Control of vapor pressure deficit (VPD) in greenhouse enhanced tomato growth and productivity during the winter season

In greenhouses during the winter season, a high vapor pressure deficit (VPD), particularly due to air exchange during midday period, can limit plant biomass and yield. Thus, the VPD control in greenhouses is of immense importance for cultivating plants. In the present study, the effects of VPD controlled by a fogging system on greenhouse environment and tomato plant growth were studied during a winter season. The VPD was effectively reduced by the fogging system from 1.4 to 0.8 kPa on average in the midday during the entire winter season. Maintaining a lower VPD in the midday increased tomato leaf stomatal index and stomatal conductance during the major part of the day, which led to increase in net photosynthetic rate. Furthermore, maintaining a lower VPD increased mean tomato biomass and yield by 17.3% and 12.3%, respectively. Thus, it is concluded that the VPD control via the fogging system promotes plant growth and productivity by improving photosynthesis during the winter season. (C) 2015 Elsevier B.V. All rights reserved.