臭氧胁迫对大豆叶片抗坏血酸-谷胱甘肽循环的影响

由于城市化的加剧导致近地面臭氧（O3）浓度日益增加，对植物生长和生态系统的功能产生了显著影响，因此准确评估近地层O3浓度升高对植物的影响具有重要意义。本文利用开顶式气室（OTCs），系统探讨了模拟O3胁迫下大豆抗氧化系统抗坏血酸（AsA）-谷胱甘肽（GSH）循环清除活性氧（ROS）的机制及其对植株生长发育的影响。结果表明，在整个生育期内，与对照相比， 80?10 nL?L-1和110?10 nL?L-1 O3可以使大豆叶片丙二醛（MDA）含量、相对电导率增大，超氧阴离子（O2 ）产生速率、过氧化氢（H2O2）含量升高，超氧化物歧化酶（SOD）活性减弱； AsA-GSH循环中的AsA、GSH含量减少，脱氢抗坏血酸（DHA）、氧化型谷胱甘肽（GSSG）含量增加，过氧化物酶（APX）、单脱氢抗坏血酸还原酶（MDHAR）、谷胱甘肽还原酶（GR）活性呈现出前期增强后期减弱趋势，而脱氢抗坏血酸还原酶（DHAR）活性呈现出增强-减弱-增强的趋势。以上结果说明，O3浓度升高促进了大豆叶片ROS的代谢速率，降低了AsA-GSH循环效率，表明抗氧化系统不能长时间忍受高浓度O3带来的氧化伤害，从而使膜脂过氧化程度加重，对大豆表现为伤害效应。

Effects of ozone on AsA-GSH cycle in soybean leaves

Widespread areas of crop production are presently at risk for damage from ambient atmospheric ozone (O3) concentrations. The concentration of tropospheric O3 has been rising due to aggravating urbanization since the Industrial Revolution, it has had a significant impact on plants and plants play an important role in adjusting structure and function of the ecosystem. Thus, to correctly evaluate how elevated O3 concentration affects plants is of great significance. AsA-GSH cycle has an important function of eliminating H2O2, and the efficiency of AsA-GSH cycle in plants can be stimulated by moderate stress conditions to scavenge reactive oxygen species (ROS). In this research, open-top chambers (OTCs) were used to investigate the mechanism of AsA-GSH cycle to eliminate ROS and the effects on growth and development of plants under troposphere O3 stress. The results showed that, compared with control, the O3 concentration of (80?10) nL?L-1 and (110?10) nL?L-1 induced an increase on malondialdehyde (MDA) content, relative electrical conductivity and a decrease on superoxide anion (O2 ) production rate, hydrogen peroxide (H2O2) content and the activities of superoxide dismutase (SOD) during the whole growth stage. Simultaneously, O3 stress resulted in lower content of ascorbic acid (AsA) and glutathione (GSH), and higher content of dehydroascorbic acid (DHA) and oxidized glutathione (GSSG) of AsA-GSH cycle. It showed a trend of increasing in earlier stage and decreasing in later stage of the activities of ascorbate peroxidase (APX), monodehydroascorbate reductase (MDHAR) and glutathione reductase (GR), while the dehydroascorbate reductase (DHAR) activity was increased in earlier period, decreased in middle period and then increased in later period compared to control, respectively. The results indicated that elevated O3 concentration accelerated ROS metabolism rates and peroxidation damage, reduced the efficiency of AsA-GSH cycle and antioxidant system could not tolerate O3-induced injure, thus increasing membrane lipid peroxidation and resulting in a significant negative effect on soybean. Also, in the early of O3 treatment, the intensity of stress was low; the protection of plants played an important role to increase the efficiency of removing ROS and reduce ROS damage by improving the efficiency of AsA-GSH cycle. With stress intensity increasing, the structure of antioxidant system in soybean leaves was damaged, resulting in rapid accumulation of ROS. And O3 stress caused an acceleration of caducity that might be in part responsible for the reduction of antioxidant ability. This paper reveals the effects of different treatments on ROS metabolic parameters and the response of AsA-GSH cycle in soybean leaves under elevated O3, which can analyze its ROS metabolic response mechanisms to elevated O3 concentration and provide references for the response mechanism of plants, and how to prevent soybean from O3 injury and predict the feasibility of soybean under future climate change.