The Effects of 3-(3,4-Dichlorophenyl)-1,1-dimethylurea on the Photosynthetic Oxygen Complex

Abstract

In the presence of trypsin and ferricyanide as external electron acceptor, lettuce chloroplasts are resistant to DCMU, showing that the inhibitory site of DCMU is only situated on the acceptor side of photosystem II. However, kinetic properties of the oxygen evolving complex are modified at non-saturating concentrations of DCMU. These changes are interpreted in terms of a model with two distinct charges separation systems on the same center: the auxiliary donor- acceptor system DQL implicated in the transitions S1 → S2 and S2 → S3 would be much less affected by DCMU than the main donor-acceptor system YQH after the first flash.