重金属镉对水稻根毛细胞钾离子吸收过程的影响

Effects of Cadmium on K^+ Uptake in Root Hair Cells of Rice

重金属镉进入植物体后会引起一系列的毒害反应,然而迄今为止有关镉毒害的机制并不明了。本研究综合使用了膜电势测定、非损伤微测和膜片钳等电生理学实验技术,检测了镉对水稻根毛细胞钾离子吸收过程的影响。研究结果显示,外源施用50μmol·L-1 CdCl2能明显造成水稻根毛细胞膜的去极化,抑制根毛细胞质膜内向K+通道活性,同时诱导外向K+通道开放,导致根系内K+外渗,进而降低了水稻根部K+含量。通过上述影响,镉扰乱了水稻根系对钾离子的吸收过程,造成钾元素缺失,成为植物体镉毒害作用的机理之一。

It has been widely documented that Cd entering plants will cause a series of detrimental consequences,but the mechanisms of Cd toxicity are not clearly understood.Using biophysical techniques including membrane potential measurements,SIET（scanning ion-selective electrode technique） for non-invasive ion flux assays,and patch clamp,we monitored the effect of Cd on potassium（K＋） uptake in root hair cells of rice.Our results showed that K＋ contents in roots were significantly reduced when treated with exogenous Cd.Further studies revealed that two cellular processes might be affected by Cd,leading to changes in ionic homeostasis.First,Cd-induced depolarization of the membrane potential was observed in root epidermal cells,attenuating the driving force for K＋ uptake.Second,the inward conductance of K＋ was partially blocked by Cd,whereas the outward K＋ conductance was Cd-inducible in the root hair cells,decreasing uptake of K＋.We propose that one of the mechanisms of Cd toxicity is to impair the uptake of K＋ thereby disturbing ion homeostasis in higher plants.