Fructan Variations in Tuberous Roots of Viguiera discolor Baker (Asteraceae): the Influence of Phenology

The content and composition of fructans in tuberous roots ofViguiera discolor Baker (Asteraceae), a perennial herbaceousspecies native to the Brazilian cerrado, are analysed accordingto season and in sequence from late dormancy (winter) to thebeginning of the next dormant period (autumn). The general patternof fructose found in decreasing concentrations of ethanol extractsis similar at each phenological phase. Hot water soluble fructans(high molecular mass inulin) are predominant throughout, particularlyin the dormant period, and account for more than half the totalfructan. Lower molecular mass components, especially free fructose,are present in higher amounts during the sprouting phase; thiswould indicate that hydrolysis occurs in association with thebreaking of dormancy. The absence of oligosaccharides of intermediatesize during the flowering/fruiting phase suggests they mightbe metabolized in the course of this process. The total concentrationof fructans and the mean molecular mass of inulin remain highin spite of these variations. (Received July 15, 1992; Accepted May 10, 1993)