水稻根尖细胞原生质膜表面电势对不同氮形态、 铝和pH的响应

相对于NO_3~--N,NH_4~+-N可以缓解植物铝毒害,但其机制还不清楚。铝在细胞膜表面的吸附量受细胞膜表面电势影响,直接影响到铝毒害。本文采用酶解法提取水稻根尖原生质体,研究了原生质膜表面zeta(ξ)电势对NH_4~+N、NO_3~--N、铝和pH的响应。结果表明,不管是否加铝,NH_4~+-N和NO_3~--N本身并不显著影响原生质膜表面ξ电势,但是加铝和降低pH均可以去极化原生质膜表面ξ电势。水稻吸收NH_4~+-N一般降低生长介质pH,吸收NO_3~--N升高生长介质pH。因此,NH_4~+-N缓解水稻铝毒的原因,不是因为NH_4~+-N本身去极化了细胞膜表面电势,而是因为水稻吸收NH_4~+-N降低了介质pH,去极化了细胞膜表面电势,从而可能降低了铝在水稻根尖表面的吸附。

Responeses of Zeta Potential of Protoplast Membrane Isolated from Rice Root Tips to Ammonium, Nitrate, Aluminum and pH

The phytotoxicity of aluminum ions can be alleviated by ammonium in rice (Oryza sativa) compared with nitrate. However, the exact mechanisms underlying this phenomenon are poorly understood. The membrane surface zeta potential plays an important role in root aluminum adsorption and toxicity. Here, the responses of membrane surface zeta potential of isolated protoplasts from rice root tips to ammonium, nitrate, aluminum and pH were examined. It was shown that, ammonium and nitrate themselves could not change the membrane surface zeta potential regardless of Al stress or not. However, both low pH and more Al could significantly depolarize membrane surface zeta potential. Because ammonium could decrease but nitrate could increase medium pH, we concluded that the decreased medium pH induced by ammonium uptake of rice root depolarized the membrane surface zeta potential and thereby alleviated rice Al toxicity compared with nitrate.