ABSTRACT
The soil solution in which seed germinate exerts more than water potential effect. It contains a bit of everything soluble in litter, humus, and mineral soil. These solutes may influence germination in various ways unrelated to moisture relations. This chapter examines the nature of this chemical environment and its possible influence on establishment. Allelopathy refers to "any direct or indirect harmful or beneficial effect of one plant on another through production of chemical compounds that escape into the environment". "Evidence for allelopathy includes: symptoms of plant damage such as reduced germination, growth, or development, presence of substances or organisms (plants or microbes) which contain or are capable of producing phytotoxic chemicals in the vicinity of affected plants, and presence of phytotoxic chemicals in the extracts of plants or soils in the vicinity of plants". One of the best-known examples of allelopathy stems from the detective work surrounding regeneration failure of Prunus serotina in western Pennsylvania.
