ABSTRACT
The gibberellins (GAs) are a group of phytohormones capable of influencing many plant development processes. A survey, aimed at the general reader of this volume, deals with the action of certain herbicides on the biosynthesis of GAs. In a series of publications, Wilkinson has attributed an inhibition of GA biosynthesis to several preemergence herbicides of the acetamide and thiocarbamate type. The following points, in particular, should be considered: Inhibition of GA biosynthesis alone cannot account for the phytotoxic effects of the herbicides since plants low in GAs are known to be quite viable. Wilkinson correctly indicated that the compounds under investigation must have several effects that are unrelated to GA biosynthesis. GAs are diterpenes and, hence, share many intermediates of the early biosynthetic steps with other terpenoids. Several branching points occur in this pathway that may lead, for example, to the side chain of cytokinins, abscisic acid, sterols, or carotenoids.
