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1.
Sci Total Environ ; 68: 127-39, 1988 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-3363314

RESUMO

An urban terrestrial microecosystem has been used under outdoor conditions to study the transfer of chemical residues within the system components. The microecosystem consisted of soil monoliths obtained from a site with an established vegetation cover dominated by goldenrod, Solidago gigantea. The microecosystem contained integrated food chain elements composed of primary producers, herbivores and carnivores. The system was stocked with indicator insect species, snails (Cepaea nemoralis) and earthworms (Allolobophora caliginosa), captured from the original site. Evaluation of the system was made using radiolabelled sodium pentachlorophenate (PCP-Na) which was applied as a single application at an equivalent rate of 5 kg ha-1. The mass balance revealed that, after 131 days, in the autumn, and after 222 days, in the winter, that 43 and 39% radiocarbon, respectively, was recoverable from the microecosystem. The unaccounted radiocarbon was very probably removed through volatilization and photomineralization of the compound. PCP residues on foliage decreased rapidly, 50% of which were metabolised within 15 days. Most of the radiocarbon remaining in the system after 131 days was in the top soil and plant litter, transmitted mainly through washing off by rain and leaf litter fall. There was a variation in the uptake of PCP-Na residues in the food chain organisms, where the total radiocarbon concentrations during the first 19 days of exposure ranged, e.g. in snails, from 3 to 0.6 micrograms g-1, in springtails from 5 to 105; in beetles (Amara fusca) from 3 to 1, in spiders from 13 to 11, and in harvestman from 31 to 77 micrograms g-1. The ecological magnification indices (EM) of all the organisms with respect to their main food source, i.e. plant litter, demonstrated no bioconcentration effects. This is attributed to the metabolism of PCP-Na by the organisms and its rapid excretion. The urban wasteland ecosystem contained in outdoor lysimeters employed as a model gives valuable information and has considerable value in predicting the ecological fate of industrial chemicals.


Assuntos
Ecologia , Poluição Ambiental , Animais , Besouros/metabolismo , Oligoquetos/metabolismo , Plantas/análise , Caramujos/metabolismo , Solo/análise , Especificidade da Espécie , Aranhas/metabolismo
2.
Planta ; 92(1): 50-6, 1970 Mar.
Artigo em Alemão | MEDLINE | ID: mdl-24500129

RESUMO

1. Lemna minor is able to reduce nitrate in the dark when the nutrient medium contains yeast extract and glucose in addition to minerals salts. 2. When organic N is offered as a source of N in addition to nitrate, the former is assimilated preferentially, but both assimilation processes take place simultaneously. 3. Assimilation of nitrate in the dark under ecological conditions can be excluded.

3.
Planta ; 69(2): 178-86, 1966 Jun.
Artigo em Alemão | MEDLINE | ID: mdl-24557848

RESUMO

Lemna minor cultured in continuous light at constant temperature exhibits a seasonal rhythm in the rate of dry matter production with a maximum in summer and a minimum in winter. This confirms the observations of PIRSON and GöLLNER in 1953. Both the protein content and the protein/carbohydrate ratio are correlated with the rate of dry matter production and reach a maximum in summer. The contents of total and of water soluble carbohydrate, however, reach a maximum in winter. The seasonal changes in this periodicity under controlled conditions correspond to the seasonal changes in the periodicity under ecological conditions and exhibit the same dependence on water temperature as the latter. Therefore it is suggested that the seasonal rhythm of growth in Lemna minor is synchronized by water temperature.

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