ACCUMULATION OF FRUCTAN TRISACCHARIDES IN LEAVES OF 4 WINTER CEREALS

Winter cereals produce substantial quantities of fructan (beta-D-fructofuranosyl polymer terminating in sucrose) and relatively little starch in stems and leaves. Although fructan is produced by economically important crops, little is known about fructan degree of polymerization (DP), distribution, synthesis, and degradation. Field studies in Maryland during winter and spring were used to examine changes in the pattern of accumulation of three fructan trisaccharides, 1-kestose, 6-kestose, and neokestose in oat (Avena sativa L.), wheat (Triticum aestivum L.), barley (Hordeum vulgare L.), and rye (Secale cereale L.). Oat contained the greatest amount of total trisaccharide followed by rye, wheat, and barley. The 1-kestose was the predominant trisaccharide in wheat, rye, and barley leaves. Wheat and rye contained significantly higher levels of 1-kestose than oat on most sample dates. Oat leaves contained significantly greater amounts of 6-kestose and neokestose than the other cereals. In April, 6-kestose accounted for 64% of the total trisaccharide in oat leaves. On most sample dates wheat and barley leaves contained no neokestose. Nystose, a DP 4 fructan, was present in leaf tissue at each sampling; however, the concentration was below 1 mg g-1 dry weight in all species examined. Rye contained significantly greater amounts of nystose than wheat, barley, and oat when averaged across sample dates. Variation in trisaccharides and nystose suggest that different enzymes may exist in oat compared to the other cereal species.