Good photosynthetic features and a favorable water regimes of woody plants improve their survival and remediation potential under unfavorable ecological conditions. Accordingly, we here present results of testing plant tolerance of Pb, Cd, Ni, and diesel fuel based on gas exchange parameters and WUE of four poplar and two willow clones grown in a greenhouse on soil culture. Photosynthesis and transpiration of plants grown on soils with individually applied heavy metals decreased significantly, but this was less obvious in the case of Cd treatment. A heavy metal mixture in the soil induced significant reduction in photosynthesis (by more than 50%). Diesel fuel as the only pollutant in soil caused very strong and significant inhibition of photosynthesis and transpiration of willow clones. The results indicate genotypic specificity of all investigated physiological parameters and mark poplar clones as very useful in phytoextraction technology for the bio-cleaning of chemically polluted soils

Pure and mixed cultures of the dicotyledons Atriplex hortensis L. (C plant) and Amaranthus retroflexus L. (C plant) were maintained under open air conditions in standard soil at low and high nitrogen supply levels.A comparison of shoot dry weight and shoot length in the various series shows that the growth of the aboveground parts of both species was severely reduced under low N conditions. In both pure and mixed cultures the differences resulting from low N vs. high N conditions was less pronounced with Atriplex (C plant) than with Amaranthus (C plant). The root dry weight of the two species was not reduced so much under low N conditions as was the shoot dry weight. The low N plants were found to contain a larger proportion of their biomass in the roots than did the high N plants. In general the root proportion of Atriplex was greater than that of Amaranthus. The contents of organic nitrogen and nitrate and the nitrate reductase activity (NRA) per g dry weight of both species decreased continually throughout the experiments. With the exception of young plants, the low N plants always had tower contents of organic nitrogen and nitrate and nitrate reductase activities than did the high N plants. The highest values of NRA were measured in the leaf laminae. The eaves also exhibited the highest concentrations of organic nitrogen. The highest nitrate concentrations, however, were observed in the shoot axis, and in most cases the lowest nitrate values were found in the laminae. At the end of ne growing season this pattern was found to have been reversed with Atriplex, but not with Amaranthus. Thus Atriplex was able to maintain a higher NRA in the laminae than Amaranthus under low N conditions.The transpiration per leaf area of the C plant Amaranthus during the course of a day was substantially lower than that of the C plant Atriplex. There were no significant differences in transpiration between the low N and high N series of Amaranthus. The low N plants of Atriplex, however, clearly showed in most cases higher transpiration rates than the corresponding high N plants. These different transpiration rates of the high N and the low N Atriplex plants were also reflected in a distinct C discrimination.The sum of these results points to the conclusion that the C plant Atriplex hortensis can maintain a better internal inorganic nitrogen supply than the C plant Amaranthus retroflexus under low N conditions and an ample water supply, due to the larger root proportion and the more pronounced and flexible transpiration of the C plant.

The objective of this study was to determine genotype influences on pedunculate oak's leaf traits: leaf area, specific leaf area (leaf area per unit of leaf mass), concentration of photosynthetic pigments, rates of photosynthesis and respiration, and nutrient concentrations (nitrogen phosphorus, potassium, calcium, and sodium). Leaf samples were taken from seventeen Q. robur genotypes originating from clonal seed orchard Banov Brod (Srem, Vojvodina, Serbia). Leaf area of the studied genotypes ranged from 248.4 to 628.8 cm2, SLA from 109.4 to 160.7 cm2 dry matter-1, rates of photosynthesis and respiration from 6.98 to 20.32 and from 6.73 to 14.65 µmol O2 m-2 s-1, respectively. The leaves of genotype 35 contained the highest concentration of photosynthetic pigments, while the lowest were recorded in genotype 29. The following pattern of nutrient concentrations was obtained for the studied genotypes: N>Ca>K>P>Na. Genotype variability of P K, Ca, and Na concentrations was more pronounced when compared with nitrogen. Estimated quantitative differences are the consequence of interaction of certain genotype and common environmental conditions for all trees. These results will provide information on intraspecific variation of the studied leaf characteristics

In the study of three different aquatic ecosystems connected with the Danube river we determined the concentrations of macronutrients (N, P, K, Ca), Na and heavy metals (Fe, Mn, Ni, Pb and Cd) in the most common submerged, floating and emerged aquatic plants: Ceratophyllum demersum, Myriophyllum spicatum, Va llisneria spiralis, Salvinia natans, Hy drocharis morsus ranae, Trapa longicarpa, Nymphoides flava, Nymphaea alba, and Phragmites communis. Analyses were done during the seasonal biomass peak (June-Au gust) in 1999. Significantly higher macronutrients and heavy metal concentrations in sub merged when compared to floating and emerged aquatic plants were found. From the heavy metal concentrations which were measured, iron showed the highest values followed by manganese, nickel and lead, while cadmium exhibited trace concentrations. The degree of metal accumulation in plant tissues (expressed as tissue metal concentration/surrounding water concentration ratio) was locality-dependent. The highest degree was recorded for Mn and Fe. The obtained results indicated an evident chemical pollution of the DTD canal section (near Novi Sad) where V. spiralis had the highest bioaccumulation of Fe and Mn.

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