Studies On Physiological Basis In Cold-tolerance Of Sugar Beet(Beta Vulgaris.L)Seedlings

Sugar beet is an important source of sugar production in our country that cultivate mainly in Sinkiang,Inner Mongolia and Hei longjiang Province where the temperature is lower in early spring and spring cold takes place frequently,which become a limitation of high and steady yeild of sugar beet.So,it is significant that study the cold-tolerance of sugar beet systematically and in-depth to breed cold-resistance sugar beet varieties and improve the cold-tolerance of sugar beet in early spring so that extend cultivation zone and prevent and reduce disasters.20 sugar beet were screened in germination stage under low temperature;Two cold-resistance sugar beet varieties were filtrated through that,compared with two cold-sensitive varieties separately as control,studied the physiological response of leaves of sugar beet seedlings about cytomembrane osmosis,activity of protective enzymes,content of osmotic adjustment substances and chlorophyll fluorescence parameters,to illuminate the cold-tolerance physiological basis of sugar beet and offer scientific basis and reference index for sugar beet cold-tolerance screening and evaluating.Meanwhile,this experiment probed chemical treatment measures to improve cold-tolerance of sugar beet,which established theoretical basis for preventing and controlling cold damage on agricultural production.The main results got as follows:1.By comparing the differences of the seed vigor of 20 sugar beet varieties under 28 ℃ and 4 ℃ and combined subordinating degree function and cluster analysis to evaluate the cold-tolerance of sugar beet germination stage comprehensively,divided the cold-tolerance of sugar beet into five class.2.By comparing the differences of low temperature physiological responses cold-tolerant tolerant varieties with cold-sensitive ones,discovered that the cold-tolerant sugar beet varieties had lower REC and MDA content of leaves,SOD activity represented a trend of rise first then fall,POD activity rose steadily,with SS and Pro increased,smaller descend range of Fv/Fm,Fv/Fo and qP and larger ascensional range.To sum up,the cold-tolerant sugar beet species enhanced own cold-tolerance by adjusting the stress-resistant physiological metabolism system.3.The principal component analysis and correlation analysis were used that simplified the evaluation index,then eight indexes were screened,including REC、MDA、SOD、POD、SS、NPQ、qP、Fv/Fo,which could be acted as authenticating method of sugar beet cold-tolerance and evaluated the cold tolerance of sugar beet seedlings comprehensively.4.The damage of leaves of sugar beet seedlings could be alleviated by exogenous S A and MeJA so that the cold-tolerance could be enhanced.