3种苜蓿属牧草耐盐性比较及相关机制分析

Comparison and analysis of salt tolerance of three Medicago species

苜蓿属牧草种间耐盐性差异显著,为研究其对盐胁迫的不同生理响应,以紫花苜蓿、金花菜和蒺藜苜蓿为材料,在0、75和150 mmol·L^(-1) NaCl浓度的营养液中培养,在NaCl胁迫处理7 d时测定植株根、茎、叶中主要离子和渗透调节物质含量,以及木质部伤流液中离子含量。结果表明:NaCl胁迫下蒺藜苜蓿表现出比紫花苜蓿和金花菜更严重的生长抑制现象,且根、茎、叶和根伤流液中Na^(+)和Cl^(-)的积累量较高。NaCl胁迫下,紫花苜蓿茎中Na^(+)离子含量显著低于金花菜和蒺藜苜蓿,紫花苜蓿、金花菜根伤流液中K^(+)、Ca^(2+)和Mg^(2+)的输送速率显著高于蒺藜苜蓿。NaCl胁迫不同程度地改变紫花苜蓿、金花菜和蒺藜苜蓿根、茎、叶中脯氨酸、糖、游离氨基酸和有机酸的积累。综合而言,紫花苜蓿和金花菜在抑制植株体内Na^(+)和Cl^(-)的吸收运输及渗透物质的积累机制方面优于蒺藜苜蓿,其原因可能与紫花苜蓿和金花菜根系有较强的拒盐能力和植株细胞的渗透调节能力有关。

There are significant variations in salt tolerance of different Medicago species.A controlled study was done to investigate the mechanism difference in salt tolerance among three Medicago species(M.sativa,M.polymorpha and M.truncatula).The plants were cultivated in a nutrient solution system with three salinity levels of 0,75,and 150 mmol·L^(-1) NaCl.After 7 days of NaCl stress,the contents of main ion and organic compound of roots,stems and leaves,and ion contents in xylem bleeding sap were determined.Under NaCl stress,M.truncatula showed more severe growth inhibition,higher Na^(+)and Cl^(-)accumulation in the roots,stems and leaves,and higher Na^(+)and Cl^(-)contents in the root bleeding sap than M.sativa and M.polymorpha.The stem Na^(+)content of M.sativa was much lower than that of the other two species.The K^(+),Ca^(2+)and Mg2+delivery rates in the root bleeding sap of M.sativa and M.polymorpha were much higher than those of M.truncatula in the 150 mmol·L^(-1) NaCl treatment.In addition,NaCl stress altered proline,sugar,free amino acid and organic acid accumulation in the roots,stems and leaves of three species with different degrees.The transportation and accumulation of Na^(+),Cl^(-),nutrient ions,and compatible solutes in roots,stems and leaves varied significantly among the three species under salt stress and non-salt stress conditions.M.sativa and M.polymorpha showed their own characteristics and were stronger than M.truncatula in inhibiting Na^(+)and Cl^(-)transportation and compatible solute accumulation in plants.