01 Rice Morphology

MORPHOLOGY OF THE RICE1 This is one of the rice production trainingmodules produced by the International RiceResearch Institute.2 This module is on the morphology of the riceplant.3-5At the end of this lesson, you will be able to:• identify and describe the morphologicalcharacters of the germinating rice seedand seedling;• identify the morphological characters of arice tiller – roots, culm and leaves – andrelate them to each other;• identify and describe the morphologicalparts of the rice inflorescence or panicle.6 The Asian rice plant, Oryza sativa, is anannual grass with vegetative parts consisting of roots, culm, and leaves. The roots, culm and leaves form a tiller. At maturity, it may or may not produce an inflorescence called a panicle which bears seeds.7 When the seed germinates in well-drainedand well-aerated soil, the coleorhiza, a covering enclosing the radicle or primary root, protrudes first.8 Shortly after the coleorhiza appears, theradicle or primary root breaks through the covering.9 Two or more sparsely branched seminalroots follow. These roots eventually die andare replaced by many secondaryadventitious roots.10If the seed germinates in water, thecoleoptile, a covering enclosing the youngshoot, emerges ahead of the coleorhiza. Thecoleoptile emerges as a tapered cylinder.mesocotyl or basal portion of the 11Thecoleoptile elongates when the seedgerminates in soil, and in darkness. Itpushes the coleoptile above the soil surface.12The first seedling leaf, or primary leaf,emerges from the growing seed. It is greenand shaped like a cylinder. It has no blade.13Thesecond leaf is a complete leaf. It isdifferentiated into a leaf blade and a leafsheath.15Can you label the parts of these seedlings?To do this, drag each label into the properbox. If the label stays, that means you got thecorrect answer. If it doesn’t, try again till youplace each of the labels properly. Toproceed, click the NEXT button.16In this section, we are going to study theparts of a tiller.The seedling will grow and develop thebranched tillers. The parts of a rice tiller arethe roots, the culm and the leaves.17Mature roots of the rice plant are fibrous andproduce smaller roots called rootlets. Allroots have root hairs to absorb moisture andnutrients.There are 2 kinds of mature roots:secondary adventitious roots andadventitious prop roots.18Secondary adventitious roots areproduced from the underground nodes ofyoung tillers.19As the plant grows, coarse adventitiousprop roots often form in whorls from thenodes of the culm above the soil surface.20Theculm, or jointed stem of rice,21is made up of a series of nodes22andinternodes.23Young internodes are smooth and solid.Mature internodes are hollow, finely groovedwith a smooth outer surface. Generally,internodes increase in length from the lowerto the upper portions of the plant. The lowerinternodes at the plant base are short andthick.24The node is the solid portion of the culm.The node or nodal region bears a leaf and abud. The bud is attached to the upperportion of the node and is enclosed by theleaf sheath. The bud may give rise to a tiller.25Early tillers arise from the main culm in analternate pattern. Primary tillers originatefrom the lowermost nodes…..26and give rise to secondary tillers.Secondary tillers produce ….tertiary tillers.27the28The node or nodal region of the culm will bear a leaf.29Leaves are borne alternately on the culm in opposite directions. One leaf is produced ateach node. Varieties differ in the number ofleaves produced.30The topmost leaf below the panicle is the flag leaf. The flag leaf contributes largely to thefilling of grains because it supplies photosynthetic products mainly to the panicle.31Theleaf sheath and leaf blade arecontinuous.collar joins the leaf blade and thecircular 32 Aleaf sheath.leaf sheath is wrapped around the culm 33Theabove the node.34The swelling at the base of the leaf sheath just above the node is the sheath pulvinus.It is frequently mistermed as the node.35Rice leaf blades are generally flat. Varieties differ in blade length, width, thickness, area, shape, color, angle and pubescence.36Note the many parallel veins in the upper surface.37The underside of the leaf blade is smooth with a prominent ridge in the middle, themidrib.38Most leaves possess small, paired ear-like appendages on either side of the base of theblade. These appendages are called auricles. Auricles may not be present onolder leaves.39Another leaf appendage is the ligule, the papery membrane at the inside juncture between the leaf sheath and the blade. Ithas either a smooth or hairlike surface. Thelength, color and shape of the ligule differaccording to variety.40Rice plants have both auricles and ligule.The common grassy weeds found in ricefields normally do not have auricles or aligule. This characteristic is often helpful inidentifying weeds in rice fields when theplants are young.41Let us pause to review this section. See if you can answer these questions.