Alteration in nitrogen metabolism and plant growth during different developmental stages of green gram (Vigna radiata L.) in response to chlorpyrifos

Chlorpyrifos is a widely used broad-spectrum organophosphate insecticide in the agricultural practice. However, extensive use of this insecticide may lead to its accumulation in ecosystem, thus inducing the toxicity to crops and vegetables. To assess chlorpyrifos-induced toxicity in plants, we performed the experiment focusing on the growth and nitrogen metabolism of green gram plant (Vigna radiata L.). 20-days-old plants were subjected to chlorpyrifos at concentrations ranging from 0 to 1.5 mM through foliar spray in the field condition. Variation in root and shoot length, activities of nitrate reductase (NR) and content of nitrate, sugar, soluble amino acid and soluble protein were studied at preflowering (5 day after treatment, DAT), flowering (10 DAT) and postflowering (20 DAT) stages of plant development. Of the various concentrations of chlorpyrifos, 0.6 and 1.5 mM showed comparatively more severe toxicity to green gram plants by decreasing root and shoot length, nitrate, NR, soluble sugar and protein content where as at low concentration (0.3 mM) of chlorpyrifos proved stimulant for same parameter. Increase in soluble amino acid was observed in age and dose dependent manner. These results reflect strong parallelism between growth and biochemical activities of the model plant. Further lower dose of chlorpyrifos proved as stimulant where as at higher concentration proved detrimental for growth and nitrogen metabolism.