Blue light effects on stomata are mediated by the guard cell plasma membrane redox system distinct from the proton translocating ATPase

The effects of blue light on stomata are critically analysed. Blue‐light‐induced increase in stomatal conductance is preceded by membrane hyperpolarization, proton efflux, potassium uptake and malate synthesis in guard cells. Hypothetically, a flavin containing plasma membrane redox system can pump protons out of guard cells on illumination with blue light. It is proposed that this electrogenic proton pump requires NAD(P)H but does not involve ATP/ATPase.