Variability of cadmium tolerance and distribution in plant organs was investigated in ten selected poplar clones from different species, hybrids and genotypes. To this end, plants were exposed for three weeks to 50 microM CdSO4 in hydroponics. Cadmium accumulation in roots, stem and leaves as well as biomass production and photosynthesis maintenance varied greatly among clones. The metal mostly accumulated in roots, up to 80% in some clones, and interestingly, only 50% in some others. In general, metal tolerance reflected the degree of photosynthesis inhibition, which was higher in clones with high cadmium accumulation in leaves. Biomass production, net photosynthesis, transpiration, and pigment content were differently reduced in cadmium-treated clones with respect to control. The variability of cadmium distribution among leaves, stem, and roots provides candidate poplars for specific phytoremediation processes of contaminated waters and soils.

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Abstract. Metal pollution in waters and soils is a major environmental and human health problem. Cadmium (Cd 2+ ) is a heavy metal displaying toxic effects in plants. In this work we studied the potentiality of Lemna minor, a monocotyledonous aquatic macrophyte, to phytoremediate cadmium-polluted waters. The plants were exposed to different cadmium concentrations 0, 13, 22 and 46µM CdSO 4 for a period of 24, 48 and 72 hours. Relative growth rates (RGR), bioconcentration factor (BCF), tolerance index (T i ), cadmium uptake in whole plant and maximum efficiency of PSII (Fv/Fm) were measured under controlled climate conditions. RGR, T i and Fv/Fm declined with increasing exposure time and cadmium concentrations, while the BCF and cadmium uptake showed an opposite behavior. Data analysis of RGR, BCF, Ti and F V /F M indicates that L. minor maintains a good capacity of growth, metal bioconcentration, tolerance and efficiency of PSII up to 48h in plants exposed to 13 and 22µM CdSO 4 . Our results exhibited that L. minor is a good cadmium accumulator and is able to remediate Cd-polluted waters, especially at low Cd concentrations.

(1) Wastewater reclamation and reuse represent a feasible solution to meet the growing demand for safe water. An environmentally sustainable technology such as phytoremediation is targeted for the reclamation of polluted waters. To this end, the capability of different plant species to tolerate and accumulate pollutants has to be investigated. In this work, eucalypt plants were studied by analysing biometric, physiological, and biochemical parameters related to cadmium (Cd) tolerance and accumulation in two clones ("Velino ex 7" and "Viglio ex 358") of Eucalyptus camaldulensis Dehnh. × E. globulus subsp. bicostata (Maiden, Blakely & J.Simm.) J.B. Kirkp exposed to 50 μM CdSO4 under hydroponics for three weeks. The results indicated that both eucalypt clones have a valuable tolerance to cadmium, expressed as the tolerance index (Ti). Biometric investigations showed that, regardless of the clone, the metal exposure affected most parameters related to biomass allocation and leaf growth. On the contrary, significant differences were found between the clones with respect to the chlorophyll content and the Chl a to Chl b ratio. These findings were also confirmed from the analysis of chlorophyll fluorescence transient (OJIP) using the JIP test. Cadmium accumulation occurred in both clones and in particular in the roots, with a poor amount of metal reaching the aerial parts, and the Velino clone showed the highest Cd accumulation. The metal uptake ratio and the phytoextraction efficiency highlight a good Cd phytoremoval ability, especially for the Velino clone. The results are discussed taking into account that, in wastewater phytoremediation systems, root biomass can be completely harvested allowing for the removal of the absorbed metal. Finally, the notable tolerance to submersion and the large environmental adaptability of eucalypt suggest that this plant species represents an interesting candidate for the phytoremediation of Cd-polluted wastewaters.

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