Effect Of NaCl Stress On Physiological And Biochemical Characteristics Of Torreya Grandis Cv. Merrillii Seedlings

Salt is one of the important environmental factors that affect plant growth. Salt stress throughion poisoning, nutritional imbalance and osmotic stress, cause plant physiological and biochemicalmetabolism disorders, which affect plant growth, yield and quality. It is of great significant forimproving the high and stable yield of crop, stengthening the management and comprehensivedevelopment of saline soil to understand the effects and mechanism of salt stress on plant andsearch for ways to improve plant salt resistance. With the aim of offering scientific basis for thepromotion and application of Torreya grandis cv. Merrillii, two-year-old grafting seedlings ofTorreya grandis cv. Merrillii were studied on the growth characteristics and physiologicalrespones under NaCl stress, simultaneously through exogenously applied salicylic acid to studytheir regulated pathway of solt resistant and reveal the mechanism of salt resistant. The mainresults are as follows:(1) NaCl stress inhibited the Torreya grandis cv. Merrillii seedlings growth for its biomass ofground part and underground part reduced, and so was the total biomass.(2) Under NaCl stress, the leaf relative water content of Torreya grandis cv. Merrilliiseedlings declined with the increase of stress level.(3) Under NaCl stress, the whole trend of leaf relative electrolyte conductivity and MDAcontent of Torreya grandis cv. Merrillii saplings increased. NaCl stress cause a large numberaccumulation of proline in torreya grandis leaves and it increased with the increase of NaClconcentration. Soluble protein was induced under0.2%NaCl stress, its content increasedsignificantly with the increase of NaCl concentration; under0.4%NaCl stress, its content was nolonger increases, appeared a downward trend.(4)NaCl stress lead to accumulation of active oxygen free radicals and removal of reactiveoxygen species mainly depend on the antioxidant enzymes. So, under0.2%NaCl stress,theactivities of SOD, POD and CAT of Torreya grandis cv. Merrillii elevated. With the increase ofsalt concentration, under0.4%NaCl stress the activities of SOD, POD and CAT began to decline.(5) Chlorophyll a, chlorophyll b, chlorophyll a+b and carotenoids all decreased under NaClstress, and the change range increased with the increase of NaCl concentration.(6) Under NaCl stress, indexes such as Net photosynthetic rate (Pn), stomatal conductance(Gs), transpiration rate (Tr) and chlorophyll fluorescence parameters (Fv/Fm) all decreased, and the lowest value were observed under0.4%NaCl stress. As for the intercellular CO2(Ci), nosignificant changes were found at0.2%NaCl, but a marked increase was observed at0.4%NaCl.(7) Through exogenously applied salicylic acid under NaCl stress, indexes such as totalbiomass, leaf RWC, proline content, soluble protein content, SOD﹑POD and CAT activities,chlorophyll and carotenoids content all increased, Photosynthetic capacity and fluorescence abilityenhanced, relative electrolyte conductivity and MDA content decreased.The research results showed that different concentrations of NaCl stress affectedphysiological and biochemical process of Torreya grandis cv. Merrillii and inhibited the growth ofTorreya grandis cv. Merrillii. Exogenously applied certain concentration of salicylic acid couldameliorate damage of NaCl stress to plants.