• Distinguish secondary adventitious roots from the adventitious prop roots.• Identify the leaf blade and the leaf sheath.• What characters are used to distinguish a rice plant from a grassy weed?• Differentiate the primary tillers from the secondary tillers.Again, click on the bullets to view the correctanswers. When done, click NEXT toproceed.42Name the three parts of a rice tiller by typing your answers in the appropriate boxes. Clickthe "CHECK ANSWERS" button to verifyyour answers. If you want to try again, click"RESET ALL". You may see the correctanswers by clicking the “VIEW ANSWERS”button. When done,click the "NEXT" button.43Can you identify and label these plant parts?Drag each label into the appropriate box.The label will stay if placed correctly.Otherwise, it will go back to its originalposition. To proceed with the slide show,click NEXT.44The terminal component of the rice tiller is aninflorescence called the panicle. Theinflorescence or panicle is borne on theuppermost internode of the culm. Thepanicle bears rice spikelets which developinto grains.panicle base often appears as a hair- 45Thelike ring, and is used as a dividing point inmeasuring culm length and panicle length.The panicle base is often called the neck.panicle axis is continuous and hollow 46Theexcept at the nodes where branches areborne.47The swellings in the panicle axis where thebranches are borne are the paniclepulvinus.48Each node on the main panicle axis givesrise to primary branches which in turn bearsecondary branches. Primary branchesmay be arranged singly or in pairs.49The panicle bears spikelets, most of whichdevelop into grains. These spikelets areborne on the primary and secondarybranches. A spikelet is a basic unit of theinflorescence or the panicle. It consists ofthe pedicel and the floret.50The floret is borne on the pedicel.rudimentary glumes are the laterally 51Theenlarged, cuplike apex of the pedicel. Therudimentary glumes are the lowermost partsof the spikelet. During threshing, therudimentary glumes are separated from therest of the spikelet.sterile lemmas are small, bractlike 52Theprojections attached to the floret.rachilla is a small axis that bears the 53Thesingle floret. It is between the sterile lemmasand the floret.54The rachilla, sterile lemmas, and therudimentary glumes all support the floret.The floret includes the lemma, palea and theflower.55The larger protective glume covering the floret is called the lemma and the smaller one is referred to as the palea.56Both the lemma and palea have ridges referred to as nerves. The lemma has 5, thepalea, 3. The middle nerve of the lemma may be smooth or hairy.57The lemma has a constricted structure in the end called the keel. In some varieties, thekeel is elongated into a thin extension, the awn.58In the floret is the flower. The flowerconsists of a pistil or the female organ,stamens or the male organs.six59and60The stamens have two-celled anthers borneon slender filaments.61The pistil contains one ovule …62and bears a double-plumed stigma ….63on a short style.64At the flower’s base near the palea are twotransparent structures known as lodicules.The lodicules thrust the lemma and paleaapart at flowering to enable the elongatingstamens to emerge out of the open floret.The lemma and palea close after the anthershave shed the pollens.65The rice grain is the ripened ovary, with thelemma, palea, rachilla, sterile lemmas andthe awn firmly attached to it.rice hull includes the lemma and palea 66Theand their associated structures -- the sterilelemmas, rachilla and awn.67The dehulled rice grain is called caryopsis, commonly referred to as brown rice becauseof three brownish pericarp layers that envelope it.68Next to the pericarp layers are the two tegmen layers and the aleurone layers.69The remaining part of the grain consists of the endosperm and the embryo.70The endosperm provides nourishment to the germinating embryo.The embryo lies on the belly side of the grainand is enclosed by the lemma. It is theembryonic organ of the seed.71The embryo contains the plumule, or embryonic leaves, and the radicle or embryonic primary root.72See if you can answer these questions.• Describe the panicle base and give the other term for panicle base• What is the basic unit of rice inflorescence?• What is the term for dehulled rice grain?