Promotion of stomatal opening in the grass Anthephora pubescens nees by a range of natural and synthetic cytokinis.

Stomatal opening in detached epidermis of Anthephora pubescens Nees incubated in the light and CO2-free air was enhanced by each of 6 natural and 4 synthetic cytokinis. Apertures were maximal following incubation with 10 mmol m(-3) cytokinin in PIPES buffer for all except N(6)-[Δ (2)-isopentyl] adenine and N(6)-[Δ (2)-sopentyl] adenosine which both opened stomata maximally at 0.1 mmol m(-3). Experiments which were undertaken to optimise the conditions of incubation showed that opening was maximal after 3 h incubation and that while 10 mmol m(-3) kinetin increased the rate of stomatal opening, it did not affect the duration. Exogenous KCl was not needed for opening and light was saturating even at the low level of 140 μmol m(-2) s(-1).