Effect of P concezntration on 65Zn uptake in gaudinia fragilis

Phosphorus‐Zn interaction was studied in Gaudiniafragilis plants grown in culture solution. The effect of different P supplies on ⁶⁵Zn uptake was measured in 21 days‐old seedlings. Zinc as ⁶⁵Zn absorbed during 24 h decreased when P concentration in the nutrient solution was increased from 0 to 10 mM. The longer the period in high P concentration, the stronger the ⁶⁵Zn uptake inhibition. The time course of ⁶⁵Zn uptake showed that both Zn‐influx and net Zn‐uptake were inhibited in 10 mM with respect to 0.1 mM P. The partitioning of the ⁶⁵Zn absorbed between shoot and root was not affected by P supply. However total ⁶⁵Zn transported to the shoot was higher in 0,1 than in 10 mM phosphate due to the higher ⁶⁵Zn absorption. The time course of the inhibition of ⁶⁵Zn influx by high P concentration showed a rapid initial decrease, probably due to a direct effect of external P concentration, followed by a slower decrease, which was atributed to the increase in the internal P concentration.