Absorption de sodium, calcium et potassium lors d'interactions ioniques au cours de la phase de germination de Raphanus sativus

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Abstract
Na+–K+ and Na+–Ca2+ interactions are measured by mineral analysis of germinating plantlets of radish (Raphanus sativus L.) in nutritive solutions enriched in these three elements. With high concentrations of CaCl2, more than 2.5 mM, the absorption of sodium is stimulated especially when there is a high percentage of this element in the external solution. On the other hand, KCl brings about a decrease in the sodium content in the hypocotyl, cotyledons and root; no one organ is affected. Only the uptake of sodium is modified not its transport, which is always proportional to the quantity absorbed. The absorption of calcium and potassium does not evolve in proportion to their external amounts, and the inhibition of accumulation of these elements by sodium is not dependent on the concentration of NaCl. The uptake of calcium is more inhibited than that of potassium which varies with the quantities of KCl and NaCl in the germination medium. Thus, potassium inhibits the uptake of sodium more than sodium inhibits that of potassium. However, whereas the absorption of sodium is only slightly modified by calcium, the absorption of calcium depends highly on the concentration of sodium.