Anatomical changes in the secondary phloem of grand fir (Abies grandis) induced by the balsam woolly aphid (Adelges piceae)

Abstract

This study examines the microscopic anatomy and seasonal changes of the secondary phloem, cambium, and a portion of the xylem of grand fir trees (Abies grandis [Dougl.] Lindl.) infested with the balsam woolly aphid (Adelges piceae Ratz.) as compared with tissues of non-infested trees.The reactivation of the vascular cambium and production of astrosclereids and resin cells are about the same in infested and non-infested trees.The infested trees exhibit sieve cells that are shorter in length, having a tangential dimension about the same as normal cells, and produce more tangential bands of phloem parenchyma cells, more fiber sclereids, biseriate rays, and lipoidal-filled ray cells, abnormally shaped ray parenchyma cell nuclei, giant cortical parenchyma cells, and traumatic resin ducts in the xylem.