1To whom all correspondence should be addressed.
The supply of 0.01 and 1.0 mM mercuric chloride inhibited substantially in vivo as well as in vitro the total nitrate reductase activity and endogenous nitrate pool in excised bean leaf segments. The in vitro specific activity remained unchanged. Percent inhibition in nitrate reductase activity by metal increased with incubation period. The toxic effect of mercury was overcome completely by the supply of glutathione, cysteine and sucrose and partially by molybdic acid and NADH. It is suggested that Hg has an inhibitory role on MR activity in bean leaf segements.
