What causes the opening and closing of guard cells of stomata during transpiration? Describe point-wise.

(N/A) - The immediate cause of the opening or closing of the stomata is a change in the turgidity of the guard cells.
- The inner wall of each guard cell,towards the stomatal aperture,is thick and elastic.
- When turgidity increases within the two guard cells flanking each stomatal aperture,the thin outer walls bulge out and force the inner walls into a crescent shape,causing the stomata to open.
- The opening of the stoma is also aided by the orientation of the cellulose microfibrils in the cell walls of the guard cells.
- These microfibrils are oriented radially rather than longitudinally,which makes it easier for the stoma to open.
- When the guard cells lose turgor due to water loss,the elastic inner walls regain their original shape,causing the stomata to close.