The metabolism of fructans in roots of Cichorium intybus during growth, storage and forcing

Abstract

During the 1993 growing season samples from field-grown roots of chicory (Cichorium intybus L. var. foliosum cv. Flash) were analysed by ion-exchange HPLC (Dionex). We measured the concentrations (μmol g-1 f. wt) of glucose, fructose, sucrose, 1-kestose and 1,1 nystose. The concentrations of the higher fructans were relative (units g-1 f. wt). The data showed a significant increase in the concentration of fructans with a high degree of polymerization (DP) during July, August and September and a decrease of the glucose concentration. The concentrations of sucrose, fructose and oligomeric fructans remained roughly constant over the same period. However, in early October, important changes occurred over a very short period. These changes included: (1) a significant increase in fructose concentration; (2) an increase in the concentration of fructans with a low DP; (3) a decrease in fructans with a high DP; (4) an appearance of alternative peaks (probably representing fructans without terminal glucose); and (5) an increase in sucrose concentration. These changes were not affected by a short-day treatment starting on 6 September. Forcing of the roots for endive production was accompanied by further breakdown, mainly of the larger fructans. Activity of SST (sucrose: sucrose fructosyl transferase) decreased slowly throughout the growing season to essentially disappear by October. Neutral invertase activity increased more gradually. SST activity decreased very rapidly during cold storage and forcing.