Pretreatment with pertussis toxin or microinjection of guanosine- 5[prime]-(3-thiotriphosphate) (GTP-[gamma]-S) into guard cells in peeled epidermis of Commelina communis L. promoted stomatal opening under subsaturating white light. Guanosine-5[prime]-(2-thiodiphosphate) (GDP-[beta]-S) and
Previous studies indicate that a continual source of adenosine 5[prime]-triphosphate is required for both opening and closing of stomata. However, vanadate (Na3VO4 at 500 [mu]M) as well as a light/dark transition induced stomatal closing in epidermal peels of Commelina communis L., showing that the