Research designed to enhance anthocyanin production in fruit has been hampered by a lack of a model system in which anthocyanin synthesis may be induced by chemical or environments factors in a similar manner as would occur in intact plants. An in vitro system has been developed using strawberry leaf discs which Alar consistently promoted anthocyanin production. Anthocyanin production was 1.27 nmoles cyanidin/cm2 with 20 mM MES [2- (morpholino) ethanesulfonic acid] buffer compared to 5.t nmoles cyanidin/cm2 in the presence of Alar. In the presence of 10 mM sucrose, anthocyanin production was 3.51 nmoles cyanidin/cm2 compared to 6.41 nmoles cyanidin/cm2 in the presence of Alar plus sucrose. Experiments with 3H-Tryptophan using strawberry leaf discs show that Alar inhibits the conversion of tryptophan to indoleacetic acid compared with those leaf discs incubated with MES alone. Exogenous applications of 0.1 mM naphthaleneacetic acid to the leaf discs inhibited anthocyanin synthesis and apparently blocked the action of Alar as an anthocyanin inducing compound. Labelled glucose experiments show that Alar promotes glucose catabolism through the pentose phosphate pathway, but only during the initial stages of anthocyanin production. Based on the data provided by these series of experiments, the mode of action of Alar in relation with anthocyanin production is associated with inhibition of auxin biosynthesis and the interference of the tricarboxylic acid cycle.