Mitigative Effect Of Exogenous 24-epicarnoside On Grape Seedings Under Copper Ion Stress

In this study,Cabernet Sauvignon was used as the test material.The grape seedlings were pretreated with different concentrations of 24-epibrassinolide（EBR）in nutrient solution,and then treated with 120μM copper ion（CuSO₄）to study the effects of exogenous EBR on the growth,active oxygen metabolism and osmotic adjustment of grape roots under copper ion stress,as well as the effects of exogenous EBR on the active oxygen metabolism,osmotic regulation,antioxidant enzyme activity,glutathione circulatory system and endogenous hormones.The main results obtained:（1）The total root length,root surface area,root volume,root diameter and root tip number of the grape seedling were reduced by copper ion stress compared with the control.The exogenous EBR pretreatment could alleviate the total root length,root volume,root mean diameter and root tip number.This experiment showed that 0.10 mg L^-1 EBR had the highest degree of alleviative effect.（2）The contents of hydrogen peroxide（H₂O₂）,superoxide anion（O₂^-）and malondialdehyde（MDA）in the root system of grape were significantly increased under copper ion stress,while the exogenous EBR treatments had the opposite effects.The damage of the active oxygen to the grape root system also decreased under EBR pretreatments,and the content of proline and soluble protein in the root system was effectively improved,while maintaining the moisture balance in the plant.（3）The content of H₂O₂,O₂^-,MDA in grape leaves increased significantly under copper ion stress.While the leaves of the grapes treated with exogenous EBR not only reduced the contents of H₂O₂,O₂^-,MDA,but also increased the contents of soluble protein and proline.Superoxide dismutase（SOD）,Catalase（CAT）,Peroxidase oxidase（POD）activity had also been improved under EBR pretreatment,making the resistance of grape seedlings increased,thereby reducing the copper ion stress on the seedlings.The experimental results showed that the treatment effect of 0.10 mg L^-1 EBR was the most obvious.（4）Copper ion stress affected the ascorbate-glutathione cycle（AsA-GSH cycle）in grapes,and the antioxidant and enzyme activity in the cycle could not maintain the balance of active oxygen metabolism.The enzyme activities of Monodehydroascorbate reductase（MDHAR）,Glutathione peroxidase（GR）,Ascorbate peroxidase（APX）and Dehydroascorbate reductase（DHAR）could be enhanced by exogenous EBR treatment.EBR pretreatment could also increase the content of Glutathione（GSH）and Ascorbic acid（AsA）,effectively remove the active oxygen free radicals and keep the grape leaves to maintain the higher AsA/DHA and GSH/GSSG ratios.What’s more,EBR could maintain the redox environment in grape,enhance the operation efficiency of AsA-GSH cycle and reduce the oxidative damage induced by copper stress on grape seedlings.The results showed that the effect of 0.10 mg L^-1 EBR on AsA-GSH cycle efficiency was the most obvious.（5）Copper ion stress also affected the content of endogenous hormones in grape seedlings.Exogenous EBR treatment could regulate the content of endogenous hormones in grapes,and increase the contents of Salicylic acid（SA）,Abscisic acid（ABA）and Jasmonic acid（JA）,and enhance the tolerance of grape seedlings to copper stress.In conclusion,under different concentrations of copper ion stress,different concentrations of EBR pretreatment played active roles in grape seedling.The antioxidant enzyme activity,osmotic regulation and glutathione cycling efficiency of grape seedlings were improved,and the production of reactive oxygen species can be inhibited,and ultimately reduced the copper ion stress on grape seedlings damage.The experimental data showed that the concentration of 0.10 mg L^-11 EBR treatment was most beneficial to seedling growth.