Effects Of CO₂ Concentrations And Temperature On Photosynthesis And Water Use Efficiency Of Winter Wheat Under Different Water Conditions

China is a big water user,but the water resources are scarce and distributed unevenly.Therefore,water regulation plays an important role in the utilization of soil water.As the global atmospheric CO₂ concentration rises sharply,the coexisting greenhouse effect will trigger global warming.Although researches on the effects of elevated CO₂ concentration or drought stress on winter wheat have been carried out,most of the studies are scenarios where single factors affect crop physiology and biochemistry.After all,there are many factors for climate change,such as how the interaction between warming and increasing CO₂ concentration under water deficit affects winter wheat leaf stomatal characteristics,leaf structure,and leaf-level water use efficiency,which is still rarely reported.The experiment was conducted in each of eight identical controlled growth chambers,which in full irrigation and regulated deficit irrigation on the basis of the set of two different CO₂ concentration(400?mol mol^-1 and 800?mol mol^-1)and two different growth temperature?21?/16?and 26?/21??to the cultivation of winter wheat for 90 days of winter wheat under different water conditions to investigate the response of leaf structure,physiological and biochemical processes and water use efficiency of winter wheat to atmospheric CO₂ concentration and temperature rise under different water conditions.We found:?1?When the water is sufficient,the stomatal density of winter wheat leaves was significantly increased by high CO₂ concentration and temperature increase.However,the stomatal density of winter wheat decreased when the water was insufficient.In addition,the combined increase of CO₂ concentration and temperature makes the distribution pattern of stomatal space in the adaxial side of winter wheat leaves more regular under different water states,while the regularity degree of the adaxial side is reduced.?2?Under full irrigation,the stomatal width,stomatal area and stomatal shape index of the adaxial leaf surface were significantly increased by increasing temperature,while the length,width,perimeter and area of the adaxial surface were significantly decreased by high CO₂ concentration.When the water was insufficient,the increase of temperature significantly reduced the stomatal area of the adaxial and abaxial surfaces by 40.3%and26.7%respectively,and the increase of CO₂ concentration significantly reduced the stomatal shape index and the stomatal shape became flat and long.?3?With the increase of CO₂ concentration,the opening and thickness of mesophyll cell decreased significantly under full irrigation.When the water was insufficient,the area and perimeter of mesophyll cells were significantly increased 16.2%and 20.1%;In addition,the thickness of mesophyll cells decreased significantly with the increase of temperature,but the area and circumference of mesophyll cells also decreased significantly with the decrease of water.?4?When water is sufficient,increasing temperature significantly reduced the starch content and total TNC in the leaves,while high CO₂ concentration significantly reduced the soluble sugar concentration.In the case of insufficient irrigation,the soluble sugar concentration was significantly increased by warming and CO₂ increasing treatments.In addition,when the soil moisture was sufficient,the increase of temperature significantly increased the carbon-nitrogen ratio of the leaves,while high CO₂ concentration significantly reduced the nitrogen content by 16.3%.When the temperature and CO₂concentration increased together,the nitrogen content of the leaves significantly increased.In regulated deficit irrigation,increasing temperature and high CO₂ concentration significantly increased the carbon content of the leaves,and the increase of CO₂concentration also significantly increased the nitrogen content.?5?Under full irrigation,high temperature and high CO₂ concentration did not significantly affect P_n.However,the joint increase of temperature and CO₂ concentration significantly reduced P_n by 19.5%.In deficit irrigation,high temperature significantly reduced P_n by 29.6%.The increase of CO₂ concentration increased Pn,but not significantly.In addition,no matter the temperature and CO₂ concentration acted alone or together,the water use efficiency?WUE?of leaves showed an increasing trend.?6?When water was sufficient,increasing temperature also increased the total biomass and leaf area of winter wheat,but did not reach a significant level,while increasing CO₂ concentration significantly increased the total biomass of winter wheat.In addition,under the condition of CO₂ concentration and temperature increased,the total biomass of winter wheat decreased by 18.9%.The total biomass of winter wheat was significantly decreased by increasing the temperature when water was insufficient.The increase of CO₂ concentration and the combined increase of CO₂ concentration and temperature did not significantly affect the increase of total biomass of winter wheat,but it significantly changed the leaf area.