Studies On Physiological And Biochemical Mechanism Of Allelopathy Of Wheat Root Exudates On Cucumber Seedling

With the development of facilities Horticulture, the areas of protected vegetables increased year by year. Cucumber (Cucumis sativus L.) is one of the major vegetables in the protected horticulture, because the continuous cropping for many years caused the the continuous cropping obstacles, and has became the one of the main bottleneck facilities development.Allelopathy was applied in the agriculture widely, especially in the crop rotation, relay intercropping and row inter-cropping. In this study, cucumber and 40 wheat varieties from Hei longjiang province were taken as experimental material. It was investigated the allelopathy of wheat root exudates, and the allelopathic potential of wheat root exudates on cucumber; to screened two wheat root exudates which showed different allelopathic effect on cucumber, one of the two wheat root exudates showed allelopathic promotion on the cucumber growth and the other showed allelopathic inhibition. The experiment studied the effect of allelopathic-promoted wheat root exudates and the allelopathic-inhibited wheat root exudates on the growth, root activity, photosynthesis, and activity of protective enzymes, content of osmotic adjustments, and the content of hormone, to provide a theory for the confirmation the physiological and biochemical mechanismof allelopathy on the cucumber and reasonable application of allelopathy varieties and alleviate continuous cropping obstaclesExperiment results show as follows:1,After treatment with the same concentration of wheat root exudates, the allelopathy of the 40 wheat root exudates on cucumber were different, there were 29 wheat root exudates which could promoted the germination of cucumber and the growth of the cucumber seedlings, the number of the wheat root exudates which showed promotion was 70.25% of 40 wheat root exudates, and others wheat root exudates showed inhibition. The L11 (Longfu04-0348) root exudates was the highest allelopathic promotion, the L5 (Longfu17) was the highest allelopathic inhibition.2,After treatment with L11 root exudates, the plant height, stem diameter, leaves area, total plant fresh weight, the dry weight and root activity of cucumber seedlings were promoted in different periods; the L5 root exudates inhibited the plant height, stem diameter, leaves area, total plant fresh weight, the dry weight and root activity of cucumber seedlings in different periods; the production of the cucumber after transplanting which treated with L11 and L5 were both increased but no significant difference.3,The photosynthesis of cucumber leaves which treated with L11 root exudates increased, the photosynthetic rates, stomatal conductance, transpiration rates and intercellular CO2 concentration, Yield, qP, ETR of cucumber seedlings were promoted in different periods, and promoted the growth of the cucumber; the photosynthesis of the cucumber leaves which treated with L5 root exudates was inhibited, the photosynthetic rates, stomatal conductance, transpiration rates and intercellular CO2 concentration, Yield, qP, ETR of cucumber leaves were decreased and the NPQ was increased in different periods.4,After treatment with the L11 root exudates, the activity of SOD,POD,CAT,AsA-POD and PPO of cucumber seedlings were increased in different periods, which enhanced the stress tolerance; after treatment with the L5 root exudates, the activity of the SOD,POD,CAT and PAL of cucumber seedlings were decreased in different periods, and reduced the stress tolerance..5,After treatment with the L11 root exudates, the content of free praline, soluble sugar and soluble protein of cucumber seedlings were increased in different periods, and enhanced the stress tolerance; after treatment with the L5 root exudates, the content of free praline, soluble sugar and soluble protein of cucumber seedlings were decreased in different periods and reduced the stress tolerance.6,After treatment with the L11 root exudates, the content of MDA of cucumber seedlings was decreased and reduced the degree of impairment of cucumber cells; after treatment with the L5 root exudates, the content of MDA was increased and inhibited the growth of cucumber seedlings.7,The content of IAA and GA3 of cucumber seedling was increased in different periods after treatment with the L11 root exudates and enhanced the stress tolerance; the content of the IAA and GA3 of cucumber seedling was decreased and the content of ABA was increased in different periods after treatment with L5 root exudates and reduced the stress tolerance.Form the above, the allelopathy of different wheat root exudates on cucumber was different; the allelopathic-promoted wheat root exudates can promote the growth of cucumber seedlings and enhanced the resistance to stress; the allelopathic-inhibited wheat root exudates show the reverse effect and inhibit the growth of cucumber seedlings.