• What part of the grain provides nourishment to the germinating embryo?To check on the correct answers, please clickon the bullets. When done, proceed to thenext slide by clicking the NEXT button.73Can you label the various parts of the spikelet and the rice flower shown on the slide? Again, drag the labels below to the corresponding boxes. Try to put the labels atthe shortest possible time. When done, clickthe NEXT button to proceed.74This concludes our lesson on the Morphology of the Rice Plant. For further questions, emailus at inquiry@.GLOSSARYAleurone layer - the peripheral layer of the endosperm, containing oil and protein. Adventitious prop roots - roots formed in higher nodes above the soil surface. Auricles - a pair of small, ear-like appendages at the base of the blade, that may not be present in older leaves.Awn - a thorn-like extension from the keel of the lemma. It is not present in all rice varieties.Brown rice (caryopsis) - the dehulled rice grain.Bud - a small protuberance on a node. It may give rise to a tiller.Coleoptile - the cylinder-like protective covering of the young plumule.Coleorhiza - the sheath covering the radicle.Collar - the joint between the leaf sheath and leaf blade.Culm - the round, smooth-surfaced, ascending axis of the shoot consisting of hollow internodes joined by solid nodes.Embryo - the miniature plant developed from the fertilized (diploid) egg called zygote, which upon germination gives rise to a young seedling. It is located on the ventral side of the seed next to the lemma.Endosperm - the nutritive tissues of the ripened ovary. It consists of the aleurone layer and the starchy endosperm. It serves as food for the germinating embryo. Flag leaf - the last leaf just below the panicle.Floret - A unit of the spikelet. It includes the lemma, palea and the flower.Flower - It consists of two lodicules, six stamens and the pistil.Grain - the ripened ovary and its associated structures.Hull - the lemma and palea, and their associated structures.Internode - the smooth, solid (when young), or hollow (when mature) part of the culm between two successive nodes.Keel - the middle nerve of the lemma.Leaf - the vegetative part of a tiller consisting of the blade and sheath.Leaf blade - the flat and free portion of the leaf.Leaf sheath - the lower part of the leaf, originating from a node and wrapped around the culm above the node.Lemma - the five-nerved bract of the floret.Ligule - a thin, upright, membranous structure attached to the base of the inside of the flower.Lodicules - the two scale-like structures near the base of the palea.Mesocotyl - the internode between the coleoptile node and the point of union of the culm and root in the young seedlings. It pushes the coleoptile above the soil surface.Midrib - the prominent ridge in the middle of the underside of the leaf blade.Neck (panicle base) - the nearly solid node between the uppermost internode of the culm and the panicle axis.Node - the solid portion of the culm. It may give rise to a leaf, a tiller, or adventitious roots.Ovary - the bulbous, basal portion of the pistil which contains one ovule.Palea - the three-nerved bract of the floret.Panicle - the terminal component of the rice plant which bears the rice spikelets. Panicle pulvini - the swellings in the axis of the primary panicle branches.Pedicel - the stalk supporting a spikelet on the panicle branch.Pericarp layer - the wall of the ripened ovary and the outermost layer of cells covering the seed.Plumule - the embryonic leaves of the young plants in the embryo. It is enclosed by the coleoptile.Pistil - the female reproductive organ consisting of the ovary, style and stigma.Primary panicle branches - the structures arising from the panicle axis. They bear the secondary branches.Primary leaf - the first seedling leaf. It does not have a leaf blade.Primary tillers - tillers arising from the lowermost nodes of the main culm.Rachilla - the small axis bearing the single floret.Radicle - the embryonic primary root.Rootlets - the lateral roots that grow endogenously from the mature root. Rudimentary glumes - the laterally enlarged, cup-like apex of the pedicel.Second leaf - the first differentiated leaf with blade and sheath.Secondary adventitious roots - roots arising from the nodes at the base of the plant. Secondary panicle branches - the branches arising from the primary branch of the panicle. They bear the spikelets.Secondary tillers - tillers arising from primary tillers.Seminal roots - sparsely branched roots that replace the radicle and are later replaced by secondary adventitious roots.Septum - the cross-sectional layer inside the node which separates adjoining internodes.Sheath pulvinus - the swelling at the base of the leaf sheath just above the node.Often mistermed as the node.Spikelet - the basic unit of the rice inflorescence consisting of the two sterile lemmas, the rachilla and the floret.Stamen - the male reproductive organ consisting of the anther and the filament.Sterile lemmas - the two flowerless bracts at the base of the spikelet.Tegmen layer - two layers of cells next to the pericarp.。