What are bundle sheath cells?

Bundle sheath cells are a layer of compactly arranged cells that surround vascular bundles within a plant's leaves and stems. These cells play crucial roles in supporting the plant's vascular system, which is responsible for the transport of water, nutrients, and sugars. The organization of bundle sheath cells helps to provide structural integrity to these vascular bundles and can also create a barrier that regulates the movement of substances into and out of the vascular system.

In specific types of plants, particularly those that undergo C4 photosynthesis, bundle sheath cells are also involved in the process of photosynthesis itself. They contain chloroplasts and play a key role in the fixation of carbon dioxide, allowing these plants to be more efficient in hot and dry conditions.

Other options may refer to functions or structures that are important but are not the correct description of bundle sheath cells. For instance, gas exchange regulation occurs primarily through stomata, starch storage is typically carried out by parenchyma cells, and nectar production is associated with specific glandular cells in flowers. Thus, the defining characteristic of bundle sheath cells as a protective and supportive layer around vascular bundles makes this answer the most accurate.