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 us ing experimentally supplied solutions at different concentrations (10( -2)-10(-4) M) and for periods from 1 to 30 d. Lead accumulation was qu alitatively 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 cel ls) and never reaches the upper part of the seta or the capsule. At th e cell level, lead localization was qualitatively assessed by X-ray TE M microanalysis. Lead is massively accumulated by cell walls and is al so present in the cytoplasm, chloroplasts, mitochondria, vacuoles and cytoplasmic reticulum. Our experiments demonstrate that F. hygrometric a 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 p lacenta suggests a special role of this tissue in detoxification mecha nisms.