Summary Suspension cultured cells of Daucus carota contained high amounts of non-cellulosic cell wall components. Only about 10 % of the total carbohydrates could be attributed to cellulose. Boron deficiency for two and five days resp. reduced the incorporation of 14C-glucose into cellulosic polysaccharides as well as the total cellulose content in crude cell wall preparations. Under B-deficiency molar ratios between individual sugar components remained rather constant with the exception of the mannose to glucose ratio in the fraction not hydrolyzed by 2M TFA («cellulosic aldoses»). As the mannose molecule exhibits two hydroxyl-groups in cis-position, boric acid may directly or indirectly influence polysaccharide synthesis by forming complexes with mannose. Moreover, B may affect the deposition of cell wall material by altering membrane properties. The changes in cell wall polysaccharide composition induced by B deficiency are relatively small in Daucus cells and are thus not the primary cause for the growth inhibition observed.