Effect of chromium on seed germination, seedling growth and yield of peas

Intact plant studies
Pea plants were raised during the winter season (November-February) in 30 cm diameter earthen pots filled with washed river sand in a net house under natural conditions of humidity, temperature and light. One group of seedlings, referred to as nitrogen-fixing (NF) plants, was inoculated with Rhizobium leguminosarum (strain PD- 12 ) and provided with nitrogen-free nutrient solution (Wilson and Reisenauer, 1963). Seedlings of the second group were not inoculated but were given the above nutrient solution supplemented with 30 mM NH4NO3. This treatment was referred to as nitrogensupplied (NS). Each pot contained two seedlings and was irrigated with 250 ml of nutrient solution every 10 days. After 40 days all plants were given C r 6 + additions every 10 days by providing them with 250 ml of an aqueous solution of K2Cr207 containing a range of C r 6 + concentrations. The K 2 C r 2 0 7 s o l u t i o n was routinely provided 2 clays after the nutrient solution. On indicated days, data on ten replicates of nitrogen fixing and of nitrogen-supplied plants at each concentration of applied C r 6+ w a s recorded. Observations for the number of seeds per pod, pods per plant and biomass production were, however, taken only at maturity.
(Accepted 2 March 1993 )
Abstract Hexavalent chromium (Cr 6+ ) supplied as potassium dichromate did not affect percent germination of pea seeds, but at concentrations above 0.5 m M suppressed growth of radicle and plumule significantly. In contrast, Cr 6+ was much more toxic when applied to 40 day old seedlings grown, either on combined nitrogen, or under nitrogen-fixing conditions. Its deleterious effect was more pronounced on the growth of roots than on shoots. Though Cr 6+ hastened flowering, the total number of flowers and consequently the n u m b e r of pods per plant was reduced drastically. In chromium-treated plants a larger proportion of pods failed to set seeds and the average number of seeds per pod was lower. All these factors contributed towards lowering seed yield of the plants receiving 0.2 mM Cr ~+ by 75-80%. The impact of this metal on growth was more severe on plants supplied with combined nitrogen than on nitrogen-fixing plants. Concentration of the metal in various plant parts was: roots > leaves > stem > pod walls > seeds.
N.R. BishnoP, Anita Dua a, V.K. Gupta b, S.K. Sawhney ~,*
"Department of Chemistry and Biochemistry, Haryana Agricultural University, Hisar 125 004, India bDepartment of Soils, Haryana Agricultural University, Hisar 125 004, India
Agriculture, Ecosystems and Environment, 47 ( 1 9 9 3 ) 4 7 - 5 7
Elsevier Science Publishers B.V., A m s t e r d a m
47
Effect of chromium on seed germination, seedling growth and yield of peas
Introduction Proliferation of industrial activity has resulted in large increase in the consumption and consequent dispersion of toxic metals such as chromium. From 1935 to 1985 chromium mining has increased 18 fold and every year about 30 000, 142 000 and 896 000 t of this metal are globally discharged into air, water and soil, respectively (Nriagu, 1988). The toxic effect of chromium, recognized as early as 1910 (Koenig, 1910), has subsequently been confirmed by several workers (Hara et al., 1976; Foroughi et al., 1976; Rehab and Wallace, 1978; Davies et al., 1978; McGrath, 1982 ). At toxic concentrations it causes chlorosis and necrosis of leaves (Barcelo et al., 1986 ), inhibits photosynthesis (Sarkar and Jana, 1987 ), causes perturbations in mineral nutrition (Turner and Rust, 1971; Misra and Jaiswal, 1982; Barcelo et al., 1985; Otabbong, 1989) and eventually results in diminished growth (Turner and Rust, 1971; Wallace et al., 1976; Vazquez et al., 1987; Otabbong, 1989). An
*Corresponding author.
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N.R. Bishnoi et al./Agriculture, Ecosystems and Environment 47 (1993) 47-57
Materials and methods
Seed germination studies
Seeds of pea (Pisum sativum L. cultivar 'Bonneville') were pre-treated by surface sterilization with 0.2% ( w / v ) mercuric chloride solution for 5 min, rinsed thoroughly with glass distilled water and then placed for germination in filter paper-lined petri dishes ( 15 cm diameter) at 25 ° C in the dark. Each petri dish had 20 ml of an aqueous solution of potassium dichromate, containing specified concentrations of C r 6 + and 2 5/tg ml-~ of streptomycin sulphate to suppress microbial growth added. The data was recorded for four replicates of each treatf chromium on seed germination has also been reported (Mukherji and Roy, 1977; Siegel, 1977; Rani et al., 1990). Pea is an important winter vegetable crop grown in the vicinity of urban centres where sewer water, often mixed with industrial discharges, is frequently used for irrigation. These soils are, hence, likely to contain elevated levels of heavy metals including chromium. The present investigations were, therefore, undertaken to ascertain and to compare its impact on growth, biomass production and economic yield of pea seedlings grown under nitrogen-fixing conditions and those supplied with a combined source of nitrogen.