Diurnal variation of the acid phosphatase activity in the leaves of Cowpea.

The activity of acid phosphatases (glycerophosphatase, phenylphosphatase and pyrophosphatase) in Cowpea (Vigna catjang) leaves has been studied at different hours of the day and a marked diurnal variation has been observed. The phosphatase activity in leaves collected between 10 A.M. to 2 P.M. was always higher than in leaves collected earlier in the morning and late at evening. Pyrophosphatase activity exhibited greater variation than phenylphosphatase and glycerophosphatase activity. The significance of the increased phosphatase activity is discussed in relation to the production of carbohydrates from organic acids in light.