Effects Of Intercropping Wheat On Photosynthetic And Antioxidant Metabolism And In Cucumber Leaves During Senescence

Plants usually produce amount of ROS?reactive oxygen species?under soil environment stress caused by continuous cropping,such as soil salinization and retarding plant growth.Accumulation of plentiful ROS destroys cell structure,promotes plant senescence and decreases yield.As an important facility cultivation model,intercropping is an effective biological measure to dilute continuous cropping obstacles and increase crop yield through reducing soil-borne diseases,improving soil nutrients and regulating microbial community structure in the rhizosphere.Different intercropping crops make different influences thanks to diversity of root exudates,interaction patterns and root network structures.It has been found that wheat intercropping enhanced related enzyme activities of sugar and nitrogen metabolism,Cs SPS and GS1 genes expression and postponed senescence.However,we still unclear the machine of ROS contents and related metabolism in cucumber leaves under wheat intercropping.We investigated the effects of cucumber?Cucumis sativus L.?with intercropped wheat?Triticum aestivum L.?on photosynthetic capacity,oxidation degree,defense enzyme activity,As A-GSH?ascorbate-glutathione?cycle,free polyamines contents and related gene expression.In this study,we investigated the effects of wheat intercropping on the photosynthesis and antioxidant capacity in aging cucumber leaves,to develop strategies to reduce the cucumber leaves senescence.The main results were as follows:1.The stomatal conductance and transpiration rate in cucumber plants under wheat intercropping were at 30 day higher than that in cucumber monoculture?control treatment?.The photosynthetic rate of cucumber leaves under wheat intercropping was also higher than the control.CO₂ concentration was lower and Rubisco?ribulose-1,5-diphosphate carboxylase/oxygenase?activity was higher in cucumber leaves intercropped with wheat than in control treatment at 40,50 day.The chlorophyll content was obviously higher than control treatment over time.2.MDA was obviously decreased in cucumber leaves intercropped with wheat as compared to the control at 50 day.H₂O₂ and O₂.^-were also obvious decrease in cucumber leaves than the control at 40 and 50 day.In the case of antioxidant enzyme,the levels of POD and SOD were all obviously increased in cucumber leaves intercropped with wheat as compared to control treatment at 40 and 50 day.3.During the period of experiment,wheat intercropping decreased DHA?dehydroascorbic acid?contents,at the same time increased the activity of ascorbic acid,APX?peroxidase?,MDHAR?monodehydroascorbate reductase?and the ratio of AsA/DHA in cucumber leaves at 40and 50 day.Concerning results of leaf GR?glutathione reductase?activity,it was increased in wheat intercropping at 50 day as compared to control treatment.4.The contents of Put?putrescine?and Spd?spermidine?were significantly decreased in cucumber leaves intercropped wheat with at 40 and 50 day,as compared to control treatment.A similar trend was observed for?Spd+Spm?/Put ratio in the cucumber leaves.The PAO?polyamine oxidase?activity in cucumber leaves was increased as compared to control treatment over time.5.The expressions of RbcL and RbcS were obviously decreased in cucumber leaves intercropped wheat with at 30 and 40 day as compared to control treatment.The contrary trends were seen in levels of RCA,TGase and SOD expression.At 50 day,the cucumber leaves expression of POD in wheat intercropping was higher than control treatment and PAO was obviously lower than control treatment.6.In this experiment,there was no significant difference in cucumber yield as compared to the control.In conclusion,wheat intercropping decreased levels of MDA,H₂O₂,O₂.^-and DHA,increased chlorophyll contents,improved activity of Rubisco,SOD,POD and PAO,raised?Spd+Spm?/Put ratio and enhanced As A-GSH cycle,such as enzyme?APX,MDHAR,GR?and As A/DHA ratio.Simultaneously,the decreased?RbcL,RbcS,PAO?and increased?RCA,TGase,SOD,POD?expressions were embodied in cucumber leaves intercropped with wheat.The cucumber leaves capacity of photosynthetic,oxygen scavenging and cell structure stability were promoted under wheat intercropping that delay senescence of cucumber leaves.