EFFECT OF CHROMIUM ON SEED-GERMINATION, SEEDLING GROWTH AND YIELD OF PEAS

Hexavalent chromium (Cr6+) supplied as potassium dichromate did not affect percent germination of pea seeds, but at concentrations above 0.5 mM suppressed growth of radicle and plumule significantly. In contrast, Cr6+ 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 Cr6+ hastened flowering, the total number of flowers and consequently the number 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 Cr6+ 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.