Inhibition of chlorophyll biosynthesis by lead in greening Pisum sativum leaf segments

Supply of 0.01 to 1.0 mM lead acetate to greening pea (Pisum sativum L.) leaf segments either in the absence or in the presence of inorganic nitrogen lowered total chlorophyll (Chi) content. During a time course study, there was not any appreciable effect of Pb2+ upto 4 h but thereafter Pb inhibited Chi synthesis. While supply of succinate, cysteine dithiothreitol, 5,5-dithio-bis-2-nitrobenzoic acid and NH4Cl had no protective action against Pb2+ toxicity, and glycine, glutamate 2-oxoglutarate, MgCl2, KH2PO4, CaCl2, KCl protected only partially, reduced glutathione (GSH) could completely overcome the inhibition of Chi biosynthesis by the metal. It is suggested that Pb2+ interferes with Chi biosynthesis through GSH availability.