Effects Of Exogenous Calcium Chloride And Calcium Nitrate On The Growth And Physiological Characteristics Of Alfalfa Under Waterlogging Stress

Alfalfa(Medicago sativa L.)is a perennial leguminous forage with high yield,good quality,multiple utilization methods and good palatability.It is currently the most widely cultivated fine forage with the highest economic value in the world.Alfalfa is highly resistant to stress,but it is easily affected by waterlogging stress when cultivated in the south of my country,which is one of the main factors restricting its expansion of cultivation area and increase of yield in the south.At present,there is a shortage of high-quality forage grass,so improving the waterlogging tolerance of alfalfa and improving the yield and quality of alfalfa under waterlogging stress are the top priorities for vigorously developing southern grassland husbandry.In this study,the waterlogging-sensitive alfalfa variety WL-712 was used as the test material.Potted planting method was used to simulate waterlogging stress conditions.The effects of exogenous calcium chloride and calcium nitrate on the agronomic characteristics of alfalfa under waterlogging stress were investigated.The impact of related physiological indicators.The main findings are as follows:1.Exogenous spraying of calcium chloride has a certain mitigation effect on the damage of alfalfa leaves and roots from waterlogging stress.The main performance is:Compared with the alfalfa treated with only waterlogging stress,spraying calcium chloride can significantly increase the plant height,root length and aboveground biomass of alfalfa under waterlogging stress(p<0.05).After spraying 5 mmol·L-1 calcium chloride,the soluble protein content in the leaves of alfalfa increased significantly under waterlogging stress(p<0.05),and the soluble sugar content in the root system was sprayed at 5 mmol·L-1 and 10 mmol·L-1 When the calcium chloride of mmol·L-1 increased,the soluble protein content increased significantly after spraying different concentrations of calcium chloride(p<0.05).Spraying different concentrations of calcium chloride on alfalfa under waterlogging stress can significantly reduce the relative electrical conductivity and MDA content of leaves and roots(p<0.05).However,the application of calcium chloride increased the activities of SOD and CAT in the leaves of alfalfa under waterlogging stress and decreased its POD activity.The activities of SOD and CAT in the roots also increased,but the POD activity was only sprayed at 10 mmol-L-1 and 15 mmol·L-1 calcium chloride treatment significantly improved.Spraying different concentrations of calcium chloride increased the total chlorophyll a,chlorophyll b and total chlorophyll of alfalfa under waterlogging stress.2.Exogenous spraying of calcium nitrate has a certain mitigation effect on the damage caused by waterlogging stress in the leaves and roots of alfalfa.The main performance is:Compared with the alfalfa that only undergoes waterlogging stress,spraying calcium chloride can increase the plant height and aboveground biomass of alfalfa under waterlogging stress,and when spraying 5 mmol·L-1 Plant height and above-ground biomass increased significantly when calcium nitrate was applied(p<0.05).Root length and underground biomass also increased when 5 mmol·L-1 calcium nitrate was sprayed.Spraying different concentrations of calcium nitrate all increased the total amount of chlorophyll a,chlorophyll b and chlorophyll of alfalfa under waterlogging stress,but the increase in their content decreased with the increase of calcium nitrate concentration.After spraying 5 mmol·L-1 and 10 mmol·L-1 of calcium nitrate,the soluble protein content in the leaves and roots of alfalfa under waterlogging stress was significantly increased(p<0.05),and the concentration of calcium nitrate was at 15 mmol·L-1,the soluble protein content in leaves and roots also increased but not significantly.However,spraying three concentrations of calcium nitrate had no significant effect on the soluble sugar content of alfalfa leaves and roots under waterlogging stress.Alfalfa under waterlogging stress sprayed with different concentrations of calcium nitrate can significantly reduce the relative conductivity and MDA content in leaves and roots(p<0.05).However,the spraying of calcium nitrate increased the SOD activity in alfalfa leaves under waterlogging stress and reduced the POD activity.The CAT activity was only increased when 5 mmol·L-1 calcium nitrate was sprayed.The activities of SOD,CAT and POD in the roots of alfalfa under waterlogging stress increased after spraying different concentrations of calcium nitrate.In summary,the addition of external sources of calcium chloride and calcium nitrate can effectively alleviate the damage of waterlogging stress on the leaves and roots of alfalfa,and the changes of various indicators in the leaves and roots are roughly the same.This conclusion provides a certain degree of theoretical reference for using exogenous additives to improve the waterlogging tolerance of alfalfa.