Effects Of Two Kinds Of Salt Stress On Growth And Physiological Characteristics Of Bromus Inermis And Evaluation Of Salt Tolerance

Bromus inermis is a high-quality forage widely planted in Northwest China,which plays an important role in the improvement of salinized grassland.In this experiment,five Bromus inermis were used as materials（materials O,P,S,T and V）.Two kinds of salt stress and three stress times were set,Na Cl∶Na₂SO₄∶Na₂CO₃=1∶4∶0（neutral salt）,Na Cl∶Na₂SO₄∶Na₂CO₃=1∶1∶8（alkaline salt）.The Electrical conductivity（EC）of each salt was set at 10,15 and 20 ms·cm^-1,and the control group was irrigated with tap water(EC was 0.27 ms·cm^-1),stressed for 30,60 and 90 d,respectively.Based on the growth,physiological characteristics and leaf anatomical structure,to explore the growth,physiological and morphological response mechanism and adaptive strategy of Bromus inermis under different salt stress and different stress time.The germplasm materials of Bromus inermis with excellent salt tolerance were selected through comprehensive evaluation,which provided a theoretical basis for the utilization of Bromus inermis in saline alkali land in the future.The test results are as follows:1.In the two kinds of salt stress,the inhibition degree of underground roots of 5 Bromus inermis materials was greater than that of aboveground parts.Low EC stress promoted the growth of material O,P,S and T,while high EC stress inhibited the growth.The growth of material V was significantly inhibited under two kinds of salt stress.The 5 materials adopted the survival strategy of allocating more energy to the aerial part at the early stage of stress,and long-term salt stress inhibited the accumulation of biomass.2.The thickness of leaf,midvein and epidermal cells of the five materials increased under EC value is10 ms·cm^-1,and vice versa under EC value is 20 ms·cm^-1.After 30 days of stress,the main vascular bundle diameter and adjacent vascular bundle spacing of five materials were less affected.Salt stress significantly inhibited the development of xylem of material O,P and S,and the development of phloem of material V,and promoted the development of xylem of material V.The xylem and phloem area of material T were significantly increased.Materials O and t significantly increased the diameter of main vascular bundle in the later stage of stress（90 d）,while those of materials P,S and V were opposite.3.Low EC stress reduced the MDA content of material O,and the proline content of material S and T under two kinds of salt stress was less than that of material O,P and V.High EC stress reduced the ability of five materials to synthesize osmotic regulators.Both salt stress inhibited the accumulation of soluble sugar in five materials.At the initial stage of stress（30 days）,the five materials could maintain the stability of F_m,F_v/F_o and F_v/F_m,and showed inhibition under long term salt stress（90 days）.4.The mean salt tolerance coefficients of the underground biomass and soluble sugar content of the five materials were small,the mean salt tolerance coefficient of proline was the largest under neutral salt stress,and the mean salt tolerance coefficient of malondialdehyde was the largest under alkaline salt stress.Chlorophyll fluorescence parameters,leaf anatomical structure and leaf layer height can be used as comprehensive identification indexes to evaluate the neutral salt tolerance of five materials,chlorophyll fluorescence parameters,leaf anatomical structure and osmotic regulators can be used as comprehensive identification indexes to evaluate the alkali salt tolerance of five materials.Material S has the strongest salt and alkali resistance and material V is the weakest.