不同NaCl胁迫对苗期扁蓿豆渗透调节物质及光合生理的影响

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(P0.05);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(P0.05)。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(P0.05)。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(P0.05)。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。

Effects of NaCl stress on substances linked to osmotic adjustment and on photosynthetic physiology of Melilotoides ruthenica in the seedling stage

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 investigated in pot experiments. Soluble protein and sugar contents of seedlings decreased with increasing NaCl concentration. 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 concentrations were significantly lower than those of controls (P<0.05). On the 7^th, 14^th and 21^st day after imposing 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 exposure time, the physical damage to M. ruthenica seedlings became more serious, while photosynthetic parameters varied with NaCl concentration and stress exposure time. On the 14^th day after imposing stress, photosynthetic rate (P_n), transpiration rate (T_r), stomatal conductance (Gs) and intercellular CO₂ concentration (C_i) increased at low, and decreased at high salt concentration. P_n, T_r, and G_s of seedlings under 50-100 mmol/L concentrations were significantly higher than those of control plants, while P_n and T_r 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, P_n, T_r, G_s and C_i 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 increasing NaCl concentration.