SECRETION OF PHYTASE FROM THE ROOTS OF SEVERAL PLANT-SPECIES UNDER PHOSPHORUS-DEFICIENT CONDITIONS

Phosphorus (P) deficiency increased the secretion of phytases from roo ts of various plant species. The secretory phytases were collected wit h a dialysis membrane tube for 24 hours from roots of sixteen plant sp ecies grown with low or adequate supply of P in nutrient solutions. Th e activity of not only secretory phytase, but also acid phosphatase, i ncreased with the low P treatment in all of the plant species examined . Secretion of phytase by the roots under P-deficient conditions was h ighest in Brachiaria decumbens CIAT 606, Stylosanthes guianensis CIAT 184 and tomato, moderate in Brachiaria brizantha CIAT6780, Stylosanthe s guianensis CIAT 2950, alfalfa, white clover and orchard grass, and l owest in Andropgon gayanus CIAT 621, Stylosanthes capitata CIAT 10280, upland rice, timothy, redtop, alsike clover, red clover and white lup in plants. An immunoreactive protein band that reacted with a polyclon al antibody raised against wheat bran phytase, corresponding to molecu lar weight 35-40 kD, could be detected in seven of the species tested. These results indicate that the secretory phytase may provide an effi cient mechanism for certain plants to utilize inositol hexaphosphate i n soil.