Inhibition of chlorophyll biosynthesis by mercury in excised etiolated maize leaf segments during greening: Effect of 2-oxoglutarate

Abstract

Mercury (0.01-1.0 m<i>M</i>) inhibited chlorophyll formation in greening maize leaf segments. However, supplementing incubation medium with 2-oxoglutarate, maintained substantially higher level of chlorophyll in absence of metal after an initial period of 8 hr. On preincubation of leaf segments with HgCl₂, per cent inhibition of chlorophyll synthesis by metal was same in the presence and absence of 2-oxoglutarate. Supply of 2-oxoglutarate (0.1-10.0 m<i>M</i>) exerted concentration dependent effect on chlorophyll formation in absence or presence of metal. Increase in δ-amino levulinic acid dehydratase as well as NADH-glutamate synthase activity and decrease in NADH-glutamate dehydrogenase activity by 2-oxoglutarate in the presence of Hg suggested that glutamate for δ- amino levulinic acid synthesis could be made available from NH₄⁺ assimilation <i>via</i>.,glutamine synthetase/g lutamate synthase pathway during mercury toxicity.