SummaryPhotosynthetic pigment composition has been a major study target in plant ecophysiology during the last three decades. Although more than 2000 papers have been published, a comprehensive evaluation of the responses of photosynthetic pigment composition to environmental conditions is not yet available.After an extensive survey, we compiled data from 525 papers including 809 species (subkingdom Viridiplantae) in which pigment composition was described. A meta-analysis was then conducted to assess the ranges of photosynthetic pigment content.Calculated frequency distributions of pigments were compared with those expected from the theoretical pigment composition. Responses to environmental factors were also analysed. The results revealed that lutein and xanthophyll cycle pigments (VAZ) were highly responsive to the environment, emphasizing the high phenotypic plasticity of VAZ, whereas neoxanthin was very stable.The present meta-analysis supports the existence of relatively narrow limits for pigment ratios and also supports the presence of a pool of free 'unbound' VAZ. Results from this study provide highly reliable ranges of photosynthetic pigment contents as a framework for future research on plant pigments.

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Phytoremediation is an emerging cost-effective, non-intrusive, esthetically pleasing, and low cost technology using the remarkable ability of plants to concentrate elements and compounds from the environment and to metabolize various molecules in their tissues. Phytoremediation technology is applicable to a broad range of contaminants, including metals and radionuclides, as well as organic compounds like chlorinated solvents, polychlorobiphenyls, polycyclic aromatic hydrocarbons, pesticides/insecticides, explosives, and surfactants. The use of plants to transport and concentrate metals from the soil into the harvestable parts of roots and above-ground shoots, usually called 'phytoextraction', has appeared on the scene as a valid alternative to traditional physicochemical remediation methods that do not provide acceptable solutions for the removal of metals from soils. Positive results are becoming available regarding the ability of plants to degrade certain organic compounds. Nonetheless, despite the firm establishment of phytoremediation technology in the literature and in extensive research study and in small-scale demonstrations, full-scale applications are currently limited to a small number of projects. At present, the phytoremediation of metal pollutants from the environment could be approaching commercialization.

In this study, we investigated the accumulation of phytochelatins (PCs) and other low molecular weight (LMW) thiols in response to Cd exposure in two contrasting ecotypes differing in Cd accumulation. Using a root elongation test, we found that the highly accumulating ecotype Ganges was more tolerant to Cd than the low Cd-accumulation ecotype Prayon. L -buthionine-(S,R)-sulphoximine (BSO), a potent inhibitor of the g -glutamylcysteine synthetase ( g -ECS) (an enzyme involved in the PC biosynthetic pathway), increased the Cd sensitivity of Prayon, but had no effect on Ganges. Although PC accumulation increased in response to Cd exposure, no significant differences were observed between the two ecotypes. Cd exposure induced a dosedependent accumulation of both Cys and a still unidentified LMW thiol in roots of both ecotypes. Root accumulation of Cys and this thiol was higher in Ganges than in Prayon; the ecotypic differences were more pronounced when the plants were treated with BSO. These findings suggest that PCs do not contribute to the Cd hypertolerance displayed by the Ganges ecotype of Thlaspi caerulescens , whereas Cys and other LMW thiols might be involved.

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