環境的變化對植物的生長與發育有很深的影響。為了減低環境逆境的影響，植物發展出許多清除自由基的防禦機制，其中包括本研究室著重的ascorbate-glutathione循環。本研究是利用自由基誘導劑2,2’-azobis(2-amidinopropane) hydrochloride (AAPH)來誘發大豆 (Glycine max cv. Essex)之氧化逆境 (oxidative stress)，並研究其生理及生化上的反應。從本實驗結果中發現，在酵素性抗氧化物質部分，有一部份酵素如superoxide dismutase、ascorbate peroxidase、catalase及guaiacol peroxidase，其酵素活性隨時間的增加有上升的趨勢；另一部份如dehydroascorbate reductase及glutathione reductase之酵素活性則有下降的趨勢。利用ascorbate peroxidase活性電泳來研究其同功?活性之變化，其結果與酵素活性實驗相類似，但是並未能夠很清楚的辨認同功?的作用。關於非酵素性抗氧化物質之部分，如total ascorbate及total glutathione (還原態＋氧化態)之含量隨著時間增加有上升的趨勢；然而，氧化態的ascorbate 及glutathione卻無明顯的增加。由此研究得知，將50 mM AAPH噴灑於大豆植株表面確實可以誘發植物一部份之抗氧化機制；故推測AAPH可能使用於模擬植物於逆境中生長。 The growth and development of plants are strongly influenced by different environmental stresses that can be initiated by oxidative stress. To cope with these stresses, plants have could develop a series of defense mechanisms and detoxification systems including ascorbate-glutathione cycle. The ascorbate-glutathione cycle is one of the most important antioxidative defense systems being in discussed plants. In this study, we investigated the physiological and biochemical responses of soybean (Glycine max cv. Essex), which is an ozone-tolerance cultivar, under oxidative stress initiated by azo compounds, 2,2’-azobis(2-amidinopropane) hydrochloride (AAPH). Results showed that 50 mM AAPH could cause visible injury on leaf tissues in soybean, reduced total chlorophyll contents and increased the levels of lipid peroxidation. Results also showed a slightly increase in activities of enzymes involved in detoxifying oxidative stress; such as ascorbate peroxidase (APX), superoxide dismutase, catalase and guaiacol peroxidase during the different incubation time. However, the activities of dehydroascorbate reductase and glutathione reductase were decreased. The APX activity in gel electrophoresis studies confirmed the enzyme activity data, but the activities of isozymes were not clearly identified. The levels of total ascorbate and glutathione contents were enhanced in soybean leaves when treated with 50 mM AAPH. However, the oxidized forms of ascorbate and glutathione contents were not significantly increased. This study suggests that some antioxidants involved in ascorbate-glutathione cycle in soybean can be induced by spraying 50 mM AAPH, and this technique could be used to screen the sensitivity of plants to environmental stress.
