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ŠUMARSKI LIST 5-6/2013 str. 18     <-- 18 -->        PDF

weight compounds such as glutathione, vitamins, uric acid and bilirubin, those compounds contribute to the total antioxidant defense (hereinafter: Antioxidant Defense System – ADS). The role of ADS is of particular importance in terms of increased production of reactive oxygen species (hereinafter: Reactive Oxygen Species – ROS) and occurrence of oxidative stress (Popović and Štajner 2008).
In terms of global climate change, abiotic stresses, such as salinity, drought, temperature, chemical toxicity and oxidative stresses are the major causes for loss of agricultural production and natural vegetation. Abiotic stress causes various morphological, physiological, biochemical and molecular changes that affect plant growth and productivity. Managing abiotic stress is especially critical to the long-term growth of tree species. Tree species are also affected by mechanical stress such as wind and gravity. Many forest trees suffer from abiotic and biotic stresses under adverse environmental conditions, including heavy metal contamination as a folow-up process (Osakabe et al., 2011).
In plants, the appearance of small, toxic oxygen species causes disruption of cellular components and membrane lipid peroxidation, whereas the activated forms of oxygen damage the molecules of chlorophyll, which is manifested by the loss of green color and reduction of photosynthesis (Heath and Packer, 1968; Pallet and Dodge, 1979; Elstner and Osswald, 1980).
Studies have shown that plants reduce concentration of contaminants in soil and groundwater during that process, from which it was established the idea of the possibilities of their growing and treatment of contaminated habitats. This way of treating soil contamination is called phytoremediation. According to the Agency for Environmental Protection of the United States, phytoremediation is a set of techniques and technologies that use plants for the purpose of cleaning contaminated sites and soils. From a diverse range of plant species used for phytoremediation, poplars are commonly used woody plant species, due to their characteristics such as large leaf surface, the conductivity of water and minerals through the entire cross-section of the tree (diffuse porous species) and easy vegetative propagation by cuttings (Pilipović, 2005). Hybrid poplars were originally bred and grown as a cash crop for such uses as pulp wood and as renewable energy source, but because of their rapid growth rate and high evapotranspiration rates, they make ideal candidates for phytoremediation (Chappell, 1997). Populus makes an excellent subject for any bioremediation study since it is fast-growing (one of the fastest growing temperate trees) and because the use of clone material ensures that experiments are repeatable and with small error.
As environmental restoration of metal-polluted soils by traditional physical and chemical meth­ods demands large investments of economic and technological resources, efforts are underway to involve in situ methods in environmental protection. Phytoremediation is an emerging technology which utilizes plants and rhizosphere microorganisms to remove and transform toxic chemicals in soils, sediments, ground water, surface water, and the atmosphere (Kumar et al., 1995; Susarla et al., 2002; Ghosh and Singh, 2005; Pajević et al., 2008). Heavy metal accumulation by plants is useful as a phyto­extraction technique in phytoremediation, which refers to the use of plants that can extract and move contaminants to their harvestable parts (Marchiol et al., 2004). The efficiency of phytoextraction depends on the metal bioavailability, as well as on several characteristics of the plant-remediator: fast growth, a deep and extended root system, the capability of (hyper) accumulating essential and unessential met­als, and the ability to translocate metals to the aerial parts (Zacchini et al., 2009).
Metal-accumulating woody species have been considered for phytoex­traction of metal-contaminated sites. Apart from cleaning the environment, another advantage of using forest plants in this technol­ogy is their high production of biomass, which can eventually be used in producing energy (Laureysens et al., 2004).
The aim of study
Cilj istraživanja
Different metals can disrupt metabolic processes and pathways in plants, especially in the thylakoid membrane, which could also result in increased production of free radical species, such as RO•, OH•, O•2– etc. Heavy metals also inactivate antioxidant enzymes (peroxidases, catalase, superoxide dismutase, etc.). Responsible for detoxification of free radical species, peroxidases can also be activated by different metals in some cases.
Biochemical profiling of oxidative stress status in woody plant is not common in Serbia and therefore the aim of this study was to examine the effect of different concentrations of three heavy metal ions, Ni3+, Cu2+ and Cd2+ on oxidative stress of three clones, two different species of poplar (Populus euramericana-M1; PE 19/66 and B 229-both Populus deltoides species). Biochemical parameters for indentifying the level of oxidative stress were: lipid peroxidation (hereinafter: LPx), ferric reducing antioxidative power assay (hereinafter: FRAP), superoxide dismutase (hereinafter: SOD) activity and soluble protein. Particularly, through in vitro experiment antioxidant potential of these three clones to different concentrations of heavy metal ions in the soil were determined. These results could give the guidelines in the selection of clones from Institute’s collection, characterized by high (or low) phytoremediation potential, in commercial production of poplar genotypes.