What is stomatal apparatus? Explain the structure of stomata with a labelled diagram.

Explanation

Stomatal apparatus : Stomatal aperture, guard cells and the surrounding subsidiary cells are together called stomatal apparatus.
Structure Components of stomatal apparatus are discussed below one by one:
(i) Stomata : Minute pores occur on the epidermal surface of leaf and also on the herbaceous stems. These pores are meant for gaseous exchange in plant.
(ii) Guard cells: Each stoma or pore is bound or guarded by two specialised kidney shaped or bean shaped epidemal cells. These are called guard cells. In grasses the guard cells are dumb bell shaped. The outer walls of guard cells are thin and the inner wall (i.e., towards the pore) is highly thickened. The guard cells possess chloroplast and regulate the opening and closing of stomata.
(iii) Subsidiary cells : Few epidermal cells in the vicinity of the guard cells become specialised in their shape and size are known as subsidary cells.