Summary. Accumulation, tissue and intracellular localisation, and toxic effects of cadmium were investigated in the liverwort Lunularia cru- ciata. The results of analyses carried out by atomic absorption spectrome- try on single plants showed that the cadmium accumulation was dose- and time-dependent. Cadmium localisation was assessed by X-ray scanning electron microscopy microanalysis in gemmalings and in the different tis- sues of the thallus and by X-ray transmission electron microscopy micro- analysis at the cellular level. The metal preferentially accumulated in the hyaline parenchyma and at the base of the gemma cups. Inside the cell, cadmium accumulated in the vacuoles and the cell wall. Metal accumula- tion was accompanied by a concomitant increase in sulphur content within the vacuoles of stressed cells. Gel-permeation chromatography showed that most of the cadmium was associated with a low-molecular-mass frac- tion eluting at a ratio of elution volume to void volume corresponding to that of phytochelatins. The excess of sulphur deposited in the vacuoles may well have been caused by the stress-induced synthesis of phy- tochelatins. At the ultrastructural level, sublethal concentrations of cad- mium caused alterations of the fine structure of the cells, inducing marked alterations of the chloroplast structure. Cadmium also induced a dose-de- pendent inhibition of apical thallus growth and gemma germination. Keywords: Heavy metal; Bryophyte; Phytochelatin; X-ray scanning elec- tron microscopy microanalysis; X-ray transmission electron microscopy microanalysis. Introduction All plants have the ability to accumulate essential oligo- elements such as Cu, Mn, and Zn from soil and water. Some plants can also incorporate heavy metals, particu- larly Cd, Cr, Pb, Co, Se, and Hg, that have no known bio- logical function but prove highly toxic for the majority of plants (Zenk 1996). Plants have an efficient defence mechanism to neu- tralise the deleterious effects of heavy metals. This system is constituted primarily by phytochelatins (PC), small peptides with a molecular mass of about 2–3 kDa made of 2–11 units of gammaglutamyl-cysteine linked to glycine or alanine residues (Cobbett 2000a). Low-molecular- weight metal complexes were also found in the freshwater moss Rhynchostegium riparioides (Jackson et al. 1991). The synthesis of phytochelatins, induced when a plant is exposed to heavy metals, does not require expression at gene level, as in the case of metallothioneins (Carginale et al. 1998, 1999); heavy metal ions activate the enzyme PC synthase catalysing the formation of new PC mole- cules (Cobbett 2000b). Bryophytes have a high capacity to accumulate metals because of their high surface-to-volume ratio and the fre- quent absence of a cuticle. They have a countergradient mechanism to concentrate heavy metals within their tis- sues. Hence, mosses are widely used as biosensors of en- vironmental pollution (Bargagli 1998, Vincent et al. 2001, Carballeira et al. 2001) and as models for morphological and genomic alteration caused by heavy metals (Basile et al. 1995, Bassi et al. 1995). Liverworts have also been proposed as bioindicators of heavy metals (Satake et al. 1983, Samecka-Cymerman et al. 1997) and are currently studied with respect to uptake as well as extracellular or intracellular compartmentalisation of heavy metals (Satake and Miyasaka 1984, Vazquez et al. 1999). It has been hypothesised that the reproductive potential of a species is one of the principal factors that determines success in a polluted environment. According to Gilbert Protoplasma (2004) 223: 53–61 DOI 10.1007/s00709-003-0028-0 PROTOPLASMA Printed in Austria Accumulation, localisation, and toxic effects of cadmium in the liverwort Lunularia cruciata V. Carginale 2 , S. Sorbo 3 , C. Capasso 2 , F. Trinchella 2 , G. Cafiero 3 , and A. Basile 1, * 1 Department of Plant Biology, University Federico II, Naples 2 Institute of Protein Biochemistry, Consiglio Nazionale di Ricerca, Naples 3 Centro Interdipartimentale di Servizio per la Microscopia Elettronica, University Federico II, Naples Received October 30, 2002; accepted April 8, 2003; published online March 4, 2004 © Springer-Verlag 2004 * Correspondence and reprints: Department of Plant Biology, University Federico II, via Foria 223, 80132 Naples, Italy.