National League for Nursing (NLN) Science Practice Exam

What is the primary function of xylem vessels in a plant?

1. Water up through the plant

2. Light energy to the leaves

3. Chlorophyll to the leaves

4. Oxygen into the leaves

The correct answer is: Water up through the plant

The primary function of xylem vessels in a plant is to transport water and dissolved minerals from the roots up through the plant. Xylem is one of the two types of vascular tissue in plants, with the other being phloem, which is responsible for transporting nutrients. The xylem enables the movement of water, which is crucial for various physiological processes such as photosynthesis, nutrient uptake, and maintaining turgor pressure in cells. This upward flow is driven by factors like transpiration, which creates negative pressure in the leaves, pulling water upward from the roots through the xylem vessels. Other options, such as the transport of light energy, chlorophyll, or oxygen, do not accurately reflect the role of xylem. Light energy is captured by chlorophyll in the leaves during photosynthesis and does not travel through xylem vessels. Chlorophyll itself is synthesized in the leaves and is not transported via xylem. Moreover, while oxygen is a byproduct of photosynthesis, it is generally released into the atmosphere rather than being transported through xylem, which instead focuses on water transport. Thus, the correct answer highlights the essential role of xylem in supporting plant hydration and nutrient transport.