Regulation Mechanism Of Molybdenum On Seedling Growth Of Lycium Ruthenicum Under Salt Stress

Lycium ruthenicum has great potential medicinal,economic and ecological value.There are serious problems of soil barrenness and salinization in many artificial planting areas in Xinjiang,China.Microelement molybdenum has significant effect on improving plant response to stress.Therefore,by simulating the salt stress environment,the growth regulation mechanism of molybdenum on Lycium ruthenicum seedlings under salt stress was studied,in order to provide scientific theoretical data for understanding comprehensively the role of molybdenum in enhancing the resistance of Lycium ruthenicum to salt damage in the future,and to provide important guidance for artificial planting of Lycium ruthenicum plants with stronger stress resistance on large areas of saline-alkali soil in Xinjiang.The main achievements are as follows:（1）Under salt stress,the seedlings of Lycium ruthenicum will show some stress symptoms,such as stem curvature,leaf wilting,crown closure and so on.The initial symptoms of stress are very obvious,and then the symptoms are alleviated,which indicates that Lycium ruthenicum has a unique response to salt stress.However,molybdenum application can effectively alleviate the symptoms of salt stress in Lycium ruthenicum seedlings.It can alleviate the damage of salt stress to seedlings mainly by increasing the thick horn tissue of cross-section cortex,enlarging the area of pith and increasing the number and aperture of xylem and phloem vessels in vascular bundles.Field experiments showed that application of molybdenum could significantly increase fruit quantity and yield of Lycium ruthenicum,decrease soil p H value,increase soil fertility and decrease soluble salt content.It can be seen that molybdenum has a significant effect on increasing the yield of Lycium ruthenicum and alleviating soil salinization.（2）The effects of molybdenum on the growth and physiological characteristics of Lycium ruthenicum seedlings under salt stress were studied by hydroponic experiments.It was found that 1μmol/LMo could promote the growth of plant height and root system of Lycium ruthenicum seedlings under salt stress,and the biomass increased significantly,which effectively alleviated the damage of salt stress on the growth of Lycium ruthenicum seedlings.The content of chlorophyll a,b and total chlorophyll in leaves of Lycium ruthenicum seedlings increased sharply under the condition of molybdenum application.The net photosynthetic rate,stomatal conductance,transpiration rate and intercellular CO₂concentration in leaves of Lycium ruthenicum seedlings also increased under the condition of molybdenum application.Under salt stress,Lycium ruthenicum seedlings accumulated a large amount of hydrogen peroxide and MDA,while molybdenum application could reduce the content of hydrogen peroxide and MDA in Lycium ruthenicum seedlings leaves.The activities of antioxidant enzymes（SOD,POD,CAT）in Lycium ruthenicum seedlings leaves were also greatly enhanced under molybdenum application conditions,effectively eliminating excess reactive oxygen radicals in seedling leaves and reducing the degree of lipid peroxidation in cell membranes.（3）Under salt stress,the contents of soluble sugar and soluble protein in Lycium ruthenicum seedlings decreased significantly,while the content of proline increased continuously.1μmol/LMo could further increase the synthesis of three osmotic regulators.Compared with soluble sugar and protein,proline content in Lycium ruthenicum seedlings increased most significantly under salt stress.Continuing to study the pathway of proline synthesis and metabolism,we found that the activities of P5CS,HXK and GDH related to the pathway of proline synthesis increased,while the activities of ornithine transaminase（Delta-OAT）increased first and then decreased,while the activities of Pro DH related to the pathway of proline degradation showed a downward trend.In summary,glutamic acid is the main metabolic pathway of proline in Lycium ruthenicum seedlings,and the osmotic regulation ability of Lycium ruthenicum seedlings can be improved by synthesizing large amounts of proline.However,how molybdenum plays a role in the proline metabolism pathway of Lycium ruthenicum seedlings is the focus of further research in the future.