Effects of Respiration Inhibitors and Uncouplers on Dark- and Light-Induced Leaflet Movements of Cassia fasciculata.

Respiration inhibitors, in particular KCN and NaN(3), inhibited slightly the dark-induced (scotonasty) as well as the light-induced (photonasty) leaflet movements of Cassia fasciculata: they act only at concentrations higher than 1 millimolar and 0.1 millimolar, respectively. Amytal induced a stronger inhibitory effect on scotonasty. Salicylhydroxamic acid, which inhibits the cyanide-insensitive respiration pathway, was also poorly effective when applied alone. KCN and salicylhydroxamic acid applied together increased the inhibition. Uncouplers of oxidative phosphorylation were very effective: 2,4-dinitrophenol and carbonylcyanide-m-chlorophenylhydrazone inhibited the scotonastic movements at concentrations higher than 10 mum and 1 mum, respectively. Although uncouplers reduced the photonastic movements at higher concentrations, they promoted leaflet opening at other concentrations in an unexpected way.