XVI International Botanical Congess

Tradeoffs between transport efficiency, drought tolerance, freezing tolerance, and mechanical strength were examined. By Poiseuille's law, wider vessels and greater vessel frequency should make wood more efficient in water transport. However, vessel diameter is well correlated with vulnerability to freeze-induced embolism (air blockage) and weakly correlated to drought-induced embolism. Some wide-vesseled species are restricted to areas where freezing never occurs. In temperate ring-porous trees, the wide earlywood vessels are prone to freeze-induced embolism, thus they have a shorter growing season than diffuse-porous trees. Wide vessels and high vessel frequency tend to mechanically weaken the wood, but other features may evolve (e.g., thicker-walled fibres) to add strength.