Translocation of Carbohydrates in the Cuthbert Raspberry

The seasonal fluctuations in reducing sugars, sucrose, starch, acid hydrolyzable carbohydrates, total carbohydrates, and the residual polysaccharides are recorded for the raspberry plant. 2. Double rings, one 15 cm. and another 30 cm. above the ground, isolating a 15 cm. segment of stem, were used to check movements of sugars. 3. In normal plants the concentration of total carbohydrates is fairly high in May, drops during June, the period of most active growth, and then increases to a maximum in August. The acid hydrolyzable carbohydrates are the largest fraction of the total carbohydrates. The concentration of reducing sugars is highest in May, drops rapidly in June, and increases slightly in July and August. A low concentration of sucrose is present at all times. Starch is never abundant, and apparently is not an important carbohydrate reserve. 4. In ringed plants the total carbohydrates accumulate above the rings, and decrease below and between them. Sucrose made the largest increase above the ring. Reducing sugars accumulated above the rings, but decreased between and below them. Apparently sucrose tends to move upward as well as downward in the bark. It does not appear to be a product of hydrolysis of hemicellulose in the isolated segment as do reducing sugars. A portion of the reducing sugars is translocatory, moving downward in the bark. 5. All carbohydrate gradients are positive. Sugars move downward with a marked positive gradient. The positive gradients of the acid hydrolyzable substances and of starch are static. These gradients are produced by temporary storage brought about by accumulations within living cells and cells associated with living cells. Ringing decreases the positive gradients of reducing sugars, indicating that some of them are mobile in the bark along a dynamic positive gradient. Much of the reducing sugars may be a temporary storage form and not functional in translocation. Therefore their positive gradient is the result of a positive dynamic gradient of mobile sugars and a positive static gradient of temporary storage sugars. 6. The insignificant and probably non-existent gradient of sucrose is increased rather than decreased, as would be expected if this sugar were moving only downward. 7. The residual substances consist of those polysaccharides, small quantities of fats, minerals, and organic nitrogen which remain after the total carbohydrates, including acid hydrolyzable substances, are subtracted from the dry weight. The residual polysaccharides are thought to include the "intussusception" material (polysaccharides of high molecular weight and their derivatives) of the cell wall. The residual polysaccharides fluctuate as the total carbohydrates (particularly reducing sugars and the "hemicelluloses") fluctuate, and in the same direction.