低温胁迫对苜蓿幼苗存活及生理生化指标的影响

Effect of Low Temperature Stress on the Survival and Physiological and Biochemical Indexes of Alfalfa Seedlings

用秋眠级为2级至9级的11个苜蓿品种,每品种被随机分为对照组和5个处理组,研究低温胁迫和苜蓿品种对幼苗存活和叶片生理生化指标的影响。结果表明:低温胁迫和苜蓿品种对幼苗存活率、叶片生理生化指标的影响均极显著,而且二者对它们的互作效应也极显著。子叶期幼苗在-7.5℃下处理12 h,存活率仅为3.26%。幼苗在-5℃下处理12 h,存活率为54.73%,但叶片游离脯氨酸含量、过氧化物酶活性、质膜相对透性和根系活力极显著提高;每天把幼苗置于-5℃下2 h至3 h锻炼7天,幼苗存活率可提高到95%以上,叶片游离脯氨酸、可溶性糖、可溶性蛋白质含量,超氧化物歧化酶活性、根系活力和质膜相对透性均极显著提高。结果表明:4级至9级品种的存活率极显著低于2级至3级的品种;6级至9级品种叶片游离脯氨酸含量、过氧化物酶活性、质膜相对透性极著显低于2级至3级的品种。

Eleven Alfalfa （Medicago sativa L. ） cuhivars , which level of fall dormancy is from 2 to 9 were selected and planted in pots in this experiment. Every. alfalfa cuhivars was divided into six groups（ a control and five treatments） randomly. The effect of low temperature stress and alfalfa cuhivars on the survival rate, physiological and biochemical indexes of alfalfa seedlings was studied. The results showed that the effect of low temperature stress, alfalfa cuhivars and interaction between them on the survival rate and physiological and biochemical indexes of alfalfa seedlings was very significant. For the seedlings having two cotyledons ,when they were exposed to the temperature of -7.5 ℃ for about 12 b, the survival rate was only 3.26 %. When they were exposed to the temperature of -5℃ about 12 b, the survival rate was 54.73 % and free proline content , peroxide isozyme （POD） activity, membrane relative penetration in the leaves and root vitality showed a significant increase than the control. If the seedlings were exposed to the temperature of - 5℃ for about 2 h -3 h per day for 7 days, survival rate would significanttly increase （ 〉 95 % ）. Free proline content, soluble sugar, soluble protein, superoxide dismutase （SOD） , activity, root vitality and membrane relative penetration in the leaves also showed very significant increase. Results also showed that for the survival rate, the cultivars which level of fall dormancy is from 4 to 9 appeared significantly lower than those which level of fall dormancy is from 2 to 3. And the similar results occurred in the free proline content, POD activity and membrane relative penetration.