Studies on Fructan Accumulation in Wheat (Triticum aestivum L.). II. Changes in degree of polymerization of fructan under treatment at 1.DEG.C. in dark.

Abstract

This study was conducted to clarify the relationship between fructan accumulation and snow tolerance by estimating the changes in degree of polymerization (DP) and concentration of fructan under treatment at 1°C in dark to mimic the conditions under snow using 3 varieties of differing wintering ability sown at optimum and late times. (1) The concentration of fructan before the cold-dark treatment in the winter hardy variety and the plants sown at optimum time was higher than the non-hardy variety and those sown late. The concentration of mono- and disaccharides in the plants sown at the optimum time was higher than those sown late, but there was no relationship between the concentration of mono- and disaccharides and wintering ability. Hardy variety contained a greater amount of long-chain fructan (DP≥9) than the non-hardy variety. The concentration of short-chain fructan (DP≤8) in the hardy variety sown late was higher than that of the non-hardy variety, but a varietal difference of this fraction was not detected in the plants sown at the optimum time. Increasing the polymerization of fructan by increasing the concentration of whole fructan is considered to be important to promote the wintering ability. (2) Treatment at 1°C in the dark was conducted to mimic the conditions under snow. The fructan decrease in the hardy variety and the plants sown at optimum time was rapid and large in the early stage of the cold-dark treatment. The decrease in long-chain fructan was greater in the hardy variety than in the non-hardy variety. The decrease in short-chain fructan was greater in the non-hardy variety sown at the optimum time and the hardy variety sown late than in the hardy and non-hardy varieties, respectively. The rate of decrease in fructan was inversely related to wintering ability. Accordingly, fructan decreased slower in the hardy variety accumulating a smaller amount of fructan than in the non-hardy variety with larger amount of fructan. These results suggest that both the fructan accumulation at early winter and the metabolism under snow affect the decrease of fructan under snow.