STUDIES IN TREE PHYSIOLOGY: II. SEASONAL CHANGES IN THE FOOD RESERVES OF FIELD BIRCH (BETULA POPULIFOLIA MARSH.)

Abstract

During the period January 1936 to July 1938, the upper parts of Betula populifolia Marsh, were analysed for water, reducing sugars, sucrose, total soluble sugars, ether-soluble material, polysaccharide hydrolysable by taka-diastase, and residual polysaccharides extracted by dilute acid. From 38 to 63% of the taka-diastase hydrolysate from the wood is non-fermentable, presumably pentose. The residual acid extract is from 69 to 100% non-fermentable. Hexosan is low in winter, rises to a maximum just before leaf-opening, decreases sharply during spring growth and accumulates in summer. Ether-soluble material is not stored in winter. Sucrose and to a lesser extent reducing sugars are high in winter. There is a significant correlation between reducing sugars and water content of the twigs. Food reserves of the cortex behave much as do those of wood.