水稻(威优49)幼苗根系K~+(~(86)Rb~+)吸收的调节

杂交稻威优49幼苗根系的K~+(~(86)Rb~+)吸收速率受到根含钾量的直接反馈调节,而与地上部的含钾量无显著相关性。随着根部含钾量的增加,K~+(~(86)Rb~+)净吸收的速率减小。净吸收速率的改变主要是由于内流速率的变化,而受外流速率变化的影响不大。根系上运K~+(~(86)Rb~+)滞后于吸收约1.5h。但上运一旦开始后,运输速率便不受根和地上部含钾量变化的影响。这表明杂交稻威优49幼苗根系K~+(~(86)Rb~+)吸收速率的改变主要受根部液泡含钾量的调节,而向上运输则决定于细胞质的K~+(~(86)Rb~+)状态。

Regulation of K~+ (~(86)Rb~+) Absorption by Roots of Hybrid Rice (Weiyou 49) Low-Salt Seedlings

The effects of internal potassium concentrations in both roots and shoots of hybrid rice Weiyou 49 (Oryza sativa L. indica) seedlings on influx and efflux of K~+(~(86)Rb~+) in roots and transport of K~+(~(86)Rb~+) to shoots were studied. The negative linear correlation between net K~+(~(86)Rb~+) influx and internal potassium concentration in roots was very significant. K~+(~(86)Rb~+) efflux, independent of its content in roots and shoots, was maintained nearly steady. The decrease of net K~+(~(86)Rb~+) influx was due to the decrease of its influx. Transport of K~+(~(86)Rb~+) to shoot started abruptly after the plant samples were incubated in 1.0 mmol/L K~+(~(86)Rb~+) medium for more than 1 h, and then the rate of transport remained constant. The above results suggested that K~+(~(86)Rb~+) concentration in the cytoplasm of root cells might determine the activity of K~+ (~(86)Rb~+) efflux and the upward transport of K~+(~(86)Rb~+), while K~+(~(86)Rb~+) concentration in vacuoles may play an important role in the regulation of potassium absorption by roots.