Comparison Of Root-Zoon Hypoxia Tolerance Among Seedlings Of Cucumber Cultivars And The Preliminary Studies On Tolerance Improvement

Twelve cucumber cultivars of different regions in our country were adopted to research their tolerance under root-zone hypoxia stress, using Fuzzy Method. And two cultivars, one tenderness to root-zone hypoxia stress, one endurance , were adopted to research their ROS mechanism and the changes of antioxidant activity under hypoxia , in order to discover the physiological basis of different hypoxia tolerance. Then the tenderness cultivar was adopted to be grafted and sprayed S3307 to improve it's hypoxia tolerance. The result as follows:Twelve cucumber cultivars were: Jinyou-1 (from Tianjin), Lufeng (from Nanjing), Jinhangua (from Dalian), Huazao-2 (from Wuhan), Baiyu-2 (from Wuhan), Heza-1 (from Heilongjiang), Zhongnong-8 (from Beijing) ,Huza-1(from Shanghai), Huza-3(from Shanghai) ,Yuexiu-2(from Guangzhou), Lvbachun-4(from Guangzhou) and Suifeng(from Guangzhou). DO was controlled by Dissolved Oxygen Adjusting Instrument. The testing items were RGR, content of MDA in root, bleeding sap speed, and soluble sugar and amino acids in bleeding sap. Fuzzy mathematics method was proposed to analyze the data. It came into conclusion that Lvbachun-4' tolerance of hypoxia was the highest. Then followed Lufeng. The most tender cultivar was Jinyou-1. Then followed Zhongnong-8.Jinyou-1 and Lvbachun-4 were adopted to research the production rate of O^-₂, content of H₂O₂ and MDA, activity of SOD, POD, CAT and ASP, and content of AsA. It came into conclusion that the production rate of O^-₂, content of H₂O₂ were higher in Jinyou-1 1 than in Lvbachun-4. The antioxidant enzyme in Lvbachun-4 were less active than in Jinyou-1 1 under the same hypoxia stress. And the content of AsA was less than that in Lvbachun-4.Using black-seed pumpkin (Cucurbita ficifolia Bouche) and towel gourd (Luffa cylindrical L) as root stock, and Jinyou-1 as scions, grafting was made to compare the different tolerance among self-root cucumber, pumpkin grafted cucumber and towel gourd cucumber. It came into conclusion that the height of plant, the diameter of shoot, and the growth speed of two kinds of grafted cucumbers were higher than self-root cucumber. SLA of grafted cucumbers were lower than self-root cucumber And the content of chlorophyll and photosynthetic rate were higher than self-root cucumber. The result showed thatmorphological index of grafted cucumber was significantly higher than self-root cucumber. Grafting could improve the tolerance of hypoxia.Jinyou-1 was adopted to be sprayed by Uniconazole (S3307). It came into conclusion that 5mg ? L S3307 improved the growth of root, decreased the content of MDA in root and creased the content of chlorophyll. S3307 of 5mg ? L-1 was effective to release the hurt of hypoxia stress.