STUDIES ON FRUCTAN ACCUMULATION IN WHEAT (TRITICUM-AESTIVUM L) .2. CHANGES IN DEGREE OF POLYMERIZATION OF FRUCTAN UNDER TREATMENT AT 1-DEGREES-C IN DARK

This study was conducted to clarify the relationship between fructan a ccumulation and snow tolerance by estimating the changes in degree of polymerization (DP) and concentration of fructan under treatment at 1 degrees C in dark to mimic the conditions under snow using 3 varieties of differing wintering ability sown at optimum and late times. (1) Th e concentration of fructan before the cold-dark treatment in the winte r hardy variety and the plants sown at optimum time was higher than th e non-hardy variety and those sown late. The concentration of mono- an d disaccharides in the plants sown at the optimum time was higher than those sown late, but there was no relationship between the concentrat ion of mono- and disaccharides and wintering ability. Hardy variety co ntained a greater amount of long-chain fructan (DP greater than or equ al to 9) than the non-hardy variety. The concentration of short-chain fructan (DP less than or equal to 8) in the hardy variety sown late wa s 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 t ime. Increasing the polymerization of fructan by increasing the concen tration of whole fructan is considered to be important to promote the wintering ability. (2) Treatment at 1 degrees C in the dark was conduc ted to mimic the conditions under snow. The fructan decrease in the ha rdy 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-chai n fructan was greater in the hardy variety than in the non-hardy varie ty. The decrease in short-chain fructan was greater in the non-hardy v ariety sown at the optimum time and the hardy variety sown late than i n the hardy and non-hardy varieties, respectively. The rate of decreas e in fructan was inversely related to wintering ability. Accordingly, fructan decreased slower in the hardy variety accumulating a smaller a mount of fructan than in the non-hardy variety with larger amount of f ructan. These results suggest that both the fructan accumulation at ea rly winter and the metabolism under snow affect the decrease of fructa n under snow.