The Identification And Mechanism Of Heat Resistance On Different Rank Of Fall-dormancy Alfalfas In Summer

In this paper,26 different fall dormancy alfalfas were chose to research the change law of 10 physiological and biochemical indexes at different times under natural high temperature in summer, then Combined the correlation with the physiological and biochemical indexes to meet the classification of different alfalfa varieties, and the form of adaptation to high temperature on Heat-resistant varieties. The results showed that:Test one:22 varieties were sowed in March 15, 2009 ,The experiment was determined by the randomized blocks design of three replications. each plot area was 9m2,the spacing was 0.3m,seeding rates was l5.5 kg/hm2. The variation of physiological and biochemical indexes were measured with temperature change in different sampling period. The results were :(1) the content of relative water and chlorophyll were decreased, while the anti-oxidation indexes such as SOD, POD and GSH-PX activity increased with the temperature increasingly; with the enhancement of cell damage, leaf conductivity and MDA content increased gradually; At the same sampling period, the change law was different for different varieties, so as the indicators of the same species in the whole trial period, showing differences between varieties;(2) In this study , 22 alfalfa varieties were divided into three types by hierarchical clustering: strong heat–resistance type, and weak heat–resistance varieties and intermediate type, respectively. The varieties of strong heat-resistant type were produced by Phabulous,Sanditi,8925mf,Powerplant,Legacy and Derby, while the intermediate heat-resistant varieties were produced byEmpress2000, AmeriGraze401, Algonquin, Hunter River, Alfaqueen,Alfking,Sitel,WL414and Millennium. The other varieties were not heat-resistant varieties;(3)There was no significant link between Fall dormancy and heat resistance; The content of Relative water and soluble protein, electrical conductivity, the activity of SOD, POD and CAT can be used as the evaluation indexes of alfalfa heat resistance.Text 2 showed that:(1) plant cells were gradually injured as the temperature increased, while the activity of protective enzymes increased; varieties which have greater thickness, nearly circular or narrow leaf blades and the thick stem were stronger heat resistance. (2) The correlation analysis showed that, the leaf area had negative correlation between the aspect ratio, plant height and leaf thickness , but showed a positive correlation among other indicators; there were significant correlation among the leaf thickness, free Proline content, stem diameter and relative water content, so the thickness of leaves, free Proline content, stem diameter and relative water content can be identified as indicators of heat resistance.