),60,50,40,20,and ;5%RWC (Dry)within S.stapﬁanus ,Hyd and 60%RWC within S.pyramidalis ,and Hyd and 60%RWC between species.[See online article for color version of thisﬁgure.]Figure 3.Global Metabolite Comparison at 100%Hydrated and at 60%RWC between S.stapﬁanus and S.pyramidalis .PLS-DA model is constructed from 105variables (i.e.,metabolites)generating a three-PLS-DA component model with R2=65.2,and Q2=61.0.S.pyramidalis :squares,100%hydrated;crosses,60%RWC.S.stapﬁanus :asterisks,100%hydrated;upside down triangles,60%RWC.[See online article for color version of this ﬁgure.]1234The Plant Cellcontrast,the concentrations of Glc,the primary substrate for glycolysis and starch biosynthesis,and kestose,another storage carbohydrate,were higher in S.stapﬁanus.Downstream of glycolysis,the difference between the two species in energy metabolism is clear.Levels of lactate and citramalate,both derived from pyruvate,were lower in S.stapﬁanus than in S.pyramidali s.In addition,concentrations of the tricarboxylic acid (TCA)cycle metabolites citrate,malate,and oxaloacetate were signiﬁcantly lower in S.stapﬁanus .In summary,the metabo-lomes of S.stapﬁanus and S.pyramidalis under fully hydrated conditions were signiﬁcantly different.S.stapﬁanus had higherconcentrations of osmolytes,lower concentrations of com-pounds that would indicate a lower apparent rate of energy metabolism,and higher concentrations of nitrogen storage compounds.Metabolic Regulation during Early Stages of Dehydration In the initial phase of dehydration,both species were sampled at 60%RWC,a dehydration level that,while nonlethal to both species,did result in a visible dehydration phenotype:leaf-curling in S.stapﬁanus and wilting and leaf curl in S.pyramidalis.Figure 4.Differences of the Metabolites in Glycolysis/TCA Cycle and Amino Acids between S.stapﬁanus and S.pyramidalis .(A)Amino acid biosynthetic pathway and glycolysis/TCA cycle.The metabolites in red indicate higher levels in S.stapﬁanus .The metabolites in blue indicate lower levels in S.stapﬁanus .The metabolites in black indicate that there were no signiﬁcant differences between S.stapﬁanus and S.pyramidalis .The metabolites in gray indicate that they are below detection level (not detected).(B)Heat map showing the ratio of the metabolite levels between S.stapﬁanus and S.pyramidalis and their statistical signiﬁcance of the differences.Cells shaded with red indicate higher levels in S.stapﬁanus with P <0.05.Cells shaded with green indicate lower levels in S.stapﬁanus with P <0.05.Cells not shaded indicate that the difference between S.stapﬁanus and S.pyramidalis are not statistically signiﬁcant (P >0.05).The number in each cell indicates the fold change between S.stapﬁanus and S.pyramidalis .Metabolic Responses to Desiccation 1235The leaf metabolism of each species responded differently to the imposition to this level of pared with its fully hydrated state,leaves of S.stapﬁanus displayed an increased abundance of many metabolites,chieﬂy,putative cellular osmo-lytes,including amino acids and antioxidants (Figure 7;see Supplemental Data Set 2online).The amino acids Gly,Ile,Leu,Pro,Trp,Tyr,and Val all increased between two-and ﬁvefold.Sugars such as Fru,Gal,Glc,maltose,rafﬁnose,sophorose,and Suc increased between 1.8-fold and more than 18-fold.The sugar alcohols arabitol and mannitol were elevated 2-and 1.6-fold,respectively,which had not been reported for S.stapﬁanus in previous studies (Gaff et al.,2009).In addition,b -tocopherol,a strong cellular antioxidant,increased more than threefold,also novel information for this species.By contrast,S.pyramidalis did not appear to respond to dehydration by instigating a signiﬁcant metabolic shift toward the production of these potentially pro-tective antioxidants and osmolytes,of which there was no apparent statistically signiﬁcant accumulation.Only the amounts of Pro,Glc,and Fru exhibited substantial elevations,but as none of these reached the threshold of signiﬁcance set for the analysis,their response to dehydration in S.pyramidalis remains to be validated.The only signiﬁcant changes in metabolites during the response of S.pyramidalis to dehydration were decreases in various metabolites,most likely due to the suppression of their biosynthesis by dehydration stress (Figure 7;see Supplemental Data Set 2online).Metabolic Regulation during the Late Stages of Dehydration toward DesiccationReduction of leaf RWC below 60%rapidly and severely damages S.pyramidalis leaves,resulting in leaf senescence.If leaves dehydrate to ;40%RWC,then extant leaves of S.pyramidalis do not survive desiccation.Therefore,only the DT S.stapﬁanus was employed to study the regulation of metabolism during stages of increasing dehydration leading to the fully desiccated state.Samples from S.stapﬁanus at four additional dehydration states were collected for analysis:50,40,and 20%RWC and dry (;5%).Compared with the fully hydrated control state,the totalnumber of metabolites with altered relative abundance increased gradually with decreasing RWC.At the dry stage,over one-half (89of 167metabolites)of the metabolome had changed signif-icantly (see Supplemental Data Set 2online)on a dry weight basis.Mapping the altered metabolites to their respective bio-chemical pathways clearly indicated that the major responses to severe dehydration were directed toward antioxidant produc-tion,continued amino acid production,and an accumulation of several carbohydrates.Further dehydration of S.stapﬁanus leaves beyond 60%RWC resulted in a signiﬁcant increase in glutathione,predominantly in the oxidized form,primarily late in the drying regimen,to an ;100-fold greater amount in desiccated versus hydrated control tissue (Figure 8;see Supplemental Data Set 2online).Coincident with the increase in glutathione,its precursors Gly (to threefold)and Cys (to twofold)also accumulated as drying continued.The most dramatic increases associated with the glutathione pathway were observed for a number of g -glutamyl dipeptides that play a role in