Effects Of Warming On Leaf Physiological Traits And Water Use Efficiency Of Tomato Plants Under Soil Phosphorus Deficiency

Tomato is an important vegetable crop planted in large areas in China,and the global warming caused by large greenhouse gas emissions will inevitably affect the yield and fruit quality of tomato.Meanwhile,as one of the three major nutritional elements of plants,phosphorus also plays a pivotal role in the tomato growth and development and its yield formation process.However,the available phosphorus content in the soil that can be absorbed and utilized by plants is very limited,and even the nonrenewable nature of phosphate rock resources means that the existing phosphorus on the earth will eventually be consumed by plants.Therefore,it is particularly important to explore the influence mechanism of temperature rise and phosphorus deficiency on the growth and Physiological ecological process of tomato.However,most previous studies only focused on the effect of single factors of increasing temperature or phosphorus deficit on the growth and physiological ecological processes of agricultural crops,and little has been reported about which increasing and phosphorus deficit synergistically affects crop growth and yield.Therefore,this study conducted a pot experiment with tomato seedlings using a large artificial climate growth box,setting two growth temperatures（25/16℃and 30/21℃）,and six phosphorus concentrations（0.004,0.012,0.02,0.06,0.1,and 0.5 m M）,by analyzing the coupling effects of warming and soil phosphorus deficiency on tomato leaves stomatal traits,photosynthetic performance,tissue nutrient elements,biomass and yield,this study deeply discuss the influence mechanism of warming regulated by phosphorus deficiency on physiological characteristics and water use efficiency,the following main conclusions are obtained:（1）The stomatal density of tomato leaves decreased significantly under low phosphorus stress,which indicating that tomato plants limited by soil phosphorus availability could adapt to low phosphorus stress by reducing stomatal density during stomatal development.The stomatal density on the adaxial surface of tomato leaves was increased by the warming.In addition,the stomatal density and stomatal opening on the abaxial surface of tomato leaves were higher than those on the adaxial surface,indicating that the responses of the adaxial and abaxial surface of tomato leaves to phosphorus supply and temperature were not completely consistent,and there were significant differences.The warming resulted stomatal opening of the leaves abaxial surface in the high phosphorus environment(P_0.5)was lower than that of other phosphorus treatments,which indicating that the stomatal opening of the leaf abaxial surface was increased in response to phosphorus deficiency after warming.（2）The leaves abaxial surface of tomato showed regular distribution in the small scale（<200μm）,but showed random distribution in the large scale（>200μm）.In the leaf adaxial surface,the warming resulted in the change of phosphorus supply levels of P_0.06,P_0.012 and P_0.1from random distribution to cluster distribution at 260μm,90μm and 120μm spatial scales,respectively.Under the two growth temperatures,the lowest phosphorus supply level P_0.004had the most regular stomatal distribution on the leaves adaxial surface,while the high phosphorus level treatment(P_0.5)was lower stomatal distribution rule degree than other phosphorus treatments on the leaves abaxial surface,which indicating that low phosphorus stress resulted in more regular stomatal distribution on tomato leaves.（3）The warming resulted in higher chlorophyll a,chlorophyll b and total chlorophyll content of tomato leaves than the control temperature,which indicating that a certain degree of warming was beneficial to the chlorophyll synthesis of tomato leaves.The increase of temperature resulted in the net photosynthetic rate of the phosphorus supply levels of P_0.012,P_0.02,P_0.1 and P_0.5 increased by 97.4%,169.8%,273.7%and 69.8%respectively,at the same time the transpiration rate under phosphorus supply levels of P_0.012 and P_0.02 increased by 74.1%and 164.8%respectively,thus which increased the water use efficiency of under phosphorus supply levels of P₀₁.（4）The net photosynthetic rate,stomatal conductance and water use efficiency of the highest phosphorus supply level P_0.5,were higher than those of the low phosphorus treatment group,which indicated that tomato leaves would respond to low phosphorus stress by reducing net photosynthetic rate,stomatal conductance and water use efficiency after warming.The water use efficiency at higher phosphorus supply levels(P_0.06,P_0.1 and P_0.5)was improved by warming,which indicating that the water use efficiency of tomato leaves at higher phosphorus supply levels would increase with warming.（5）The phosphorus content in leaves was higher than that in roots,which indicating that the growth of tomato leaves was more dependent on phosphorus than that in roots.The warming resulted in higher carbon,nitrogen and phosphorus contents in high phosphorus environment(P_0.5)than those in low phosphorus treatment group,The carbon,nitrogen and phosphorus contents of leaves in the high phosphorus environment(P_0.5)were higher than those in the low phosphorus treatment group,which indicating that the absorption process and utilization efficiency of the carbon and nitrogen of tomato leaves under the warming would be limited by the phosphorus supply level.When the phosphorus supply level was P_0.5,the carbon and nitrogen absorption process and utilization efficiency of leaves were the highest.Secondly,the contents of carbon,nitrogen and phosphorus in tomato leaves and roots were higher under the control temperature,which indicating that warming would reduce the absorption process and utilization efficiency of carbon,nitrogen and phosphorus in tomato plants.（6）The warming significantly increased the biomass of tomato roots.Under the two growth temperatures,the biomass of tomato leaves and roots in the high phosphorus environment(P_0.5)was significantly higher than that of the other phosphorus treatments,which implying that phosphorus deficiency exerted some inhibitory effect on the growth process of tomato.However,the fruit fresh weight of tomato of P_0.5 at control temperature（25/16℃）was significantly higher than that in the warming and low phosphorus treatment groups,which indicating that warming and low phosphorus resulted in a reduction of tomato yield.Overall,our results suggested that warming optimized leaf gas exchange efficiency of tomato by increasing the stomatal density and regularizing the stomatal distribution pattern under the condition of soil phosphorus deficiency,and thus improved plant biomass,net photosynthetic rate and water use efficiency of tomato plants,which could alleviate the physiological stress from phosphorus deficiency.These results will not only provide data for understanding physiological response mechanism of tomato to soil phosphorus deficiency and warming,but also provide scientific basis for the formulating fertilization strategies for tomato plantation under global warming.