Submitted to: Agricultural and Forest Meteorology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: May 15, 2006
Publication Date: October 12, 2006
Citation: Bunce, J.A. 2006. Use of a minimally invasive method of measuring leaf stomatal conductance to examine stomatal responses to water vapor pressure difference under field conditions. Agricultural and Forest Meteorology. 139:335-343. Interpretive Summary: Knowledge of the actual rates of water loss from leaves is important in studies of the drought resistance of crops. However, previous methods of measuring the rate of water loss require enclosing the leaf, which changes the environmental conditions and the rate of water loss. I developed a new method to measure rates of water loss of leaves without enclosing them. This method will be of use to researchers trying to improve the drought resistance of crops.
Technical Abstract: Most methods of measuring the diffusive conductance to water vapor of individual plant leaves potentially change the leaf environment by enclosing part of the leaf in order to measure the rate of water vapor exchange and the driving force for that exchange. Some types of porometers rely on the assumption that stomatal responses to the altered environment lag the measurement interval, but do not record the prior environmental conditions. Here I combined leaf temperature measurements with environmental measurements in an energy balance approach to estimate stomatal and boundary layer conductances of upper canopy leaves of three crop species. Stomatal conductances measured with this method were highly correlated with measurements obtained with a steady-state portable photosynthesis system. However, the photosynthesis system often reduced the leaf to air water vapor pressure difference during the measurements sufficiently to increase stomatal conductance. The method provides a new way to simultaneously determine the natural environmental conditions and stomatal and boundary layer conductances of leaves.