glutathione recycling via the g -glutamyl cycle (Grzam et al.,2007).These included,on a dry weight basis:g -glutamylphenylalanine (up to 1873-fold),g -glutamyltryptophan (up to 955-fold),and g -glutamylisoleucine (up to 21-fold).Addi-tional glutathione conjugates with increased relative abundance included g -glutamyl-Glu,Met,Ile,and Leu (Figure 8).The increase in g -glutamyl dipeptides during dehydration is a novel discovery and,given the magnitude of the response in S.stapﬁanus during dehydration,it appeared possible that this might be an important aspect of the mechanism of desiccation tolerance in this plant and perhaps for vegetative desiccation tolerance in general.To explore the latter possibility,we ex-tended the metabolite proﬁle to investigate whether or not g -glutamyl dipeptides accumulated in response todehydrationFigure 5.The Relative Amounts of Asn,Gln,and Allantoin between S.pyramidalis and S.stapﬁanus under Fully Hydrated Condition by Box Plots.The box represents the middle 50%of the distribution and upper and lower whiskers represent the entire spread of the data.The hyphen refers to the median.The outlier determined by the statistical program R,if any,is represented by a circle.The y axis is the median scaled value (relative level).The P values for all comparisons are referenced in the Supple-mental Data online.P,S.pyramidalis ;S,S.stapﬁanus.Figure 6.The Relative Amounts of Several Osmolytes between S.pyramidalis and S.stapﬁanus under Fully Hydrated Conditions by Box Plots.The P values for all comparisons are referenced in the Supplemental Data online.P,S.pyramidalis ;S,S.stapﬁanus .1236The Plant Cellin two other species that have long served as models for vege-tative desiccation tolerance:the bryophyte T.ruralis (moss)and the lycophyte (spike moss)S.lepidophylla .The results of this analysis are presented in Figure 9.In T.ruralis ,the four most dehydration responsive g -glutamyl dipeptides,as evidenced by a statistically signiﬁcant increase in accumulation in the dried state,are g -glutamyl-isoleucine (26-fold),-leucine (19-fold),-va-line (20-fold),and -phenylalanine (22-fold).For S.lepidophylla ,the accumulation levels are less but still signiﬁcant for g -glu-tamyl-isoleucine (twofold),-leucine (twofold),Met (twofold),and -Thr (1.6-fold).Along with the increased abundance of glutathione pathway metabolite,the concentrations of related compounds ophthal-mate and 2-aminobutyrate (Figure 8;see Supplemental Data Set 2online)also increased during dehydration.Ophthalmate (glu-2-aminobutyrate-gly)is an analog of glutathione that has not been previously reported in plants and has not been demonstrated to have antioxidant properties.Other antioxidants that accumu-lated in dehydrating S.stapﬁanus leaves included a -,b -,and d -tocopherols (2.8-,35-,and 89-fold,respectively;Figure 10),and the polyamine putrescine (up to twofold)and its precursor agmatine (up to 4.7-fold),which are known to have antioxidant activities that prevent lipid peroxidation.Ascorbate does not appear to be an important antioxidant in S.stapﬁanus ,as its concentrations did not display signiﬁcant alterations in response to dehydration stress.Lysolipids accumulated in the latter stages of dehydration when the RWC of leaves reaches 20%or lower (Figure 11;see Supplemental Data Set 2online).Of the seven lysolipids identiﬁed,1-palmitoylglycerophospocholine appeared to increase to the greatest degree,a 45-fold elevation,but several others increased between two-and 10-fold above control concentrations.The accumulation of these compounds might have signiﬁcant ramiﬁ-cations for membrane properties in desiccating tissues.A steady accumulation of many amino acids was observed during the progression of desiccation in S.stapﬁanus (Figure 12;see Supplemental Data Set 2online).These included the branched chain amino acids (Ile [up to 16-fold],Leu [up to 6.9-fold],and Val [up to 16.5-fold]),and the aromatic amino acids (Phe [up to 3.3-fold],Trp [up to 18-fold],and Tyr [up to eightfold]).The most prominent amino acid accumulations were for Pro (up to 34.5-fold)and His (up to 21-fold).The nitrogen storage and ammonia capture metabolites Asn (which was in greater abundance in S.stapﬁanus than in S.pyramidalis ),allantoin,and Gln also exhibited a positive response to dehydration (Figure 13).Changes in these metabolites were not readily identiﬁed by the statistical analysis,possibly ob-scured by the wide dynamic range of these metabolites in the fully hydrated group.Asn decreased rapidly during initial dehy-dration to 60%RWC.During later stages of dehydration,Asn accumulated dramatically,with allantoin and Gln exhibiting a similar pattern.Carbohydrates are another major class of metabolites that accumulate in leaf tissues in response to dehydration in all vegetative DT tracheophytes studied to date (Alpert and Oliver,2002).In S.stapﬁanus ,as reported earlier (Whittaker et al.,2004),Suc accumulated steadily during dehydration to a maximum elevation of 10.5-fold above control concentrations in the des-iccated state (Figure 14,see Supplemental Data Set 2online).Rafﬁnose and stachyose also gradually increased over the course of dehydration,and reached 74-and 62-fold increases in concentration,respectively,above the hydrated control.Sig-niﬁcant increases were also observed for maltotetraose (up to 46-fold)and myo-inositol (up to threefold),which are likely synthesized from glucose-6-phosphate,which might store phos-phate during the dehydrationprocess.Figure 7.Heat Map of Metabolic Responses of S.stapﬁanus and S.pyramidalis to the Dehydration Stress Reducing RWC from Fully Hy-drated to 60%.Cells shaded with red indicate higher levels in 60%RWC conditions with P <0.05.Cells shaded with green indicate lower levels in 60%RWC conditions with P <0.05.Cells not shaded indicate that the difference between 60%and fully hydrated are not statistically signiﬁcant (P >0.05).The number in each cell indicates the fold change between 60%and fully hydrated.Metabolic Responses to Desiccation 1237。

