There has been an increasing interest in using non-destructive thermal imagery to determine leaf temperature of plants. Leaf temperature has been proven as an indicator of plant responses to various stressors (CHAERLE and VAN DER STRAETEN 2000), in particular for plant water availability (JONES 1999). The theory is that a reduced stomatal aperture restricts transpiration and consequently heat dissipation, resulting in an increase in leaf temperature (GATES 1964).