Effect of vapor pressure deficit on the photosynthesis, growth, and nutrient absorption of tomato seedlings

Abstract

Vapor pressure deficit (VPD) is the main driving force of plant water transport and affects the nutrient absorption of plants. Exploring the nutrient absorption, growth, and photosynthetic characteristics of different tomato cultivars under different VPDs is of great importance for the cultivation of tomato. This experiment featured two levels of VPD (high 2.2/low 0.9 kPa) and two tomato cultivars (Solanumlycopersicum L., cv. Jinpeng and cv. Zhongza) for a total of four treatments in two controlled environment growth chambers. After about 4 weeks, the seedlings (at the three true-leaf stage) were transplanted into pots flled with inorganic medium and watered with nutrient solution. 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 (Kplant), as well as significantly increased absorption of potassium (K) and calcium (Ca) in various organs. 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 anatomical modifications of the stomata; significant reductions in stomatal aperture and length restricted photosynthesis and biomass accumulation. Moreover, the E and Kplant of Zhongza were reduced by stomatal state changes that prevent excessive transpiration. High VPD limited plant transpiration and mass flow of water, 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.