Benzyladenine accelerates chloroplast differentiation and stimulates photosynthetic enzyme activity in cucumber cotyledons

Abstract

The chloroplasts of etiolated cucumber cotyledons had crystalline prolamellar bodies, whereas those treated with benzyladenine (BA) have a well-developed plastid membrane system. After 4 h of exposure to light, grana were formed in the chloroplasts of BA-treated cotyledons but not in the controls. The specific activities of ribulose 1,5-diphosphate carboxylase, and NADP-dependent glyceraldehyde 3-phosphate dehydrogenase increased 75 and 50% respectively during BA treatment in the dark, while there was little change in the controls. On exposure to light, enzyme activities increased in both control and BA-treated cotyledons. Inhibitors of protein synthesis eliminated the BA stimulation of ribulose diphosphate carboxylase but had little effect on the BA stimulation of NADP-dependent glyceraldehyde 3-phosphate dehydrogenase activity. This study indicates that BA stimulates structural differentiation of the chloroplast and enhances activities of photosynthetic enzymes, even in the dark.