Transpiration and Energy Exchange

Transpiration from a plant leaf is considered as a gaseous diffusion process driven by the net radiation absorbed by a leaf. The transpiration process is formulated analytically and the required transpiration rates are given for specified environmental conditions. Transpiration is limited by the internal diffusion resistance of a leaf; values of the resistance are reported for a number of native species. The midday slump of photosynthesis and transpiration, which often occurs during warm summer days, can be explained on a biochemical-biophysical basis related to high leaf temperatures.