Pyruvate Kinase Activity of Wheat Plants Grown under Potassium Deficient Conditions.

The activity of pyruvate kinase was determined in the first leaves of wheat plants grown under K(+)-deficient conditions. An enhancement of the enzyme activity compared with the normal plants was found to start from eighth day of growth, and about 4-fold increase in the enzyme activity was observed in 14-day wheat leaves. The addition of K(2)SO(4) to the nutrient solution given to the K(+)-deficient plants at tenth day resulted in the restoration of the enzyme activity to the normal level after 3 days.

Biosynthesis of starch in chloroplasts.

The enzymic synthesis of ADP-glucose and UDP-glucose by chloroplastic pyrophosphorylase of bean and rice leaves has been demonstrated by paper chromatographic techniques. In both tissues, the activity of UDP-glucose-pyrophosphorylase was much higher than ADP-glucose-pyrophosphorylase. Glycerate-3-phosphate, phosphoenolpyruvate and fructose-1,6-diphosphate did not stimulate ADP-glucose formation by a pyrophosphorylation reaction.