Partial Separation and Characterization of Soluble Phosphatases from Leaves of Wheat Grown Under Phosphorus Deficiency and Water Deficit

Soluble phosphatases from wheat leaves have been separated into two fractions by CM-cellulose chromatography. The phosphatase(s) in the fraction adsorbed by CM-cellulose (Fraction B) were identical with an electrophoretic band of phosphatase activity which increased with phosphorus (P) deficiency. The phosphatase activity in this fraction increased specifically as the concentration of phosphate in the sampled tissues fell from 0.8% to 0.2% dry weight. Phosphatase activity in Fraction B may be due to an isozyme of acid phosphatase. Phosphatase activity in the fraction not adsorbed by CM-cellulose (Fraction A) increased with both P deficiency and water deficit, and was higher in young than in mature leaves. The Fraction A phosphatase which increased with water deficit was probably another isozyme of acid phosphatase: however the Fraction A phosphatase which increased with P deficiency was probably not an acid phosphatase because it had activity only against p-nitrophenylphosphate and ATP. In expanding leaves of P deficient plants, phosphatase activities in Fractions A and B declined after P was supplied to adequate levels. However, in fully expanded leaves, high phosphatase activities persisted after the resupply of P. These results are discussed in relation to the use of measurements of phosphatase activity as a biochemical marker of P deficiency.