Effects Of Drought And Salt Stress On Physiological And Ecological Responses Of Dalbergia Odorifera T.Chen To Exogenous Substances Application

Dalbergia odorifera T.Chen is a precious tree species of redwood and also one of the precious Chinese medicinal materials.It is also an excellent tree species of urban green space with great potential for development.It is a rare species of redwood unique to China,and it is one of the second-class important protected plants in China.It is an endemic specie to China used in commercial trade because of its high technological value and medicinal value.Unreasonable harvesting causes its wild resources to be depleted day by day.D.odorifera native to Hainan can grows in high-temperature and rainy environment.It is also distributed in Guangdong,Guangxi,Sichuan and Fujian after introduction and cultivation.The introduction and cultivation of D.odorifera facing inland areas was restricted by drought stress,and the application of D.odorifera as a protective forest in coastal beach area is limited by salt stress.Therefore,it’s important to study the resistance of D.odorifera against drought and salt stress to promote its introduction and cultivation in differents areas.In this study,one-year-old seedlings of D.odorifera from Jianfengling,Ledong County,Hainan Province,were used as experimental materials.The physiological and ecological effects of exogenous calcium chloride(5 mmol/L)and melatonin(600μmol/L)on the physiological and ecological effects of drought stress on the seedlings of D.odorifera were studied.Application of exogenous potassium silicate(1 mmol/L)and betaine(10 mmol/L)the physiological and ecological effects of salt stress on D.odorifera.The purpose of this study was to improve the tolerance to drought stress and salt stress,to solve the key scientific problems in the introduction and cultivation of D.odorifera in Subtropical region,and to solve the key scientific problems in its use as a protective forest in coastal beach areas.The main conclusions of this study are as follows:(1)Drought stress had a negative effect on the growth,development and physiological and ecological of D.odorifera.Under normal water,adding exogenous calcium chloride,melatonin and both combined had a beneficial effect on the growth,development,physiological and ecological of D.odorifera,combined with the analysis of membership function,The growth-promoting effect of the interaction between them was better than that of adding calcium chloride and melatonin alone,and the effect of adding calcium chloride alone was better than that of adding melatonin alone.Compared with the control,only adding exogenous calcium chloride,melatonin and its interaction under drought stress can through leaf water status(leaf relative water content,leaf dew point water potential,leaf instantaneous water use efficiency),pigment content(chlorophyll a,chlorophyll b,total chlorophyll,carotenoid),gas exchange(photosynthetic rate,Stomatal conductance,intercellular carbon dioxide concentration,transpiration rate),Redox equilibrium(hydrogen peroxide content,peroxidase activity,catalase activity,superoxide enzyme activity,ascorbic acid content),osmotic regulation balance(proline content,Soluble protein content,soluble sugar content),cell membrane permeability(malondialdehyde content,relative conductivity of leaves),endogenous hormone content(auxin content)and other aspects of regulation to improve the drought resistance of D.odorifera,combined with membership function analysis,the effect of interaction on drought resistance of D.odorifera was better than that of adding melatonin and calcium chloride alone,and adding melatonin alone on the drought resistance of D.odorifera was better than that of adding calcium chloride alone,but it could not reach the growth level of D.odorifera under normal water condition.(2)Salt stress could inhibit the growth and development of D.odorifera and adversely affect the physiological and ecological of the seedlings.Under normal water condition,adding exogenous potassium silicate,betaine and exogenous potassium silicate and betaine at the same time had a beneficial effect on the growth,development and physiological and ecological of D.odorifera,combined with the analysis of membership function,The growth-promoting effect of potassium silicate alone was better than that of betaine alone,and both of them were superior to their interaction.Under salt stress,exogenous potassium silicate,betaine and their interaction were added separately,through leaf water status(leaf relative water content,leaf dew point water potential,leaf instantaneous water use efficiency),pigment content(chlorophyll a,chlorophyll b,total chlorophyll,carotenoid),gas exchange(photosynthetic rate,Stomatal conductance,intercellular carbon dioxide concentration,transpiration rate),redox equilibrium(superoxide dismutase activity,reduced glutathione content),osmotic regulation balance(Proline content,soluble sugar content,soluble protein content),cell membrane permeability(relative conductivity of leaves)and other aspects of regulation to improve the tolerance of the seedlings of D.odorifera in salt stress environment,combined with the analysis of membership function,the effect of interaction was better than that of adding betaine and potassium silicate alone to enhance the tolerance of D.odorifera in salt stress environment,The effect of adding betaine alone was better than that of adding potassium silicate alone,but it could not reach the growth level of D.odorifera under normal water condition.(3)The effects of exogenous calcium chloride,melatonin and their interaction on the growth of D.odorifera were different,and the interaction effect was the best.The effects of exogenous calcium chloride,melatonin and their interaction on the tolerance of D.odorifera under drought stress were different and the interaction effect was the best.The effects of exogenous potassium silicate,betaine and their interaction on the growth of D.odorifera were different,between which adding exogenous potassium silicate alone had the best effect.The effects of exogenous potassium silicate,betaine and their interaction on the tolerance of D.odorifera under salt stress were different,and the interaction effect was the best.The effects of different exogenous substances on the growth and stress resistance of the same plant were different,and the effects of different exogenous substances on the resistance of the same plant under different stresses were different.