STUDY OF THE SEASONAL AND DAILY DISTRIBUTION OF SORBITOL AND RELATED CARBOHYDRATES WITHIN APPLE SEEDLINGS BY ANALYSIS OF SELECTED TISSUES AND ORGANS

Abstract

Selected tissues and organs of apple (Malus pumila Mill.) seedlings were analyzed for sorbitol, sucrose, glucose, fructose, and starch in each of the months of June to October inclusive, 1969, and over a 24-hour period in July. The seedlings were artificially defoliated three weeks prior to the first sampling. High concentrations of sorbitol, in contrast to relatively small quantities of the sugars, were found in leaf, petiole, bark, and wood of both stem and root tissues, between July and October. There was also a tendency toward a decreasing leaf-to-stem concentration of these constituents. In June, low sorbitol levels were associated with unusually high concentrations of sucrose in root and stem tissues. Over the 24-hour period in July, the patterns in the distribution of the carbohydrate constituents in leaf, stem-bark, and root-bark were similar to those described between July and October. The maximum level of sorbitol occurred during the daytime. Substantial quantities of starch, increasing in concentration toward the root, were present throughout the season in all tissues below the leaf.