ABSTRACT
Understanding the relationships between the dose of a phytotoxin and its effects is crucial in many types of allelopathy studies. However, realistic considerations of dose/response relationships and time of exposure are too infrequently considered in allelopathy studies. Examples are given of the proper methods for conducting dose/response studies. Synergism has been invoked in many allelopathy papers, without sufficient proof. The use of dose/response studies in determination of interactions (both antagonistic and synergistic) between different compounds is discussed. Dose/Response studies are also crucial to understand the modes of action of phytotoxins. For example, the dose/response relationships and their timing with different effects can strongly suggest that certain responses are closer to the molecular target site than others. Differences in slopes of dose/response curves suggest differences in modes of action, whereas similar slopes suggest similar modes of action. Very accurate dose/response curves are usually needed to prove hormesis (stimulatory effects of phytotoxins at subtoxic doses). Little is known about hormesis of allelochemicals, a phenomenon that might be very important in allelopathy. Finally, the effects of different target plant densities on dose/response relationships, as well as dose/response relationships generated by different allelochemical-producing donor plant densities are discussed. These methods can be crucial to proving allelopathy and to understand the mechanisms of allelopathy.
