Studies of the Formation and Translocation of Carbohydrates in Plants: III. The Carbohydrates of the Leaf and Leaf Stalks of the Potato. The Mechanism of the Degradation of Starch in the Leaf

Abstract

1. In the potato leaf when the tubers are beginning to develop the principal sugar present is saccharose; its amount increases from sunrise up to 2 p.m., following approximately the curve of temperature. It then falls during the rest of the day and night. The rise and fall are both linear. 2. The hexoses are present in the leaf in very small amounts—generally less than 1 per cent, of the total dry weight of the leaf. They fluctuate considerably during the early part of the day, the fluctuations being apparently determined by conversion into or formation from starch. 3. During the early part of the day up to 2 p.m. the proportion of starch changes very little, the small fluctuations which occur being related to changes in the starch. The starch is apparently formed from the hexoses.