Cinnamic acid inhibition of detritus feeding

Abstract

AN important advance in ecology has been the general acceptance of Fraenkel's postulate that certain chemicals in plants deter herbivores^1–3. Such chemicals are usually termed secondary plant substances because they are not involved in primary metabolic pathways. Very little of the annual production of biomass by higher plants is consumed by herbivores or phyto-pathogens⁴. Instead, most of the biomass becomes litter and eventually decays through the activity of decomposers. The secondary compounds that deter grazers while the plants are alive do not disappear immediately when plants senesce and die. We have therefore investigated whether these anti-herbivore substances continue to inhibit consumption by organisms feeding on litter or detritus. We report here that cinnamic acids, one type of secondary plant substances found in detritus, inhibit feeding by detritivores. This inhibition occurs at concentrations found in nature and may be a major factor controlling the rate of decay of organic matter.