Influence of age and illumination on distribution of several calvin cycle enzymes in greening barley leaves.

Activities of phosphoriboisomerase, phosphoribulokinase, and ribulose 1,5-diphosphate carboxylase, protein content, and chlorophyll accumulation in dark-grown barley seedlings were measured before and after illumination. Enzymatic activities, levels of soluble protein, and accumulation (upon illumination) of chlorophyll in leaves declined from tips toward the base. In response to increasing time of illumination, chlorophyll accumulation and activities of phosphoribulokinase and ribulose 1,5-diphosphate carboxylase (enzymes located in chloroplasts) increased most in tip portions whereas activity of phosphoriboisomerase and levels of soluble protein (constituents not confined to chloroplasts) increased similarly in all sections of the leaf. Maximum activity of phosphoribulokinase and maximum accumulation of chlorophyll shifted toward median portions of the leaf blade with increased age of seedling before illumination. Maximum activity of ribulose 1,5-diphosphate carboxylase and maximum level of soluble protein occurred in all leaf sections when the seedlings were 7 days of age before illumination.