Final answer:
Vascular tissue, and specifically lignified xylem cells within it, provide structural support to plants, allowing them to grow vertically and support leaves. Ground tissue in the stems also contributes to this support and may store resources.
Step-by-step explanation:
The tissue that provides vertical support to the plant and elevates leaves is known as vascular tissue. Within the vascular tissue, it is specifically the xylem cells that are responsible for this support. Xylem cells incorporate lignin into their walls, which makes them lignified and strong enough to resist the force of gravity. As a result, plants can grow tall and reach sunlight.
Plants have three tissue systems: the dermal tissue, the vascular tissue, and the ground tissue. The ground tissue contributes to the plant's support system as well, and in stems, it functions to provide support. This ground tissue may also store water and sugars. However, the main structural support comes from the lignified xylem cells within the vascular tissue.
The stem of the plant contains these tissues and supports leaves and other structures like flowers and fruits. Through this combined support system, plants are held upright and are capable of transporting fluids and nutrients, necessary for the plant's growth and survival.