Effects of cadmium on ammonia assimilating enzymes and ultrastructures of leaf and nodule in mungbean <i>Vigna radiata </i>L. Wilczek

Abstract

Mungbean plants <i>(Vigna radiata) </i>were grown in earthen pots for three weeks. Cadmium sulphate (3CdSO₄.8H₂O) were foliarly applied at the concentrations of 40, 60, 80 and 100 <i>μ</i><i>M</i> at weekly intervals. The activities of ammonia ,assimilating enzymes, viz. glutamate dehydrogenase, glutamine synthetase and glutamate oxoglutarate aminotransferase were inhibited to variable extents in the root nodules. Of these enzymes, GDH and GOGAT registered maximum decline. The fine structures of chloroplasts in cadmium-treated plants were degenerated similar to the senescing leaves. The principal symptoms of cademium action were the presence of osmiophilic plastoglobuli and a disorganisation of the lamellar structures, mainly grana stacks. In Cd²⁺-treated nodules, the peribacteroid membrane around the bacteroids seem to degenerate. Probably considerable amount of poly- β - hydroxybutyrate granules, inside the bacteroids ,renders the root nodules ineffective. Uptake of cadmium in different plant parts and Cd²⁺ content in soil increased with the increasing concentrations of cadmium.