Mechanism of Stomatal Opening

It has been known for over a century that stomata open because of reversible turgor changes in the guard cells. Stomata open when turgor in the guard cells is high and close when it is low. It is clear that the turgor would increase only if the solute content of guard cells would be higher than the neighbouring epidermal cells.

Falling of solute content would decrease turgor. How do the two guard cells on swelling form an aperture? The cell wall of guard cells is peculiar because the cellulose micro fibrils which constitute the major structural feature of plant cell are arranged radially extending from the centre towards the periphery.