Mechanism of opening and closing of stomata is controlled by
a)	Guard cells	b)	Accesary cells	c)	Epidermal cells	d)	None of these

(a)

Opening and closing of stomata is controlled and regulated by guard cells of stomata. Each stoma is surrounded by two small specialised green epidermal cells. These two cells are called as guard cells. Their walls are differentially thickened and elastic. The shape of guard cells are kidney shaped and dump-bell shaped in dicot and monocot, respectively