The Study On The Responses Of Five Forages To Drought And Salt Stress

Plant growth and development are affected by environmental constraints, and droughtand salt stresses are the two main factors that affect seed germination and plant growth.Medicago sativa （L.）, Astragalus adsurgens （Pall.）, Coronilla varia （L.）, switchgrass and reedcanarygrass were used as the experimental materials. The effects of drought and salt （NaCl）stress on seed germination of three legumes and the physiological and biochemical responsesof switchgrass and reed canarygrass to salt （NaCl） stress were investigated to probe thecombined effect of drought and salt stress on seed germination and the mechanism of plantvegetative growth affected by salt stress. For seeds, the experiment was carried out in anorthogonal design: an L9（3⁴） orthogonal array was adopted to assign three factors （species,PEG solution and NaCl solution） and one vacancy. Each factor was placed into three levels.Germination tests of seeds of Medicago sativa, Astragalus adsurgens and Coronilla variawere conducted. For plants of vegetative growth, a single factor experiment was conducted toinvestigate the physiological and biochemical responses of leaves and roots in switchgrassand reed canarygrass to NaCl-salinity stress (1,3,5,10,15g·kg^-1NaCl for switchgrass and1,3,5g·kg^-1NaCl for reed canarygrass). The treatment time was30days. The results showed asfollows:1) The seed germination of the three species was inhibited by drought and salt stress. Thegermination percentages, radicle and hypocotyl lengths and seedling fresh weights of thethree species decreased as a result of the combined effects of PEG and NaCl. But the seedgermination of Medicago sativa was not inhibited by5%PEG+50mM NaCl, and Seedlingdry weights of three species were not significantly changed by drought and salt stress.2) Under NaCl-salinity stress, the increase of the activity of antitoxidant enzymes and thecontents of the antioxidant （GSH）, osmolytes and ions alleviated the damage of NaCl toswitchgrass and reed canarygrass.3) The order of the antioxidant indices sensitivity to NaCl-salinity, the relationshipbetween osmotic adjustment indices and the contents of Na⁺and Cl^-in the soil, and themodels of these paired indices in root and leaf of switchgrass were different from reedcanarygrass.From the results above, we can come to the conclusion that Drought and salt stress inhibited the germination of M. sativa, A. adsurgens and C. varia seeds, but the responses ofthe seeds of different species to drought and salt stress differed. The physiological andbiochemical responses of switchgrass to NaCl-salinity were different from reed canarygrass.