Features of chemicals which break seed dormancy and the mechanisms of their action are discussed with reference to results obtained with red rice (Oryza sativa) and other relevant research. The significance of chemical structure, including the nature and location of functional groups, is considered, and the fact that similar structures can elicit different biochemical responses is illustrated with examples. As yet it is unclear whether changes in cell pH, highly correlated with the uptake of, and metabolism to, weak acids, and which some consider a possible trigger or marker in dormancy breaking, are causative, consequential or merely correlative. Uptake and metabolism of dormancy-breaking compounds is, or can be, very rapid and the importance of establishing the time course of dormancy-breaking, as opposed to germination events, is emphasized.
