渗透胁迫对青杨叶片氧自由基伤害及膜脂过氧化的影响

EFFECTS.OF OSMOTIC STRESS ON OXYGEN FREE RADICAL DAMAGE AND MEMBRANE LIPID PEROXIDATION OF LEAVES IN POPULUS CATHAYANA REHD

采用PEG-6000对青杨叶片进行渗透胁迫处理,研究其O_2^(?)产生速率、SOD和CAT活性水平及MDA含量的变化,并测定了相应发生的质膜透性和叶水势的改变。结果表明,青杨叶片的O_2^(?)产生速率随PEG浓度的加大而增加,在-2.5--1.25MPa间,胁迫强度与O_2^(?)生成量成正比。MDA含量的变化趋势与O_2^(?)产生速率的变化趋势相似;在一定胁强范围内,SOD和CAT的活性水平亦与O_2^(?)的变化相一致;细胞质膜透性的加大和叶水势的降低与MDA含量的增高呈明显的正相关,经统计处理结果之差有极显著意义。说明青杨叶片的渗透胁迫损伤,是由O_2^(?)引发的膜脂过氧化,致使MDA含量增高,破坏了细胞膜系统所致。

It is well known that the osmotic stress may induce oxygen free radicalgeneration and cause various degree injuries to some plant species. In thispaper the leaves of P. cathayana Rehd. were treated with different osmoticpressures by PEG-6000 to study the mechanism of leaf injury. The resultsshowed that the generation rate of superoxide free radical (O_2^-) increasedwith the increase in PEG concentration. The stress strength was in directproportion to the amount of O_2^- generation between -2.5 to -1.25 MPa. Thetrend of change in MDA contents was similar to that in O_2^- generation rate.In certain range of stress strength, the activity levels of SOD and CAT co-rresponded to the change in O_2^-. There was a positive correlation betweenincrease of cytoplasmic membrane permeability, leaf water potential decreaseand increment of MDA content. The conclusion obtained from this study maybe that osmotic stress damage of leave in P. cathayana is caused by membr-ane-lipid peroxidation firstly, meanwhile increase in MDA content, and cy-toplasina system destruction.