Temperature-Induced Change in the Water Relations of Abies amabilis (Dougl.) Forbes.

Water conductance through Abies amabilis seedlings was measured while the roots were exposed to temperatures from 15 to 0.25 degrees C. Before conductance was measured, the seedlings were preconditioned for 3 months at either a high temperature (23 degrees C) or a low temperature (3 degrees C). For both groups of seedlings, conductance decreased as root temperature decreased. Conductance was lowest at 0.25 degrees C. In addition, preconditioning at 3 degrees C for 3 months significantly lowered conductance to water at all root temperatures. Under the same environmental conditions, seedlings preconditioned at 3 degrees C had less than 25% of the transpirational water loss of seedlings preconditioned at high temperature. A decrease in leaf osmotic potential also resulted from low temperature preconditioning. In trees growing in the subalpine forest, which is the natural habitat of Abies amabilis, both decreased leaf conductance to water vapor and lower osmotic potentials were evident in winter. Since in winter the temperature of the soil in the subalpine zone remains less than 1 degrees C for many months, lowered leaf conductance and decreased osmotic potentials appear to be mechanisms which aid in preventing desiccation damage.