Mechanism of aluminum injury and tolerance in plant in terms of the function of plasma membrane.

为研究小麦品种阿特拉斯66 （Atlas 66）和Scout 66 （Scout 66）在酸性条件下对铝胁迫的早期反应，对其铝耐受性和铝敏感性进行了研究。10muM AlCl_3处理不超过3 h，对Scout根系伸长的抑制作用明显，超过6 h，对Atlas根系伸长的抑制作用仅为部分抑制，Atlas根系0 ~ 5mm和5 ~ 10 mm的Al含量低于Scout。Atlas和Scout都预先加载了pH为5.5的K^+，并将其转移到不同pH值的蒸馏水中，以监测K^+的流出。pH值降低导致两个品种K^+的外排增加，且在pH值4.2时，Scout的外排速率是Atlas的两倍。低至5muM浓度的AlCl_3可显著抑制pH值为4.2的K^+外排，这种作用在Scout中更为明显。Ca^<2+>对K^+外流也有抑制作用。钒酸盐增加了K^+的流出，这一结果表明H^+泵参与了K^+的流出。这些结果表明，低细胞外pH值可能导致细胞质H^+浓度增加，随后质膜去极化，这可能被K^+和H^+的外排所修饰。Atlas和Scout在低pH下K^+外排的特征性差异可能是由与质膜电位相关的差异引起的。我们比较了铝对两种不同铝敏感性小麦（Triticum aestivum L.）的质膜囊中钙离子（^<45>Ca^<2+>）流入的影响。钙通道阻滞剂Bepridil和铝抑制了两个品种的内流。然而，这两种处理的效果在两个品种之间没有差异。此外，我们还从细胞的角度探讨了铝对根伸长的抑制机制。铝对细胞伸长区有明显的抑制作用，细胞伸长明显受到抑制，但细胞直径增加。两个铝敏感性不同的品种在伸长区木质素化同时抑制根系生长。少

In order to characterize the mechanism of Al tolerance (Atlas 66) and Al sensitivity (Scout 66) in two cultivars of wheat (Triticum aestivum L.), the early responses to Al stress under acidic conditions were investigated. Marked inhibition of root elongation of Scout was observed upon treatment with 10muM AlCl_3 for less than 3 h. Root elongation of Atlas was only partially inhibited by the treatment with 10muM AlCl_3 for more than 6 h.Levels of Al in two portions of roots, namely, portions 0-5 mm and 5-10 mm from the tip, were lower in Atlas than those in Scout.Both Atlas and Scout were preloaded with K^+ at pH 5.5 and transferred to distillled water at various pH values to monitor the efflux of K^+. A reduction in the pH induced increases in the efflux of K^+ in both cultivars, and the rate of efflux in Scout was twice that in Atlas at pH 4.2. AlCl_3 at concentrations as low as 5muM markedly repressed K^+ efflux at pH 4.2 and this effect was more pronounced in Scout. Ca^<2+> also had … More a repressive effect of K^+ efflux. Vanadate increased K^+ efflux, a result that suggests the involvement of a H^+ pump in K^+ efflux. These results suggest that a low extracellular pH may cause an increase in the cytoplasmic concentration of H^+ that is followed by depolarization of the plasma membrane, which may be modified by the efflux of K^+ and H^+. The characteristic defference in terms of K^+ efflux between Atlas and Scout at low pH may be caused by differences associated with plasma membrane potentials.We compared the effect of aluminum on the calcium (^<45>Ca^<2+>) influx through putative calcium channels of plasma membrane vesicles isolated from two wheat (Triticum aestivum L.) cultivars differing in Al sensitivity. Bepridil, a calcium channel blocker, and aluminum suppressed the influx in both cultivars. However, no differences were observed in the effects of these treatments between the two cultivars.Furtheremore, we investigated the mechanism of the inhibition of root elongation by Al from the cellular point of view. Al inhibit the cell elongation at the elongation zone specifically, where cell elongation was markedly inhibited but the cell diameter increased. Lignification in the elongation zone coincided with an inhibition of root growth of two cultivars differing in Al-sensitivity. Less