Comprehensive Evaluation Of The Drought Resistance Of Five Forage Grasses

The germination, morphology and physiological reaction of five species of forage grasses under drought stress were studied by combination of germination and pot experiments. The ability of drought resistance was evaluated by using subordination function method. The main results were as follows:(1) Using PEG-6000 simulated drought stress, the relative germination rate, the relative germination potential, the simplified vigor index, the germination index, the germination vigor index and the drought index of the seeds for the five forage grasses decreased with the water potential decreasing,while the ration of radicle and embryo increased. The PEG of low concentrations (-0.3Mpa) can promote the germination of Agropyron mongolicum and A. gropyon cristatum×A. desertorum cv. Hycrest Mengnong. The critical germination points of the five species of forage seed were-0.6MPa.(2) The relative germination rate and relative germination potential, the simplify vigor index and germination index, the simplify vigor index and germination vigor index, the germination index and the simplify vigor index were extremely negative correlated (p<0.01). The relative germination rate and the ration of radicle and embryo were negative correlated (p<0.05)(3) Under drought stress, The average daily growth rate showed as increase-decrease trends with the extension of drought stress period, the relative growth rate decreased gradually, while the root cap ratio increased gradually.(4) As the extension of drought stress period, The WSD, cell membrane permeability and MDA contents of the seedlings for the five grasses generally increased, Pro contents, chlorophyll contents, SOD activity, CAT activity and POD activity showed as increase-decrease trends.(5) RWC and WSD, Chlorophyll content and SOD activity, cell membrane permeability and POD activity were extremely negative correlated each other (p<0.01). POD activity negatively correlated with MDA content (p<0.05).(6) According to the comprehensive evaluation by using fuzzy membership function method, the drought resistance at germination period showed as:Bromus inermis> A gropyon cristatum×A. desertorum> Agropyron mongolicum> Agropyron desertorum> Psathyrostachys junce, and it ranked as:Agropyron desertorum> Agropyron mongolicum> Bromus inermis> A gropyon cristatum×A desertorum cv> Psathyrostachys juncea. The ability of drought resistance of germination period were not always consistent with that of seedling period. The drought resistance of Bromus inermis is the best at germination period and moderate at seedling period of the five grasses. The drought resistance of Psathyrostachys juncea is poor at germination period and better at seedling stage. The drought resistance of Agropyron desertorum is the weakest at both germination and seedling periods.