Involvement of cytokinins and adenosine 3′,5′-cyclic monophosphate in stomatal movement in Vicia faba
by Morsucci R., Curvetto N., Delmastro S.(1991)
Evidence was obtained for the involvement of adenylate cyclase and cyclic AMP in cytokinin-induced stomatal movement in Vicia faba. Epidermal peelings, stained for a transmission electron microscopy search of adenylate cyclase activity, showed scarce or no activity in control stomata, and a low activity in guard cells from kinetin-treated leaves; but in the latter, a high activity associated with nuclear membrane and chloroplasts was observed.
In contrast, guard cells from kinetin riboside- or adenosine-treated leaves showed high staining in plasmalemma, nuclear membrane, endoplasmic reticulum, mitochondria and tonoplast, but none in chloroplasts.
Stomatal aperture was stimulated by adenosine (Ade), kinetin riboside (KR) and kinetin (K) at 10 nM – 0.1 mM in darkness. Ade and KR (10 nM) enhanced stomatal aperture in light, but kinetin had no effect on inhibited stomatal aperture at higher concentrations.
Methyladenosine (M-Ade) and 2′-deoxyadenosine (D-Ade) were compared with Ade, KR and zeatin riboside (ZR) in their ability to open stomata at 10 nM and in darkness; similar responses were found with M-Ade, Ade, KR and ZR, but with D-Ade the aperture was much more reduced.
The results are discussed in terms of cAMP metabolism, and a central role for the purine nucleoside structure in the interaction of either Ade or KR with their putative site(s) of action on plasmalemma of guard cells of V. faba is proposed.