Molecular mechanism of Al tolerance by the small molecules produced in plant.

研究了铝诱导荞麦中草酸的分泌。150muM Al脉冲处理3 h，草酸分泌维持8 h，草酸分泌在离根尖0 ~ 10mm区域。阴离子通道抑制剂苯乙二醛（PG）抑制草酸分泌50%。单独施用25muM Al和p10mM PG对荞麦根伸长均无抑制作用，但在Al和PG的共同作用下，其根伸长的抑制作用可达40%，且抗Al荞麦叶片和根中均有Al的积累。对其内部解毒机理进行了研究。叶片中积累的铝约90%存在于细胞液中，其中草酸为优势有机酸。纯化叶片细胞液中的Al复合物，得到Al与草酸的比例为1:3的复合物。荞麦的根和叶的铝耐受性是通过形成非植物毒性的草酸铝（1:3）复合物实现的。铝增强铁离子Fe^<2+>-介导的脂质过氧化。绿原酸（CGA）和咖啡酸（CA）保护细胞免受Al和Fe^<2+>联合施用引起的脂质过氧化和活力丧失，表明苯丙素具有抗氧化分子的作用。

Al induced secretion of oxalic acid in buckwheat was investigated. Secretion of oxalic acid was maintained for 8 h by a 3-h pulse treatment with 150muM Al. Oxalic acid was found to be sereted in the region 0 to 10 mm from the root tip. Anion-channel inhibitor, phenylglyoxal (PG), inhibited the secretion of oxalic acid by 50%. Root elongation in buckwheat was not inhibited by 25muM Al or p10mM PG alone but was inhibited by 40% in the presence of Al and PG.Furthermore, Al resistant buckwheat accumulate Al in the leaves and roots. The internal detoxification mechanism was studied. About 90% of Al accumulated in the leaves was found in the cell sap, in which the dominant organic acid was oxalic acid.Purification of the Al complex in the cell sap of leaves resulted in a complex with a ratio of Al to oxalic acid of 1 : 3. Al tolerance in the roots and leaves of buckwheat is achieved by formation of a nonphytotoxic Al-oxalate (1 : 3) complex.Al enhances ferrous ion Fe^<2+>-mediated peroxidation of lipids. Chlorogenic acid (CGA) and caffeic acid (CA) protected the cells from both lipid peroxidation and the loss of viability caused by the combined application of Al and Fe^<2+>, indicating that the phenylpropanoids acted as antioxidant molecules.