Selectivité de fixation du sodium au niveau des embryons et des jeunes plantes sensible ou tolerante au NaCl

Abstract

Embryos and young plants of tomato, radish, and red cabbage germinated in different media showed an ascending degree of tolerance to NaCl. Red cabbage embryos were tolerant to salinity and showed the highest K+ and Ca2+ fixation capacities which were correlated to the lowest initial adsorption of Na+. Furthermore, initial accumulation of K+ and Ca2+ in red cabbage was increased with increasing NaCl in the medium. Conversely, salt-sensitive tomato embryos showed the lowest initial internal ratios of Ca2+/Na+ and K+/Na+, and increasing NaCl concentrations did not provoke any increase in contents of K+ and Ca2+. No correlation was found between tolerance to salinity and Na+ content of young plants. However, Ca2+ accumulation capacity in a (NaCl + CaCl2) medium was associated with the degree of tolerance, although the ratio of internal Ca2+/Na+ decreased. In tomato and red cabbage, a competitive interaction was found between K+ and Na+ at high salt concentrations, while in radish allosteric interactions were observed. Thus, radish accumulated more K+ than Na+ at high KCl and NaCl concentrations and young plants of radish and red cabbage had the highest selectivity for potassium. Plant tolerance to salinity, during seed germination, was correlated to accumulations of K+ and Na+ in embryos. The mobilization of Ca2+ stored in the seed does seem to have a regulatory role in the plasmalemma selectivity.