Pavement cells

Pavement cells are a cell type found in the outmost epidermal layer of plants. The main purpose of these cells is to form a protective layer for the more specialized cells below.[1] This layer helps decrease water loss, maintain an internal temperature, keep the inner cells in place, and resist the intrusion of any outside material.[2] They also separate stomata apart from each other as stomata have at least one pavement cell between each other.[3]

They do not have a regular shape. Rather, their irregular shapes help them to interlock with each other like puzzle pieces to form a sturdy layer.[4] This irregular shape that each individual cell takes on can be influenced by the cytoskeleton and specific proteins.[5] As the leaf grows, the pavement cells will also grow, divide, and synthesize new vacuoles, plasma membrane parts, and cell wall components. A thick external cell wall influences the direction of growth by impeding expansion towards the outside of the cell and instead promote expansion parallel to the epidermis layer.[6] Data suggest that waviness of pavement cells may be initiated by compressive mechanical stresses in a feedback loop that solidifies and augments cell shapes resulting in local reinforcement of the cell wall.[7][8]