Determination of the relative activity of aqueous plant-derived smoke solutions used in seed germination

The promotion of germination of certain seeds by plant-derived smoke and aqueous smoke solutions is well known. Different batches of smoke solutions can differ in the concentration of active compounds. In this study, the germination of Grand Rapids lettuce seed was used as a bioassay to demonstrate, and assess the differences between five types of smoke solutions. Germination was done in a controlled environment, using novel 'through-flow germination boxes', instead of traditional petri dishes. The optimum dilution levels of the smoke solutions were determined by comparing them to a standard smoke solution. Each of the smoke solutions tested was related numerically to the standard solution, this being given a value of 1. A numerical value is used to indicate the concentration level of each smoke solution. The five smoke solutions tested differed markedly from each other in their effect on the germination of the lettuce seed, emphasising the need for quality control in the production of aqueous smoke solution for commercial and experimental applications, as in field restoration programmes.