The Physiological Role of Inulin in Wild Cardoon (Cynara cardunculus L. var. sylvestris Lam.)

Wild cardoon (Cynara cardunculus L.) is a widespread Mediterranean plant that accumulates inulin in its roots. This study aimed to analyze the enzyme systems involved in inulin metabolism in the roots of one Sicilian wild cardoon population in relation to the plant’s growth and development stages. During the winter season, the plant showed slow growth; its biomass was represented mainly by leaves and saccharides were mobilized into its roots. During the spring season, the plant doubled its growth rate and differentiated its reproduction organs as a consequence of the cold conditions. The maximum activities of the 1-SST were recorded in line with the high sucrose and inulin levels in roots, which increased quickly. The increase in the 1-FEH activity suggests that fructan-hydrolyzing activity is associated with the sprouting and elongation of plant stalks. The peak of the invertase activity occurred before the 1-FEH peak. The inulin accumulation in the wild cardoon roots was associated with the plant’s reproduction. Sequential 1-SST and 1-FEH activities and the involvement of invertase and 1-FFT in carbohydrate mobilization, in response to the additional energy demand of the plant for stalk elongation before and for capitula development were observed, along with subsequent grain ripening.