APICAL AND RADIAL GROWTH OF WHITE SPRUCE (PICEA GLAUCA (MOENCH) VOSS) AT CHALK RIVER, ONTARIO, CANADA

Abstract

Apical and radial growth, and the developmental anatomy of vegetative and reproductive buds of Picea glauca, were investigated. Apical growth of the leader occurred from mid-May until mid-July, that of the side branches from mid-May until late June or early July. Total apical growth of the side branches, in general, diminished with their distance from the leader. Initiation of radial growth started in the main axis behind the terminal bud and moved basipetally along the trunk. Cessation of radial growth followed the same order.The apex of the vegetative bud developed in late July or early August includes a central zone, a peripheral zone with needle primordia, and a basal zone of thick-walled cells. Reproductive buds could be recognized by early August as oblong structures with globose appendages. By mid-August, these appendages had differentiated into either pollen sacs with pollen mother cells in the male buds, or into bracts and ovuliferous scales in the female ones. The female cone entered winter with little visible internal differentiation. The influence of temperature fluctuations on vegetative and reproductive growth is discussed.