《植物生理学报》 2011, 47(5): 481-487

重金属镉对水稻根毛细胞钾离子吸收过程的影响

李隼¹, 黄胜东², 赵福庚^1,*

1南京大学生命科学学院, 南京210093; 2江苏省农业科学院粮食作物研究所, 南京210014

通信作者：赵福庚；E-mail: fgzhao@nju. edu. cn;；Tel: 025-83592684

摘　要：

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50 μmol•L-1 CdCl 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。

关键词：水稻; 重金属镉; 钾离子吸收

收稿：2011-01-16   修定：2011-04-18

资助：江苏省自然科学基金(BK2010388)和林业公益性行业科研专项经费(200904001)

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

LI Sun¹, HUANG Sheng-Dong², ZHAO Fu-Geng^1,*

¹School of Life Sciences, Nanjing University, Nanjing 210093, China; ²Institute of Food Crops, Jiangsu Academy of Agricultural Sciences, Nanjing 210014, China

Corresponding author: ZHAO Fu-Geng; E-mail: fgzhao@nju. edu. cn;; Tel: 025-83592684

Abstract:

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.

Key words: rice; cadmium; potassium uptake