INDUCTION OF SOLUBLE PHOSPHATASES UNDER IONIC AND NONIONIC OSMOTIC STRESSES IN WHEAT

The effects of phosphorus deficiency, salt stress (NaCl) and non-ionic osmotic stresses (caused by mannitol or polyethylene glycol) were compared in plants and calli of wheat varieties differing in salt and drought tolerance. In calli, phosphorus deficiency induced a high increase in soluble acid phosphatase activity; under osmotic stress conditions a similar increase was found only in cells subjected to NaCl, while in cells grown in the presence of mannitol phosphatase activity did not change. In wheat seedlings, phosphatase activity increased both in roots and shoots under phosphorus deficiency and, especially in the shoot, under salt and non-ionic osmotic stresses as well. Contrary to phosphorus deficient conditions, the induction of phosphatase activity under ionic and non-ionic osmotic stresses was not accompanied by a decrease in phosphorus content, These results suggest that the induction of acid phosphatase under osmotic and salt stresses may have a cause other than a low phosphate level. The Mg2+ activated alkaline phosphatase activity specific for the shoot decreased under all stress conditions.