采用盆栽法研究不同浓度NaCl（0，50，100，150，200，250，300mmol／L）胁迫对扁蓿豆苗期有机渗透调节物质及光合参数的影响。结果表明，相同胁迫天数下，随盐浓度的升高。扁蓿豆可溶性蛋白含量、可溶性糖含量呈降低趋势，脯氨酸含量呈升高趋势。各个观测期和浓度之间存在差异，胁迫第7和14天，300mmol／L浓度下可溶性蛋白含量显著低于对照（P＜0．05）；胁迫第7，14和21天，50～100mmol／L浓度下，可溶性糖含量明显高于对照，但胁迫第28天，250～300mmol／L浓度处理显著低于对照（P＜0．05）。胁迫第7天，150～300mmol／L浓度处理、胁迫第14天，200～300mmol／L浓度处理、胁迫第21天，250～300mmol／L浓度处理扁蓿豆脯氨酸含量均分别显著高于对照及其他处理（P＜0．05）。可见，盐胁迫下，扁蓿豆产生的3种渗透调节物质调节方式不同，盐胁迫对扁蓿豆幼苗的抑制程度与盐浓度、胁迫时间呈正比。不同的胁迫浓度和胁迫时间，扁蓿豆3个观测期光合参数变化不尽相同。胁迫第14天，叶片净光合速率（Pn）、蒸腾速率（Tr）、气孔导度（Gs）和胞间CO2浓度（Ci）随盐浓度的升高呈先上升后降低的趋势。50～100mmol／L浓度处理Pn、Tr和Gs显著高于对照，但300mmol／L浓度处理Pn和Tr显著低于对照及其他处理（P＜0．05）。胁迫第28天，4个光合参数随盐浓度的升高而降低。叶片气孔限制值（Ls）和水分利用效率（WUE）在胁迫14和28d时，变化规律一致，随盐浓度的升高呈上升趋势。%The effects of various levels of NaCl stress [0 (control),50,100,150,200,250,300 mmol/L]on the osmotic adjustment matters and photosynthetic physiology of Melilotoides ruthenica seedlings were investi-gated in pot experiments.Soluble protein and sugar contents of seedlings decreased with increasing NaCl con-centration.However,proline content increased with increased NaCl concentration.The contents of soluble protein,sugars,and proline differed under different salt concentrations and stress exposure times.On the 7 th day and 14 th day after imposing stress,soluble protein contents of seedlings exposed to 300 mmol/L NaCl con-centrations were significantly lower than those of controls (P <0.05).On the 7 th ,14 th and 21 st day after impos-ing stress,soluble sugar contents of seedlings exposed to 50 or 100 mmol/L NaCl concentration were higher than those of the controls,while on 28 th day after stress,soluble sugar contents of seedlings exposed to 250 or 300 mmol/L NaCl concentrations were significantly lower than those of the controls (P <0.05).On the 7 th day after imposing stress (150-300 mmol/L NaCl),the 14 th day after imposing stress (200-300 mmol/L NaCl) and on the 28 th day after imposing stress (250 or 300 mmol/L NaCl),the proline content was significantly higher than that of the control and other treatments (P <0.05).Hence under salt stress,three indicators of osmotic adjustment had different time signatures.With increases in both NaCl concentration and stress expo-sure time,the physical damage to M.ruthenica seedlings became more serious,while photosynthetic parame-ters varied with NaCl concentration and stress exposure time.On the 14 th day after imposing stress,photosyn-thetic rate (Pn ),transpiration rate (Tr ),stomatal conductance (Gs)and intercellular CO2 concentration (Ci ) increased at low,and decreased at high salt concentration.Pn ,Tr ,and Gs of seedlings under 50-100 mmol/L concentrations were significantly higher than those of control plants,while Pn and Tr of seedlings under 300 mmol/L were significantly lower than those of control plants and of other treatments (P <0.05).On 28 th day after imposing stress,Pn ,Tr ,Gs and Ci were decreased with increasing of salt concentrations.On the 14 th and 28 th days after imposing stress,stomatal limitation (L s )and water use efficiency (WUE)increased with in-creasing NaCl concentration.
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