Influx and efflux of phosphorus in roots of wheat plants in non-growth-limiting concentrations of phosphorus

COGLIATTI D; SANTA MARÍA G

JOURNAL OF EXPERIMENTAL BOTANY

OXFORD UNIV PRESS

Lugar: Oxford; Año: 1990 vol. 41 p. 601 - 607

0022-0957

The regulation of net phosphorus uptake was studied in wheat plants at ambient non-growth-limiting P-concentrations. Wheat (Triticum aestivum cv. Klein Atalaya) seedlings were grown from germination in culture solutions containing 0.05, 0.5 and 5.0 mol m−3 phosphate. Only small increments in plant P-concentration and specific accumulation rate for phosphorus were found when ambient P-concentration was increased 100 times. P-influx, estimated by 32P-uptake, was markedly greater with increased external P-concentration, but only small changes in Vmax and no changes in Km were found. Indirect estimation of P-efflux in a time-course of 32P-uptake, and direct P-efflux measurements in ?wash out? experiments indicated that P-efflux markedly increased in higher ambient P-concentration. The increase in P-efflux almost completely neutralized the higher P-influx observed in 5.0 mol m−3 relative to 0.05 mol m−3 phosphate. It is postulated that in non-limiting P-concentration net P-uptake is mainly controlled by P-efflux.