高低温胁迫对番茄叶片抗坏血酸代谢系统的影响

为探明番茄在温度逆境下抗坏血酸（AsA）代谢系统抗氧化的生理机制，以番茄幼苗为试材，分别研究了高温（40℃）和低温（5℃）胁迫（0、4、8、12、24、36h）下，叶片AsA代谢的主要酶L-半乳糖-1，4-内酯脱氢酶（GalLDH）、脱氢抗坏血酸还原酶（DHAR）、抗坏血酸过氧化物酶（APX）、单脱氢抗坏血酸还原酶（MDHAR）和谷胱甘肽还原酶（GR）活性与AsA、脱氢抗坏血酸（DHA）和AsA＋DHA含量的变化。结果表明：在高温和低温胁迫下，除36h外，番茄叶片AsA、DHA和AsA＋DHA含量和GalLDH、DHAR、APX、MDHAR及GR活性均明显高于25℃（CK）处理，H2O2含量始终明显高于CK，AsA／DHA始终明显低于CK，说明短时间（24h）高温和低温胁迫，番茄幼苗以AsA为核心的抗氧化系统功能明显增强，但长时间（36h）温度胁迫，AsA抗氧化系统的功能明显下降，导致H2O2的积累。

Effects of High and Low Temperature Stresses on Ascorbic Acid Metabolism System in Tomato Leaves

In order to investigate the effects of high and low temperature stresses on the ascorbic acid(AsA) metabolism systerm in tomato leaves,the activities of enzymes related with AsA metabolism,including L-galactono-1,4-lactone dehydrogenase(GalLDH),dehydroascorbate reductase(DHAR),ascorbate peroxidase(APX),monodehydroascorbate reductase(MDHAR) and glutathione reductase(GR),as well as contents of AsA,dehydroascorbic acid(DHA) and AsA+DHA were studied under the high(40℃) or low(5℃) temperature stresses for 0,4,8,12,24 hours and 36 hours respectively.The results showed that under the high and low temperature stresses,the contents of AsA,DHA and AsA+DHA and the activities of GalLDH,DHAR,MDHAR,APX and GR were all significantly higher than those under the control temperature(25℃) except treated for 36 hours.The content of H2O2 was significantly higher than that of the control while the ratio of AsA to DHA was significantly lower.It was proposed that the AsA antioxidant system in tomato could be increased under high or low temperature stresses in short time.However,with the lasting stress,the AsA antioxidant system functionally decreased,which might be responsible for the high accumulation of H2O2.