Certified Arborist Practice Test

The bark of a tree plays a crucial role primarily in protecting the tree against environmental factors. It acts as a protective layer that shields the internal tissues from physical damage, pests, pathogens, and harsh weather conditions. The outermost layer of the bark, called the cork, is composed of dead cells that are highly water-resistant, helping prevent excessive water loss and providing insulation against temperature extremes.

While other functions are important for a tree's overall health and survival, they do not align specifically with the primary function of the bark. Water absorption occurs mainly through the roots, not the bark. Photosynthesis is facilitated by the leaves, where chlorophyll captures sunlight to convert carbon dioxide and water into energy. The support structure of the tree is primarily provided by the wood (xylem) rather than the bark. Thus, the primary association of bark is indeed its protective role within the tree’s anatomy.