National League for Nursing (NLN PAX) Practice Exam

Xylem vessels are specialized structures in plants that play a crucial role in the transportation of materials. Specifically, they are responsible for carrying water and dissolved minerals from the roots of the plant to the various parts, including the leaves and stems. This transportation process is vital for plant survival, as water is essential for photosynthesis, nutrient transport, and maintaining turgor pressure to support the plant structure.

The movement of water through the xylem occurs through a process called transpiration, where water evaporates from the surface of leaves, creating a negative pressure that pulls more water upward from the roots through the xylem vessels. This functioning of xylem as a one-way transport system highlights its role in ensuring that water reaches all parts of the plant, allowing for proper physiological functioning.

In contrast, the other options pertain to different processes or components that the xylem does not participate in. For example, the transport of food from the leaves involves phloem vessels, which carry sugars and nutrients formed during photosynthesis. Carbon dioxide enters the leaves through small openings called stomata, while chlorophyll is a pigment within the chloroplasts that captures light energy for photosynthesis, rather than being transported. Thus, the correct answer emphasizes the