Abstract Young willow plants (Salix‘aquatica gigantea’) were grown in hydroponic culture media, and 14C–labelled sodium bicarbonate was fed to the roots. Uptake of 14C-label in the leaves and shoots was assayed after two different feeding periods (6 h, 48 h). Even during the shortest feeding period, 14C-label had been transferred to the leaves and shoots. Compared with the longer feeding period, after the 6 h feeding period more label was in the form of acid-labile products, whereas after the 48 h feeding period most of the label was in acid-stable products.
A second experiment was designed to test whether carbon uptake by roots affects the growth of young willow plants. Uniform rooted cuttings were grown in hydroponic cultures at five different levels of bicarbonate: 0, 0.015, 0.147 0.737, and 1.473 mol m−3 NaHCO3. After a 4-week growing period we determined the biomass of leaves, shoots, roots and cuttings.
Production of total dry matter (shoots, leaves and roots) increased with increasing bicarbonate concentration. Saturation of dry matter production was reached at 0.737 mol m−3 NaHCO3, but a higher concentration of NaHCO3 (1.470 mol m−3) caused a slight decrease in the dry matter production. At 0.737 mol m−3 NaHCO3 the total dry weight increased by 31.1%, which suggests that uptake of dissolved carbon dioxide through the roots might affect carbon budgeting in young willow plants.