CARBOHYDRATES AND THEIR EFFECTS ON GROWTH AND ESTABLISHMENT OF TILIA AND BETULA .1. SEASONAL-CHANGES IN SOLUBLE AND INSOLUBLE CARBOHYDRATES

Changes in starch, sugar and total carbohydrate concentrations were monitored in roots, stems and leaves of newly transplanted Tilia and Betula plants throughout one growing season. Sucrose, glucose and fructose were present with small amounts of sorbitol. Concentrations of starch and sugar and the total carbohydrate content of the roots of both species declined between planting and early June, the result of reduced concentrations within primary roots, and the death of fine roots. It is suggested that this decline in root carbohydrate is partly explained by translocation to the above-ground organs to support budburst and early leaf growth. New roots and increases in the total root carbohydrate were measured much sooner after transplanting Betula than Tilia. By early July total carbohydrate in the roots of both species had increased considerably, a change attributable to increased starch concentrations in primary roots; fine roots, in contrast, contained least carbohydrate at this time. Most rapid growth of all the constituent plant parts occurred between early July and late August; shoot growth terminated at the latter date, the time of the total plant carbohydrate peak. Fine root carbohydrates increased in this period and some fine roots thickened into coarse roots. Following leaf fall, which accounted for 14% and 42% losses of total plant carbohydrate in Tilia and Betula, respectively, root carbohydrate represented more than 50% of the total plant carbohydrates persent in both species. Whilst primary roots were the principal reservoir of carbohydrate for Tilia, fine roots were more important for Betula. The species differences are related to known differences in their ease of establishment.