Study On Physiological Mechanism Of Grafted Cucumber With Different Rootstocks To Improve Its Rhizosphere High Temperature Tolerances

Cucumber(Cucumis sativus L.)originated in warm areas,is thermophilic vegetable,and plays an important role in China’s vegetables annual supply.However,in the middle and lower reaches of the Yangtze River and the south of China in summer,the high temperature often has a serious impact on the production of cucumber,which is the main limiting factor for the summer,autumn delay and facility cultivation.Therefore,it is of great practical significance to carry out the research on the physiological mechanism of heat injury and heat adaptation and the cultivation techniques of heat tolerance in cucumber.In this study,the growth and physiological changes of six melon crops under the high temperature stress were investigated undei high temperature treatment in the artificial climate chamber by hydroponic cultivation method.The results showed that the six kinds of melons had different high temperature tolerance.And the changes of growth,leaf photosynthetis,physiology and fruit quality of self-rooted cucumber seedlings(Cucumis sativus ’Chunqiuwang No.2’)and grafted cucumber seedlings(Cucurbita ficifolia Bouch6,Cucurbita moschata,Cucurbita maxima ×Cucurbita moschata ’Yongzhen No.8’,Luffa cylindrica ’Wuyexiang’and Momordica charantin ’Aomei’)were studied.Grafted cucumber on Luffa cylindrica ’Wuyexiang’ showed highly resistance to high temperature stress.The physiological characteristics and fruit quality of grafted cucumber plants and self-rooted cucumber plants were measured in greenhouse with high temperature in summer.The major results were as follows:1.To investigate the growth and physiological responses of 6 cucurbit crops(Cucumis sativus ’Chunqiuwang No.2’,Cucurbita ficifolia Bouch6,Cucurbit moschata,Cucurbita maxima×Cucurbita moschata ’Yongzhen No.8’,Luffa cylindrica ’Wuyexiang’ andMomordica charantin ’Aomei’)to 35℃ high root-zone temperature stress in a hydroponic production.The results showed that the plants of Luffa cylindrica ’Wuyexiang’ increased the most.Meanwhile,high root-zone temperature stress significantly increased the activity of antioxidant enzymes,proline content and malondialdehyde(MDA)content for different cucurbit crops.The plants net photosynthetic rate(Pn),stomatal conductance(Gs),transpiration rate(Tr)and root activity decreased significantly.The results demonstrated that different cucurbit crops have different tolerance to high root-zone temperature stress.Luffa cylindrica’Wuyexiang’exhibited the highest tolerance to high root-zone temperature stress,which could be used as heat-resistant rootstocks for cucurbit crops.2.By hydroponic cultivation method,Cucurbita ficifolia,Cucurbita moschata,Cucurbita maxima× Cucurbita moschata ’Yongzhen No.8’,Luffa cylindrica ’Wuyexiang’and Momordica charantin ’Aomei’ as rootstock,Cucumis sativus ’Chunqiuwang ’No.2’ as the scion,survival rate and change of growth,photosynthesis and biochemical indexes after treated by high temperature(350C)in rhizosphere were analyzed.The results showed that,Cucurbita ficifolia Bouche anvil grafting survival rate is highest.Grafted cucumber seedlings on different rootstocks had different degrees of plant height,stem diameter,blade number and leaf area under high temperature stress in rhizosphere,grafted seedling of Luffa cylindrica ’Wuyexiang’ increment was the largest.The antioxidant enzyme activity and proline content of grafted cucumber on different rootstocks and self-rooted seedlings were increased by rhizosphere high temperature treatment,and grafted seedlings were significantly higher than those of self-rooted seedlings.Meanwhile,malondialdehyde(MDA)content of grafted cucumber on different rootstocks and self-rooted seedlings was decreased by rhizosphere high temperature treatment,and the self-rooted seedlings were significantly lower than the grafted seedlings.Comprehensive growth,photosynthetic and physiological indicators,Luffa cylindrica ’Wuyexiang’ rootstocks were the best,which could improve the tolerance to rhizosphere temperature.3.By hydroponic cultivation method,Cucurbita ficifolia Bouche,Cucurbita moschata,Cucurbita maxima×Cucurbita moschata ’Yongzhen No.8’,Luffa cylindrica ’Wuyexiang’and Momordica charantin ’ Aomei’ as rootstock,Cucumis sativus ’Chunqiuwang No.2’ as the scion,change of fruit quality and physiological characteristics after treated by 35℃high temperature in rhizosphere were analyzed.The results show that,after treated by high temperature(35℃)in rhizosphere,the activity of antioxidant enzymes,proline content,MDA content and soluble sugar content of the grafted seedlings and the self-rooted seedling during flowering and fruiting period increased significantly,and the activity of root decreased,while the soluble protein content was fluctuated.The fruit quality of Cucurbita moschata grafting was the best,and Luffa cylindrica ’Wuyexiang’ grafting followed.It is suggested that there is obvious difference in tolerance to high temperature in rhizosphere among grafted cucumber on different rootstocks during flowering and fruiting period.In which,tolerances of Luffa cylindrica ’Wuyexiang’ is stronger.4.Studied the effects of greenhouse high temperature on physiological characteristics and fruit quality of grafted cucumber plants with different rootstocks(Cucurbita ficifolia,Cucurbita moschata,Cucurbita maxima× Cucurbita moschata ’Yongzhen No.8’,Luffa cylindrica ’Wuyexiang’ and Momordica charantin ’Aomei’),and Cucumis sativus’Chunqiuwang ’No.2’ self-rooted seeding.The results showed that,the contents of malondialdehyde(MDA)and proline in leaves of grafted seedlings and self-rooted seedling increased with the high temperature of greenhouse,and the root activity decreased.The MDA content in grafted plant leaves was lower than that in self-rooted plants,and the root activity was significantly higher than that of the self-rooted plants.There was no significant difference in the soluble protein content between the fruits of grafted seedlings and self-rooted seedling.The content of soluble sugar,free amino acid and Vc of the grafted plant were higher than those of the self-rooted plant,among which,the fruit quality of the Luffa cylindrica ’Wuyexiang’ grafted seedling is the best.