VIEW ARTICLE

Nutrient Content of Artificially Defoliated Branches of Betula papyrifera. H. L. Gross, Research Officer, Canada Department of Fisheries and Forestry, Canadian Forestry Service, Box 490, Sault Ste. Marie, Ontario; M. J. Larsen, Research Scientist, Canada Department of Fisheries and Forestry, Canadian Forestry Service, Box 490, Sault Ste. Marie, Ontario. Phytopathology 61:631-635. Accepted for publication 20 December 1970. DOI: 10.1094/Phyto-61-631.

Branches of Betula papyrifera were subjected to two classes of defoliation in the summer of 1968: Class I, removal of half-leaves; and Class II, removal of whole leaves. Groups of branches (three branches/group) of each class and undefoliated controls were analyzed for nitrogen, starch, hexose, hexose-pentose, and ether-soluble extractives. Starch and nitrogen were significantly reduced in defoliated samples harvested during the subsequent dormant season and again in June 1969. A causal relationship apparently exists between the extent of defoliation and the observed syndrome involving subsequent amounts of nitrogen in branches, phenological responses, and death of branches.