Assessment of physiological and biochemical responses, metal tolerance and accumulation in two eucalypt hybrid clones for phytoremediation of cadmium-contaminated waters.

Eucalyptus is a promising species for ecological restoration but plant performances under environmental constraints need to be better investigated. In particular, the toxic effects of metals on this plant species are poorly described in the literature. In this work, morpho-physiological and biochemical responses to cadmium were analysed in two eucalypt genotypes (hybrid clones of Eucalyptus camaldulensis × Eucalyptus globulus ssp. bicostata J.B. Kirkp named Velino ex 7 and Viglio ex 358) exposed for 3 weeks to 50 µM CdSO4 under hydroponics. The two eucalypt clones showed a different sensitivity to the metal. The growth reduction caused by cadmium was less than 30% in clone Velino and about 50% in clone Viglio. Cadmium mostly accumulated in plant roots and, to a lesser extent, in stem, as highlighted by the low translocation factor (Tf) measured in both clones. Net photosynthesis measurement, chlorophyll fluorescence images, transpiration values and chlorophyll content revealed a cadmium-induced impairment of physiological processes at the leaf level, which was more evident in clone Viglio. Metal binding and antioxidative compound content was differentially affected by cadmium exposure in the two eucalypt clones. Particularly, the content of thiols like cysteine and glutathione, organic acids like oxalate and citrate, and polyamines were markedly modulated in plant organs by metal treatment and highlighted different defence responses between the clones. Cadmium tolerance and accumulation ability of the eucalypt clones were evaluated and the potential of E. camaldulensis for the reclamation of metal polluted-waters is discussed.

Screening of poplar clones for cadmium phytoremediation using photosynthesis, biomass and cadmium content analyses.

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.