中文摘要：

相对于NO3^-N，NH4^＋-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（ζ）电势对NH4^＋-N、NO3^--N、铝和pH的响应。结果表明，不管是否加铝，NH4^＋-N和NO3^--N本身并不显著影响原生质膜表面ζ电势，但是加铝和降低pH均可以去极化原生质膜表面亭电势。水稻吸收NH4^＋-N一般降低生长介质pH，吸收NO3^--N升高生长介质pH。因此，NH4^＋-N缓解水稻铝毒的原因，不是因为NH4^＋-N本身去极化了细胞膜表面电势，而是因为水稻吸收NH4^＋-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。

英文摘要：

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