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ŠUMARSKI LIST 5-6/2012 str. 48     <-- 48 -->        PDF

rhizosphere flora degrade and sequester organic and inorganic pollutants (Pillon-Smits, 2005). Results of various researches (Chen et al. 2003; Johnson et al., 2004; Rentz et al., 2003) showed increase of hydrocarbon degradation and microorganisms abundance with the use of plants for phytoremediation where even combining more than one species showed good results (Palmroth et al, 2002; Maila et al, 2005). Amongst various tree species used for phytoremediation in the Northern Hemisphere, poplars (Populus sp.) proved to be the best candidates for this purpose. Due to their biology of pioneer species of emerging alluvial soils, characterized by very rapid growth and highly developed root capable to uptake large amounts of water, it makes them ideal candidates for phytoremediation (Licht and Isebrands, 2005). Numerous researches show their potential for phytore­mediation of different types of contaminants from heavy metals (Banuelos et al., 1997; Di Baccio et al., 2003; Pilipović et al., 2005), to nutrients (Fraser et al., 2004) and organics (Wittig et al., 2003; Xingmao and Burken, 2004) very often linked to biomass production (Licht and Isebrands, 2005).
Petrol refinery situated at the banks of Danube in Novi Sad was severely damaged in 1999, where according to Nježić and Ačanski (2009) from 73 569 tons of oils stored in the tanks, 90 % was burned, 9.9 % leaked to the surface while 0.1 % leaked to the Danube, where contaminated area was more than 1.5 ha. This leakage caused substantial ecological problem due to vicinity of the Danube and wells that are used as sources for city’s water supply. Considering above mentioned research results, together with the ecological impact of crude oil contamination and site specific soil conditions for growing of plants, the aim of this study was to investigate potential of different poplar clones for phy­to­remediation through assessment of the crude oil contamination effects on the poplar growth and physiology.
Materials and methods
Materijali i metode
Experiment design and plant material
The experiment was established in May 2011 as greenhouse pot experiment in semi controlled conditions with control of irrigation and outer light and temperature. For growing of plants, crude oil contaminated soil from petrol refinery in Novi Sad was added in different volume shares (0, 5, 25, 50, 75 and 100 %) to uncontaminated alluvial soil. Treatments contained from 0.011 to 11.039 g kg–1 of total petroleum hydrocarbons (TPH) and 0.005 to 6.839 g kg–1 of mineral oils (Table 1). After preparation substrate was transfer­red to 13 liter pots in which were planted 4 cuttings of poplars in 3 repetitions for each clone/treatment. Three poplar clo­nes: (i) Populus × euramericana clone ´Pannonia´; (ii) Populus deltoides clone ´Bora´; (iii) Populus nigra × P. maximowitzii) × P. nigra var. Italica clone ´9111/93´ were selected from the clonal archive of the Institute of Lowland Forestry and Environment, Novi Sad, Serbia. After planting of cuttings, pots were irrigated in order to obtain retention water capacity and during the growing of plants pots were irrigated with 0.7 liters of water in the period of 3–7 days depending upon substrate, weather and duration of experiment. During the growth of plants physiological parameters were assessed in August, while after growth cessation and forming of terminal bud plants were harvested for measurement of biomass.
Investigated parameters – Istraživani parametri
In this experiment following parameters were assessed: (i) net photosynthesis (NPR) and dark respiration rate (DDR) rate; (ii) chlorophyll fluorescence (Fv/Fm); (iii) chlorophyll and carotenoid contents, (iv) nitrate reductase activity (NRA); (v) proline content and (vi) fresh biomass of plants. All physiological parameters were assessed on first fully developed leaf from top with Leaf Plastochron Index value of LPI=5 (Dickmann, 1971). Bulk samples from each repetition were taken for all physiological analysis. Net photosynthesis (NPR) and dark respiration rate (DRR) was assessed polar graphically with use of Clark type electrode according to Walker (1987), while chlorophyll fluorescence was measured by Fluorimeter PSM, BioMonitor, AB and ex­press­ed as Fv/Fm ratio. Concentration of acetone extracted leaf pigments of poplar clones was determined by spectrometry (Wettstein, 1957). Nitrate reductase activity (NRA) was assessed in vivo in leaves according to Hageman and Reed, (1980). Free proline content was assessed in fresh plant material according to Bates (1973). At the end of experiment, plants were harvested and their biomass was instantaneous­ly weighted on laboratory scale to determine fresh biomass of shoots and roots. Data were analyzed by two-way ANOVA and differences between clones and interactions between clone and treatment were analyzed with Duncan’s multiple range test. For statistical analysis was used Statistica 10 software.