ION COMPARTMENTATION IN THE RED ALGA CALOGLOSSA-LEPRIEURII IN RESPONSE TO SALINITY CHANGES - FREEZE-SUBSTITUTION AND X-RAY-MICROANALYSIS

The elemental content of cell compartments in the euryhaline red macro alga Caloglossa leprieurii (Montagne) J. Agardh subjected to different salinities, was determined by X-ray microanalysis of freeze-substitut ed thin sections. Data are given for three compartments; cell wall, va cuole and cytoplasm. The most abundant elements detected were potassiu m, sodium and chlorine, with a sulphur peak in the cell wall indicatin g the presence of sulphated polysaccharides. With salinity upshock the cytoplasm is maintained low in K, Na and Cl, whereas in the vacuoles they increased. High levels of K and Na located in the cell wall refle ct cation binding to negatively charged polysaccharides. Hyposaline sh ock resulted in decreased K, Na and Cl levels in all compartments, tho ugh K was retained in the cytoplasm. Results are discussed with regard to the role of ion compartmentation in the salt tolerance of this alg a, and the cation exchange properties of the cell wall are emphasized.