山桐子幼苗对极端高温和高温干旱复合胁迫的生理响应OA北大核心CSTPCD

[Objective]This study aims to understand the resistance ability of Idesia polycarpa to extreme high temperatures through investigating the physiological response of I.polycarpa seedlings to extreme high temperature stress and combined stress of high temperature and drought,so as to provide a reference and scientific theoretical basis for its cultivation and introduction,as well as for the production and survival under extreme high temperature.[Method]In this experiment,2-year-old I.polycarpa'Yuji'seedlings were used as test material.The temperature and water were controlled in an artificial climate chamber to simulate extreme high temperature,and high temperature plus drought stress environment,with the natural environment served as the control.The I.polycarpa'Yuji'seedlings were subjected to the above conditions and their morphological and physiological changes were measured.[Result]Under the extreme high temperature stress and combined stress of high temperature and drought,I.polycarpa'Yuji'seedlings wilted,the branches and trunks crumpled,and the seedlings died.The seedling height,diameter,root length,root surface area,root average diameter,biomass,leaf epidermal thickness,palisade tissue thickness,and spongy tissue thickness were all decreased to different degrees.Photosynthesis(Pn)rate was significantly decreased,stomatal conductance(Gs)and transpiration rate(Tr)gradually decreased,intercellular carbon dioxide concentration(Ci)gradually increased.Pn was mainly limited by non-stomatal factors.In terms of antioxidant system,high temperature stress caused SOD activity first increase and then decrease,high temperature and drought combined stress led SOD activity and POD activity decrease,and both stresses promoted an increase in MDA content.High temperature stress made soluble protein content first rise and then fall,high temperature and drought combined stress led a decrease in soluble protein content,and both stresses caused an increase in soluble sugar content.The effects of the combined stress on morphology and physiology were greater than those of high temperature stress.[Conclusion]I.polycarpa'Yuji'seedlings can tolerate the conditions of a daily average temperature of 40.0℃,and the daily maximum temperature of 62.0℃for 24 h.If the conditions last more than 24 h,the seedlings will be subject to severe persecution.Both the high temperature stress and the high temperature and drought combined stress seriously affect I.polycarpa'Yuji'seedlings,and the victimization degree caused by the combined stress is greater than that caused by high temperature stress.