Absorption of cobalt by excised barley roots

Co absorption by excised roots of Hordeum vulgare L. appearsto be an active process exhibiting a Q₁₀ of 2.2. The effectsof poisons also indicate active absorption. After 1 hr difluorodinitrobenzeneat a concentration of 5000 µM inhibited it to 20% of thecontrol, while dinitrophenol (500 µM) and carbonyl cyanidephenylhydrazone (100 µM) inhibited it to 43% and 38% respectively.A study of absorption kinetics over a concentration range of1 through 100 µM CoCl₂ indicated that a number of carriersites were available for absorption depending upon the concentration.Results which were consistent with this interpretation wereobtained when the concentration of a competing ion, Ni, wasvaried. An exchangeable, absorbed fraction amounting to about25% of the total cobalt present in the tissue after 1 hr ofabsorption was found. (Received September 28, 1973; )