ICSE Class 10 Answered

K⁺Ion Concentration Theory:

It is a recent theory. According to this theory, the stomatal opening and closing depends on the generation of a potassium ion gradient. ATP produced in the guard cells during photosynthesis is utilised to pump the potassium ions of the adjacent cells into the guard cells. Increase in K⁺ion concentration in the guard cells makes them hypertonic, so more water is drawn inside the cells. Thus, the guard cells become turgid, widening the stomatal opening