Sam observed a slide containing the lower epidermis of a leaf under a microscope. A number of tiny openings between the epidermal cells were present as shown…

Sam observed a slide containing the lower epidermis of a leaf under a microscope. A number of tiny openings between the epidermal cells were present as shown below in the diagram:

(a) What are these tiny openings called?

(b) Name the cells that regulate the opening and closing of the structures.

(c) Which ion is responsible for the opening and closing of the openings?