Effects of light regime on antioxidant content of foliage in a tropical forest community

A basic tenet of plant ecology is char under high light and limiting nutrie nt levels, carbon becomes relatively more available for investment in anti- herbivore defense. Rarely considered in discussions of such defense investm ents, however, is the necessity for plants to defend themselves against oxi dative damage caused by light exposure itself To determine if the ability t o respond to elevated levels of light exposure by increasing production of antioxidant compounds is a general characteristic of foliage in tropical pl ants, we conducted a broad survey of antioxidant content in foliage of 55 s pecies in a tropical forest community by comparing individuals within fores t gaps to conspecifics in the closed canopy forest. To do so, we devised a rapid assay to use under field conditions. Of the 41 species of shrubs, tre es, and lianas demonstrating a discernible difference in antioxidant conten t under the two light regimes, 34 (68%) showed higher antioxidant content u nder high light conditions. In a quantitative laboratory-based study using four of these species, light was associated with a 15 to 45 percent increas e in water-soluble antioxidants in three species; one species displayed a 1 18 percent increase in fat-soluble antioxidants as well. Thus, changes in t he chemistry of plant foliage in response to light may reflect plant invest ments in defense against abiotic stress factors as well as investments in d efense against biotic stress factors.