水分胁迫下植物体内OH的产生与细胞的氧化损伤

Generation of Hydroxyl Radicals and Its Relation to Cellular Oxidative Damage in Plants Subjected to Water Stress 

干旱是植物组织的一种重要的胁迫因子。它能干扰植物细胞中活性氧产生与清除的平衡，导致植物细胞遭受氧化胁迫。过去十多年来，人们对水分胁迫下植物体内活性氧的产生、活性氧对植物的伤害及植物保护系统的作用进行了大量的研究，取得了明显的进展［１～４］。然而，水分...

The hydroxyl radical ( ·OH) is one of the most reactive radicales known to chemistry and is believed to be a major active free radicle responsible for modifications of macromolecules and cellular damage. Two lines of evidence strongly indicate that ·OH radicals are generated in a Fenton type Haber Weiss reactions in plants subjected to water stress. Firstly, water stress causes an increase in the concentration of catalytic metals, which are critical for Fenton like reactions to proceed in vivo. Furthermore, submillimolar concentrations of H 2O 2 and ascorbic acid(or O -· 2) in the drought stressed plants are large enough to support the Fenton type Haber Weiss reactions. Secondly, there is oxidation of proteins and lipids in the drought stressed plants; a process that requires a catalytic metal and that, at least for protein oxidation, is mediated by the ·OH radicals. Protein oxidation is thought to involve binding of metal ions to the proteins and subsequent site specific attack by the ·OH radicals arising from the metal catalysed decomposition of H 2O 2. It has been proposed that protein oxidation may be a better index than lipid peroxidation because the latter yields many different products and these only appear after a lag period. The validity of malondialdehyde (MDA), an early product of lipid peroxidation, as an index of lipid peroxidation has been argued by the non specific method of its measurement. The ·OH radicals are not the only necessary initiator for lipid peroxidation and lipid peroxidation is not usually involved in plants exposed to water stress.