Abstract: Transpiration, influenced by many environmental variables, is one of the important physiological activities for plants. The responses of transpiration to environmental factors (solar radiation, vapor pressure deficit and soil water potential) were examined for some tree species (Osmanthus fragrans, Cinnamomum camphora and Liquidambar formosana) over three years with distinguished precipitation amounts (drought summer in 2013 and wet in 2014 and 2015) based on a recently developed transpiration model (the modified Jarvis-Stewart model). The model calculates transpiration from a maximum value scaled down by three functions of individual environmental factors. The functions were rigorously parameterized simultaneously using an advanced optimization algorithm. The results indicated that: (1) The transpiration response of O. fragrans and L. formosana to solar radiation was more sensitive than  C. camphora, while C. camphora transpiration was more sensitive to VPD than O. fragrans and L. formosana. (2) On average during the whole growing season, the primary impact factor of plant transpiration was water potential in 2013, and VPD in 2014 and 2015. (3) The dual impact of VPD to transpiration was observed in 2013, in which an optimal VPD for transpiration occurred. Away from this optimal VPD value, transpiration decreased. In 2014 and 2015, transpiration increased with VPD.

Key words: maize, brassinosteroid, nitric oxide, low temperature, oxidative damage.