Disks prepared from the storage tissues of carrot (Daucus carota) were able to absorb boron from boric acid solutions (0�1 mM). At 25�C, net influx ceased 3-4 hr after the tissue was placed in boric acid solution. At equilibrium the tissues were able to maintain an internal concentration of diffusible boron in excess of that in the external solution. Boron uptake was inhibited by anoxia, 2,4.dinitrophenol, and at 1�C; and, in the presence of these inhibitors, the equilibrium concentration of boron in the tissues only approached that in the external solution. The capacity of the tissues to accumulate boron developed 2-3 days after the beginning of a washing treatment. Boric acid (0�1 mM) in this washing solution inhibited the development of this capacity.