超氧化物歧化酶在苜蓿抗寒锻炼过程中的作用

Effect of superoxide dismutase on cold acclimation of alfalfa

对苜蓿Medicago sativa抗寒锻炼过程中膜透性和超氧化物歧化酶(SOD)活性进行测定,通过苜蓿组织冰冻半致死温度(LT50)说明在抗寒锻炼过程中苜蓿抗寒性的变化。结果表明,在不同低温处理下,苜蓿叶片和根茎组织电解质透出率呈现出S型曲线变化。抗寒锻炼过程中,苜蓿组织LT50从9月初的-6.9℃下降到11月初的-15.6℃,下降了8.7℃。随着秋季气温的下降,苜蓿叶片SOD活性显著增加,11月上旬达到最高峰,此后显著下降。这说明SOD在抗寒锻炼过程中起着重要的保护作用,当苜蓿获得抗寒能力后,SOD活性逐渐下降。在抗寒锻炼过程中,苜蓿根茎SOD活性的变化与叶片中SOD活性的变化规律不一致,苜蓿根茎中SOD活性水平显著高于叶片中的SOD活性水平。聚丙烯酰胺凝胶电泳分析结果显示,不同苜蓿品种具有6条共同的SOD同工酶酶带。适应高寒地区气候条件的当地材料同德杂种苜蓿表现出与其他苜蓿品种较大的特异性。抑制试验表明苜蓿SOD为CuZn-SOD。

This study was conducted to measure the changes of electrolyte leakage （EL） and the activities of superoxide dismutase （SOD） during cold acclimation on alfalfa （Medicago sativa）. The cold acclimation of alfalfa was described by the median lethal temperatures （LT50） of alfalfa leaves. The measurement results indicated that the EL of alfalfa tissue under low-temperature treatments presented a curve change like ＂S＂ fitted Logistic Function. During cold acclimation LT50 of alfalfa declined 8. 7 ℃, from -6.9℃ of early September to -15.6 ℃ of early November. As air temperatures fell from autumn to winter, the activities of superoxide dismutase in alfalfa leaf obviously increased, and upto top in early November, afterwards it declined quickly. It is clear that the superoxide dismutase has an important role of protecting alfalfa tissue during cold acclimation. The dramatic difference of the SOD activities between leaf and crown was observed, and there was higher level of SOD activity in alfalfa crown more than in leaf. Polyacrylamide gel electrophoresis on Alfalfa was performed. Six common isoenzynic bands for various alfalfa cultivars appeared on gel. The differences of SOD band were observed on ‘Td alfalfa’ which adapts to cold weather in alpine area. Inhibition experiment indicated that SOD types of alfalfa are CuZn-SOD.