Study On Physiological Response Of Ardisia Japonica To Salt-alkali Stress

Ardisia japonica(Thunb)Blume is a low ornamental shrub belonging to the genus Ardisia.Its ornamental value and medicinal value were high,and was widely used as ground cover in gardens.The growth and adaptability in saline soils with different ingredients and concentrations were very important for the selection of salt-tolerant plants,improving the utilization rate of saline-alkali land,promoting the wide application of A.japonica in gardens,and improving the economic benefits of A.japonica.The physical effect and tolerance mechanisms of NaCl,Na2CO3 and NaCl+Na2CO3(1:1)mixed salt-alkali at 0.2%,0.3%,0.4%,0.5%,0.6%treatment on three-year-old A.japonica by measuring the plant height growth,root water content,stem water content and leaf water content,membrane lipid peroxidation products,osmotic adjustment substances,chlorophyll content,chlorophyll fluorescence parameters,light and indicators.The following conclusions were obtained:1 With the increasing of salt-alkali concentration and the extension of stress time,the height growth,root water content,stem water content,and leaf water content of A.japonica decreased gradually.2 With the increasing of salt-alkali concentration,the soluble protein and soluble sugar content in the leaves of A.japonica increased first and then decreased.The content of MDA of A.japonica leaves increased with the prolong of stress time.The content of SOD increased first and decreased with the extension of the stress time.3 With the increasing of stress time,the leaf chlorophyll content,the original light energy conversion efficiency(Fv/Fm)and the electron transfer rate(ETR),photochemical quenching coefficient(qp)of A.japonica decreased,PS Ⅱeffective photochemical quantum yield(Fv’/Fm’)increases first and then decreases,and the minimum initial fluorescence(Fo)increased.With the increasing of photosynthetic active radiation,the net photosynthetic rate of A.japonica first increased and then decreased slightly.The changes of maximum net photosynthetic rate(Pmax),light saturation point(LSP),dark respiration rate(Rd),transpiration rate(Tr)and single leaf water use efficiency(WUE)of A.japonica leaves were basically the same.All of which gradually decreased with the increasing of salt-alkali concentration,and the light compensation point(LCP)showed an upward trend with the increasing of salt-alkali concentration.4 Through the comparison of membership functions,the effects of the three salt-alkali treatments on A.japonica were Na2CO3>NaCl+Na2CO3>NaCl.It showed that Na2CO3 salt inhibited the growth of plant stronger than that of NaCl.5 The adaptation mechanism of A.japonica to high concentration salt-alkali stress was analyzed from three aspects:composition and structure,function and metabolism,and growth;The reasons for the decline of growth rate of A.japonica were analyzed by energy utilization.In summary,0.3%NaCl salt,0.2%Na2CO3 salt,0.3%NaCl+Na2CO3 salt-alkali concentration did not have significant effect on the growth and physiology of A.japonica.The effects of three salt treatments on the A.japonica were Na2CO3>NaCl+Na2CO3>NaCl.