Study On Physiological And Biochemical Characteristics Of Different Salt-tolerant Cucumber Cultivars

Soil salinization is one of the important factors that influence crop growth. How to settle soilsalinization is an urgent and important task in our age which haunted by increasing population,decreasing infield and lacking of fresh water. By far selection and gene engineering of salt-tolerantcultivars are more economical and effective ways to solve this problem. Also illustratingphysiological and biological characteristics of plant saline tolerance essentially is also important.Salt-tolerant cucumber cultivars (Zhongnong 12, Jinchun 5, Changchunmici) and salt-sensitivecultivars (Yuyuanyouxiu, Xinxiu, Jinyou 1) were treated with NaCl solution in this paper. Seedgermination, seedling growth, physiological and biological characteristics of different salt-tolerantcultivars during seed stage and seedling stage, and cell ultrastructures were studied and analyzed,which provided theoretical foundation for identification and breeding of salt-tolerant cucumbercultivars, and enhancing cucumber saline tolerance. The following conclusions were drawn fromour experiment:1. Cucumber seed germination was inhibited under salt stress. Germination vigor andgermination rate of salt-tolerant cultivars were significantly higher than that of salt-sensitivecultivars.2. Cucumber seedling growth was inhibited under salt stress. Stem length became shorter andstem diameter became thinner. It was more distinctive in salt-tolerant cultivars than in salt-sensitivecultivars. Stem length could be seen as an physiological indicator in cucumber saline tolerance atseedling stage.3. Under salt stress, Chlorophyll content and root activity in salt-tolerant cultivars andsalt-sensitive cultivars went down.. The reduction in salt-tolerant cultivars was significantly lowerthan in salt-sensitive cultivars.4. Under salt stress, the great free proline content accumulated, free proline content insalt-tolerant cultivars was significantly higher than in salt-sensitive cultivars under salt stress, andthe trend was stable, change of free proline content was not stable during seedling stage. Freeproline content could be an indicator of cucumber saline tolerance during seed stage.5. Under salt stress, Relative conductancerate and MDA content increased., The increasedegree was lower in salt-tolerant cultivars than in salt-sensitive cultivars. ,the trend was stable. Relative conductance rate and the relative stability of MDA content to NaCl could be thephysiological indicator of cucumber saline tolerance.6. Under salt stress, POD and CAT activity decreased, The reduction degree was lower insalt-tolerant cultivars than in salt-sensitive cultivars, the trend was stable. So POD and CAT activityto NaCl could be the indirect biochemical indicator of cucumber saline tolerance.7. Under salt stress, the content of soluble protein decreased. The decrease of soluble proteinwas significant smaller in salt-tolerant cultivars than in salt-sensitive cultivars, the trend was stable.Soluble protein content to NaCl could be seen as an indicator of cucumber saline tolerance.8. Under salt stress, the content of Na~+ in root and leaf significant increase, the content of K~+significant decrease, The decrease of soluble protein was significant smaller in salt-tolerantcultivars than in salt-sensitive cultivars, the ratio of Na~+ and K~+ have changed. Na~+/K~+ insalt-tolerant leaf was significantly lower than in salt-sensitive leaf. And it indicated that nutrientbalance was relatively. So the content of Na~+,K~+ and Na~+/K~+ in salt-tolerant leaf can use assalt-tolerant indicators.9. Chloroplast, grana lamella could be a cellular indicator of cucumber saline tolerance duringseed and seedling stage. The ultrastructure of mitochondrion could be a cellular indicator ofcucumber saline tolerance during seedling stage.