What is Proton Transport Concept in Stomata?

Levitt in 1974 has proposed a synthetic theory on the mechanism of stomatal movement taking all earlier observations into account. The observed facts are:

(a) During opening of stoma, starch disappears from the guard cells.

(b) Photoactive opening is dependent on the chloroplast of the guard cells.

(c) Low C0₂ concentration causes stomatal opening.

(d) High pH in guard cells cause stomatal opening.

(e) There is a direct relation between K⁺ accumulation and stoinatal opening.