抗寒锻炼中紫花苜蓿非结构性碳水化合物转化转运与抗寒性关系

The relationship between the transformation and transport of non-structural carbohydrates and cold resistance in Medicago sativa during cold hardening

为研究抗寒锻炼过程中紫花苜蓿根、叶中非结构性碳水化合物转化转运与抗寒性的关系,以抗寒性强的苜蓿品种肇东和抗寒性弱的赛迪10为对象,刈割7 d后,分别进行降温处理(CH_(1))和低温处理(CH_(2)),并以再生7 d的植株(CK)和正常生长植株为参照,分析抗寒锻炼过程中苜蓿根、叶中可溶性糖和淀粉含量变化及品种间差异。结果表明:抗寒锻炼后苜蓿根、叶的半致死低温(LT_(50))随可溶性糖、淀粉含量的增加而降低,根、叶LT_(50)与可溶性糖和淀粉含量呈显著负相关。在正常生长条件下再生14 d,2个品种根、叶可溶性糖和淀粉含量均降低。而CH_(1)处理下苜蓿根、叶可溶性糖含量增加、叶淀粉含量降低,根淀粉含量变化较小,赛迪10根、叶中可溶性糖含量显著高于肇东,叶淀粉含量显著低于肇东。CH_(2)处理后肇东根中可溶性糖含量增加,淀粉含量降低,赛迪10的变化相反,赛迪10根中可溶性糖含量低于肇东。抗寒锻炼改变了苜蓿可溶性糖在地上、地下的转运方向,正常生长植株根中淀粉转化成可溶性糖,转运到叶中,与叶中由淀粉转化形成的可溶性糖一起用于地上器官的再生。抗寒锻炼初期(CH_(1))2个品种叶中淀粉降解成可溶性糖,并向根部转运,根、叶中可溶性糖含量增加,在此阶段赛迪10比肇东消耗较多叶淀粉;抗寒锻炼后期(CH_(2)),不同抗寒性品种根中淀粉与可溶性糖的转化方向不同,肇东根中淀粉向可溶性糖转化,赛迪10根中可溶性糖向淀粉转化。以上结果表明,苜蓿在抗寒锻炼初期消耗较少的非结构性碳水化合物,后期根中淀粉向可溶性糖转化,有利于品种抗寒性增加,这为揭示苜蓿品种抗寒性差异提供了重要线索。

This research studied the transformation and transportation of non-structural carbohydrates in the roots and leaves of Medicago sativa and their relationship with cold resistance during cold hardening in two alfalfa varieties:Zhaodong,a strongly cold resistant variety,and was Sardi 10,a weakly cold resistant variety.Experimental plants were subjected to a cooling treatment to simulate early cold-hardening(CH_(1)),a low-temperature treatment to simulate advanced cold-hardening(CH_(2)),or normal growth conditions(CK)over seven days following cutting.Changes in soluble sugar and starch contents in roots and leaves and the difference between the two varieties were analyzed in regrowth after the seven days to assess cold resistance.It was found that:After cold hardening,the semi-lethal low temperature(LT_(50))of alfalfa roots and leaves decreased with increase in their soluble sugar and starch contents,and there were significant negative correlations between the LT_(50) and the soluble sugar and starch contents of roots and leaves.After 14 days of regeneration under normal growth conditions,the soluble sugar and starch contents in the roots and leaves decreased.However,soluble sugar content in roots and leaves of alfalfa increased,starch content in leaves decreased,and starch content in roots changed little after CH_(1) treatment.The soluble sugar content in the roots and leaves of Sardi 10 was significantly higher than that in Zhaodong,while the content of starch in the leaves of Sardi 10 was significantly lower than Zhaodong.After CH_(2) treatment,the soluble sugar content in Zhaodong roots increased and starch content decreased.The changes in soluble sugar and starch contents in Sardi 10 roots were opposite to those in Zhaodong,and soluble sugar content in Sardi 10 roots was lower than Zhaodong.Cold hardening changed the aboveground-belowground direction transfer of soluble sugar.Starch in the roots of normally growing plants was converted into soluble sugar,which was transported to the leaves and used together with the soluble sugar transformed from the starch of leaves to regenerate aboveground organs.In CH_(1),the starch in the leaves of the two varieties was degraded into soluble sugar,which was transported to the roots,resulting in an increased soluble sugar content in the roots and leaves.At this stage,more leaf starch was consumed in Sardi 10 than Zhaodong.In CH_(2),Sardi 10 and Zhaodong had reverse starch-sugar transformation directions in the roots,with the transformation from starch to soluble sugar in Zhaodong roots and from soluble sugar to starch in Sardi 10 roots.These results indicate that alfalfa consumes less non-structural carbohydrates during early cold hardening,but transforms starch into soluble sugar in the root in the later stages,resulting in increased root cold resistance.This data provides important insight into the reasons for differences in cold resistance among alfalfa varieties.