The utilization of carbohydrates in aspen roots following partial or complete top removal

Abstract

The decline in carbohydrates in roots of aspen (Populustremuloides Michx.) as a consequence of shoot production and the contribution of new shoots to root carbohydrate levels was investigated as part of a study of the factors controlling aspen regrowth following top removal. The level of non structural carbohydrates in the roots of young aspen shoots which had been clipped during the growing season was estimated at the commencement of the dormant season. Segments of the roots were then placed in growth cabinets and kept either in darkness or in one of two light regimes having equal quantum flux densities, but with quality akin to either normal sunlight or shade. Shoot growth in darkness was greater from roots taken from plots where clipping had been conducted in midseason rather than later in the season, suggesting that some carbohydrate replenishment had taken place in those plots. Carbohydrate concentration in roots placed in the three light regimes declined to approximately the same extent over the 8 weeks of the experiment, but total weight of shoots was greater in light than in darkness, which suggests that newly synthesized carbohydrates were retained in the tops for growth. While shoots in normal and shade quality light were not phenologically different, shoots in normal light had greater leaf development than shoots in shade light and were heavier, presumably as a consequence of the greater leaf development leading to a greater net photosynthesis.