High-temperature Disruption of Guard Cells of Vicia faba

Increased variability in stomatal aperture at high temperatures can be attributed, in part, to the differential sensitivity of guard cells to thermal damage. Individual stomata become increasingly open at higher temperatures until guard cells are lethally damaged; at that temperature, apertures decrease. The extent of irreversible damage causing closure was estimated by K(+) uptake, neutral red accumulation, and visual scoring of chloroplasts.This study found that visual scoring of chloroplast disruption provided the best estimate of guard cell viability at high temperature. Removal of the damaged guard cells from the population sample resulted in a constant coefficient of variability for apertures over the temperature range 25 to 50 C.