Physiological Response Of Primula Forbesii Franch. To Cadmium Stress And Mitigation Effect Of Exogenous Salicylic Acid

In recent years,with the development of society,the problem of heavy metal pollution in soil has become more and more serious,especially cadmium（Cd）pollution,which affects plant growth in varying degrees and seriously endangers human health.Primula forbesii Franch.is a unique Primula plant in China.It mainly produces in Yunnan,Sichuan and other places.It blossoms in early spring with bright colors,rich flower patterns,strong flower fragrance,high ornamental value,and can self-sow and multiply,so it is a ground cover plant with great potential for popularization.At present,the physiological response of P.forbesii to cadmium and the alleviating effect of exogenous substances have not been reported at home and abroad.In this paper,the possibility of the application of P.forbesii as an ornamental ground cover plant in cadmium-contaminated soil was studied.The physiological response of P.forbesii seed germination and plant growth under cadmium stress and the alleviation effect of exogenous salicylic acid on the seed germination and plant growth of P.forbesii under cadmium stress were studied.The main conclusions are as follows:1.Different concentrations of cadmium stress on Seed Germination of P.forbesii showed that low concentration（0.5 mg/L）of cadmium stress promoted seed germination of P.forbesii;moderate cadmium stress（10 mg/L）significantly reduced seed germination rate,germination index,root length and fresh weight of P.forbesii;serious cadmium stress（20-40 mg/L）significantly inhibited seed germination of P.forbesii.2.The growth,photosynthesis,osmotic regulation,membrane lipid peroxidation,antioxidant system and ion content in roots,stems and leaves of P.forbesii under different cadmium concentrations were studied.Under cadmium stress,the plant of P.forbesii was short,its leaves and stems showed purple red,and its leaves showed yellow spots.Light cadmium stress（5,50 mg/kg）promoted photosynthesis of P.forbesii,and inhibited photosynthesis of P.forbesii when cadmium concentration exceeded 100 mg/kg.Under high concentration of cadmium stress,cell membrane permeability increased,osmotic regulators leaked,soluble sugar and soluble protein content decreased,superoxide anion radical production rate,H₂O₂content and MDA content increased.Cadmium content in leaves,stems and roots of P.forbesii increased significantly,zinc content decreased significantly,potassium content in leaves and stems increased first and then decreased,potassium content in roots decreased,calcium and magnesium content in leaves and roots increased significantly.P.forbesii can increase the activity of CAT,POD,APX and GR,As A content and GSH content to reduce injury caused by cadmium.3.This study showed that exogenous salicylic acid at a certain concentration could effectively alleviate the damage of cadmium stress on P.forbesii seed germination.When the cadmium stress concentration was 10 mg/L,the optimal alleviating concentration of exogenous salicylic acid soaking seeds was 25μmol/L,which might cause new stress damage to P.forbesii seed germination.4.Through spraying different concentrations of exogenous salicylic acid on P.forbesii under 150mg/kg cadmium stress,this study concluded that spraying a certain concentration of exogenous salicylic acid could alleviate the damage of cadmium stress on P.forbesii plants to a certain extent.Based on the analysis of various indicators,the best mitigation effect of spraying 100μmol/L exogenous salicylic acid on P.forbesii plants under 150 mg/kg cadmium stress was obtained.This study explored the seed germination,plant growth and physiological response of P.forbesii under cadmium stress,as well as the mitigation effect of exogenous salicylic acid on it under cadmium stress,explored the possibility of planting and cultivation of P.forbesii in cadmium-contaminated soil,and provided theoretical basis for applying exogenous substances to improve the resistance of P.forbesii to cadmium.The application of new flower-scented ground cover plants in gardens polluted by cadmium in soil provides a theoretical basis.