TISSUE AND CELL LOCALIZATION OF EXPERIMENTALLY-SUPPLIED LEAD IN FUNARIA-HYGROMETRICA HEDW USING X-RAY SEM AND TEM MICROANALYSIS

Lead accumulation in the moss Funaria hygrometrica was investigated using experimentally supplied solutions at different concentrations (10(-2)-10(-4) M) and for periods from 1 to 30 d. Lead accumulation was qualitatively and quantitatively measured by X-ray SEM microanalysis in different tissues. Lead is preferentially accumulated in some tissues (gametophyte hydroids, sporophyte hydroids at foot level, transfer cells) and never reaches the upper part of the seta or the capsule. At the cell level, lead localization was qualitatively assessed by X-ray TEM microanalysis. Lead is massively accumulated by cell walls and is also present in the cytoplasm, chloroplasts, mitochondria, vacuoles and cytoplasmic reticulum. Our experiments demonstrate that F. hygrometrica shows a marked capability to sequestrate lead in particular tissues, so that it never reaches the upper part of the seta nor the capsule, in the conditions used here. The massive accumulation of lead at the placenta suggests a special role of this tissue in detoxification mechanisms.