Effect of phosphorus deficiency and water deficit on phosphatase activities from wheat leaves

Wheat was sown in a phosphorus (P) deficient soil. Plants at low levels of applied P had lower growth rates and lower concentrations of phosphate in the shoots than plants grown with ‘high P’. Activities of both insoluble and soluble phosphatase increased with P deficiency in the mature leaves. Soluble phosphatase activities increased 2.5–3.0 fold as the concentration of phosphate in the leaves fell from 0.4% to 0.1% dry weight This increase was not a consequence of reduced growth, as severe nitrogen deficiency had no effect on phosphatase activity. Soluble phosphatase activities were higher in young than in mature leaves, and also increased 3–4 fold with severe water deficit. However these increases in activity were not accompanied by low concentrations of phosphate. Moreover, soluble phosphatase activities in mature leaves of plants grown under conditions of water deficit rapidly decreased after rewatering. In contrast, the high soluble phosphatase activities in mature leaves of P deficient wheat persisted for up to 12 d after the resupply of P to adequate levels