Plant response and tolerance mechanism to ionic stress in rhizosphere.

在铝胁迫下，小麦根部细胞伸长的抑制快于细胞分裂的抑制。抑制细胞伸长导致细胞长度缩短，直径增大。在延伸区的受抑细胞中观察到明显的木质素沉积。在茶叶中，铝通过减少锰的运输而抑制了锰的毒害。研究了排除有机酸与耐铝性的关系。有机酸对铝毒害的有效抑制顺序为柠檬酸&GT；苹果酸&GT；琥珀酸。在耐磷饥饿机制方面，磷饥饿条件下筛选的胡萝卜细胞柠檬酸合成酶活性高于野生胡萝卜。另一方面，柠檬酸消耗酶NADP-ICDP活性较低，Rupin根排除了大量酸性磷酸酶。酸性磷酸酶的分子分析表明，其分子量为72 KDa。此外，编码被排除的酸性磷酸酶的基因由2207个碱基组成，黄瓜在磷饥饿下分泌核黄素。核黄素排除量与Fe~(2+)~(3+)还原活性呈正相关，但核黄素排除量与Fe~(2+)~(3+)还原活性共存刺激了Fe~(2+)还原活性。

In the root of wheat subjected to Al stress, the inhibition of cell elongation occurred faster than that of cell division. The inhibition of cell elongation induced the decrease of the length and increase of the diameter of cell. Marked deposition of lignin was observed in the inhibited cell in elongation zone. In tea, Al repressed the Mn toxicity by reducing the transport of Mn. The interelationship between exclusion of organic acids and Al tolerance was investigated. The order of effective repression of Al toxicity by organic acids was citrate > malate > succinate.As to the tolerance mechanism to phosphate starvation, carrot cells selected under phosphate starvation showed a stronger activity of citric acid synthetase than that of wild one. On the other hand, the activity of citrate consuming enzyme, NADP- ICDP was lower in the selected cells.Rupin roots excluded a large amount of acid phosphatase. The molecular analysis of acid phosphatase showed that M.W.was 72 KDa. Furthermore, cDNA encoding the excluded acid phosphatase consisted of 2207 bases.Cucumber plant excreted riboflavin under phosphate starvation. There was positive relaitonship between the amount of riboflavin exclusion and Fe^<3+> reducing activity but its coexistence stimulated the Fe^<3+> reducing activity.