Four selected NaCl-tolerant cell lines of Sour orange (Citrus aurantium) were compared with the nonselected cell line in their growth and internal ion content of Na+, K+, and Cl− when exposed to increasing NaCl concentrations. No difference was found among the various NaCl-tolerant cell lines in Na+ and Cl− uptake, and all these cell lines took up similar or even larger amounts of Na+ and Cl− than the NaCl-sensitive cell line. Exposure of cells of NaCl-sensitive and NaCl-tolerant lines to equal external concentrations of NaCl, resulted in a greater loss of K+ from the NaCl-sensitive cell line. This observation leads to the conclusion that growth and ability to retain high levels of internal K+ are correlated. Exposure of the NaCl-tolerant cell lines to salts other than NaCl resulted in even greater tolerance to Na2SO4, but rather poor tolerance to K+ introduced as either K2SO4 or KCl; the latter has a stronger inhibitory effect. The NaCl-sensitive cell line proved to be more sensitive to replacement of Na+ by K+. Analyses of internal Na+, K+, and Cl− concentrations failed to identify any particular internal ion concentration which could serve as a reliable marker for salt tolerance.
Four selected NaCl-tolerant cell lines of Sour orange (Citrus aurantium) were compared with the nonselected cell line in their growth and internal ion content of Na+, K+, and Cl− when exposed to increasing NaCl concentrations. No difference was found among the various NaCl-tolerant cell lines in Na+ and Cl− uptake, and all these cell lines took up similar or even larger amounts of Na+ and Cl− than the NaCl-sensitive cell line. Exposure of cells of NaCl-sensitive and NaCl-tolerant lines to equal external concentrations of NaCl, resulted in a greater loss of K+ from the NaCl-sensitive cell line. This observation leads to the conclusion that growth and ability to retain high levels of internal K+ are correlated. Exposure of the NaCl-tolerant cell lines to salts other than NaCl resulted in even greater tolerance to Na2SO4, but rather poor tolerance to K+ introduced as either K2SO4 or KCl; the latter has a stronger inhibitory effect. The NaCl-sensitive cell line proved to be more sensitive to replacement of Na+ by K+. Analyses of internal Na+, K+, and Cl− concentrations failed to identify any particular internal ion concentration which could serve as a reliable marker for salt tolerance.