Abstract:

The growth and physiological indices of Melilotoides ruthenica seedlings under different NaCl stresses (0, 50, 100, 150, 200, 250, 300 mmol·L^-1) were investigated by pot experiment. Results showed that the plant height, leaf area, stem diameter of Melilotoides ruthenica seedling decreased with NaCl concentration increasing, whereas root/shoot ratio increased with NaCl concentration increasing at the same time. The plant heights of M. ruthenica seedling on the 14th day, 21st day and 28th day after the NaCl stresses of 150~300 mmol·L^-1 were significantly lower than control (P<0.05). The leaf area and stem diameter on 14th day, 21st day and 28th day after the NaCl stress of 300 mmol·L^-1 were significantly lower than control (P<0.05), whereas root/shoot ratios were significantly higher than control and other treatments (P<0.05). Different parts of M. ruthenica seedling had differentsensitivity to salt stress. The chlorophyll, malondialdehyde and leaf relative water contents as well as relative conductivity of seedling varied along with different salt concentrations and stress times. On 14th day after stress, malondialdehyde content under 200~300 mmol·L^-1 concentration was significantly lower than control (P<0.05). On 21st and 28th day after stress, malondialdehyde contents under 100~300 mmol·L^-1 concentration were significantly lower than control (P<0.05). The relative water contents of leaves after the NaCl stresses of 250~300 mmol·L^-1 for 14 days, the NaCl stress of 200~300 mmol·L^-1 for 21 days and the NaCl stresses of 150~300 mmol·L^-1 for 28 days were significantly lower than control and other treatments (P<0.05). The critical concentration of NaCl inhibiting the growth of M. ruthenica seedling decreased with the increases of NaCl concentration and stress time, whereas the damaged seedlings of M. ruthenica increased with the increases of NaCl concentration and stress time.

Key words: Salt-stress, Melilotoides ruthenica, Seedling stage, Growth, Physiological mechanism

摘要：

采用盆栽法研究不同浓度NaCl（0， 50， 100， 150， 200， 250， 300 mmol·L^-1）胁迫对扁蓿豆（Melilotoides ruthenica）苗期生长及生理指标的影响。结果表明：相同胁迫天数下，随盐浓度的升高扁蓿豆株高、叶面积、茎粗均呈降低趋势，根冠比呈增大趋势。胁迫第14，21和28 d，150~300 mmol·L^-1浓度下株高显著低于对照（P<0.05）；300 mmol·L^-1浓度下，叶面积、茎粗均显著低于对照（P<0.05），根冠比显著大于对照及其他各浓度处理（P<0.05）。即盐胁迫下，扁蓿豆各生长部位对盐敏感性不同。扁蓿豆叶绿素、丙二醛（MDA）、叶片相对水分含量和相对电导率在不同胁迫时期，不同盐浓度影响有差异。胁迫第14 d时200~300 mmol·L^-1浓度处理、胁迫第21 d和28 d时100~300 mmol·L^-1浓度处理均使扁蓿豆MDA含量显著高于对照（P<0.05）；胁迫第14 d时250~300 mmol·L^-1浓度处理、胁迫第21 d时200~300 mmol·L^-1浓度处理、胁迫第28 d时150~300 mmol·L^-1浓度处理均使其叶片相对水分含量显著低于对照和其他浓度处理（P<0.05）。可见，随着胁迫时间的延长，抑制扁蓿豆幼苗生长的临界盐浓度值在减小，即盐胁迫对扁蓿豆幼苗的抑制程度与盐浓度、胁迫时间成正比。

关键词: 盐胁迫, 扁蓿豆, 苗期, 生长, 生理机制