外源2，4-表油菜素内酯对NaCl胁迫下紫花苜蓿幼苗光合特性及离子吸收、运输和分配的影响

摘要

The aim of this study was to explore the salt resistance and physiological regulation mechanisms in-duced by exogenous 2,4-epibrassinolide (EBR)in alfalfa (Medicago sativa )seedlings.The effect of EBR on photosynthetic pigment contents,gas exchange parameters,and ion uptake,transport,and disputation in seedlings of M.sativa cv.Zhongmu No.3 and M.sativa cv.Longzhong under NaCl stress were investigated u-sing a hydroponic method.In the 150 mmol/L NaCl stress treatment,alfalfa seedling leaves showed significant decreases in photosynthetic pigment contents and photosynthetic ability,and disrupted metabolic processes of ion uptake,transport,and disputation.When EBR at 0.1 μmol/L was supplied to seedlings under NaCl stress, the chlorophyll a,b,and a+b contents increased,the chlorophyll a/b increased,and the chlorophyll/carote-noid decreased.Also,the photosynthetic rate,transpiration rate,stomatal conductance,water use efficiency, and photosynthetic ability increased after 0.1 μmol/L EBR treatment.These changes would facilitate the accu-mulation of aboveground and underground biomass.In the NaCl-stressed seedlings treated with 0.1 μmol/L EBR,the Na+ and Cl- contents and the Cl-/Na+ in different organs (leaf,stem,and root)significantly de-creased,and the contents of K+ ,Ca2 + ,and Mg2 + and the K+/Na+ ,Ca2 +/Na+ ,and Mg2 +/Na+ significantly increased.The transport ratio of inorganic ions and transport selectivity ratio of cations were effectively regula-ted in the seedlings treated with EBR.Together,these results show that EBR treatment effectively alleviated photo inhibition caused by NaCl stress in alfalfa seedlings,and promoted the synthesis and accumulation of or-ganic matter.Treatment with EBR also improved the selective absorption and transport of inorganic ions,help-ing to maintain the metabolic ion balance and improve the NaCl-resistance of alfalfa seedlings.%为明确外源2，4-表油菜素内酯（2，4-epibrassinolide，EBR）诱导紫花苜蓿幼苗抗盐性的效果及其可能的生理调节机制，采用营养液水培法，以紫花苜蓿品种‘中苜3号’和‘陇中苜蓿’为材料，研究 NaCl 胁迫下施用外源 EBR对紫花苜蓿幼苗光合色素含量、气体交换参数及离子吸收、运输和分配的影响。结果表明，1）150 mmol／L NaCl 胁迫下，苜蓿幼苗叶片的光合色素含量显著降低，光合能力及地上、地下生物量显著下降，苜蓿幼苗体内无机离子的吸收、运输和分配等代谢过程失调。2）NaCl 胁迫下，施用0．1μmol／L 外源 EBR 后，苜蓿幼苗叶片的 Chla、Chlb、Chla＋b、Chlx·c 含量及 Chla／Chlb 显著提高，Chl／Car 显著降低，P n 、T r 、Gs 、WUE 均显著提高，光合能力增强，促进了地上、地下生物量的积累。苜蓿幼苗不同器官（叶片、茎秆、根系）中的 Na＋、Cl－含量及 Cl－／Na＋显著下降， K＋、Ca2＋、Mg2＋含量及 K＋／Na＋、Ca2＋／Na＋、Mg2＋／Na＋显著升高，体内无机离子的运输比及阳离子的运输选择性比率得到有效调控。3）说明外源 EBR 能够有效缓解盐胁迫对苜蓿幼苗造成的光抑制，增强有机物的合成和积累，促进对无机离子的选择性吸收和运输，维持体内的离子代谢平衡，提高苜蓿幼苗的耐盐性。