Response Of Catalpa Bungei To Salt Stress And Mitigation Effect Of Exogenous Abscisic Acid

Catalpa bungei is a unique and valuable timber tree species in China.Salinized soil area in Jiangsu is large,which seriously restricts the development of Catalpa bungei timber forest industry.Abscisic acid(ABA),as a recognized stress hormone,plays an excellent regulatory role in inducing plants to enhance their stress resistance.It is of great significance to select salt-tolerant and saltresistant varieties of Catalpa bungei and explore the response mechanism of growth and physiological level of Catalpa bungei to salt stress and the effect of ABA on growth physiology of Catalpa bungei under salt stress,which is of great significance to promote the rapid development of Catalpa bungei in salinized areas.In this study,the growth and physiological changes of Catalpa bungei seedlings under salt stress(0.5% Na Cl)were studied by pot experiment,and the alleviating effects of different ABA concentrations(15 mg/L,25 mg/L,35 mg/L)on Catalpa bungei seedlings under salt stress at different stages(before and after salt stress)were discussed.To provide theoretical basis for improving salt-tolerance of Catalpa bungei.The main results are as follows:1.Under salt stress,the seedling leaves of the two cultivars showed different degrees of salt damage symptoms,among which the salt damage symptoms of the leaves of Su Qiu 1 were more serious than Catalpa bungei 008-1.The salt damage index of Su Qiu 1 increased gradually with the extension of salt stress time,and the salt damage index of Su Qiu 1 was higher than Catalpa bungei008-1 at all time periods.Under 28 days of stress,most branches of Su Qiu 1 were withered,leaves fell and died,while Catalpa bungei 008-1 had most tips and leaf margins withered,deciduous and some died.2.Salt stress had certain effect on physiology of Catalpa bungei.With the extension of stress time,the relative electrical conductivity of the seedlings of the two cultivars increased first and then decreased.Chlorophyll content and relative water content of leaves showed a decreasing trend.Soluble sugar content,soluble protein content,free proline content and SOD activity increased first and then decreased.The relative electrical conductivity of Catalpa bungei 008-1 was significantly lower than that of Su Qiu 1,while the chlorophyll content,relative water content,soluble sugar content,soluble protein content,free proline content and SOD activity of Catalpa bungei 008-1were significantly higher than those of Su Qiu 1.3.In the early stage of salt stress,exogenous ABA can alleviate the effects of salt stress on Catalpa bungei seedlings to some extent.And it was found that 35 mg/L exogenous ABA significantly increased seedling height diameter increment,early germination of new leaves and survival rate of Catalpa bungei under salt stress.At the same time,35 mg/L ABA treatment reduced the relative electrical conductivity of Catalpa bungei under salt stress,increased chlorophyll content,leaf relative water content,soluble sugar content,soluble protein content,free proline content,increased SOD,POD and CAT activities,and promoted the accumulation of endogenous hormones.The effect of salt stress on photosynthetic system was alleviated4.In the late stage of salt stress,exogenous ABA can alleviate the effects of salt stress on the seedlings of Catalpa bungei to some extent.It was found that exogenous ABA treatment at 25mg/L significantly increased the seedling height increase,promoted the early germination of new leaves and improved the survival rate of Catalpa bungei under salt stress.At the same time,25mg/L ABA sprayed after salt stress significantly reduced the relative electrical conductivity of Catalpa bungei under salt stress,increased the relative water content,soluble sugar content,soluble protein content and free proline content of leaves,increased the activities of SOD,POD and CAT,promoted the accumulation of endogenous hormones,and improved the photosynthetic parameters and chlorophyll fluorescence parameters.5.The membership function was used to comprehensively evaluate the application of abscisic acid in the early stage of salt stress and the late stage of salt stress,and it was found that the overall effect of abscisic acid in the late stage of salt stress was better.