Which wood type is primarily active in the tree's growth phase and involved in water conduction?

The correct answer emphasizes the role of sapwood in a tree's growth and water conduction processes. Sapwood is the outer, younger layer of wood that is actively involved in transporting water and nutrients from the roots to the leaves. This living tissue plays a critical role in the physiological processes of the tree, particularly during the growth phase, where it facilitates the movement of water through the xylem vessels.

In sapwood, the cells are still functioning, enabling the transport of vital resources that support growth and photosynthesis. As trees age, the inner core becomes heartwood, which primarily serves as structural support and is not actively involved in water conduction.

Heartwood, while important for tree stability, is primarily dead tissue and does not conduct water. Latewood refers to the denser, more compact wood produced at the end of the growing season, contributing more to structural stability than to active growth and water movement. Phloem, on the other hand, is the layer responsible for transporting sugars and nutrients produced by photosynthesis rather than water.

Thus, the role of sapwood in water conduction and its active participation during the growth phase distinguish it as the correct answer.