Which of the following best describes the function of bundle sheath cells?

The role of bundle sheath cells in plants is primarily associated with the protection of vascular bundles, particularly in C4 and CAM photosynthetic pathways. These specialized cells form a protective sheath around the vascular tissue, helping to minimize the exposure to air and preventing gas exchange that could lead to water loss. The compact arrangement of these cells ensures that the vascular tissue is shielded from environmental stresses and potential damage, thereby supporting the plant's overall health and functionality.

While bundle sheath cells have other roles in certain types of photosynthesis, such as aiding in the fixation of carbon dioxide during the Calvin cycle in C4 plants, their defining characteristic is their protective function around the vascular bundles. This is crucial for maintaining the integrity of the plant's transport system, which is essential for the movement of water, nutrients, and photosynthates throughout the plant.