The procedures involving the analysis of synergism between allelochemicals have basically involved the use of fixed concentrations. This work deals with theoretical model involving four possibilities of response: one demonstraing the existence of synergism (possibility A of the model); one demonstraing the absence of synergism (possibility B of the model) and two showing that a substance potentializes the effect of another (possibilities C and D of the model). Two isolated chemical substances (3,4,5-trimetoxybenzoic acid [S1] and 3,4-dimetoxybenzoic acid [S2]) were used to test the model, isolated from Parkia pendula leaves with known allelopathic activity , in the following combinations: pure S1; pure S2, and combinations S1 and S2, in the following ratios 3:1; 1:1; and 1:3. As indicators, the weeds Mimosa pudica and Senna obtusifolia were used. The results, based on analysis of the four possibilities established in the theoretical model, allowed to infer the absence of synergistic effect between the two tested substances. The variations observed between the obtained results and the possibility B of the model can be attributed to the inhibition potential of the substance and the sensitivity of the receiving species to the tested substances.
allelopathy; inhibition; model; weeds
