Phosphorus uptake and translocation in salt-stressed melon plants

Melon seedlings (Cucumis melo L. cv. Galia) were grown hydroponically to st udy the effect of salinity (80 mmol/L NaCl) on phosphate (Pi) uptake and tr anslocation at two levels of Pi (25 mu mol/L and 1 mmol/L). Net uptake rate s of Pi were determined by depletion of the medium and by plant content. Sa linity decreased Pi uptake at low Pi (high affinity uptake mechanism), 25 m u mol/L, although no specific competitive inhibition of Pi uptake by Cl- wa s observed. When plants were grown with high Pi (1 mmol/L), the uptake of P i through the low affinity system was increased by 80 mmol/L NaCl. Salinity also reduced the phosphorus flux, as Pi, through the xylem. It is hypothes ised that high levels of NaCl decrease the mobility of Pi stored in vacuole s, and as a result, inhibit export from this storage compartment to other p arts of the plant.