Are Laboratory Bioassays for Allelopathy Suitable for Prediction of Field Responses?

One concern often voiced by researchers of allelopathic interactions is that many laboratory bioassays do not adequately predict the responses observed in field situations. The questions that arise are: (1) What criteria should be implemented to design ecologically relevant bioassays? (2) What species (crops or weeds) are involved in the interaction? (3) Are we investigating allelopathy of debris/residues or interactions involving living plants? (4) Which plant indicator species are actually cohabiting with the species under investigation? and (5) What are appropriate experimental controls? It is difficult to design a bioassay that can be used to examine responses in all species. In fact, each bioassay must be designed specifically to assess species interactions after careful consideration of growth habit, biotic characteristics, and ecophysiological factors. The objective of this paper is to discuss the significance of bioassays designed to study a particular aspect of allelopathy. We conclude that through a laboratory bioassay we can not demonstrate that allelopathy is operational in natural settings. An investigator should consider allelopathy as one component in a multifaceted approach to ecology and address key questions to determine the relevance of a particular assay. Due to the complexity of field interactions and responses, one can only hope to predict and describe some of the cause-and-effect relationships observed in a field setting. An accurate assessment of these main effects will prove invaluable in directing the focus of future research emphasis.