Anatomy and chemistry of aspen branches afflicted with drooping aspen disease

Abstract

Anatomical and chemical comparisons were made of branch wood from drooping and nondrooping aspen (Populus tremuloides) collected near Aspen, Colorado. Drooping and nondrooping branches did not differ in the lengths or diameters of vessel elements or in their content of pectin or glucomannan. Individual growth rings were of uniform thickness in drooping branches, but they were thicker on the top than on the bottom of nondrooping branches. Compared with nondrooping branches, drooping branches had narrower growth rings, less tension wood, more extractable material, less lignin, less xylose, more cellulose, more glucose, and more gelatinous fibres. It is concluded that the drooping habit is caused by alterations in the formation of tension wood.