Removal of boron from the nutrient solution reduced root elongation within 24 h in V. faba seedlings. This was accompanied by a reduction in rubidium uptake per plant as well as an altered distribution within the root. Although the uptake by the terminal centimetre was reduced in boron deficiency, there was little effect on older tissue. The proportion of absorbed Rb transported to the shoot, efflux rates, and other uptake characteristics were similar for deficient and normal tissue. The reduced uptake is considered to be a secondary effect associated with the requirements of boron for root elongation and metabolism.