Effects of salicylic acid on growth and physiological characteristics of Astragalus mongholicus seedlings under NaHCO3 stress
[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 NaHCO3 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 NaHCO3 stress as control 1(CK1),and the treatmentwithout SA and NaHCO3 stress as control 2(CK2)were designed,and the seed germination index,seedling growth and physiological index of Astragalus mongolicus were measured.[Result]In response to NaHCO3 induced stress in CK2,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 CK2,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 NaHCO3 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.
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