Competitive inhibition and selectivity enhancement by Ca in the uptake of inorganic elements (Be, Na, Mg, K, Ca, Sc, Mn, Co, Zn, Se, Rb, Sr, Y, Zr, Ce, Pm, Gd, Hf) by carrot (Daucus carota cv. U.S. harumakigosun) |
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Authors: | Takuo Ozaki Shizuko Ambe Tomoko Abe Arokiasamy J Francis |
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Institution: | (1) Japan Atomic Energy Research Institute, Tokai, 319-1195 Ibaraki, Japan;(2) RIKEN (The Institute of Physical and Chemical Research), Wako, 351-0198 Saitama, Japan;(3) Brookhaven National Laboratory, 11973 Upton, NY |
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Abstract: | We investigated the uptake of inorganic elements (Be, Na, Mg, K, Ca, Sc, Mn, Co, Zn, Se, Rb, Sr, Y, Zr, Ce, Pm, Gd, and Hf)
and the effect of Ca on their uptake in carrots (Daucus carota cv. U.S. harumakigosun) by the radioactive multitracer technique. The experimental results suggested that Na, Mg, K, and
Rb competed for the functional groups outside the cells in roots with Ca but not for the transporter-binding sites on the
plasma membrrane of the root cortex cells. In contrast, Y, Ce, Pm, and Gd competed with Ca for the transporters on the plasma
membrane. The selectivity, which was defined as the value obtained by dividing the concentration ratio of an elemental pair,
K/Na, Rb/Na, Be/Sr, and Mg/Sr, in the presence of 0.2 and 2 ppm Ca by that of the corresponding elemental pair in the absence
of Ca in the solution was estimated. The selectivity of K and Rb in roots was increased in the presence of Ca. The selectivity
of Be in roots was not affected, whereas the selectivity of Mg was increased by Ca. These observations suggest that the presence
of Ca in the uptake solution enhances the selectivity in the uptake of metabolically important elements against unwanted elements. |
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Keywords: | Calcium carrot competition inorganic elements multitracer selectivity uptake |
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