Differential action of Cu²⁺ and Cd²⁺ on chlorophyll biosynthesis and nitrate reductase activity in Vigna sinensis L. (Savi)

Exposure of 7 day old etiolated Vigna sinensis L. (savi) leaf segments to heavy metals viz. Cu²⁺ and Cd²⁺ for 24 hours brought about the inhibition of chlorophyll biosynthesis. The synthesis of chl. a was inhibited more than that of chl. b at all concentrations of Cu²⁺ and Cd²⁺. The degree of inhibition of chlorophyll biosynthesis was more with Cd²⁺ as compared to Cu²⁺. However, in vivo nitrate reductase activity Cd²⁺ increased in the stressed leaf segments at low concentration of Cu²⁺ and Cd²⁺, where the increase was higher due to Cu²⁺. Observations in the present study are discussed with regard to the metal toxicity on chlorophyll biosynthesis and nitrate reductase activity.