Abstract: Freezing and thawing often occur in spring in saline areas of the Northeast China. In order to explore the effects of freeze-thaw and saline-alkali stress on the absorption and transport of mineral ions in alfalfa,in this study,'Longmu 807’alfalfa seedlings were used as test materials to investigate the effects of the freeze-thaw cycle (freezing-thaw cycle,FT) and freeze-thaw cycle + saline-alkali (freezing-thaw cycle and saline-alkali,FT+SA) stresses on the mineral elements absorption and transportation in the vegetative organs of alfalfa seedlings. The results showed that under FT and FT+SA stresses,the content of Na⁺in roots of alfalfa seedlings increased,while the content of Na⁺ in stems and leaves decreased;however,the contents of K⁺,Ca²⁺,Mg²⁺,Fe³⁺,Mn²⁺,Zn²⁺,Cu²⁺and the ratios of K⁺/Na⁺,Ca²⁺/Na⁺,Mg²⁺/Na⁺decreased in root,stem and leaf,and the reduction level under FT+SA stress was higher than that under FT stress. The selective transport capacity of Mg²⁺in roots is higher than that of K⁺ and Ca²⁺,and the K⁺ transport capacity from stems to leaves is higher than that of Mg²⁺and Ca²⁺. Ability to limiting Na⁺ and inhibiting K⁺,Ca²⁺,Mg²⁺ selective transport in the root,and the ability of stem to selectively transport K⁺,Ca²⁺,Mg²⁺to leaves is higher under FT+SA stress than those under FT stress. The correlation between the ions is relatively high,which jointly maintains the ion balance of the plant. Under FT and FT+SA stresses,the distribution and transportation of the above mineral ions were affected in roots,stems and leaves of alfalfa seedlings,which was related to the cold and saline-alkali resistance of alfalfa seedlings.

Key words: Alfalfa, Freezing-thaw cycle and saline-alkali stress, Vegetative organ, Mineral ion, Ion steady-state equilibrium

摘要： 我国东北盐渍区春季常发生冻融现象，为探究冻融和盐碱双重胁迫对苜蓿矿质离子吸收和转运的影响，本研究以'龙牧807’苜蓿(Medicago sativa L.)幼苗为试材，对其进行冻融循环(Freezing-thaw cycle，FT)和冻融循环＋盐碱(Freezing-thaw cycle and saline-alkali，FT+SA)胁迫，分析FT和FT+SA胁迫对苜蓿幼苗营养器官矿质离子吸收及运输能力的影响。结果表明：苜蓿幼苗在FT和FT+SA胁迫下，根部Na⁺含量增加，而茎和叶部Na⁺含量降低，且根、茎、叶部K⁺，Ca²⁺，Mg²⁺，Fe³⁺，Mn²⁺，Zn²⁺，Cu²⁺含量和K⁺/Na⁺，Ca²⁺/Na⁺，Mg²⁺/Na⁺比值均降低，在FT+SA胁迫下降低的水平高于FT胁迫；根部对Mg²⁺选择性运输能力高于K⁺和Ca²⁺，茎和叶部K⁺运输能力高于Mg²⁺和Ca²⁺，根部限Na⁺能力和抑制K⁺，Ca²⁺，Mg²⁺选择性运输能力以及茎向叶部选择性运输K⁺，Ca²⁺，Mg²⁺的能力均为FT+SA胁迫高于FT。各离子间相关性较高，共同维系植株的离子平衡。FT和FT+SA胁迫影响苜蓿幼苗对上述矿质离子在根、茎、叶营养器官的分布和运输，与苜蓿幼苗的抗寒和抗盐碱有一定的相关性。

关键词: 紫花苜蓿, 冻融循环＋盐碱胁迫, 营养器官, 矿质离子, 离子稳态平衡