有机化合物的陆地和水生环境毒性的计算机预测研究英文

有机化合物的陆地和水生环境毒性的计算机预测研究
程飞雄，沈
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托福阅读tpo27R-2原文+译文+题目+答案+背景知识

托福阅读tpo27R-2原文+译文+题目+答案+背景知识原文 (1)译文 (4)题目 (6)答案 (16)背景知识 (17)原文The Formation of Volcanic Islands①Earth’s surface is not made up of a single sheet of rock that forms a crust but rather a number of “tectonic plates” that fit closely, like the pieces of a giant jigsaw puzzle. Some plates carry islands or continents, others form the seafloor. All are slowly moving because the plates float on a denser semi-liquid mantle, the layer between the crust and Earth’s core. The plates have edges that are spreading ridges (where two plates are moving apart and new seafloor is being created), subduction zones (where two plates collide and one plunges beneath the other), or transform faults (where two plates neither converge nor diverge but merely move past one another). It is at the boundaries between plates that most of Earth’s volcanism and earthquake activity occur.②Generally speaking, the interiors of plates are geologically uneventful. However, there are exceptions. A glance at a map of the Pacific Ocean reveals that there are many islands far out at sea that are actually volcanoes----many no longer active, some overgrown with coral----that originated from activity at points in the interior of the Pacific Plate that forms the Pacific seafloor.③How can volcanic activity occur so far from a plate boundary? The Hawaiian islands provide a very instructive answer. Like many other island groups, they form a chain. The Hawaiian Islands Chain extends northwest from the island of Hawaii. In the 1840s American geologist James Daly observed that the different Hawaii islands seem to share a similar geologic evolution but are progressively more eroded, and therefore probable older, toward the northwest. Then in 1963, in the early days of the development of the theory of plate tectonics. Canadian geophysicist Tuzo Wilson realized that this age progression could result if the islands were formed on a surface plate moving over a fixed volcanic source in the interior. Wilson suggested that the long chain of volcanoes stretching northwest from Hawaii is simply the surface expression of a long-lived volcanic source located beneath the tectonic plate in the mantle. Today’s most northwest island would have been the first to form. They as the plate moved slowly northwest, new volcanic islands would have forms as the plate moved over the volcanic source. The most recentisland, Hawaii, would be at the end of the chain and is now over the volcanic source.④Although this idea was not immediately accepted, the dating of lavas in the Hawaii (and other) chains showed that their ages increase away from the presently active volcano, just as Daly had suggested. Wilson’s analysis of these data is now a central part of plate tectonics. Most volcanoes that occur in the interiors of plates are believed to be produced by mantle plumes, columns of molten rock that rise from deep within the mantle. A volcano remains an active “hot spot” as long as it is over the plume. The plumes apparently originate at great depths, perhaps as deep as the boundary between the core and the mantle, and many have been active for a very long time. The oldest volcanoes in the Hawaii hot-spot trail have ages close to 80 million years. Other islands, including Tahiti and Easter Islands in the pacific, Reunion and Mauritius in the India Ocean, and indeed most of the large islands in the world’s oceans, owe their existence to mantle plumes.⑤The oceanic volcanic islands and their hot-spot trails are thus especially useful for geologist because they record the past locations of the plate over a fixed source. They therefore permit the reconstruction of the process of seafloor spreading, and consequently of the geography of continents and of ocean basins in the past. For example, given thecurrent position of the Pacific Plate, Hawaii is above the Pacific Ocean hot spot. So the position of The Pacific Plate 50 million years ago can be determined by moving it such that a 50-million-year-old volcano in the hot-spot trail sits at the location of Hawaii today. However because the ocean basins really are short-lived features on geologic times scale, reconstruction the world’s geography by backtracking along the hot-spot trail works only for the last 5 percent or so of geologic time.译文火山岛的形成①地球的外壳并不是由单块岩石形成的，而是许多的"构造板块"严密的组合在一起的，就像是一个巨大的拼图。

比较相同地域物种与种群间基因漂移揭示披碱草属物种的基因渗入

AbstractElymus(Elymus L.) affiliated with grass family (Poaceae) grain subfamily (Pooideae) of Triticeae, there are a lot of the genus morphology variation, frequent natural hybridization between species. Introgression through hybridization is a creative evolutionary process, which can produce and accumulate genetic novelties faster than through mutation alone and plays critical roles in driving speciation. Natural hybridization and polyploidization have long been recognized as important causes of plant diversification and speciation. Interspecific or intergeneric hybridization is widespread and evolutionarily important phenomena in plants,which play important roles in the formation of new species. When closely related species in the same geographic distribution, the hybridization phenomenon may occur, genes from one genus or species through hybridization and backcross or introgressive hybridization and other variety of ways to enter other gene bank, which makes the original varieties in morphological characteristics and biological characteristics, etc.One of the challenges in evolutionary biology is to understand the evolution of speciation with incomplete reproductive isolation as many taxa have continued gene flow both during and after speciation. Comparison of population structure between sympatric and allopatric populations can reveal specific introgression and determine if introgression occurs in a unidirectional or bidirectional manner. Simple sequence repeat markers were used to characterize sympatric and allopatric population structure of plant species, Elymus alaskanus (Scribn.and Merr.) LÖve, E.caninus L., E.fibrosus (Schrenk) Tzvel.,and E.mutabilis (Drobov) Tzvelev. Our results showed that genetic diversity (HE) at species level is E.caninus(0.5355) > E.alaskanus(0.4511) > E.fibrosus(0.3924) > E.mutabilis(0.3764), suggesting that E.caninus and E.alaskanus are more variable than E. fibrosus and E.mutabilis. Gene flow between species that occurs within the same geographic locations versus gene flow between populations within species was compared to provide evidence of introgression. Our results indicated that gene flow between species that occur within the same geographic location is higher than that between populations within species, suggesting that gene flow resulting from introgressive hybridization might have occurred among the sympatric populations of these species,and may play an important role in partitioning of genetic diversity among and within populations.The migration rate from E.fibrosus to E.mutabilis is highest(0.2631) among the four species studied. Asymmetrical ratesof gene flow among four species were also observed. The findings highlight the complex evolution of these four Elymus species.Key words: Elymus, Gene flow, Introgressive hybridization, Population structure缩写词表缩写词英文名称中文名称Abbr. English Name Chinese NamePCR polymerase chain reaction 聚合酶链式反应RFLP RestrictionFragment Length Polymorphism 限制片段长度多态性标记RAPD Random Amplification Polymorphic DNA 随即扩增多态性分子标记AFLP Amplification Fragment Length Polymorphism 扩增片段长度多态性分子标记SSR Simple sequence repeats 简单重复序列SDS Sodium dodecyl sulfate 十二烷基磺酸钠PAGE polyacrylamidegelelectrophoresis 聚丙烯酰胺凝胶电泳AGE agarosegelelectrophoresis 琼脂糖凝胶电泳Na Nunber of alleles 等位基因数Ne Effective Number of alleles 有效等位基因数Ho HeterozygosityObserved 观察杂合度He HeterozygosityExpected 期望杂合度I Shannon’sdiversityindex 香农多样性指数目录摘要 (I)Abstract (II)缩写词表 (IV)1文献综述 (1)1.1四种披碱草材料概况及其染色体组成 (1)1.2分子标记在遗传学的应用 (2)1.2.1分子标记的作用 (2)1.2.2 RFLP分子标记技术 (2)1.2.3 AFLP分子标记技术 (3)1.2.4 RAPD分子标记技术 (3)1.2.5 SSR分子标记技术 (4)1.3基因漂移 (4)1.4群体结构与遗传多样性 (5)1.5研究现状 (5)2 引言 (7)3 材料与方法 (8)3.1供试材料 (8)3.2 DNA提取 (9)3.3. PCR扩增及聚丙烯酰胺凝胶电泳 (10)3.3.1 PCR扩增程序 (10)3.3.2 PCR产物检测 (10)3.4 数据分析 (11)4 数据结果与分析 (12)4.1 披碱草物种与群体间的遗传多样性分析 (12)4.2 披碱草物种群体间的基因迁移率与方向 (13)4.3贝叶斯聚类分析 (15)4.4 F统计显著性分析 (15)4.5 UPGMA聚类分析的树状图 (17)5 讨论 (19)5.1相同地域基因渐渗大于不同地域 (19)5.2物种间与种内的遗传多样性 (19)6 结论 (21)参考文献 (22)致谢 (28)作者简介 (29)硕士期间发表论文 (30)1文献综述1.1四种披碱草材料概况及其染色体组成天然杂交和多倍体化一直被认为是植物多样性和物种形成的重要原因。

