Inhibitors of Gibberellin Biosynthesis: Applications in Agriculture and Horticulture

Abstract

Plant growth regulators (PGRs) represent only a comparatively small portion (approximately 4%) of the pesticide market. In 1987, the sales of such compounds, including desiccants and defoliants, accounted for some U.S. $720 million.1,2 Most of the plant growth regulators are compounds that reduce longitudinal shoot growth—plant growth retardants. In some cases, for instance, in barley, growth retardation can be induced by ethephon, an ethylene-releasing compound. Daminozide, which is active in apple, peanuts, and some ornamentals, is supposed to inhibit the translocation of gibberellins (GAs)3,4 and lead to a more rapid degradation of these hormones.5 However, the majority of compounds used to reduce shoot growth act primarily by blocking certain steps in the biosynthetic pathway leading to vegetative growth-active GAs. These include well-established compounds, such as chlormequat chloride (CCC) and mepiquat chloride, as well as several new inhibitors of GA biosynthesis that have been found during recent years. It is the intention of this paper to give an up-to-date survey of the most relevant compounds and also identify further possibilities for their practical application.