CHANGES IN NITROGEN-METABOLISM ENZYME-ACTIVITIES OF VICIA-FABA IN RESPONSE TO ALUMINUM AND CADMIUM

Nodules of faba bean (Vicia faba L. cv. Giza 3) plants grown in pots c ontaining clay-loam soil for 90 d have an active nitrate reductase (NR ), while the leaves did not show detectable activity. Spraying the pla nt with increasing concentrations of Al3+ or Cd2+ (0 - 1000muM) signif icantly inhibited the nodules NR activity, the decline being more pron ounced in Cd2+ treatment. The specific activity of glutamate-oxaloacet ate transaminase (GOT) and glutamate-pyruvate transaminase (GPT) were more prominent in the 60- than in 90-d-old plants; GOT was always high er than GPT. Furthermore, GOT was more sensitive to Al3+ and Cd2+ trea tments and its activity was significantly decreased when the metal con centration increased. Also, Cd2+ proved to be more effective than Al3 in suppressing the GOT activity in the nodules, with less significant effect observed in the leaves. In contrast, GPT was hardly affected b y the various metal treatments, particularly in the leaves.