外源脯氨酸对盐胁迫下甜瓜幼苗根系抗坏血酸-谷胱甘肽循环的影响

以2个不同耐盐强度的甜瓜品种‘玉皇’（耐盐性强）和‘雪美’（耐盐性弱）为材料,采用营养液栽培方法,研究外源脯氨酸对盐胁迫下甜瓜幼苗根系抗坏血酸-谷胱甘肽循环的影响。结果显示：（1）盐胁迫下,2个甜瓜品种根系内的还原型抗坏血酸（ASA）、还原型谷胱甘肽（GSH）含量降低,氧化型谷胱甘肽（GSSG）含量升高,且‘雪美’变化幅度大于‘玉皇’;（2）盐胁迫下,施用外源脯氨酸提高了2个甜瓜品种根系中ASA和GSH的含量,降低了GSSG含量,同时也提高了GSH/GSSG的比值,且对‘雪美’的作用大于‘玉皇’;（3）盐胁迫处理3 d时,2个甜瓜品种根系的抗坏血酸过氧化物酶（APX）、脱氢抗坏血酸还原酶（DHAR）、谷胱甘肽还原酶（GR）活性均下降,且‘雪美’下降的幅度较大;随着胁迫时间的延长（5 d时）,‘玉皇’幼苗根系内APX、DHAR、GR活性有所上升,‘雪美’根系中这3种酶活性则进一步降低;（4）盐胁迫下,施用外源脯氨酸提高了2个甜瓜品种根系内的APX、DHAR和GR的酶活性,且对‘雪美’的作用大于‘玉皇’。本研究结果表明,外源脯氨酸可以通过增加非酶促抗氧化物质ASA、GSH的含量和抗氧化酶活性,提高抗坏血酸-谷胱甘肽循环清除活性氧的能力,从而缓解盐胁迫对甜瓜植株的伤害。

Effects of Exogenous Proline on the Ascorbate-Glutathione Cycle in Roots of Cucumis melo Seedlings under Salt Stress

To study the effects of exogenous proline on the ascorbate-glutathione cycle in roots of melon seedlings under salt stress,two melon cultivars（ Cucumis melo ‘Yuhuang ＇and‘Xuemei＇） under differing salt tolerances were investigated in a nutrient solution culture system. The results showed that：（ 1） The content of reduced ascorbic acid（ ASA） and reduced glutathione（ GSH） decreased and oxidized glutathione（ GSSG） increased in the two melon cultivars under salt stress,with C. melo‘Xuemei＇showing a larger range than C. melo‘Yuhuang＇.（ 2） Exogenous proline had greater effects on‘Xuemei＇than on‘Yuhuang＇in increasing the content of ASA and GSH while decreasing the content of GSSG,and therefore the ratio of GSH /GSSG increased.（ 3） After 3 days salt treatment,‘Xuemei＇showed a markedly larger decreasing range in the activities of ascorbate peroxidase（ APX）,dehydroascorbate reductase（ DHAR） and glutathione reductase（ GR）. Five days later,enzyme activity increased in ‘Yuhuang ＇but decreased in ‘Xuemei＇with the extension of stress time.（ 4） Exogenous proline had larger impact on ‘Xuemei＇than on ‘Yuhuang ＇in regards to increasing the activities of APX,DHAR and GR. These results indicated that exogenous proline can clean reactive oxygen species（ ROS） caused by salt stress through increasing the activities of antioxidant enzyme and non-enzymatic antioxidant content,such as ASA and GSH,and can thus improve the ascorbate-glutathione cycle to protect melon seedlings from damage caused by salt stress.