Absorption of cobalt by excised barley roots

Co absorption by excised roots of Hordeum vulgare L. appears to be an active process exhibiting a Q10 of 2.2. The effects of poisons also indicate active absorption. After 1 hr difluorodinitrobenzene at a concentration of 5000 μM inhibited it to 20% of the control, while dinitrophenol (500 μM) and carbonyl cyanide phenylhydrazone (100 μM) inhibited it to 43% and 38% respectively. A study of absorption kinetics over a concentration range of 1 through 100 μM CoCl2 indicated that a number of carrier sites were available for absorption depending upon the concentration. Results which were consistent with this interpretation were obtained when the concentration of a competing ion, Ni, was varied. An exchangeable, absorbed fraction amounting to about 25% of the total cobalt present in the tissue after 1 hr of absorption was found.