Uptake of calcium by excised barley roots

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Abstract
The uptake of Ca by 6-day-old excised barley roots appeared to be largely nan-metabolic. The Ca uptake at pH 5 was found to be insensitive to low temperature and dinitrophenol. The uptake of Ca45 was a reflection of isotopic exchange for initially present inert Ca in the root. This equilibration process was not affected by dinitrophenol. There was a large uptake of Ca by this material at pH 11. This uptake was also largely non-metabolic. Only a small fraction of the Ca uptake at high pH could be accounted for by an increase in organic acids or by precipitation as CaCO3. It is postulated that much of the Ca in young barley roots is associated with the cell surface region. It is proposed that the Ca which is active in influencing the absorption of other ions is localized on this surface.