Stomata are tiny openings present on the leaf epidermis of plants.
They aid in the exchange of gases during photosynthesis.
Stomatal opening: Stomatal opening can be understood by the potassium ion influx theory that was proposed by Levitt:
In the light, in the cells of leaves, starch is converted into malic acid.
In guard cells, this acid dissociates into malate ion and H+ ion (proton).
Guard cells and epidermal cells exchange H+ ions and K+ ions (potassium). This exchange is an active process and ATP (Adenosine triphosphate) is required for this.
To neutralise K+ ions, chloride ions make KCl (Potassium chloride) and malate ions form potassium malate.
Now, osmotic concentration of guard cells increases due to potassium malate.
Water enters into the guard cells from nearby cells and turgor pressure increases.
Increased turgor pressure causes the guard cells to open.
