Alleviating Effects Of Different Alleviating Agents On Strawberry Seedlings Under NaCl Stress

Object:This trial involves exposing a strawberry seedling to NaCl stress,exogenous Spermidine Melatonin,and CaCl₂to investigate its impact on growth indicators,photosynthetic properties,antioxidant defense systems,and ion content.Providing theoretical basis for exploring the physiological and biochemical impact of strawberry seedlings under NaCl stress.Methods:‘Sweet Charles’with 7-8 leaves is experimental materials and 5 g·L^-1of NaCl as a concentration of salt stress,exogenous application of Spd,MT and CaCl₂,at 3d,6d and 9d sampling respectively.Results:（1）NaCl stress significantly reduces the growth and development indicators（plant height,stem diameter,fresh weight per plant,relative water content）,photosynthetic pigment content（Chl a,Chl b,Chl a+b,Car）,photosynthetic characteristic index（Pn,Ci,Tr,Gs）,ion content(K⁺,Ca²⁺,Mg²⁺),and GSH/GSSG ratio,improved oxidase activity（POD,CAT,SOD,APX）,non-enzymatic system GSH,Pro,SP,MDA content,O₂^-generate rate and Na⁺content of strawberry seedlings in the entire treatment period.（2）Exogenous application Spd,MT and CaCl₂can improve the plant height,stem diameter,fresh weight per plant,relative water content of strawberry seedlings under NaCl stress,enhance the plant resistance,relieve salt stress on plant growth and development inhibition.The Spd 0.5 mmol·L^-1is the best treatment,the CaCl₂5 mmol·L^-1is the weakest.（3）Under the NaCl stress,exogenous application of Spd,MT and CaCl₂can improve the photosynthetic content（Chl a,Chl b,Chl a+b,Car）and improve photosynthetic characteristics（Pn,Ci,Tr,Gs）of strawberry seedlings.It indicates that the exogenous application of a mitigation agent protects the photosynthetic mechanism of the strawberry seedlings and effectively mitigate the damage to the strawberry light system.The MT 0.1 mmol·L^-1is the best treatment,the MT 0.5 mmol·L^-1is least effective.（4）Exogenous application of Spd,MT and CaCl₂can improve the antioxidant enzyme activity（POD,CAT,SOD,APX）,non-enzymatic system GSH,Pro,SP,reduce the ratio of GSH/GSSG,MDA content and O₂^-generation rate of strawberry seedlings under NaCl stress.The results indicated that exogenous mitigators could reduce the degree of membrane lipid peroxidation and alleviate the oxidative stress caused by salt stress on strawberry seedlings.The Spd 0.5 mmol·L^-1is the best treatment,while CaCl₂5 mmol·L^-1is the least effective.（5）Under NaCl stress,exogenous application of Spd,MT and CaCl₂can increase the K⁺,Ca²⁺and Mg²⁺content of strawberry seedlings,and reduce Na⁺content.The ion balance of strawberry seedling leaves is reduced in order to reduce the negative effects of ionic toxicity on plants.The Spd 0.5 mmol·L^-1is the best treatment,while CaCl₂5 mmol·L^-1is the least effective.Conclusion:Comprehensive evaluation of different concentrations of Spd,MT and CaCl₂,ranked from high to low:Spd 0.5 mmol·L^-1>MT 0.3 mmol·L^-1>MT 0.1 mmol·L^-1>CaCl₂10 mmol·L^-1>Spd 1.0mmol·L^-1>Spd 0.25 mmol·L^-1>CaCl₂20 mmol·L^-1>MT 0.5 mmol·L^-1>CaCl₂5 mmol·L^-1.Discover Spd 0.5 mmol·L^-1,MT 0.3 mmol·L^-1and 0.1 mmol·L^-1,CaCl₂10 mmol·L^-1of strawberry seedlings under NaCl stress relieve the best.