| The increasing soil salinisation has seriously affecting plant growth and production.The breeding and utilization of salt-tolerant plants is a direct and powerful measure to improve the productivity and utilisation rate of saline soil.Therefore,the biennial and five-year potted seedlings of Callerya tsui(F.P.Metcalf)Z.Wei&Pedley and Millettia pachycarpa Benth.were selected as experimental materials.With 0%as the control(CK),concentrations of 0.2%,0.4%,0.6%,0.8%and 1.0%NaCl stress were set and their growth,physiological and photosynthetic indices were observed on days 0,10,20,30 and 40 of stress,respectively.In order to explore the tolerance and corresponding physiological response mechanism of C.tsui and M.pachycarpa,and provide reference for their salt resistance evaluation and scientific basis for their popularization and application.The main results are as follows:(1)With the increase of NaCl concentration,the relative growth of plant height and ground diameter of M.pachycarpa and C.tsui indicated a trend that first increasing and then decreasing.When the concentration of NaCl was 1.0%and the stress was 40d,the relative growth of plant height and ground diameter was the lowest,and the impact of M.pachycarpa was more obvious,all the biennial plants withered and died.(2)Under NaCl stress,the change trends of the physiological and biochemical indexes of M.pachycarpa and C.tsui were basically the same:the relative water content of leaves indicated a decreasing trend with increasing NaCl concentration and prolonging the stress time,the Malondialdehyde(MDA)and Proline(Pro)contents indicated a continuous increasing trend with prolonging the stress time and increasing NaCl concentration,and the SOD activity and soluble protein contents indicated an increasing trend followed by a decreasing trend with prolonging the stress time.There were differences in the magnitude of variation,with the biennial seedlings of M.pachycarpa and C.tsui showing greater variation than the five-year old seedlings;the C.tsui was more active in all physiological and biochemical indices and indicated greater tolerance.(3)The chlorophyll contents of C.tsui and M.pachycarpa indicated a trend of first increasing and then decreasing with the increase of stress time and NaCl concentration.The chlorophyll and carotenoid contents of C.tsui and M.pachycarpa were promoted by lower concentration of NaCl(0%～0.6%)stress,but both of them were indicated a decreasing trend with the increase of NaCl concentration,the decrease of biennial seedlings was greater than that of five-year old seedlings.M.pachycarpa was more affected at higher concentration.(4)Under NaCl stress,the Pnmax,LSP,LCP and Rd of C.tsui and M.pachycarpa indicated an overall decreasing trend with the increase of NaCl concentration.In the early period of stress(0～20 d),under 0%-0.4%NaCl stress,the Pnmax of C.tsui and M.pachycarpa increased slightly at first,and then decreased with increasing stress time and stress concentration.The Rd of M.pachycarpa biennial seedlings under low concentration of NaCl(0%～0.4%)stress increased at the beginning of the stress period(0～20 d)compared to CK.(5)In conclusion,C.tsui had a good ability to adapt to NaCl stress,while M.pachycarpa had a relatively poor ability to adapt to NaCl stress.C.tsui and M.pachycarpa had certain adaptability under 0%～0.6%NaCl stress.Under 0.8%NaCl stress,C.tsui and M.pachycarpa were affected by salt.Under 1.0%NaCl treatment,C.tsui biennial seedlings indicated scorched and wilted leaf edges with more leaf drop,while five-year old seedlings had less leaf drop;M.pachycarpa biennial seedlings died,while five-year old seedlings leaf drop was more serious at the end of the experiment,which greatly affected their ornamental effects.According to the value of membership function,C.tsui and M.pachycarpa resistance strength under NaCl stress was ranked as follows:five-year seedlings of C.tsui>biennial seedlings of C.tsui>five-year seedlings of M.pachycarpa>biennial seedlings of M.pachycarpa. |
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