Influencing factors for transpiration rate: A numerical simulation of an individual leaf system

This paper establishes a 3-dimensional mathematical model to investigate the relationship between transpiration rate and environmental factors via a finite element and controlled variable method. The results show that an increase in photosynthetically active radiation (PAR), ambient temperature and air velocity promote transpi-ration, and an increase in relative humidity (RH) leads to a decrease in the transpiration rate. However, the transpiration rate decreases with increasing relative humidity. The reason for this phenomenon is that the vapour pressure deficit (VPD), the diffusion resistance of vapour through the boundary layer, and leaf stomatal conductance are strongly affected by these environmental factors. Stomatal conductance controls the diffusion of water vapour from the mesophyll interstitial spaces to the stomatal surface. The boundary layer resistance and VPD control the diffusion of water vapour from the pore surface to the environment. When the boundary layer resistance does not change, VPD determines the transpiration rate of the leaf. In contrast, the transpiration rate of the leaf is synergistically affected by the VPD, boundary layer resistance and stomatal conductance (gs). Due to the influence of the transpiration rate and energy exchange, the leaf temperature increases with increasing PAR, RH and ambient temperature and decreases with increasing air velocity. This research can provide some guid-ance for agricultural production and the development of bionic materials with thermal infrared properties similar to those of natural leaves.