Site of inhibition by 2-amino-1,1,3-tricyanopropene of photosynthetic oxygen evolution by spinach leaf chloroplasts (Short Communication)

2-Amino-1,1,3-tricyanopropene inhibits photosynthetic O₂ evolution, but, unlike 3-(3,4-dichlorophenyl)-1,1-dimethylurea, has little effect on the steady-state fluorescence of chlorophyll. In chloroplasts prepared from spinach leaves and inhibited by 2-amino-1,1,3-tricyanopropene, a 3-(3,4-dichlorophenyl)-1,1-dimethylurea-sensitive photoreduction of ferricyanide may be restored by addition of semicarbazide. It is concluded that 2-amino-1,1,3-tricyanopropene acts at a point close to the photo-oxidation of water.