How do stomata control rate of transpiration

Key features of guard cell

The cellulose cell wall on the inner side of the guard cell is thicker than on the rest of the cell

Some of the cellulose microfibrils in the cell wall are arranged in ring shapes

What happens in light conditions,

The stomata open allowing carbon dioxide to diffuse into the leaf

Light conditions trigger solutes such as the potassium ion to be transferred into guard cells, lowering water potential of interior of guard cells

Water moves into guard cells by osmosis , causes guard cells to swell, they say the guard cells become turgid.

Why does stomata close at night

To reduce water loss, as photosynthesis doesnt take place during the night anyway

What happens when stomata close under drought conditions

Reduces water loss from the plant