外源水杨酸对NaCl胁迫下白榆幼苗光合作用及离子分配的影响

以1年生白榆幼苗为研究对象,设置0、0.5、1.0和2.0 mmol·L^-1水杨酸(SA)与0、50、100和150 mmol·L^-1 NaCl处理组合,考察盐胁迫下白榆幼苗生物量、光合色素含量、光合作用参数及根叶离子含量、分配、运输的情况,探讨外源SA对NaCl胁迫下白榆幼苗耐盐生理特征的影响。结果表明:(1)NaCl胁迫显著抑制了白榆幼苗的生长、光合色素含量及光合能力,并破坏了白榆体内离子平衡。(2)喷施外源SA使盐胁迫下白榆幼苗的干重和根冠比均不同程度升高,0.5和2.0 mmol·L^-1 SA不同程度提高了50和100 mmol·L^-1 NaCl处理组幼苗叶片光合色素含量。(3)0.5 mmol·L^-1 SA显著提升了50 mmol·L^-1 NaCl处理组白榆幼苗的净光合速率(Pn)、气孔导度(Gs)和蒸腾速率(Tr),1.0和2.0 mmol·L^-1 SA对150 mmol·L^-1 NaCl处理组幼苗净光合速率改善效果较好,外源SA对100 mmol·L^-1 NaCl处理组幼苗的光合作用参数无显著影响。(4)NaCl胁迫下,外源SA处理的白榆幼苗叶和根Na^+含量及Na^+/K^+、Na^+/Ca^2+和Na^+/Mg^2+显著降低,离子选择运输系数SK,Na、SCa,Na和SMg,Na升高,从而促进了幼苗K^+、Ca^2+和Mg^2+由根向叶片的转运;隶属函数分析发现对白榆幼苗叶和根中离子含量改善效果最好的SA浓度分别为1.0和2.0 mmol·L^-1。因此,适宜浓度的外源水杨酸能够有效改善NaCl胁迫下白榆幼苗的光合能力,有效调节白榆幼苗体内离子状态,从而增强白榆对NaCl胁迫的抗性。

Effect of Salicylic Acid on Photosynthesis and Ion Distribution of Ulmus pumila Seedlings under NaCl Stress

To study the effects of exogenous salicylic acid(SA)on salt tolerance physiology of Ulmus pumila seedlings under NaCl stress,we explored the effects of 0,0.5,1.0 and 2.0 mmol·L^-1 SA on the photosynthetic rate and ion distribution of annual U.pumila seedlings under different NaCl concentrations(0,50,100 and 150 mmol·L^-1).The results showed that:(1)NaCl stress significantly inhibited the growth and photosynthetic capacity of U.pumila seedlings,and the ion balance was destroyed.(2)After spraying exogenous SA,the dry weight and root-shoot ratio of U.pumila seedlings increased in varying degrees.0.5 and 2.0 mmol·L^-1 SA improved the chlorophyll and carotenoids pigment contents in leaves of U.pumila seedlings under 50 and 100 mmol·L^-1 NaCl stress.(3)The net photosynthetic rate(Pn),stomatal conductance(Gs)and transpiration rate(Tr)of U.pumila seedlings significantly increased with the addition of 0.5 mmol·L^-1 SA under 50 mmol·L^-1 NaCl treatment.And 1.0 and 2.0 mmol·L^-1 SA have better improvement effect on the net photosynthetic rate(Pn)of seedlings under 150 mmol·L^-1 NaCl,while the exogenous SA had no significant effect on the photosynthetic parameters under 100 mmol·L^-1 NaCl.(4)The content of Na^+and the ratios of Na^+/K^+,Na^+/Ca^2+,Na^+/Mg^2+in leaves and roots of U.pumila were reduced by using exogenous SA under salt stress,while the ion-selective transport coefficients SK,Na,SCa,Na and SMg,Na were increased which promoted the transfer of K^+,Ca^2+,and Mg^2+from roots to leaves.Membership function analysis found that the SA concentrations with the best improvement effect on the ion content in leaves and roots of U.pumila were 1.0 and 2.0 mmol·L^-1,respectively.Therefore,appropriate concentration of exogenous salicylic acid can improve the photosynthetic capacity and regulate the ion state of U.pumila seedlings effectively under NaCl stress,thus enhancing the resistance of U.pumila to NaCl stress.