Structure of Stomata

Structure of Stomata

The epidermis of leaves and green stems possess many small pores called stomata. The length and breadth of stomata is about 10-40µ and 3-10µ respectively. Mature leaves contain between 50 and 500 stomata per mm2. Stomata are made up of two guard cells, special semi-lunar or kidney-shaped living epidermal cells in the epidermis. Guard cells are attached to surrounding epidermal cells known as subsidiary cells or accessory cells. The guard cells are joined together at each end but they are free to separate to form a pore between them. The inner wall of the guard cell is thicker than the outer wall (Figure 11.14). The stoma opens to the interior into a cavity called sub-stomatal cavity which remains connected with the intercellular spaces.