Comparative Study On The Response Of Rhus Chinensis Mill.and R.taisanensis S.B.Liang To Drought Stress And Waterlogging Stress

With the continuous change of global climate,drought and waterlogging disasters occur frequently,and plant growth and development are seriously affected.It is more and more important to explain the mechanism of drought and waterlogging tolerance of plants.Therefore,in this experiment,the seedlings of Rhus chinensis Mill.and R.taisanensis S.B.Liang were used as experimental materials,and five time gradients(0d,5d,10 d,15d,20d)were set up to compare the morphological and physiological responses of the two species of Rhus to drought and flooding stress.The comprehensive evaluation of its stress resistance was carried out by using membership function and other methods,which provided a theoretical basis for the selection of drought and waterlogging tolerance germplasm and the application of stress resistance cultivation.The main results are as follows :(1)Under drought stress,with the prolongation of stress time,the damage degree of leaves of two kinds of Rhus increased gradually.On the 10 th day of stress treatment,the tail of leaves of Rhus chinensis Mill.curled and the plant wilted,while on the 15 th day of stress treatment,the edge of leaves of R.taisanensis S.B.Liang curled and wilted.The leaf relative water content,leaf thickness,upper and lower epidermis thickness,sponge tissue thickness,palisade tissue thickness and xylem area of the two kinds of Rhus showed a downward trend.The photosynthesis of the two species of Rhu was inhibited to varying degrees,showing that chlorophyll content,carotenoid content,net photosynthetic rate(Pn),transpiration rate(Tr),stomatal conductance(Gs),maximum photochemical efficiency of PSII(Fv/Fm),potential photochemical efficiency(Fv/Fo),and photochemical quenching coefficient(q P)all showed a downward trend,while intercellular carbon dioxide concentration(Ci)decreased first and then increased,and non-photochemical quenching coefficient(NPQ)increased first and then decreased.The relative conductivity and MDA content of the two kinds of Rhus showed an upward trend,and the osmotic adjustment substances were significantly accumulated.Among them,the contents of proline(Pro),soluble sugar(SS)and soluble protein(SP)in the leaves of Rhus chinensis Mill.increased first and then decreased,while the contents of Pro and SS in the leaves of R.taisanensis S.B.Liang continued to increase,and the content of SP increased first and then decreased.The contents of superoxide anion,hydrogen peroxide and anthocyanin in the two species of Rhus showed a continuous upward trend.The activities of SOD,APX and CAT increased first and then decreased,and the activity of POD showed a continuous upward trend.(2)Under waterlogging stress,with the prolongation of stress time,the damage degree of the leaves of the two kinds of Rhus gradually increased.The leaves of Rhus chinensis Mill.began to fade green and yellow on the 10 th day of stress treatment,and the plants wilted.However,the leaves of R.taisanensis S.B.Liang began to wilt on the 15 th day of stress treatment.The leaf relative water content,leaf thickness,upper and lower epidermis thickness,sponge tissue thickness,palisade tissue thickness and xylem area of the two kinds of Rhus showed a downward trend.The photosynthesis of the two species of Rhus was inhibited to varying degrees.The chlorophyll content,carotenoid content,Pn,Tr,Gs,Fv/Fm,and Fv/Fo all showed a downward trend,while Ci and q P decreased first and then increased,ФPSII increased first and then decreased,and NPQ continued to increase.Relative conductivity,MDA content,SS,SP and Pro content showed an upward trend.The contents of superoxide anion,hydrogen peroxide and anthocyanin in the two species of Rhus showed a continuous upward trend.The activities of SOD,CAT and APX increased first and then decreased,and the POD activity showed a continuous upward trend.(3)In summary,combined with correlation analysis,principal component analysis and membership function,the comprehensive evaluation of two kinds of Rhus showed that R.taisanensis S.B.Liang had stronger drought tolerance and waterlogging tolerance.