Vapor Pressure Deficit (VPD) Effects on the Physiology and Yield of Greenhouse Tomato

Abstract

Tomato production represents >70% of all greenhouse vegetables produced in Quebec, Canada. To obtain high yields and high quality fruit, an adequate control of greenhouse environmental characteristics, including the vapor pressure deficit (VPD), is necessary. Our study examines four VPD treatments (0.5 kPa day and night, 0.8 kPa day and night, 0.8 kPa day 0.5 kPa night, and automatic VPD management according to transpiration) and three photoperiods [12 h, 14 h, and variable-12 h (summer) 16 h (winter)] on growth, yield, and photosynthetic capacity of tomato plants. Greenhouse temperature was maintained at 22C day/18C night. Pure CO2 was injected into the greenhouse to maintain a constant atmospheric concentration of 800 ppm throughout the experiment. Growth, yield, and leaf mineral composition were determined monthly for each treatment during the experiment. The photosynthetic rate of the 5th and 10th leaves also were measured in addition to the content of chlorophyll a and b. Our results indicated an increase in total yield and photosynthetic rate under a VPD of 0.8 kPa during day and night. An increase in leaf mineral concentration also was noted in plants grown under high VPD. Differences in yield and photosynthetic capacity were not found between the three photoperiods studied. However, there was a tendency to have higher yields under longer photoperiods.