Response To NaCl Stress And Salt Tolerance Evaluation Of Gleditsia Sinensis And Elaeagnus Angustifolia

Drought is often accompanied by soil salinization.Under the arid environment,the evaporation of soil surface water intensifies,which causes the underground salt to accumulate on the surface with the increase of soil capillary water,leading to soil salinization.Selecting drought resistant and salt tolerant plants for planting in saline alkali soil is an important way for biological improvement and effective utilization of saline alkali soil.In this study,Gleditsia sinensis and Elaeagnus angustifolia were used as experimental materials.The changes of seed germination,seedling growth and physiology with treatment time(7d,14 d,21d,28d)were measured and analyzed by simulating salt stress environment with different concentrations of NaCl(50,100,150,200 mmol · L-1),Salt tolerance was evaluated.The purpose of this study is to understand the growth adaptability of two tree species in saline alkali environment,and to provide basis for screening and rational utilization of salt tolerant tree species in saline alkali soil biological improvement.The main conclusions are as follows(1)Mild(50 mmol·L-1)salt stress had no obvious inhibition on germination rate,vigor index and radicle length of Gleditsia sinensis seeds,and even was beneficial to the improvement of seed germination potential and germination index.With the increase of stress concentration,seed germination of Gleditsia sinensis and Elaeagnus angustifolia were significantly inhibited.Compared with the control,the decline of each index of Elaeagnus angustifolia was greater than that of Gleditsia sinensis.(2)In the seedling stage,the plant height growth and biomass accumulation of the two tree species were inhibited under salt stress.With the increase of stress concentration,the plant height growth decreased by Elaeagnus angustifolia<Gleditsia sinensis,and the biomass accumulation of Elaeagnus angustifolia > Gleditsia sinensis.With the increase of stress days,the biomass accumulation of each stress concentration decreased by Elaeagnus angustifolia < Gleditsia sinensis,and the root shoot ratio increased gradually and significantly in the late stage of stress(21-28 days)Higher than the control.The leaf growth parameters(total leaf area,average leaf area,leaf area,specific leaf area and average leaf number)of the two tree species also decreased with salt stress,but the decline range of leaf growth parameters of Elaeagnus angustifolia was less than that of Gleditsia sinensis under high concentration(150 mmol·L-1 and 200 mmol·L-1)salt stress.(3)Malondialdehyde(MDA)content in root,stem and leaf increased with the increase of stress concentration and time.Meanwhile,the activities of catalase(CAT),peroxidase(POD),superoxide dismutase(SOD),soluble sugar(SS),soluble protein(SP)and proline(Pro)also increased.When the stress concentration was more than 150 mmol·L-1,CAT,SOD and Pro in leaves and roots of the two species decreased.Photosynthetic rate(Pn),transpiration rate(Tr),stomatal conductance(Gs),intercellular CO2 concentration(Ci),light use efficiency(LUE)and CO2 use efficiency(CUE)decreased with the increase of stress concentration and time,but stomatal limit(Ls)and water use efficiency(WUE)increased with the increase of stress degree.Except Ci,all indexes of Elaeagnus angustifolia were lower than those of Gleditsia sinensis.(4)The results showed that both Gleditsia sinensis and Elaeagnus angustifolia showed certain salt tolerance,and the salt tolerance of Elaeagnus angustifolia was better than that of Gleditsia sinensis.