ACCEPTOR OF LIGHT ENERGY IN PHOTOACTIVATION OF DIPHENYLETHER HERBICIDES

Diphenylether herbicides can be classified into two groups. One group, without the ortho-substituent on one benzene ring, is active in the light or dark, but the other group, having ortho-substituent(s), requires light for activation. The activation mechanism by light seems to be a photobiochemical process. A natural albino mutant was found to be tolerant to nitrofen (2,4-dichloro-4′-nitrodiphenylether) in light. Artificial white mutants of rice plants were also found to be tolerant to the herbicide, while yellow mutants were susceptible. Chlorotic seedlings induced by 3,4-dichlorobenzyl N-methylcarbamate were relatively tolerant to nitrofen. The dominant pigment(s) extracted from the yellow mutants were xanthophylls. These pigments, which are contained in the yellow mutants in large amounts, seem to make an important contribution to the photoactivation of ortho-substituted diphenylether herbicides as the acceptors of light energy. © 1969, American Chemical Society. All rights reserved.