Physiological Response Of Different Gramineae Grasses To Drought And Low-Temperature Stress

In order to solve shortage problem of adverse resistance and high yield fine grass resources during implementing conservation tillage technology system and the strategy of returning the grain plots to forestry and grass in northwestern china, this study adopted 8 forage species such as Phleum Pratense, Agropyron desertorum, Festuca arundinacea, Bromus Inermis, Elymus dahuricus, Elymus junceus, Agropyron elongatum and Agropyron trachycaulum (imported from USDA—ARS Wind Erosion Research Unit KSU) as experiment materials with the number ofⅠ,Ⅱ,Ⅲ,Ⅳ,Ⅴ,Ⅵ,Ⅶ,Ⅷin consideration of clear expression.In jointing stage dynamic changes of the correlation with physiological and biochemical indexes such as chlorophyll, praline, soluble sugar and fluorescence of chlorophyll, MDA, SOD, CAT and POD of 8 forage species were determined with the experiment on pot culture with water stress. The conclusion as follows: the variations of chlorophyll content decreases with increased water stress, the content of chlorophyll was least under severe water stress;the content of proline slow increased with slow increased water stress, the proline content sharply increased with sharply increased water stress; soluble sugar contents sustainable increased with aggravation water stress; the content of Fv / Fm,Fv / Fo,ΦPSII were increased first with water stress and then decreased, the content of Fv / Fm,Fv / Fo,ΦPSII were highest at SWS disposal method;as to SOD, CAT and POD, with the increasing water stress, enzyme activity increased and then began to decrease, and the protective enzyme content increased greatly under low water stress, but the increase tended to slow when water stress became moderate and high; the activity of SOD sharply decreased when water stress became high; the content of MDA sustainable increase with aggravation water stress. At last, fuzzy subordination method was used for comprehensive evaluation of grass drought resistance and the result of the 8 species wasⅣ>Ⅰ>Ⅴ>Ⅲ>Ⅵ>Ⅱ>Ⅷ>Ⅶ.The dynamic variation of proline, soluble sugar and protein, MDA, SOD, CAT and POD were determined using cold hardening, freezing treatment, thawing and recovering growth under controlled temperature condition during with different growth phases including before cold hardening(day/night: 25/20℃), after cold hardening(2℃) , after freezing treatment(25℃) , thawing and 15 days after recovering growth(day/night: 25/20℃). The conclusion as follows: the soluble sugar content increased after cold hardening and freezing treatment, then began to decrease after recovering growth; the proline content changed greatly(P<0.05) due to different treatments, increased to highest after freezing treatment, then decreased greatly, the proline content ofⅠ,Ⅵ,Ⅷchanged greatly; the change trend of soluble protein content ofⅠ,Ⅱ,Ⅲshowed increasing-decreasing-increasing, and decreased to least, soluble protein content ofⅤ,Ⅵ,Ⅶ,Ⅷsustainable increased firstly and decreased after recovering growth; the activity of SOD,CAT and POD under different temperature changed differently due to different 8 forage species, that of most species decreased to least after freezing treatment, then increased after recovering growth, SOD were the most sensitive to temperature changing. Fuzzy subordination method was used for comprehensive evaluation of physiological parameter and the cold resistance result of the 8 species wasⅧ>Ⅰ>Ⅲ>Ⅵ>Ⅳ>Ⅶ>Ⅴ>Ⅱ.Under water and temperature stress, proline,soluble sugar and SOD were more sensitive to different treatments and the law were more significant, which accounted for bigger percentage in drought resistance and cold resistance comprehensive evaluation; Factors analysis indicated that osmoregulation substances and protective enzyme played the main role to main factors of drought resistance and cold resistance, between partial main factors some indirect effect existing. Integrated drought resistance and cold resistance evaluation result showed:Ⅰ,Ⅲ,Ⅳhad strong effect of drought resistance and cold resistance evaluation.