水杨酸对NaHCO_(3)胁迫下黄芪幼苗生长及生理特性的调节效应

Effects of salicylic acid on growth and physiological characteristics of Astragalus mongholicus seedlings under NaHCO_(3)stress

【目的】探究外源水杨酸(SA)缓解盐碱胁迫黄芪种子萌发及幼苗生长生理特性的效应。【方法】以蒙古黄芪为供试材料,利用100 mmol/L的NaHCO_(3)溶液模拟盐碱胁迫,分别设置0.1,0.2,0.3,0.4,0.5 mmol/L外源SA对黄芪种子萌发、幼苗生长进行调节,并以未加SA无NaHCO_(3)胁迫处理为对照1(CK1),未加SA及NaHCO_(3)胁迫为对照2(CK_(2)),测定蒙古黄芪种子萌发指标、幼苗生长及生理指标。【结果】NaHCO_(3)胁迫下(CK_(2))黄芪种子萌发、幼苗生长及生理受到明显抑制,与CK1相比,黄芪种子发芽率、发芽势、发芽指数和活力指数分别降低93.96%、93.45%、97.26%、97.50%,幼苗株高、单株鲜重、根系活力分别降低35.97%、37.61%、72.65%;超氧化物歧化酶(SOD)、过氧化物酶(POD)和过氧化氢酶(CAT)活性及可溶性蛋白、脯氨酸(Pro)受到不同程度的抑制,叶片质膜透性、丙二醛(MDA)含量显著增加;与CK_(2)相比,添加不同浓度外源SA后蒙古黄芪种子萌发及幼苗生长显著提高(P<0.05),叶片质膜透性及膜脂过氧化产物MDA含量分别降低了40.21%~56.56%、20.09%~46.39%,抗氧化酶SOD、POD、CAT活性及根系活力得到不同程度增强,渗透调节物质游离脯氨酸、可溶性蛋白积累量显著提高了7.63%~86.95%、5.51%~41.75%。【结论】外源SA可以有效调节NaHCO_(3)胁迫对黄芪种子萌发及幼苗生长的抑制,缓解渗透压并降低膜脂过氧化对黄芪幼苗带来的损伤,增强黄芪种子及幼苗对盐碱胁迫的适应性及抗盐碱能力,其以0.3 mmol/L缓解效果最佳。

[Objective]This study aims to investigate the physiological effects of exogenous Salicylic acid(SA)on the mitigation of seed germination and seedling growth in Astragalus mongolicus under saline-alkali stress conditions.[Method]Astragalus mongolicus was utilized as the test material,and saline-alkali stress was simulated using a 100 mmol/L NaHCO_(3)solution.Exogenous SA solutions with concentrations of 0.1,0.2,0.3,0.4,0.5 mmol/L were set to modulate seed initiation and seedling growth in Astragalus mongolica.Two control groups,treatment without SA and NaHCO_(3)stress as control 1(CK1),and the treatmentwithout SA and NaHCO_(3)stress as control 2(CK_(2))were designed,and the seed germination index,seedling growth and physiological index of Astragalus mongolicus were measured.[Result]In response to NaHCO_(3)induced stress in CK_(2),Astragalus experienced substantial inhibition in seed germination,seedling growth,as well as physiological and biochemical processes.Compared with CK1,the germination rate,germination potential,germination index,and vitality index of Astragalus seeds exhibited significant reductions of 93.96%,93.45%,97.26%,and 97.50%,respectively.Seedling height,fresh weight,and root activity showed substantial reductions of 35.97%,37.61%,and 72.65%,respectively.Moreover,the activities of antioxidant enzymes,the activities of superoxide dismutase(SOD),peroxidase(POD),catalase(CAT),soluble protein and proline(Pro)were inhibited to varying degrees,while the permeability of plasma membrane and the content of malondialdehyde(MDA)experienced significant increases.In comparison with CK_(2),the introduction of exogenous salicylic acid(SA)resulted in significant enhancements in the germination and seedling growth of Astragalus mongolica(P<0.05).Furthermore,there were notable reductions in plasma membrane permeability and the content of membrane lipid peroxidation product malondialdehyde(MDA),ranging from 40.21%to 56.56%and 20.09%to 46.39%,respectively.The activities of antioxidant enzymes,including SOD,POD,and CAT,as well as root activity,displayed varying degrees of enhancement.Additionally,there was a noteworthy increase in the accumulation of free proline and soluble proteins,which are essential osmoregulatory substances,by percentages ranging from 8.86%to 25.57%and 13.10%to 42.13%,respectively.[Conclusion]Exogenous Salicylic acid has proven to be a potent regulator of the inhibitory effects of NaHCO_(3)stress on both seed germination and seedling growth in Astragalus.It alleviates effectively osmotic pressure and mitigates damage caused by membrane lipid peroxidation in Astragalus seedlings.Furthermore,it enhances the adaptability and salt-alkali resistance of both Astragalus seeds and seedlings when exposed to salt-alkali stress.The concentration of 0.3 mmol/L exhibits the optimal alleviating impact.