| Strawberry（Fragaria×ananassa Duch.）is widely planted all over the world because of its high economic benefits.In the process of strawberry production,high-temperature and high-light stress,as an important abiotic stress factor that limits the growth of strawberry seedlings,seriously affects the growth and development of strawberry seedlings.Therefore,it is of great significance to explore how to alleviate the impact of high-temperature and high-light stress on strawberry seedlings.In this study,strawberry‘Xue Lixiang’was used as the experimental material to study the effects of high-temperature and high-light stress on the physiological and biochemical characteristics of strawberry and the mitigation effect of chitosan on high-temperature and high-light stress.The main research results are as follows:1.High-temperature and high-light stress lead to a downward trend in strawberry seedling chlorophyll,net photosynthetic rate,stomatal conductance,photochemical efficiency,quantum transfer rate and other indicators.Chitosan pretreatment alleviated the decrease of chlorophyll content and photosynthetic rate caused by high-temperature and high-light stress;alleviated the photoinhibition of photosystem II（PSII）by high-temperature and high-light stress.Under high-temperature and high-light stress for 8 h,the chlorophyll content in strawberry plants increased by 16.9%after chitosan treatment compared with non-chitosan（H2O treatment）;the net photosynthetic rate increased by74.9%;the maximum photochemical efficiency increased by 20.1%.Among them,100mg·kg-1chitosan treatment can better alleviate the decrease of each index caused by high-temperature and high-light stress.2.Under the stress of high-temperature and high-light stress,the content of osmotic adjustment substances in each treatment showed an upward trend.Chitosan treatment can increase the content of osmotic adjustment substances in strawberry seedlings under high-temperature and high-light stress.Eight hours after high-temperature and high-light stress,compared with non-chitosan treatment,the content of proline in strawberry seedlings increased by 17.2%,the content of soluble sugar increased by 54.8%,and the content of soluble protein increased by 35.2%.Resistance of strawberry seedlings to high-temperature and high-light stress.Among them,100 mg·kg-1chitosan treatment can better improve the proline content under high-temperature and high-light stress,and improve the stress resistance of strawberry seedlings.3.The activity of antioxidant enzymes in strawberry seedlings showed an upward trend due to high-temperature and high-light stress.Chitosan treatment improves the activity of SOD,POD,and CAT compared with non-chitosan treatment.POD can be combined with CAT,SOD and other enzymes coordinated to remove O2-and H2O2in plants,so that under high-temperature and high-light stress,the contents of O2-and H2O2in strawberry seedlings treated with chitosan decreased by 19.3%and 22.2%respectively（stress after 8 h）.Reduce the damage of active oxygen to the photosynthetic structure and cell membrane of strawberry seedlings,reduce the relative conductivity of tissues,and reduce the production of malondialdehyde（MDA）.4.High-temperature and high-light led to the ascendent trend of the activity of key enzymes and antioxidants in the AsA-GSH cycle in strawberry seedlings.Under high-temperature and high-light stress,pre-spraying chitosan increased the four key enzyme activities of APX,GR,DHAR and MDHAR in the AsA-GSH cycle by 21.9%,27.5%,14.9%and 24.3%（8 h after stress）;the content of AsA,GSH and AsA/DHA,GSH/GSSG increased by 17.1%,17.4%,25.6%and 31.2%（8 h after stress）respectively compared with non-chitosan treatment. |
