Allelopathy and Autotoxicity in Three Eastern North American Ferns

Abstract

the other to physical and biological conditions, and so limit the success of the species. Although environmental (abiotic) conditions are extremely important, biotic conditions, particularly those created by the sporophytes or gametophytes, may also be of critical importance in the establishment of new individuals of the same or another species. Therefore, these factors may regulate both population density and community composition. Chemical inhibition of one plant by another, or allelopathy, has been known for over a century (Muller, 1966) and has been much studied in flowering plants and conifers. The phenomenon of antibiosis is also well known to microbiologists. However, relatively little research has been devoted to plant inhibitors produced by non-seed plants, other than microorganisms (Rice, 1967). Bohm and Tryon (1967) reported that many species of ferns produce phenolic compounds. They examined 46 species for the presence of hydroxylated cinnamic and benzoic acids and found a basic complement of cinnamic acids (p-coumaric, caffeic, and ferulic) in the ferns they tested. Also generally present were p-hydroxybenzoic, protocatechuic, and vanillic acids. Sinapic, syringic, and o-coumaric acids were reported to be less common. In a follow-up study, Glass and Bohm (1969) found similar phenolic compounds in 46 additional species. The presence of a basic complement suggests that the well established pathways of phenolic metabolism in the seed plants also function in ferns. Many of the phenolic compounds found in ferns are known to be allelopathic in many species of higher plants, either directly or indirectly, such as after microbial decomposition (Rice, 1974). Most phenolic acids are at least slightly soluble in water. With the increasingly acidic rainfall in the northeastern United States (Likens et al., 1970; Bormann & Likens, 1977), weak organic acids such as the phenolics may be leached quite readily either from the leaves during the growing season or from senescent plants. A wide variety of organic and inorganic sub