Which tree structure is primarily responsible for mechanical support?

The xylem is primarily responsible for providing mechanical support in trees. This is due to its structure, which consists of thick-walled cells that contribute to the rigidity and strength of the plant. As trees grow, the xylem transports water and nutrients from the roots to the leaves, but its structural properties are what allow the tree to stand upright and resist various stresses such as wind and weight from branches and foliage.

Xylem cells are composed of lignin, a complex organic polymer that reinforces the cell walls, making them tough and resilient. This enhances the overall stability of the tree, enabling it to maintain its structure over time and support the weight of its own biomass. In essence, while the xylem serves multiple functions including conduction of water, its primary role in mechanical support is essential for the tree's survival and health. Other structures like phloem, cambium, and bark serve different functions related to nutrient transport, growth, and protection, but they do not play a direct role in providing mechanical support.