Carbohydrate Reserves, Translocation, and Storage in Woody Plant Roots

All of the perennial organs of a woody plant may serve a storage function, but the highest concentrations of carbohydrate reserves are usually found in root tissues. These root reserves change dramatically throughout the year, decreasing rapidly with budbreak and early vegetative and reproductive development, and then increasing late in the growing season, usually after cessation of vegetative growth and fruit maturation. Accumulation of these reserves is very sensitive to late-season stresses and management practices, and decreased accumulation can profoundly affect a tree's performance the following year. These root reserves apparently play important and specific roles in supplying substrates for shoot respiration and growth, especially in woody species that flower and begin fruit development before substantial canopy development. Although phloem transport may be involved in root-to-shoot transport, considerable xylem transport occurs in some early flowering and fruiting species. Regulation of mobilization of root reserves remains unclear, but both gibberellins and auxins are possibly involved. Unfortunately, despite their apparent importance, mobilization, transport and the specific functions of root reserve carbohydrates are only superficially defined for any woody plant.