NITROGEN METABOLISM AS A BIO INDICATOR OF CU STRESS IN VIGNA RADIATA

The possible involvement of Cu on N - metabolism in relation with protease activity, proline, amino acid contents and protein oxidation was observed. These were monitored as bio-indicators in the seedlings of Vigna radiata treated with (0-25 ppm) CuSO4 to ascertain the role of Cu in generation of oxidative stress. Copper is an essential nutrient element for the plant growth, may be toxic when in excess by their participation in redox cycles producing hydroxyl radicals ((OH)-O-center dot) which are extremely toxic to the living cells. Cu produced a significant inhibition of growth as well as a reduction in the water contents in the roots and the leaves of the seedlings. Results showed an increase in the protease activity and decrease in the protein contents, which may be attributed with the plant defense against metal toxicity through hydrolysis of the oxidative proteins. An inverse relation between protease activity and other nitrogen compound showed the effective hydrolyzing role of protease due to which decrease in proline and total amino acid contents were observed, exhibited the highest sensitivity to excess metal, followed by the plant dry weight accumulation, leaf area formation. Decrease in proline contents support the sensitivity of Vigna radiata and weak defense of species against Cu stress.