Étude des capacités d'échange et des sélectivités cationiques de parois isolées des racines de Cochlearia anglica et de Phaseolus vulgaris cultivés sur des milieux diversement salés

Abstract

Cochlearia anglica L. (halophyte) and Phaseolus vulgaris L. (glycophyte) were grown in media of different salinities. The root cell walls were isolated and then equilibrated with various salt solutions. There were differences between cell walls from C. anglica and P. vulgaris in both the cationic exchange capacity (computed by the sum of parietal cations) and the cell wall selectivity (evaluated by the centesimal proportion of each cation). In cell walls from plants grown without NaCl, the number of exchange sites was greater for the halophyte than for the glycophyte. Growing the plants on 42 and 85 mM NaCl medium reduced or reversed the disparities between the two species: with C. anglica, the cell wall cationic exchange capacity decreased when the growth medium salinity increased whereas this capacity tended to rise for P. vulgaris. However, the culture medium salinity did not affect the cell wall selectivity of these species for major cations. For Ca2+, the selectivity of cell walls from P. vulgaris was higher than that of cell walls from C. anglica; for the other cations, the situation was reversed.