SEASONAL-VARIATIONS IN SOLUBLE SUGARS AND STARCH WITHIN WOODY STEMS OF CORNUS-SERICEA L

Carbohydrate composition changed seasonally in red osier dogwood (Corn us sericea L.) stem tissues. Starch concentration was highest in fall and decreased to a minimum in midwinter. Coincident with the breakdown of starch in fall, there was an increase in the concentrations of sol uble sugars. Soluble sugars were present in highest concentrations in midwinter. Glucose, fructose, sucrose, and raffinose were the predomin ant soluble sugars present in both bark and wood tissues. In early spr ing, the soluble sugar concentration decreased and the concentration o f starch increased. The seasonal interchange between sugars and starch did not simply reflect a general quantitative shift in the balance be tween sugars and starch because qualitative changes in soluble sugars were also noted. The most striking changes involved the trisaccharide raffinose. Raffinose was barely detectable in summer and early fall, b ut increased to one fifth and one third of the total soluble sugars in January samples of bark and wood tissues, respectively. The potential physiological role of raffinose in overwintering red osier dogwood ti ssue is discussed.