The Effect Of Vapor Pressure Deficit On Photosynthetic Characteristics And Nutrient Absorption Of Tomato At Different Temperatures

Vapor pressure deficit（VPD）is an important factor affecting plant growth and nutritional status.The effects of VPD on tomato growth,photosynthetic,water and nutrient absorption were observed and analyzed under low temperature,moderate temperature and high temperature.The purpose of this study was to explore the photosynthetic physiology and nutrient absorption mechanism of tomato at different temperatures,and to provide theoretical basis for tomato cultivation in greenhouse.The main research results are as follows:（1）This experiment featured two levels of VPD（high 2.2/low 0.9 k Pa）and two tomato cultivars（Solanumlycopersicum L.,cv.Jinpeng and cv.Zhongza）for a total of four treatments.The stomatal characteristics,leaf moisture status,net photosynthetic rate（An）,and plant growth of Jinpeng were not significantly different under the two VPD treatments,but high VPD resulted in a significantly increased transpiration rate（E）and whole plant hydraulic conductance(K_plant),as well as significantly increased absorption of potassium（K）and calcium（Ca）in various organs.The increase in K absorption could promote the opening of stomata and maintain a stable An and water supply capacity to adapt to a high VPD environment.In contrast,Zhongza had lower biomass,smaller stem height,and lower total leaf area under high vs.low VPD conditions.At high VPD,the reduction of photosynthesis in Zhongza was mainly caused by stomatal factors;significant reductions in stomatal aperture and length restricted photosynthesis and biomass accumulation.Moreover,the E and K_plant of Zhongza were reduced by stomatal state changes that prevent excessive transpiration.High VPD limited plant water status,which reduced the absorption and accumulation of nutrients.Overall,these results suggest tomato cultivars differ in their stomatal sensitivity.Specifically,increasing VPD resulted in increased levels of some nutrients in certain organs in the cultivar with lower stomatal sensitivity;however,the cultivar with higher stomatal sensitivity demonstrated opposite trends.（2）The different sensitive tomato varieties treated with long-term VPD had the same physiological response under long time different VPD.Decrease of VPD significantly increased the horizontal and vertical diameter of different tomato varieties,fruit weight and sugar to acid ratio,and decreased the content of organic acids.（3）In the experiment of low temperature artificial climate chamber,low VPD promoted the photosynthesis of tomato mainly by promoting stomatal opening.Low VPD significantly promoted the uptake of N,P and K in leaves,especially the P content in leaves.Under low VPD treatment,the photosynthetic performance of plants was improved by the significant increase of large amount of elements and chlorophyll content.In conclusion,the decrease of VPD at low temperature can promote the nutrient absorption and the improvement of photosynthesis.（4）In the greenhouse experiment,the spring suitable temperature experiment and the summer high temperature experiment were carried out in batches.The reduction of VPD promoted the photosynthesis,plant and root growth of tomatoes,and alleviated the water loss of leaves.Photosystem II under different VPD treatments（PSⅡ）excitation energy distribution（β）,photosystem systemⅠ（PSⅠ）excitation energy distribution（α）and excitation energy imbalance coefficient（β/α-1）parameters are not significantly different.The spring experiment,the chlorophyll fluorescence parameters of tomatoes under different VPD treatments:no significant difference;on the contrary,in a high-temperature greenhouse environment,high VPD treatments affected the photochemical reaction of tomato leaves,causing damage to the photosynthetic system and plant dissipation excess light energy.Reducing VPD can protect the photosystem,relieve the stress on the leaves,apromote the photosynthesis of the leaves,and benefit the growth and development of tomatoes.