进口鸡肉传带禽伤寒沙门氏菌的定量风险评估

进口鸡肉传带禽伤寒沙门氏菌的定量风险评估李建军1，高梦昭2，3，邓　柯2，3，李艺超2，3，郭瀚民2，3，方海萍1，赵明刚1（1.海关总署标准法规研究中心，北京　100013；2.清华大学统计学研究中心，北京　100084；3.清华大学工业工程系，北京　100084）摘　要：为分析进口鸡肉携带禽伤寒沙门氏菌（Salmonella gallinarum）的风险水平，以及不同风险因子的影响大小，利用定量评估方法，通过场景分析，确定了影响鸡肉传带禽伤寒沙门氏菌风险的14个因子，依此构建风险评估数学模型，并参照2017年巴西禽伤寒沙门氏菌流行数据，对进口鸡肉传带禽伤寒沙门氏菌风险进行了定量评估。

结果显示：鸡肉传带禽伤寒沙门氏菌的风险主要取决于鸡群病流行率及鸡群数量，其他因素影响很小；当进口鸡肉来源鸡群禽伤寒沙门氏菌流行率维持在0.05的水平时，其传带疫病的风险概率在0.1%左右。

鉴于该疫病在世界各地多发，为防控禽伤寒沙门氏菌传入，应采取严格措施避免输华鸡肉源自感染鸡群。

关键词：禽伤寒沙门氏菌；进口鸡肉；定量评估；数学模型中图分类号：S851.3 文献标识码：B 文章编号：1005-944X（2021）01-0030-05DOI：10.3969/j.issn.1005-944X.2021.01.007 开放科学（资源服务）标识码（OSID）：Quantitative Risk Assessment ofSalmonella gallinarum Transmitted by Imported ChickenLi Jianjun1，Gao Mengzhao2，3，Deng Ke2，3，Li Yichao2，3，Guo Hanmin2，3，Fang Haiping1，Zhao Minggang1（1. Center for International Inspection and Quarantine Standards and Technical Regulations，General Administration of Customs，Beijing　100013，China；2. Center for Statistical Science of Tsinghua University，Beijing　100084，China；3. Department of Industrial Engineering，Tsinghua University，Beijing　100084，China）Abstract：In order to analyze the risk level of Salmonella gallinarum transmitted by imported chicken and the impact of different risk factors，14 relevant factors were determined through scenario analysis and the quantitative assessment method，based on which，a mathematical model for risk assessment was established to quantitatively assess the potential risk referring to the prevalence data of Salmonella gallinarum in Brazil in 2017. The results showed that the risk mainly depended on the prevalence rate in farms and the number of farms rather than other factors. If the herd prevalence rate of Salmonella gallinarum transmitted by imported chicken remained at the level of 0.05，the risk probability of transmission of disease would be about 0.1%. Considering frequent occurrence of the disease all around the world，strict measures should be taken to prevent any introduction of Salmonella gallinarum transmitted by imported chicken into China.Key words：Salmonella gallinarum；imported chicken；quantitative assessment；mathematical model收稿日期：2020-08-25　修回日期：2020-09-08基金项目：“十三五”国家重点研发计划项目（2016YFD0501101）通信作者：赵明刚。

写昆虫的英语作文

Insects are a class of creatures that have fascinated humans for centuries due to their incredible diversity,unique behaviors,and vital roles in ecosystems.Here is an English essay about insects,exploring their characteristics,importance,and some of the most common species.The Marvel of Insects:A World of Tiny GiantsInsects are the most diverse group of animals on our planet,with over a million described species and many more yet to be discovered.They belong to the class Insecta within the phylum Arthropoda,characterized by a chitinous exoskeleton,a threepart body head, thorax,and abdomen,three pairs of jointed legs,compound eyes,and one pair of antennae.Characteristics of Insects1.Exoskeleton:Insects possess a hard,protective exoskeleton made of chitin,which provides structural support and protection from predators and environmental factors.2.Metamorphosis:Many insects undergo metamorphosis,a process of development that includes four distinct life stages:egg,larva,pupa,and adult.This allows for drastic changes in form and function as they grow.3.Reproduction:Insects reproduce at an astonishing rate,with many species laying hundreds or even thousands of eggs at a time,ensuring the survival of their species.4.Diversity:Insects are incredibly diverse in size,shape,and color,ranging from the tiny fairyfly to the large,colorful butterflies and beetles.Importance of Insects1.Pollination:Many insects,particularly bees,butterflies,and moths,play a crucial role in pollinating plants,which is essential for the production of fruits,vegetables,and nuts.2.Decomposition:Insects such as beetles and flies are vital in breaking down dead organic matter,recycling nutrients back into the ecosystem.3.Food Source:Insects are a primary food source for many animals,including birds, reptiles,and other insects.4.Biological Control:Some insects,like ladybugs and praying mantises,are natural predators of pests,helping to control populations of harmful insects in agriculture.Common Insect Species1.Butterflies and Moths Lepidoptera:Known for their beautiful wings and patterns,they are important pollinators and serve as a food source for many animals.2.Beetles Coleoptera:With the largest number of species,beetles are incredibly diverse, from the small ladybugs to the large,shiny scarabs.3.Ants,Bees,and Wasps Hymenoptera:These social insects are known for their complex colonies and roles in pollination and pest control.4.Flies Diptera:Although many species are considered pests,some,like the hoverfly,are beneficial pollinators.5.Dragonflies and Damselflies Odonata:These agile fliers are predators of other insects and are important for controlling mosquito populations.Conservation and InsectsInsects face numerous threats,including habitat loss,pesticide use,and climate change.It is crucial to protect their habitats and reduce the use of harmful chemicals to ensure the survival of these essential creatures.ConclusionInsects are not just a part of nature they are the backbone of many ecosystems.Their survival is intertwined with ours,and understanding their importance can lead to better stewardship of our environment.As we continue to explore the world of insects,we uncover the intricate connections that bind us all in the web of life.This essay provides a comprehensive overview of insects,their characteristics,ecological importance,common species,and the need for conservation efforts.It is a testament to the significance of these tiny creatures in the grand scheme of life on Earth.。

