Trunk

The trunk is the large, vertical part of a tree, especially in large trees. It is the extension of the roots, connecting the underground root system to the upper branches. The trunk provides the tree with structural support and allows the branches to receive sunlight.

In addition to its structural role, the trunk transports water and minerals from the roots and sugar produced by the branches. This transport occurs through specialized tubes that form pathways within the trunk.

Structure

The trunk consists of several layers. The outermost layer is the bark, which protects the tree from heat, disease, pests, and minor damage. Below this is a living layer that produces new cells. In the middle lies hard wood that is largely responsible for structural support.

The living layer in the middle of the trunk produces new cells each year. In trees growing in regions with distinct seasons, this growth creates concentric rings visible in the wood. These rings can be used to estimate the age of the tree and the environmental conditions it experienced.

Variation among plants

Not all plants develop a true trunk. Small plants and shrubs often have many stems extending from the ground and lack a single trunk. Palms and similar plants have trunks that do not increase in diameter uniformly; their internal structure differs from that of trees with wood.

Uses

The trunk is the primary source of commercial wood, used for construction, furniture, ships, and fuel. The bark of some trees is harvested for medicine, dye, and other products. Excessive trunk harvesting reduces forest cover and affects the livelihoods of local communities.