Calcium uptake by excised maize roots and interactions with alkali cations.
Ca(2+) uptake was studied in short-term experiments using 5-day-old excised maize roots. This tissue readily absorbs Ca(2+), and inhibition by dinitrophenol and low temperature shows that the process is metabolically mediated. The uptake of Ca(2+), like that of other cations, is influenced by the counter ion, the pH and concentration of the ambient solution, and the presence of other cations. The rate of uptake from various salts decreases in the following order: NO(3) (-) > Cl(-) = Br(-) > SO(4) (2-). K(+) and H(+) greatly interfere with Ca(2+) absorption, while Li(+) and Na(+) have only slight effects.
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Mineral Nutrition Laboratory, USDA, ARS, SWCRD, Beltsville, Maryland 20705.