库车前陆盆地克拉苏构造带的构造特征与油气

库车前陆盆地克拉苏构造带的构造特征与油气【摘要】库车前陆盆地克拉苏构造带位于中国西部，具有复杂多样的地质构造特征。

本文结合前人研究成果，阐述了克拉苏构造带的地质特征和油气资源分布特征，探讨了构造特征对油气勘探潜力的影响，并分析了控制因素。

通过对勘探开发现状的调研，揭示了克拉苏构造带在油气勘探开发中的重要性。

本文总结了克拉苏构造带的意义，并展望了未来的研究方向，为该地区的油气资源开发提供了理论支持和实践指导。

本文的研究成果对于深化对克拉苏构造带的认识，提高油气勘探开发的效率具有重要意义。

【关键词】库车前陆盆地、克拉苏构造带、地质特征、油气资源、油气勘探、勘探潜力、控制因素、勘探开发、意义、展望。

1. 引言1.1 背景介绍库车前陆盆地位于新疆维吾尔自治区西部，是中国重要的油气资源集中区域之一。

克拉苏构造带是库车前陆盆地内最重要的构造带之一，对整个盆地内的地质演化和油气积累具有重要影响。

本文旨在对克拉苏构造带的构造特征与油气资源进行深入探讨，为该区域的油气勘探开发提供科学依据。

克拉苏构造带地处古特提斯洋闭合过程中的构造变形区，受燕山运动和喀喇昆仑造山运动的影响，形成了复杂多样的构造形态。

在该区域，发育有多期构造运动，造就了丰富的油气资源。

油气资源分布特征主要受构造控制，随着构造的不断演化，油气勘探开发的难度也在逐渐增加。

为了更好地开发这一区域的油气资源，需要深入研究克拉苏构造带的构造特征及其与油气勘探潜力的关系，分析控制因素，总结勘探开发现状，以期挖掘出更多的油气资源，为我国能源安全做出贡献。

1.2 研究意义The study of the Kuqa Foreland Basin Kulasu Structural Belt has significant importance in the field of geology and petroleum exploration. Understanding the geological features of this region can provide valuable insights into the tectonic evolution and sedimentary processes that have shaped the area over millions of years. By analyzing the distribution of oil and gas resources in the Kulasu Structural Belt, researchers can identify potential areas for exploration and development.2. 正文2.1 克拉苏构造带的地质特征克拉苏构造带位于库车前陆盆地西部，是一个重要的构造带，具有独特的地质特征。

天然气高速非达西渗流动态产能计算

高速非达西流和气体 PVT 参数变化对产能影响
p pc = 已知一天然气藏，外边界封闭， γ g = 0. 6 ，
4. 62 MPa， T pc = 200K， T = 395K， K = 0. 5 μm2 ，岩石：
－4 －1 压缩系数 C f = 3. 0 × 10 MPa 。计算出压缩因
( )
（ 11 ）
对式（ 11 ）采用时间向后，空间中心差分的方
2
2. 1
天然气 PVT 参数计算模型
压缩因子计算模型天然气压缩因子计算采用 Dranchuk 等人通过
（ 12 ） M i = R w 2 e 2 i Δx · 式中： M i 为系数，
［5 ］
μ C t i Δx · ；R 为 K Δt i w
况下达西流和非达西流对应的 IPR 曲线，可以看出 PVT 参数变化和 PVT 参数不变 2 种情况下高速非达西流的产能高于达西线性流时的产能；随井底流产量差异变大。压降低，
图4
不同地层压力投产的动态无阻流量曲线
7
结
论
（ 1 ）建立了考虑真实气体 PVT 参数随压力变
图2 达西流与高速非达西流情况下的产能曲线
引
言
方程来描述
［10 ］
： dp μ（ p） v + βρ g v2 = dr K （ 1）
真实气体的地下渗流是个不稳定的非线性渗流过程，在气藏开发中，地层压力随时间发生变化，气气体按非达西体的高压物性参数随压力发生变化，渗流规律流动，渗流过程较为复杂。目前在国内外部分学者是基于气体流学者对气井产能的研究中，
收稿日期： 20110524 ；改回日期： 20110702 “973 ” “温室气体提高石油采收率的资源化利用及地下埋存” （ 2006CB705804 ）基金项目：国家重点基础研究发展计划计划 1996 年毕业于石油大学（华东）油气田开发工程专业， 2005 年毕业于中国地质大学（北京）矿产普查与勘探专作者简介：崔传智（ 1970 －），男，获硕士学位，业，获博士学位，现为中国石油大学（北京）在站博士后，从事油气田开发工程科研工作。

小学下册A卷英语第1单元暑期作业

小学下册英语第1单元暑期作业英语试题一、综合题(本题有100小题，每小题1分，共100分.每小题不选、错误，均不给分)1.What do we call the part of the eye that gives it color?A. RetinaB. PupilC. IrisD. CorneaC2.The city of Rome is known for its ________ (古代遗址).3.I like to play ________ on the computer.4.What is the largest land animal?A. RhinoB. HippoC. GiraffeD. ElephantD5.What is the main ingredient in bread?A. RiceB. FlourC. SugarD. SaltB6.The __________ (植物的生长) is affected by temperature.7.My _______ (狗) loves to play in the snow.8.The stars shine _______ (在夜空中)。

9.I have a toy _______ that rolls and spins everywhere I take it.10.We have _____ (两) hands.11.What is the term for a baby armadillo?A. PupB. KitC. CalfD. HatchlingA12.I like to go ______ (滑雪) with my friends during winter break.13.What do we call a written record of someone's life?A. BiographyB. AutobiographyC. MemoirD. Journal14.What do we call a person who writes poems?A. AuthorB. PoetC. NovelistD. PlaywrightB15.What is the primary function of leaves on a plant?A. PhotosynthesisB. GrowthC. ReproductionD. Defense16.The main gas released by burning fossil fuels is ______ dioxide.17.The _____ (小鸟) sings sweetly.18.The __________ (历史的理解) fosters empathy.19.Energy from the sun is called ______ energy.20.What is the name of the activity of exploring new places?A. TravelingB. VisitingC. TouringD. ExploringA21.I have a toy _______ that can bounce.22. A compound can have different ______ based on its structure.23.The first president of the United States was _____.24.What do you call the outer layer of the Earth?A. MantleB. CoreC. CrustD. LithosphereC25.Which of these is a type of music?A. JazzB. PaintingC. PoetryD. Sculpture26. A ______ is a large natural elevation of the Earth's surface.27.What do we call the game played on a board with black and white squares?A. Snakes and LaddersB. ChessC. CheckersD. Monopoly28. A ________ (秋天) garden is full of colors.29.An acid reacts with a base to produce _______ and water.30.The Earth's surface is shaped by both internal and external ______.31.The fish are _______ (swimming) in the tank.32.We can ___ a fun day at the beach. (have)33.The ______ (小鱼) swims in schools with others.34.What do we call the hot liquid rock that comes from a volcano?A. LavaB. MagmaC. AshD. Smoke35.The _____ (青蛙) croaks loudly at night. It is a common sound near ponds. 青蛙在夜晚呱呱叫。

