Photosynthetic and Physiological Responses of Red Bud Taro Transplantating Seedlings under Salt Stress

The photosynthetic and physiological responses of Jiangxi Yanshan red bud taro(Colocasia esculenta L.Schott var.cormosus cv.Hongyayu)transplantating seedlings under 50,100,150,200,250mmol· L-1 and 0(CK)of salt stress were studied using its transplantation seedlings.The results showed that:(1) The biomass and root shoot ratio of seedling increased under low salt stress(50mmol·L-1),and inhibited under high salt stress(100~250mmol·L-1).(2)Under low salt stress,the photosynthetic rate(Pn),stomatal conductance(Gs),stomatal limitation value(Ls),water use efficiency(WUE)and instantaneous carboxylation efficiency(CUE)of seedling significantly increased compared with the control(0mmol· L-1),its intercellular CO2 concentration(Ci)decreased significantly compared with the control,and its transpiration rate(Tr)had no significant difference compared with the control.Under the high salt stress,Pn,Ls,WUE,CUE,Gs and Tr of seedling decreased significantly and its Ci increased significantly compared with the control.(3)Under low salt stress,the maximal fluorescence(Fm),photochemical quenching coefficient(Fv /F0)and photochemical quenching coefficient(q P)of seedling significantly increased compared with the control;initial fluorescence(F0)decreased significantly compared with the control.PSⅡ maximal photochemical efficiency(Fv /Fm),actual photochemical efficiency of PSⅡ(ΦPSⅡ),open PSⅡreaction center capture the excitation energy efficiency(Fv ′/Fm ′)and non photochemical quenching coefficient(NPQ) had no significant difference compared with the control.Under the high salt stress,F0,Fm,Fv /Fm,Fv /F0,ΦPSⅡ,Fv ′/Fm ′and q P of seedling decreased significantly compared with the control;NPQincreased significantly compared with the control.(4)Under salt stresses,soluble protein content,peroxidase,superoxide dismutase and catalase activities of seedling increased first and then decreased compared with the control,reaching the peak at 50mmol·L-1,while its content of total soluble sugar and proline were increased significantly compared with the control;its MDA content and plasma membrane permeability had no significant change at 0~50mmol·L-1 and began to increase significantly from 100mmol·L-1;its chlorophyll content and root activity had no significant change at 0~50mmol·L-1 and began to decrease significantly from 100mmol·L-1.The study indicated that Jiangxi Yanshan red bud taro transplantation seedlings salt tolerance threshold was 50mmol·L-1,which could promote the increase of the soluble protein content,the activities of peroxidase,superoxide dismutase and catalase;maintain the membrane permeability,the chlorophyll content and root activity;increase PSⅡ maximal photochemical efficiency;improve the PSⅡelectronic transfer activity,maintain actual photochemical efficiency of PSⅡ,waste excess light energy as heat by the effective starting non radiative heat energy dissipation mechanisms,thus protect the photosynthetic apparatus,and ultimately enhance net photosynthetic rate and increase the biomass.