Synergy Assessment for Plant Growth by Independent Joint Action Theory

Calculating the predicted biological efficacy of a mixture and determining the significance of the difference between the predicted efficacy and the measured efficacy of that mixture are fundamental when assessing the synergy of mixtures. The Independent Joint Action theory and Bliss's formula are well-known and widely accepted for predicting pesticide mixture effects that are expressed in terms of percent mortality. Bliss's formula, however, is not applicable to growth-affecting components, such as plant growth regulators. Therefore, there is an unmet need of critical importance: an appropriate method for assessing synergy of growth-affecting mixtures needs to be identified within the scientific community. The formula, G((1 + 2 center dot center dot n)) = G(1)G(2) . . . G(n)/(G(CTL))(n-1), which was derived from the Independent Joint Action theory, is presented for calculating the predicted efficacy for mixtures of growth-affecting components that either promote or inhibit growth. Its application is demonstrated by analyzing data from a greenhouse assay in which a mixture of S-abscisic acid and gibberellic acid was used to promote the growth of corn seedlings.