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This study compared the heavy metal bioaccumulation capacity in the epiphytic moss Scorpiurum circinatum and the epiphytic lichen Pseudevernia furfuracea, exposed in bags for 3 months in the urban area of Acerra (S Italy). The content of Al, As, Cd, Co, Cr, Cu, Fe, Mn, Mo, Ni, Pb, Ti, V, and Zn was measured by ICP-MS. The results showed that both species accumulated all the heavy metals assayed. The moss had the highest bioaccumulation capacity for all metals and showed a more constant and linear accumulation trend than the lichen. Intra-tissue heavy metal bioaccumulation was assessed by X-ray microanalysis applied to ESEM operated in high and low vacuum and ESEM modes.

This paper presents the results of a bioaccumulation study of trace elements in the Naples urban area based on the use of the moss Sphagnum capillifolium (Ehrh.) Hedw. and the lichen Pseudevernia furfuracea (L.) Zopf exposed in bags in 23 sites. Moss and lichen bags were exposed for 4 months starting from the beginning of July 1999. Bags gathering was carried out after 10 weeks of exposure, at the end of the dry season, and after 17 weeks, during the wet season. The elements Al, As, Ca, Cd, Cr, Co, Cu, Fe, K, Mg, Mn, Mo, Ni, Pb, Ti, V and Zn were analysed by inductively coupled plasma-mass spectrometry ICP-MS in both biomonitors. For the majority of the elements the total amounts found in S. capillifolium were higher than in P. furfuracea whether considering the whole period of exposure or the weekly uptake. It was observed that there was a much greater difference in metal accumulation by P. furfuracea between the dry and wet seasons compared with S. capillifolium. In the wet period, the lichen seems to accumulate a larger quantity of metals. With the exception of Mn, trace element concentrations did not appear to be significantly affected by the washing away of rainfall. K loss during exposure suggested cell membrane damage in both organisms. For P. furfuracea the K leakage was limited to the dry period of exposure. A clear distinction between "lithophilic" and "anthropogenic" elements was achieved by cluster analysis. Significant correlations were found among Fe-Cu-Cr-Ni, Pb-Cd-Co, V-Cr-Ni, Zn-Ni-Pb, suggesting a common source for each group of elements.

Heavy metals enter ecosystems by both natural and anthropogenic processes. An excess of metals in the environment damages plant metabolism, leading to oxidative stress in the cell. Most metal ions present in the cell are bound to low molecular mass ligands. The major types of S-containing ligands involved in metal binding are derived from cysteine. The authors show, for the first time in Scorpiurum circinatum, a Mediterranean epiphytic moss, that cysteine synthesis is linked to environmental heavy metal pollution. In moss bag exposed in strongly heavy metals polluted sites, O-acetylserine(thio)lyase (OASTL) activity seems strongly related to heavy metal exposure. In addition, heavy metal exposure in S. circinatum caused ultrastructural alterations of vacuolar system and thylakoid organisation, as shown through Transmission Electron Microscopy (TEM) observations. Because S. circinatum is able to tolerate and accumulate various heavy metals, the authors suggest the OASTL enzymatic assay in S. circinatum as biomarker of heavy metals.

The effects of the heavy metals lead (Pb) and cadmium (Cd) on the ultrastructure and the induction of Heat Shock Protein 70 (HSP 70) have been studied in Elodea canadensis Michx. As for the ultrastructural effects, sublethal concentrations of the metals caused alterations of the cell fine ultrastruc- ture. Lead and cadmium induced alterations: chloroplast were swollen with altered thylakoid organization, many cy- toplasmic vesicles appeared, cell wall organization changed. As for HSP, cadmium stress caused the most severe damages, inducing (and/or enhancing) proteins reacting vs HSP70 antibodies, suggesting that these molecular chaperones might be involved in the resistance to toxic effects of cadmium and lead in E. canadensis. Therefore, the induction of HSP 70 in E. canadensis would confer a higher re- sistance to pollutants under stressful conditions, lethal for other mosses and higher plant species.

Dried mosses (five moss species) were progressively extracted and subjected to a four-step Craig distribution. Seven pure flavonoids were isolated and identified. The flavonoids were the flavones apigenin, apigenin-7-O-triglycoside, lucenin-2, luteolin-7-O-neohesperidoside, saponarine and vitexin; and the biflavonoid bartramiaflavone and they were submitted to biological tests. The tests were performed in vitro on spore germination and protonemal growth of the moss Tortula muralis and on seed germination and root growth of Raphanus sativus. Flavonoids caused a decrease in the percentage of spore germination, protonemal development and root growth. In addition they caused morphological alterations, such as forked tips, swollen apices, rounded cells and early formation of brood cells in the protonemata. Data were discussed in relation to the presence of allelochemicals in mosses. © 2003 Elsevier Science Ltd. All rights reserved.