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ŠUMARSKI LIST 5-6/2013 str. 22     <-- 22 -->        PDF

in FRAP unit values: 12,64 % (0,5 MPC), 13,49 % (3 MPC), and 38,29 % and 23,99 % (1 MPC and 2 MPC).
Values of MDA products obtained after lipid peroxidation are shown in figure 3. In regard to the copper treatment in clone M1 only increase of 53,3 % (1 MPC) in MDA content was recorded, while the values in all other treatments were similar to those of the control. There was a significant decrease of 54,94 % (1 MPC) in clone B 229 compared to control, and this trend was recorded even in 3 MPC treatment, where a decrease of 51,32 was recorded. In clone PE 19/66 the MDA content was decreased in all treatments compared to the control, ranging from 25,65 % in 0,5 MPC, to 44,99 % (3 MPC). The greatest decrease of 56,38 % (2 MPC) was recorded compared to control. Treatment with different cadmium concentrations revealed a decreasing trend of MDA content in clone M1 in all treatments, and the values ranged from 54 % (0,5 MPC) to 46,33 % (3 MPC). The greatest decrease of 47,41 % was recorded in 1 MPC compared to control. Clone B 229 showed no significant differences compared to control, except in 2 MPC, where there was a slight increase of 27,15 % compared to control. An increasing trend in MDA content was observed in clone PE 19/66 in all treatment and it ranged from 21,4 % (0,5 MPC) to 58,79 % (3 MPC). In regard to different nickel treatment, clone M1 showed various responses to all treatments. Increase of 13,81 % was recorded in 0,5 MPC treatment and of 20,52 % in 3 MPC, while a decrease of 16,22 % was recorded in 1 MPC compared to control. Clone B 229 showed a slight decline compared to control in almost all applied treatments, except in 2 MPC where increase of 12,33 % was recorded. Clone PE 19/66 showed a decreasing trend compared to control ranging from 33,25 % (0,5 MPC) to 44,67 % (3 MPC).
Results of SOD values in all three clones and different heavy metal treatments are shown in figure 4. In regard to copper treatment, clone M1 revealed significant increase compared to control and the values ranged from 110,59 % (0,5 MPC) to 25,19 % (2 MPC). An increase of 72,45 % was recorded in 3 MPC treatment compared to control. Clone B 229 showed a decreasing trend compared to control. Decrease of 40,87 % was recorded in 0,5 MPC, 47,61 % in 2 MPC, and of 80,41 % in 3 MPC. PE 19/66 also revealed a decreasing trend in SOD values ranging from 61,88 % (0,5 MPC), and 89,28 % (3 MPC). In regard to cadmium treatment clone M1 showed decreasing trend in all treatments compared to control. Decrease of 55,86 % was recorded in 0,5 MPC, and of 33,29 % in 3 MPC. Clone B 229 showed significant increase in SOD values in all treatments except in 3 MPC where the values were very similar to those of the control. Almost linear increasing trend was observed ranging from 31,68 % (0,5 MPC) to 73,86 % (2 MPC). Clone PE 19/66 showed a noticeable decline of 48,63 % after 1 MPC treatment, and then it regained the values similar to those of the control in 3 MPC treatment. In regard to nickel treatment, clone M1 showed various responses to dif­ferent concentrations of nickel in the substrate. Decrease of 33,06 % in 1 MPC treatment, and slight increase in 2 MPC treatment were observed and increase of 16,47 % was noticed in 3 MPC compared to control. Clone B 229 showed trend of decreasing values ranging from 28,62 % (0,5 MPC) to 58,33 % (3 MPC) compared to control. Clone PE 19/66 showed similar decreasing trend ranging from 61,63 % (0,5 MPC) to 79,53 % (3 MPC).
Environmental stress is the major cause of crop and forest loss worldwide. Future issues such as the insufficiency of provisions, environmental conservation and production increase in biomass will depend on plant biotechnologies. An in-depth understanding of the physiological stress responses and the molecular events in woody plants, which are some of the major components of the global ecosystem and biomass resources, is now required (Osakabe et al., 2011).
Nickel is one of the essential micronutrients for plants, animals, and humans, but toxic at elevated concentrations. As we mentioned before, nickel belongs to heavy metals also. The aim of study of Krstić et al. (2007) was to analyze Ni concentration in certain plant species affected by Ni contamination of air and surface soil. Ambrosia artemisifolia and Taraxum officinale accumulated the greatest amounts of Ni (10.72 and 10.61 μg/g, respectively). It may be concluded that the analyzed plant species exhibit various phytoremediation potential for Ni under the same ecological conditions. It is necessary to have that fact in mind while observing any chemical impact of heavy metals on poplar clones, since it showed various antioxidative answers. High­er concentrations of cadmium and copper resulted in higher amount of soluble proteins in all clones and treatments of nickel show­ed only small changes in synthesis of soluble proteins in shoots. It may indicate that in young poplar shoots the synthesis of protein antoxidative system is starting while applying high concentration of cadmium and copper.
Cadmium effects often show its negative influence on biomass production, leaf number and area. Those are the symptoms that cadmium treatments usually cause and they are visually reported, but Pilipović et al. (2005) also measured photosynthetic and dark respiration rates, leaf concentration of photosynthetic pigments, nitrate reductase activity, as well as cadmium concentrations in leaves, stem, and roots in poplar clones PE 4/68, B-229, 665, and 45/51. Plants were grown hydroponically under controlled conditions and treated with two different cadmium (Cd) concentrations (10(–5) and