TPO听力27-30

TPO-27Conversation 11. Why does the woman go to the information desk?●She does not know where the library computers are located.●She does not know how to use a computer to locate the information she needs.●She does not have time to wait until a library computer becomes available.●The book she is looking for was missing from the library shelf.2. Why does the man assume that the woman is in Professor Simpson’s class?●The man recently saw the woman talking with Professor Simpson.●The woman mentioned Profe ssor Simpson’s name.●The woman is carrying the textbook used in Professor Simpson’s class.●The woman is researching a subject that Professor Simpson specialized in.3. What can be inferred about the geology course the woman is taking?●It has led the woman to choose geology as her major course of study.●It is difficult to follow without a background in chemistry and physics.●The woman thinks it is easier than other science courses.●The woman thinks the course is boring.4. What topic does the woman need information on?●The recent activity of a volcano in New Zealand●Various types of volcanoes found in New Zealand●All volcanoes in New Zealand that are still active●How people in New Zealand have prepared for volcanic eruptions5. What does the man imply about the article when he says this:●It may not contain enough background material.●It is part of a series of articles.●It might be too old to be useful.●It is the most recent article published on the subject.Lecture 16. What is the lecture mainly about?●The transplantation of young coral to new reef sites●Efforts to improve the chances of survival of coral reefs●The effects of water temperature change on coral reefs●Confirming the reasons behind the decline of coral reefs7. According to the professor, how might researchers predict the onset of coral bleaching in the future?●By monitoring populations of coral predators●By monitoring bleach-resistant coral species●By monitoring sea surface temperatures●By monitoring degraded reefs that have recovered8. Wh at is the professor’s opinion about coral transplantation?●It is cost-effective.●It is a long-term solution.●It is producing encouraging results.●It does not solve the underlying problems.9. Why does the professor discuss refugia? [Choose two answers]●To explain that the location of coral within a reef affects the coral’s ability to survive●To point out why some coral species are more susceptible to bleaching than others●To suggest that bleaching is not as detrimental to coral health as first thought●To illustrate the importance of studying coral that has a low vulnerability to bleaching10. What does the professor imply about the impact of mangrove forests on coral-reef ecosystems?●Mangrove forests provide habitat for wildlife that feed on coral predators.●Mangrove forests improve the water quality of nearby reefs.●Mangrove forests can produce sediments that pollute coral habitats.●Mangrove forests compete with nearby coral reefs for certain nutrients.11. According to the professor, what effect do lobsters and sea urchins have on a coral reef?●They protect a reef by feeding on destructive organisms.●They hard a reef by taking away important nutrients.●They filter pollutants from water around a reef.●They prevent a reef from growing by preying on young corals.Lecture 212. What does the professor mainly discuss?●Some special techniques used by the makers of vintage Cremonese violins●How the acoustical quality of the violin was improved over time●Factors that may be responsible for the beautiful tone of Cremonese violins●Some criteria that professional violinists use when selecting their instruments13. What does the professor imply about the best modern violin makers?●They are unable to recreate the high quality varnish used by Cremonese violin makers.●Their craftsmanship is comparable to that of the Cremonese violin makers.●They use wood from the same trees that were used to make the Cremonese violins.●Many of them also compose music for the violin.14. Why does the professor discuss the growth cycle of trees?●To clarify how modern violin makers select wood●To highlight a similarity between vintage and modern violins●To explain why tropical wood cannot be used to make violins●To explain what causes variations in density in a piece of wood15. What factor accounts for the particular density differential of the wood used in the Cremonese violins?●The trees that produced the wood were harvested in the spring●The trees that produced the wood grew in an unusually cool climate●The wood was allowed to partially decay before being made into violins●.The wood was coated with a local varnish before it was crafted into violins16. The professor describes and experiment in which wood was exposed to a fungus before being made into a violin. What point does the professor make about the fungus?●It decomposes only certain parts of the wood.●It is found only in the forests of northern Italy.●It was recently discovered in a vintage Cremonese violin.●It decomposes only certain species of trees.17. Why does the professor say this:●To find out how much exposure students have had to live classical music●To use student experiences to support his point about audience members●To indicate that instruments are harder to master than audience members realize●To make a point about the beauty of violin musicConversation 21. Why has the student come to see the professor?●To find out her reaction to a paper he recently submitted●To point out a factual error in an article the class was assigned to read●To ask about the suitability of a topic he wants to write about●To ask about the difference between chinampas and hydroponics2. What does the professor imply about hydroponics?●It was probably invented by the Aztecs.●It is a relatively modern development in agriculture.●It requires soil that is rich in nutrients.●It is most successful when extremely pure water is used.3. Why does the professor describe how chinampas were made?●To emphasize that the topic selected for a paper needs to be more specific●To encourage the student to do more research●To point out how much labor was required to build chinampas●To explain why crops grown on chinampas should not be considered hydroponic4. What does the professor think about the article the student mentions?●She is convinced that it is not completely accurate.●She believes it was written for readers with scientific backgrounds.●She thinks it is probably too short to be useful to the student.●She has no opinion about it, because she has not read it.5. What additional information does the professor suggest that the student include in his paper?● A comparison of traditional and modern farming technologies●Changes in the designs of chinampas over time●Differences in how various historians have described chinampas●Reasons why chinampas are often overlooked in history booksLecture 36. What does the professor mainly discuss?●Comparisons between land animals and ocean-going animals of the Mesozoic era●Comparisons between sauropods and modern animals●Possible reasons why sauropods became extinct●New theories about the climate of the Mesozoic era7. What point does the professor make when she compares blue whales to large land animals?●Like large land animals, blue whales have many offspring.●Like large land animals, blue whales have proportionally small stomachs.●The land environment provides a wider variety of food sources than the ocean.●The ocean environment reduces some of the problems faced by large animals.8. According to the professor, what recent finding about the Mesozoic era challenges an earlier belief?●Sauropod populations in the Mesozoic era were smaller than previously believed.●Oxygen levels in the Mesozoic era were higher than previously believed.●Ocean levels in the Mesozoic era fluctuated more than previously believed.●Plant life in the Mesozoic era was less abundant than previously believed.9. Compared to small animals, what disadvantages do large animals typically have? [Choose two answers]●Large animals require more food.●Large animals have fewer offspring.●Large animals use relatively more energy in digesting their food.●Large animals have greater difficulty staying warm.10. Why does the professor discuss gastroliths that have been found with sauropod fossils?●To show that much research about extinct animals has relied on flawed methods●To show that even an incorrect guess can lead to useful research●To give an example of how fossil discoveries have cast doubt on beliefs about modern animals ●To give an example of a discovery made possible by recent advances in technology11. What did researchers conclude from their study of sauropods and gastroliths?●That gastroliths probably helped sauropods to store large quantities of plant material in theirstomachs●That sauropods probably used gastroliths to conserve energy●That sauropods may not have used gastroliths to aid in their digestion●That sauropods probably did not ingest any stonesLecture 412. What is the lecture mainly about?●Various ways color theory is used in different fields●Various ways artists can use primary colors●Aspects of color theory that are the subject of current research●The development of the first theory of primary colors13. What does the professor imply about the usefulness of the theory of primary colors?