Application of a coupled model of photosynthesis and stomatal conductance for estimating plant physiological response to pollution by fine particulate matter (PM2.5)

Fine particulate matter (PM2.5) is a current environmental issue that has an impact on the global ecology. Vegetation is a known sink for PM2.5 deposition but the effects of these particles on plant growth, and specifically on plant photosynthesis by changing their leaf water potential, are still not well understood. This study aimed to determine and characterize possible relationships between PM2.5 and plant photosynthesis under different PM2.5 concentrations. Both indoor and outdoor measurements were carried out to evaluate the variation dynamics of net photosynthetic rate and stomatal conductance of four plant species with different leaf characteristics under different PM2.5 levels. A calibrated coupled model of photosynthesis and stomatal conductance was developed to estimate the relationship between plant photosynthesis and PM2.5 reliably. Net photosynthetic rate and stomatal conductance declined over time at elevated PM2.5, with large variations with PM2.5 concentrations. Using a calibrated model of photosynthesis coupled to stomatal conductance, we show that PM2.5 can influence plant photosynthesis that primarily occurs through the stomata on leaves. Although the effect of particles on plant photosynthesis was not as high as that of photosynthetically active radiation, temperature, and CO2 concentration around the leaf, the effect from PM2.5 can be significant, in particular, in highly polluted atmospheres.