紫花苜蓿种子吸胀期胚根线粒体AsA-GSH循环对低温胁迫的响应

Response of the mitochondrial AsA-GSH cycle during alfalfa seed germination under low temperature stress

为探究胚根线粒体抗坏血酸-谷胱甘肽(AsA-GSH)循环响应低温胁迫的抗氧化作用机制,以紫花苜蓿种子为材料,研究了不同温度(10和20℃)处理下发芽特性、不同吸胀时间(6、12和24 h)胚根线粒体AsA-GSH循环酶活性、抗氧化物以及过氧化氢(H_(2)O_(2))含量的变化规律。结果表明,吸胀12和24 h后,10℃处理的胚根线粒体H_(2)O_(2)含量高于20℃。吸胀24 h期间,10℃处理的胚根线粒体谷胱甘肽还原酶(GR)活性均低于20℃。吸胀12和24 h后,10℃处理的胚根线粒体抗坏血酸(AsA)含量均低于20℃。10℃条件下吸胀24 h后,与20℃处理相比,胚根线粒体谷胱甘肽(GSH)含量显著降低(P<0.05)。苜蓿种子在10℃条件下吸胀萌发时,主要通过降低AsA-GSH循环中GR、单脱氢抗坏血酸还原酶(MDHAR)、过氧化物酶(POD)活性和AsA、GSH含量,使胚根线粒体内的H_(2)O_(2)积累,产生氧化损伤,继而影响种子萌发的正常进程。

This study investigated the response to low temperature stress of the ascorbic acid-glutathione(AsAGSH)cycle in radicle mitochondria of alfalfa(Medicago sativa)seeds.Alfalfa seeds were germinated at two temperatures(10 or 20℃)and during imbibition antioxidant mechanisms,including hydrogen peroxide content,AsA-GSH cycle enzyme activity and antioxidant content were measured in radicle mitochondria imbibed for different times(6,12 and 24 h).It was found that the H_(2)O_(2)content of radicle mitochondria under low temperature(10℃)was higher than that under normal temperature(20℃)after 12 and 24 hours imbibition.The glutathione reductase(GR)activity of radicle mitochondria at 10℃was lower than that at 20℃after imbibition for 6,12 and 24 h.After 12 and 24 h imbibition,the ascorbic acid(AsA)content of radicle mitochondria at 10℃was lower than that at 20℃.After 24 h imbibition under low temperature stress,the glutathione(GSH)content of radicle mitochondria decreased significantly(P<0.05)compared with seeds imbibed at normal temperature.During imbibition under low temperature,the normal process of seed germination was inhibited by oxidative damage,mainly through decrease in the activities of GR,monodehydroascorbate reductase,and peroxidase and decreased levels of AsA and GSH in the AsA-GSH cycle,which led to the accumulation of H_(2)O_(2)in the radicle mitochondria.