Effect of ammonium on potassium uptake through high affinity transport system for K~+ (K~+-HATS) of different crops

This paper studied the dynamic characteristics of K+ uptake by 5 plants and the effects of NH+4 on K+ uptake.The experiment was carried out by hydroponics and with application of ion channel inhibitor TEA at low K+ concentration. Under with or without NH+4 the dynamic parameters of K+ uptake were assessed.The results indicated that the K+ uptake curve by high affinity transport system for K+(K+-HATS) in root cells could be described by the Michaelich-Menten equation.There was relatively little difference(below 50%) in Km among different plants,showing a small diversity in affinity of K+-HATS to K+.For different plants there was significant difference in Vmax of K+-HATS,e.g.the Vmax of wheat was 11 times more than that of soybean,which indicated a great discrepancy in K+-carrier number,and this discrepancy resulted in a great diversity in K+ uptake of plants under lower K+ concentration.Ammonium could greatly decrease the rate of K+ uptake by plants.Compared with lack of NH+4 the Vmax of soybean was only 20% of that under with NH+4 application.The affinity of K+-HATS of plants to K+,however,was less affected by NH+4,and reduction of Km for all plants used in this experiment was less than 10%.The results above showed that for the K+-HATS of plants the effects of NH+4 on the K+ uptake were mainly due to competition of NH+4 for the K+-carrier at the cell membrane.