What function do phellem cells serve in plant tissue?

Phellem cells, also known as cork cells, are involved in the outer protective layer of a plant, specifically forming part of the periderm. These cells serve several critical functions that enhance the plant's survival and health. One of their primary roles is to thicken the plant's exterior, providing physical protection against herbivores, pathogens, and environmental stressors.

In addition to their structural function, phellem cells are important for insulation. They help to prevent water loss by creating a barrier that reduces transpirational water loss, thereby aiding in the plant's ability to retain moisture in its tissues. This protective role is especially vital in harsher environments, allowing the plant to maintain its health over time.

Furthermore, these cells contain suberin, a waxy substance that contributes to the impermeability and durability of the tissue, reinforcing their protective capabilities. Due to these various functions—thickening, insulation, and protection—phellem cells are crucial for the overall health and adaptability of the plant.