Question

Stomata of plants open due to the influx of potassium ions.

Answer 1

Hint: Movement of water takes place from higher concentration to the lower concentration by the process of osmosis.

Complete answer
Influx in the movement of molecules inside the cell whereas Efflux means the movement is outward.
Potassium ion pump theory was proposed by Levitt 1974.
In Light
Starch is converted into phosphoenol pyruvic acid (PEP). PEP combines with $C{O_2}$to produce oxaloacetic acid and then into malic acid.
Malic acid dissociates into malate ion and \[{H^ + }\]in the guard cells.
\[{H^ + }\] are transported to epidermal cells and ${K^ + }$ are taken into the guard cells i.e. ${H^ + } - {K^ + }$ ion exchange takes place here. It is an active process which requires energy i.e. ATP.
Due to active transport of ${K^ + }$ into the vacuoles of guard cells, the ${K^ + }$ concentration increases which causes sufficient osmotic pressure to absorb water from surrounding cells.
Increased turgor pressure of guard cells due to entry of water results in stomatal pores to open.

Note:Increase in the turgidity is affected by the influx of potassium ion which helps in pushing out the outer thin wall of guard cell as compared to the thicker liver wall helping the guard cells to open.