Drought Resistance and Internal Water Balance of Oak Seedlings

Abstract

The two components of drought resistance—drought tolerance (ability to withstand drought) and drought avoidance (ability to postpone drought)—were measured on greenhouse-grown seedlings of white oak, black oak, northern red oak, and post oak. Leaf water characteristic curves, relating leaf water potential to leaf relative water content, were developed for the four species. The effect of decreasing soil and leaf water potential on the transpiration rate was determined. Small reductions in leaf water potential in the range of -8 to -16 bars resulted in a large decrease in the transpiration rate attributed to stomatal closure.Post oak was the most drought resistant of the four species, primarily because of greater drought tolerance of leaf and root cells. Black oak and white oak differed little in tolerance and avoidance. Drought avoidance of red oak leaves was significantly lower than that of the other species, and drought tolerance of red oak roots was the lowest of the four species. Forest Sci. 18:34-40.