Heavy Metals Stress on Poplar: Molecular and Anatomical Modifications
Heavy metal stress responses vary from plant to plant depending on the type of heavy metals and require a coordinated interplay of complex physiological and biochemical processes, gene expression, protein modification and changes in metabolites compositio
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Abstract
Heavy metal stress responses vary from plant to plant depending on the type of heavy metals and require a coordinated interplay of complex physiological and biochemical processes, gene expression, protein modification and changes in metabolites compositions leading to proper stress signal and tolerance. Fast-growing tree species, such as poplar, have been studied as possible candidate in phytoremediation approaches to clean up soil or water polluted by organic and inorganic compounds. In particular poplar is known both for the ability to uptake (i.e. phytoextraction) and to stabilise heavy metals (i.e. phytostabilisation) into their tissues, thus reducing the mobility of these contaminants in the soil profile. Compared to other plant species, poplar trees have several advantageous characteristics, such as deeper root system, higher transpiration activity, and productivity. Moreover, they produce economically valuable nonfood biomass exploitable both for wood and bioenergy production. Since the availability of the genome sequence of Populus trichocarpa and the development of highthroughput technologies, poplar has also emerged as the model system for tree biology studies. In this chapter, we examine the effects of heavy metals on anatomical traits and molecular machinery that are responsible for their accumulation and tolerance in poplar. Starting with this deeper molecular information, this chapter could provide new ideas for improving poplar trees with traits conferring heavy metals tolerance.
L. Sebastiani (*) A. Francini S. Romeo A. Ariani A. Minnocci BioLabs, Institute of Life Sciences, Scuola Superiore Sant’Anna, Piazza Martiri della Liberta`, 33, 56127 Pisa, Italy e-mail: [email protected] R.K. Gaur and P. Sharma (eds.), Approaches to Plant Stress and their Management, DOI 10.1007/978-81-322-1620-9_15, # Springer India 2014
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Keywords
Cadmium Copper Model system Organs anatomy Oxidative stress Phytoremediation Proteomic Transcriptomic Zinc
Introduction The term “heavy metals” (HMs) has been widely used in scientific literature for many years, even if the International Union of Pure and Applied Chemistry consider this term meaningless and misleading (Duffus 2002). Authoritative definition cannot be found in the relevant literature, but usually the name identifies both metals and metalloids associated with toxicity and environmental contamination. In this chapter, it is not possible to discuss in detail these definition problems and at the same time we cannot ignore the scientific publications using these terms. For such reasons we maintain the general term “heavy metals” and will use it more specifically to identify a group of metals classically associated with the scientific literature on poplar tree: Cu, Cd, Cr, Fe, Mn, Ni, Pb and Zn. Heavy metals can be found as natural constituents of the Earth’s crust and geological processes, such as alteration and erosion of the geological underground materials can release these elements in soils,
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