REMOTE ESTIMATION OF LEAF TRANSPIRATION RATE AND STOMATAL-RESISTANCE BASED ON INFRARED THERMOMETRY

A remote method was developed for monitoring leaf transpiration rate and stomatal resistance on a realtime base. The method utilizes leaf temperatures measured with an infrared radiometer as integral inputs for a model to compute those parameters. The model is based on the energy balance of a plant leaf, accounting for moisture transfer processes in the stomata and boundary layer. Remotely determined transpiration rates and stomatal resistances were compared with those measured with a steady state porometer. The corresponding values obtained from the two methods were linearly related (r=0.79** and 0.93** for transpiration and stomatal resistance, respectively); but the porometer transpiration rates were somewhat higher than those obtained by the "remote" method, probably because the air in the porometer cuvette was drier than the ambient air. On the other hand, the stomatal-resistance values from the two methods fell on the 1:1 line with a high correlation coefficient, suggesting that the "remote" method produces excellent estimates of actual stomatal resistance. © 1990.