Study On Physiological And Biochemical Characteristics Of Fraxinus Chinensis ’Jingguan’ Under Salt Stress

Fraxinus chinensis ‘Jinguan’ is a natural variation specie Fraxinus chinensis, andmaintain a good resistan quality from Fraxinus chinensis. Because of its beautiful treeand golden leaves in three quarters, Fraxinus chinensis ‘Jinguan’ became an excellentlandscaping caiye specie in recent years。 As people’s awareness of environmentalprotection, saline greening suffered more and more people’s attention. Therefore, toidentify salt tolerance of Fraxinus chinensis ‘Jinguan’ and explore the salt tolerancemechanism are of great significance in saline greening cultivation and horticulture forFraxinus chinensis ‘Jinguan’.In this experiment,3-year-old cutting Fraxinus chinensis‘Jinguan’, Fraxinus chinensis is budding rootstocks and Grafting Fraxinus chinensis‘Jinguan’as test material, at a concentration of0(CK),0.15%,0.30%,0.45%,0.60%ofunder NaCl stress, all three seedlings chlorophyll content, photosynthetic fluorescenceparameters, electrical impedance spectroscopy parameters, relative conductivity (REC),superoxide dismutase (SOD), peroxidase (POD), soluble protein and mineral elementswere studied. The results showed that:(1) cutting and grafting of Fraxinus chinensis ‘Jinguan’ chlorophyll a, b and chlorophyll（a+b） was gradually reduced variation; Fraxinus chinensis leaf chlorophyll a, b,chlorophyl（l a+b）was changed after the first and then decreased. NaCl stress promoteddecomposition of chlorophyll chlorophyll of cutting and grafting of Fraxinus chinensis‘Jinguan’ or hinder the chlorophyll chlorophyll synthesis; lower salt stress can promotethe synthesis of chlorophyll of Fraxinus chinensis; cutting Fraxinus chinensis ‘Jinguan’leaf chlorophyll a/b was changed first decreased and then rise again to reduce whilewhich of Fraxinus chinensis leaf was in the opposite direction of change, chlorophyll a/b of grafting Fraxinus chinensis ‘Jinguan’ leaf was gradually rising trend, three seedlingschlorophyll a/b were no obvious law at all, so chlorophyll a/b can not be a reliableindicator for Fraxinus chinensis ‘Jinguan’ and Fraxinus chinensis under NaCl stress.(2) In this study, transpiration rate (Tr) of three seedlings gradually reduced with this saltconcentration increases, water deficit did not appear. Cuttings Fraxinus chinensis‘Jinguan’ stomatal conductance (Gs) and intercellular CO2concentration (Ci) changes inthe opposite direction, indicating that leaf photosynthesis is inhibited due to non-stomatalfactors; the Gs and Ci of grafting Fraxinus chinensis ‘Jinguan’ and Fraxinus chinensis early direction of change are reduced, when NaCl is greater than0.30%,Gs continue toreduce and Ci is increased, so it can be Inferred that reasons for the decline of graftingFraxinus chinensis ‘Jinguan’ and Fraxinus chinensis leaf net photosynthetic rate (Pn)was stomatal limitation under low salt stress and non-stomatal limitation under high saltstress, the turning point of NaCl treatment was0.30%. Grafting Fraxinus chinensis‘Jinguan’ and Fraxinus chinensis photosynthetic organs sensitive NaCl concentration was0.30%.(3) each point on the chlorophlly fluorescence curve of three seedings showed differenttrends with NaCl concentration increased. When the NaCl concentration is higher than0.30%, the value of each point on the chlorophyll fluorescence curve of cutting Fraxinuschinensis ‘Jinguan’ and Fraxinus chinensis began to fall and the difference is significantwith the control, value on each point on the leaf chlorophyll fluorescence curve ofgrafting Fraxinus chinensis ‘Jinguan’ under0.45%NaCl treatment starts to decrease.(4) After different concentrations of NaCl stress, high frequency and low frequencyresistance of cutting and grafting Fraxinus chinensis ‘Jinguan’ leaves graduallydecreased while which of Fraxinus chinensis decreased after the first rise; Extracellularresistivity and intracellular resistivity of cutting and grafting Fraxinus chinensis‘Jinguan’ leaves decreased gradually while which of Fraxinus chinensis decreased afterthe first rise; Relaxation time and relaxation time distribution coefficient of cutting andgrafting Fraxinus chinensis ‘Jinguan’ leaves decreased while relaxation time of Fraxinuschinensis decreased and relaxation time distribution coefficient of Fraxinus chinensisdecreased after the first rise.(5). SOD activity in leaves of three seedlings increased gradually with the increase ofNaCl concentration, while POD activity of which is increased first and then decreased orfirst decreased and then increased to reduce. MDA content of Fraxinus chinensis leavesrised first and then decreased with increasing concentrations of NaCl while which of theother two seedlings showed decreased; Soluble protein conent of three seedings firstrised then decreased along with the NaCl concentration. According to the size of therelative conductivity, salt resistance strength of three seedings were deduced in the order:Fraxinus chinensis, grafting Fraxinus chinensis ‘Jinguan’ and cutting Fraxinus chinensis‘Jinguan’. the conclusions were drawed based on the above indicators: the largesttoleration of NaCl for cutting Fraxinus chinensis ‘Jinguan’ was0.30%while which ofgrafting Fraxinus chinensis ‘Jinguan’ and Fraxinus chinensis was0.45%.(6) K+content in roots, stems xylem and leaves of cutting Fraxinus chinensis ‘Jinguan’dencreased gradually with the increase of NaCl concentration while which in stemsphloem indreased gradually. K+content in stems phloem and leaves of grafting Fraxinuschinensis ‘Jinguan’ and Fraxinus chinensis decreased gradually while which in rootsrised and in stems xylem first rised then decreased. Mg2+content order in various tissues of three seedings under salt stress were: leaves＞roots＞stems xylem＞stems phloem；chlorophyll content reduction was not caused by a lack of Mg2+. Ca2+content in leavesand stems xylem of cutting Fraxinus chinensis ‘Jinguan’ decreased gradually whilewhich in roots first rised then decreased and in stems phloem indreased gradually; Ca2+content in roots, stems xylem and leaves of grafting Fraxinus chinensis ‘Jinguan’ andFraxinus chinensis first rised then decreased. K+,Ca2+,Mg2+content tends in varioustissues of was different from grafting Fraxinus chinensis ‘Jinguan’ and Fraxinuschinensis, probably because the roots of cutting Fraxinus chinensis ‘Jinguan’ wasdifferent. The salt tolerance of cutting Fraxinus chinensis ‘Jinguan’ was weaker thangrafting Fraxinus chinensis ‘Jinguan’ and Fraxinus chinensis.