●It is not very useful to artists.●It has been very useful to scientists.●It is more useful to artists than to psychologists.●It is more useful to modern-day artists than to artists in the past.14. Why does the professor mention Isaac Newton?●To show the similarities between early ideas in art and early ideas in science●To explain why mixing primary colors does not produce satisfactory secondary colors●To provide background information for the theory of primary colors●To point out the first person to propose a theory of primary colors15. According to the pro fessor, what were the results of Goethe’s experiments with color? [Choose two answers]●The experiments failed to find a connection between colors and emotions.●The experiments showed useful connections between color and light.●The experiments provided valuable information about the relationships between colors.●The experiments were not useful until modern psychologists reinterpreted them.16. According to the professor, why did Runge choose the colors red, yellow and blue as the three primary colors?●He felt they represented natural light at different times of the day.●He noticed that they were the favorite colors of Romantic painters.●He performed several scientific experiments that suggested those colors.●He read a book by Goethe and agreed with Goethe’s choices of colors.17. What does the professor imply when he says this?●Many people have proposed theories about primary colors.●Goethe discovered the primary colors by accident.●Goethe probably developed the primary color theory before reading Runge’s le tter.●Goethe may have been influenced by Runge’s ideas about primary colors.TPO-28Conversation 11. What is the conversation mainly about?●Criticisms of Dewey’s political philosophy●Methods for leading a discussion group●Recent changes made to a reference document●Problems with the organization of a paper2. Why is the student late for his meeting?●Seeing the doctor took longer than expected.●No nearby parking spaces were available.●His soccer practice lasted longer than usual.●He had problems printing his paper.3. What revisions does the student need to make to his paper? [Choose three answers]●Describe the influences on Dewey in more detail●Expand the introductory biographical sketch●Remove unnecessary content throughout the paper●Use consistent references throughout the paper●Add an explanation of Dewey’s view on individuality4. Why does the professor mention the political science club?●To encourage the student to run for club president●To point out that John Dewey was a member of a similar club●To suggest an activity that might interest the student●To indicate where the student can get help with his paper5. Why does the professor say this:●To find out how many drafts the student wrote●To encourage the student to review his own work●To emphasize the need for the student to follow the guidelines●To propose a different solution to the problemLecture 16. What is the lecture mainly about?●The importance of Locke’s views to modern philosophical thought●How Descartes’ view of knowledge influenced tre nds in Western philosophy●How two philosophers viewed foundational knowledge claims●The difference between foundationalism and methodological doubt7. Why does the professor mention a house?●To explain an idea about the organization of human knowledge●To illustrate the unreliability of our perception of physical objects●To clarify the difference between two points of view about the basis of human knowledge●To remind students of a point he made about Descartes in a previous lecture8. What did Locke believe to the most basic type of human knowledge?●Knowledge of one’s own existence●Knowledge acquired through the senses●Knowledge humans are born with●Knowledge passed down from previous generations9. According to the professor, what was Descartes’ purpose f or using methodological doubt?●To discover what can be considered foundational knowledge claims●To challenge the philosophical concept of foundationalism●To show that one’s existence cannot be proven●To demonstrate that Locke’s views were essentially corre ct10. For Descartes what was the significance of dreaming?●He believed that his best ideas came to him in dreams●He regarded dreaming as the strongest proof that humans exist.●Dreaming supports his contention that reality has many aspects.●Dreaming illustrates why human experience of reality cannot always be trusted.11. According to Descartes, what type of belief should serve as a foundation for all other knowledge claims?● A belief that is consistent with what one sees and hears● A belief that most other people share● A belief that one has held since childhood● A belief that cannot be falseLecture 212. What is the main purpose of the lecture?●To show that some birds have cognitive skills similar to those of primates●To explain how the brains of certain primates and birds evolved●To compare different tests that measure the cognitive abilities of animals●To describe a study of the relationship between brain size and cognitive abilities13. When giving magpies the mirror mark test, why did researchers place the mark on magpies’ throats?●Throat markings trigger aggressive behavior in other magpies.●Throat markings are extremely rare in magpies.●Magpies cannot see their own throats without looking in a mirror.●Magpies cannot easily remove a mark from their throats.14. According to the professor, some corvettes are known to hide their food. What possible reasonsdoes she provide for this behavior? [Choose two answers]●They are ensuring that they will have food to eat at a later point in time.●They want to keep their food in a single location that they can easily defend.●They have been conditioned to exhibit this type of behavior.●They may be projecting their own behavioral tendencies onto other corvids.15. What is the professor’s attitude toward the study on p igeons and mirror self-recognition?●She is surprised that the studies have not been replicated.●She believes the study’s findings are not very meaningful.●She expects that further studies will show similar results.●She thinks that it confirms what is known about magpies and jays.16. What does the professor imply about animals that exhibit mirror self-recognition?●They acquired this ability through recent evolutionary changes.●They are not necessarily more intelligent than other animals.●Their brains all have an identical structure that governs this ability.●They may be able to understand another animal’s perspective.17. According to the professor, what conclusion can be drawn from what is now known about corvettes’ brains?●The area in corvids’ brains tha t governs cognitive functions governs other functions as well.●Corvids’ brains have evolved in the same way as other birds’ brains, only more rapidly.●Corvids’ and primates’ brains have evolved differently but have some similar cognitive abilities.●The cognitive abilities of different types of corvids vary greatly.Conversation 21. Why does the man go to see the professor?●To learn more about his student teaching assignment●To discuss the best time to complete his senior thesis●To discuss the possibility of changing the topic of his senior thesis●To find out whether the professor will be his advisor for his senior thesis2. What is the man’s concern about the second half of the academic year?●He will not have time to do the necessary research for his senior thesis.●He will not be allowed to write his senior thesis on his topic choice.●His senior thesis advisor will not be on campus.●His student teaching requirement will not be complete before the thesis is due.3. What does the man imply about Professor Johnson?●His sabbatical may last longer than expected.●His research is highly respected throughout the world.●He is the English department’s specialist on Chaucer.●He is probably familiar with the literature of the Renaissance.4. Why does the man want to write his senior thesis on The Canterbury Tales? [Choose two answers]●He studied it during his favorite course in high school.●He has already received approval for the paper from his professor.●He thinks that the knowledge might help him in graduate school.●He has great admiration for Chaucer.5. Why does the professor say this:●She is uncertain whether the man will be able to finish his paper before the end of the summer.●She thinks the man will need to do a lot of preparation to write on a new topic.●She wants to encourage the man to choose a new advisor for his paper.●She wants the man to select a new topic for his paper during the summer.Lecture 36. What is the lecture mainly about?●The differences in how humans and plants sense light●An explanation of an experiment on color and wavelength●How plants sense and respond to different wavelengths of light●The process by which photoreceptors distinguish wavelengths of light7. According to the professor, what is one way that a plant reacts to changes in the number of hours of sunlight?●The plant absorbs different wavelengths of light.●The plant begins to flower or stops flowering.