Introduction

The fructans (polymers of fructose) besides starch are the most widespread reserve polysaccharides in higher plants (1-2). Approximately 45,000 plant species use fructans as their main storage carbohydrate (3-4). Some of the prominent families of the fructan flora are Poaceae (e.g. wheat and barley), Liliaceae (e.g. onion, tulip) and Asteraceae (jerusalem artichoke, chicory). Inulin, a p 2 —»1 polymer of fructose is a storage carbohydrate in tubers of jerusalem artichoke (Helianthus tuberosus) (5) and roots of chicory (Cickorium intybus) (6). In inulin and levan, the fructose chain emerges from the fructose part of the sucrose molecule by p 2 -»1 and p 2 -> 6 linkages, respectively. In general inulin is a typical fructan of dicotyledonous plants and levan is more commonly found in monocots. Besides inulin and levan, there are neo-kestose series where chain elongation occurs at glucose moiety of sucrose or in both directions. The main types of fructans are summarized in Table 1.

In addition to the role of fructans as a plant carbohydrate reserve, they may have other functions including involvement in the osmotic adjustment of fructan-accumulating plants, in drought (1) and cold tolerance (12-14) and in sink regulation (4,14,15). In Helianthus tuberosus , the average degree of polymerization (DP) of the fructan pool declines with decreasing

Table 1

Linkage involved in different types of fructans

Table 1

Linkage involved in different types of fructans

Type of fructan

Linkage

Example

Reference

P-D-fructosyl units

(Gl-2Fl-2Fn)

Cichorium intybus

0 0

Post a comment