Inhibitory effect of piperidinoethylesters of alkoxyphenylcarbamic acids on photosynthesis.

Piperidinoethylesters of 2-, 3- and 4-alkoxysubstituted phenylcarbamic acids (alkoxy = methoxy - decyloxy) inhibit photosynthetic processes in algae and plant chloroplasts. The inhibitory activity is strongly dependent on the alkyl chain length of the alkoxy-substituent showing a typical quasi-parabolic dependence with maximum effect at 6-8 carbon atoms in the alkyl chain. The alkoxy-substitution in position 2 decreases the inhibitory activity of a compound when compared with its 3- and 4-substituted analogues. ESR studies of spinach chloroplasts confirm that the compounds studied cause destruction of PS II whereby, in the presence of the most effective of the derivatives tested, Mn2+ ions are released from the protein complex.