●The number of photoreceptors in the plant increases.●The plant’s rate of photosynthesis increases.8. Why does the professor think that it is inappropriate for certain wavelength of light to be named “far-red”?●Far-red wavelengths appear identical to red wavelengths to the human eye.●Far-red wavelengths have the same effects on plants as red wavelengths do.●Far-red wavelengths travel shorter distances than red wavelengths do.●Far-red wavelengths are not perceived as red by the human eye.9. What point does the professor make when she discusses the red light and far-red light that reaches plants?●All of the far-red light that reaches plants is used for photosynthesis.●Plants flower more rapidly in response to far-red light than to red light.●Plants absorb more of the red light that reaches them than of the far-red light.●Red light is absorbed more slowly by plants than far-red light is.10. According to the professor, how does a plant typically react when it senses a high ratio of far-red light to red light?●It slows down its growth.●It begins photosynthesis.●It produces more photoreceptors.●It starts to release its seeds.11. In the Pampas experiment, what was the function of the LEDs?●To stimulate photosynthesis●To simulate red light●To add to the intensity of the sunlight●To provide additional far-red lightLecture 412. What does the professor mainly discuss?●Evidence of an ancient civilization in central Asia●Archaeological techniques used to uncover ancient settlements●The controversy concerning an archaeological find in central Asia●Methods used to preserve archaeological sites in arid areas13. What point does the professor make about mound sites?●They are easier to excavate than other types of archaeological sites.●They often provide information about several generations of people.●They often contain evidence of trade.●Most have been found in what are now desert areas.14. Why does the professor compare Gonur-depe to ancient Egypt?●To point out that Gonur-depe existed earlier than other ancient civilizations●To emphasize that the findings at Gonur-depe are evidence of an advanced civilization●To demonstrate that the findings at these locations have little in common●To suggest that the discovery of Gonur-depe will lead to more research in Egypt15. What does the professor imply about the people of Gonur-depe?●They avoided contact with people from other areas.●They inhabited Gonur-depe before resettling in Egypt.●They were skilled in jewelry making.●They modeled their city after cities in China.16. Settlements existed at the Gonur-depe site for only a few hundred years. What does the professor say might explain this fact? [Choose two answers]●Wars with neighboring settlements●Destruction caused by an earthquake●Changes in the course of the Murgab River●Frequent flooding of the Murgab River17. What is the professor’s opinion about the future of the Gonur-depe site?●She believes it would be a mistake to alter its original form.●She doubts the ruins will deteriorate further.●She thinks other sites are more deserving of researchers’ attention.●She is not convinced it will be restored.TPO-29Conversation 11. What is the conversation mainly about?●What the deadline to register for a Japanese class is●Why a class the woman chose may not be suitable for her●How the woman can fix an unexpected problem with her class schedule●How first-year students can get permission to take an extra class2. Why does the man tell the woman that Japanese classes are popular?●To imply that a Japanese class is unlikely to be canceled●To explain why the woman should have registered for the class sooner●To encourage the woman to consider taking Japanese●To convince the woman to wait until next semester to take a Japanese class3. Why does the man ask the woman if she registered for classes online?●To explain that she should have registered at the registrar’s office●To find out if there is a record of her registration in the computer●To suggest a more efficient way to register for classes●To determine if she received confirmation of her registration4. What does the man suggest the woman do? [Choose two answers]●Put her name on a waiting list●Get the professor to sign a form granting her permission to take the class●Identify a course she could take instead of Japanese●Speak to the head of the Japanese department5. What does the man imply when he points out that the woman is a first-year student?●The woman has registered for too many classes.●The woman should not be concerned if she cannot get into the Japanese class●The woman should not register for advanced-level Japanese classes yet●The woman should only take required courses at this timeLecture 16. What does the professor mainly discuss?●Causes of soil diversity in old-growth forests●The results of a recent research study in a Michigan forest●The impact of pedodiversity on forest growth●How forest management affects soil diversity7. According to the professor, in what way is the soil in forested areas generally different from soil in other areas?●In forested areas, the soil tends to be warmer and moister.●In forested areas, the chemistry of the soil changes more rapidly.●In forested areas, there is usually more variability in soil types.●In forested areas, there is generally more acid in the soil.8. What does the professor suggest are the three main causes of pedodiversity in the old-growth hardwood forests she discusses? [Choose three answers]●The uprooting of trees●The existence of gaps●Current forest-management practices●Diversity of tree species●Changes in climatic conditions9. Why does the professor mention radiation from the Sun?●To point out why pits and mounds have soil with unusual properties●To indicate the reason some tree species thrive in Michigan while others do not●To give an example of a factor that cannot be reproduced in forest management●To help explain the effects of forest gaps on soil10. Why does the professor consider pedodiversity an important field of research?●It has challenged fundamental ideas about plant ecology.●It has led to significant discoveries in other fields.●It has implications for forest management.●It is an area of study that is often misunderstood.11. Why does the professor give the students an article to read?●To help them understand the relationship between forest dynamics and pedodiversity●To help them understand how to approach an assignment●To provide them with more information on pits and mounds●To provide them with more exposure to a controversial aspect of pedodiversityLecture 212. What is the main purpose of the lecture?●To explain how musicians can perform successfully in theaters and concert halls with pooracoustics●To explain how the design of theaters and concert halls has changed over time●To discuss design factors that affect sound in a room●To discuss a method to measure the reverberation time of a room13. According to the lecture, what were Sabine’s contr ibutions to architectural acoustics? [Choose two answers]●He founded the field of architectural acoustics.●He developed an important formula for measuring a room’s reverberation time.●He renewed architects’ interest in ancient theaters.●He provided support for using established architectural principles in the design of concert halls.14. According to the professor, what is likely to happen if a room has a very long reverberation time?●Performers will have to make an effort to be louder.●Sound will not be scattered in all directions.●Older sounds will interfere with the perception of new sounds.●Only people in the center of the room will be able to hear clearly.15. Why does the professor mention a piano recital? [Choose two answers]●To illustrate that different kinds of performances require rooms with different reverberationtimes●To demonstrate that the size of the instrument can affect its acoustic properties●To cite a type of performance suitable for a rectangular concert hall●To exemplify that the reverberation time of a room is related to its size16. According to the professor, what purpose do wall decorations in older concert halls serve?●They make sound in the hall reverberate longer.●They distribute the sound more evenly in the hall.●They make large halls look smaller and more intimate.●They disguise structural changes made to improve sound quality.17. Why does the professor say this:●To find out if students have understood his point●To indicate that he will conclude the lecture soon●To introduce a factor contradicting his previous statement●To add emphasis to his previous statementConversation 21. Why does the student go to see the professor?●To explain why he may need to hand in an assignment late●To get instruction on how to complete an assignment●To discuss a type of music his class is studying●To ask if he can choose the music to write about in a listening journal2. What does the student describe as challenging?●Comparing contemporary music to earlier musical forms●Understanding the meaning of songs that are not written in English●Finding the time to listen to music outside of class●Writing critically about musical works3. Why does the student mention hip-hop music?●To contrast the ways he responds to familiar and unfamiliar music。