Clarification of the mechanism of Al tolerance operated while both binding with root and elongation of root.

区分根与根结合时和根伸长时根对铝离子的反应，对于阐明耐铝性的机制具有重要意义。研究结果如下。高浓度铝处理的根尖细胞铝含量与不同植物的耐铝性呈负相关，而与根尖部分和根尖分离细胞壁的CEC均不相关。铝处理后根尖细胞壁CEC变化不大，与耐铝性无关。铝处理显著降低了铝敏感植物根尖部分K、P、Mg的含量。水稻、玉米、豌豆、小麦和高粱等对铝敏感的品种也表现出相同的趋势。EPMA分析表明，20um Al处理1h后，耐铝水稻根尖2 mm处的K和Cl含量较高，而铝敏感大麦的K和Cl含量较低。K从根部流出的结果与前人的结果一致。培美他滨…任何一种植物根尖细胞的质膜(PM)在100µM铝处理1h(FDA-PI荧光染色)后都是正常的；在不含铝的基质中，经过几个小时的根再伸长，对铝敏感的植物根尖细胞质膜的破坏相当严重，但在铝处理后的短期后处理中，柠檬酸恢复了其正常的透性。从铝敏感植物根尖细胞中分离出的原生质体，经过铝的短暂处理后，经过低渗处理后，质膜透性显著增加。在铝敏感植物中，原生质体和原生质膜的铝浓度比接近于1。根中有机酸，尤其是柠檬酸的释放量的差异，并不与植物种类和品种之间耐铝性的差异相对应。铝处理后，铝敏感植物根尖细胞的质膜可能更快地被铝离子饱和，使其透性增加，最终可能导致钾的渗漏和铝的渗入。根的伸长加速了铝的毒害。根尖细胞质膜中的脂质成分可能最终决定了根尖细胞的耐铝性。较少

Discrimination of the responses of root to Al ions while binding with root from that while root elongation is important to clarify the mechanism of Al tolerance. Results are as follows. Al content in root-tip cells treated with high concentration of Al correlated negatively with Al tolerance among plant species, but did not correlate with CECs both of root-tip portion and cell wall isolated from root-tip portion. CEC of cell wall from root-tip portion hardly changed after Al treatment, and did not correlated with Al tolerance, either. The concentrations of K,P and Mg in root-tip portion considerably decreased with Al treatment in Al-sensitive plant species. The same tendency was observed in Al-sensitive cultivars of rice, maize, pea, wheat and sorghum. The concentrations of K and Cl in 2 mm tip-portion of roots treated with 20 muM Al for 1 h were higher in Al-tolerant rice, but lower in Al-sensitive barley by EPMA analysis. Efflux of K from root agreed with the former result. Permeabil … More ity of the plasma membrane (PM) of root-tip cells in any kind of plant species was normal just after the treatment with 100 muM Al for 1 h (FDA-PI fluorescence staining) ; destruction of the PM was considerable in Al-sensitive plant speecies following several hours of re-elongation of root in the medium without Al, but a short-term post-treatment with citric acid following the treatment with Al restored its normal permeability. The permeability of PM of protoplasts isolated from root-tip cells of Al-sensitive plant species was considerably incteased after hypotonic treatment without Al following a temporaty treatment with Al. Al concentration ratio of protoplasts to protoplast ghosts was nearly one in Al-sensitive plant species. Differences in amounts of the release of organic acids, especially citric acid, from roots did not correspond to the differences in Al tolerance among plant species and cultivars. PM of root-tip cells of Al-sensitive plants may be saturated with Al ions more instantly after Al treatment, increased its permeability, and finally K leakage and Al permeation from PM may be induced considerably in Al-sensitive plants. Elongation of root accelerates Al toxicity. Lipid composition of PM of root-tip cells may finally determine Al tolerance. Less