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1

Effect of soil pollution on bacterial resistance to lead ions: an experimental approach

100%
Blaszak M., Bienkowska D.
Polish Journal of Ecology
|
2009
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tom 57
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nr 3
555-560
The objective of the laboratory experiment was to study the resistance to lead ions of bacteria isolated from soil with various level of contamination with this element. Lead (II) acetate trihydrate was applied to the soil (sandy loam) in two doses so that the total content of lead corresponded to weak (250 mg kg⁻¹) and strong (5000 mg kg⁻¹) contamination of soil with lead. From each of the soil (control, weakly and strongly contaminated soil) bacterial isolates were obtained and several dozen of them were randomly chosen for the experiment. The isolates were severally point wise cultured in three repetitions onto microbiological medium contaminated with lead (1000 mg dm⁻³) and on the same control medium. The diameter of grown “twin” colonies in both cultures were compared. For each isolate separately the resistance index (RI) was described as a ratio of bacterial cultures diameter of the soil isolate cultured on the contaminated medium to the diameter of the same isolate cultured on the control medium. On the basis of the various RI results, the bacteria were divided into four resistance groups (RG) of approximate resistance index: I group, RI = 0 – entirely sensitive bacteria (no growth on the contaminated medium); II group 0
2
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Virtual screening strategies in drug design – methods and applications

84%
Bielska E., Lucas X., Czerwoniec A., Kasprzak J. M., Kaminska K. H., Bujnicki J. M.
BioTechnologia. Journal of Biotechnology Computational Biology and Bionanotechnology
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2011
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tom 92
|
nr 3
3

Role of clonal integration in life strategy of sandy dune plant, Eremosparton songoricum (Litv.) Vass (Fabaceae): experimental approach

67%
Wang J.-C., Shi X., Yin L.-K., Zhang D.-Y.
Polish Journal of Ecology
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2011
|
tom 59
|
nr 3
A systematic knowledge of clonal integration is an important step in understanding the ecological implication of clonality. This study focuses on the performance of rhizomatous clonal plants under different situations and we proposed a hypothesis that clonal integration will significantly improve the disturbance and drought resistance ability and the competitive ability of Eremosparton songoricum. In 2009, the experiments were carried out in two natural populations. Rhizome was either severed (S) or not (I) in four treatments that include control (C), drought (D), disturbance (E), and competition (F). The biomass and the root-shoot ratio were compared in different experimental treatments. Under drought and disturbance treatments, the biomass of ramet with severed rhizome was significantly less than that of intact ramets, and both were lower than the samples under the control treatment. The differences in root-shoot ratio were opposite to the biomass in drought and disturbance treatments. The ramet biomass under the competition treatment had the same result as that under the drought and disturbance treatments. However, th e root-shoot ratio was highest in FS (competition treatment with severed rhizome) and lowest in FI (competition treatment with intact rhizome) under competition and control treatments. Our results suggest that clonal integration enhances the disturbance and drought resistance ability rather than the competitive ability of Eremosparton songoricum. This may be one of the various reasons why E. songoricum is distributed in sand dunes of droughty conditions with more disturbances but less competition. Integration proved to be important for the species occupying adverse patches. For E. songoricum, the existence of rhizome reduces the impact of environmental stress and improves the fitness in association with its location at the dune.
4

The role of lake shore sand deposits as bank of ciliate, rotifer and crustacean resting forms: experimental approach

67%
Kalinowska K., Ejsmont-Karabin J., Rybak J. I.
Polish Journal of Ecology
|
2010
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tom 58
|
nr 2
The experiment, with the use of sand deposit from hygroarenal (shore sand beach wetted by lake waves) of the beach of eutrophic Lake Mikołajskie (Masurian Lakeland, Poland), was performed in order to test the hypothesis that shore sand deposit is the bank of resting forms of ciliate, rotifer and crustacean species. The experiment was conducted over a 38 days period in March-April 2004. Frozen sand taken in winter was exposed in aquariums filled with pre-filtered (GF/C) lake water in stable temperature (20ºC), oxygen saturation and 12:12 light/dark conditions. Samples (three replicates) were taken each day. A total number of 44 ciliate, 59 rotifer and 9 crustacean taxa were identified during the studied period. Resting forms of different species and/ or taxonomic groups developed in different time and it may be the result of different strategies in colonization of new habitats. Organisms forming resting cysts such as ciliates (11 species) and bdelloid rotifers appeared after the first day of the incubation whereas organisms hatching from resting eggs (monogonont rotifers and crustacea) were observed from the 2nd-3rd day of the experiment. The numbers of all the studied groups of organisms increased gradually and then strongly decreased indicating probably nutrient and/or organic matter limitation. The highest numbers of ciliates (731 ind. cm⁻² of sand) was found on the 5th day, rotifers (987 ind. 100 cm⁻²) on the 23rd day, cladocerans (60 ind. 100 cm⁻²) on the 21st day and copepods (30 ind. 100 cm⁻²) on the 33rd day of the experiment. The results of this study suggests that shore sand deposits being the temporal refugium for the small-bodied invertebrates transported here with the wave action may also play an important role as the transfer for their further dispersal in addition to postulated ways of expansions such as wind, rain, animals and surface runoff.
5

Effect of patchy distribution of soil nutrients on root morphology and biomass allocation of selected grassland species: experimental approach

67%
Zaller J. G.
Polish Journal of Ecology
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2007
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tom 55
|
nr 4
Nutrient distribution in natural habitats is usually patchy in space and time, however most knowledge about plant growth and behaviour is based on experiments conducted under spatially homogenous conditions. Evidence has accumulated that the growth and competitive interaction of plant species are strongly affected by heterogeneous rather than homogeneous resource distribution, even when the total resource supply remains similar. For this study it is hypothesized that infestations of grasslands with the nitrophilous weed Rumex obtusifolius L. (broadleaved dock) are partially the consequence of its ability to exploit spatial nutrient heterogeneity. This was tested in a full-factorial pot experiment with homogeneously or heterogeneously distributed nitrogen and/or potassium at either normal or increased soil moisture where R. obtusifolius was grown together with three other grassland species (grass: Arrhenatherum elatius L., non-leguminous herb: Taraxacum officinale Weber, leguminous herb: Trifolium repens L.). The species differed significantly in their root morphology (root length and diameter, specific root length, number of root tips) and biomass allocation response to nutrient distribution, as well as to the nutrient type used to create patches and to soil moisture (e.g., significant species × treatment interactions). Generally, the root system of A. elatius showed the highest plasticity to imposed treatments, followed by T. officinale, R. obtusifolius and T. repens. Unexpectedly, root morphology of R. obtusifolius was unresponsive to soil heterogeneity and less responsive to nutrient type and irrigation than that of the other species. Nutrient type used to create patches influenced the biomass allocation to the root system of R. obtusifolius while nutrient distribution and irrigation showed no effect on biomass allocation. Exploitation of soil nitrate-nitrogen and potassium was similar among species but exploitation was individually affected by nutrient type, nutrient distribution and irrigation suggesting that species-specific differences in nutrient storage capacities in roots or adjustments regarding root nutrient uptake kinetics may play an important role. Results from this study show that R. obtusifolius does not seem to have superior traits to utilize soil nutrient heterogeneity, certain nutrient types or higher soil moisture that differentiates it from the other grassland species tested. The observed effects might have consequences for the long-term competitive relationships between species in the grassland community suggesting that cultural and biological management measures oriented towards the improvement of the competitive ability of co-occurring grassland species might also be important in heterogeneous soils.
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