Fructan composition in adventitious tuberous roots of Viguiera discolor Baker (Asteraceae) as influenced by daylength

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Short (8–10h) photoperiods stimulated branching, flowering and enlargement of adventitious tuberous roots of Viguiera discolor Baker, a native plant of the Brazilian cerrado. Inulin was mostly accumulated in parenchyma cells associated with secondary xylem of tuberous roots. Accumulation was greater in plants grown under conditions that induce flowering (1) than in plants grown under conditions that do not induce flowering (NI) (photoperiods longer than 12 h), Although total fructan concentration was similar in both conditions [approx. 460 mg (g dry mass)−1], the amount of inulin in I was 10 times that of oligosaccharides, whereas in NI it was 6 times greater. In addition, the relative molecular mass of inulin was slightly lower in NI 16600) than in I (18600), but considerably higher than those reported for other Asteraceae (approx. 5500). The results suggest that flower-inductive conditions affect fructan metabolism in Viguiera discolor without altering the total fructose.

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