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Two microcosm experiments were conducted to study the role of extraradical mycelium (ERM) of arbuscular mycorrhizal fungi (AMF) in establishment and growth of tree species used for revegetation in anthropogenic substrates. Inoculated or non-inoculated Acer pseudoplatanus, Alnus glutinosa or Salix purpurea seedlings were grown with Calamagrostis epigejos (a grass spontaneously colonising degraded ecosystems) in two substrates (fly ash and coal mine spoil) either in direct root contact or in rhizoboxes with interaction only via ERM network.In both experiments, inoculation with AMF mostly had a positive effect on the growth of trees and increased the aggregation of fly ash. When plants grew in direct root-to-root contact, grass presence negatively affected tree growth, but it significantly improved mycorrhizal development (colonization of tree seedlings, spore number and ERM length). When grass and tree roots interacted via the ERM network, tree seedlings were successfully colonised by the ERM spreading from the C. epigejos roots. Mechanical disturbance of the ERM links between plants reduced AMF development and tree height in both substrates, but tree shoot biomass was not affected. In fly ash, inoculated, non-disturbed treatments showed significant transfer of 32 P from the grass to the tree seedlings.It can be concluded that roots of A. pseudoplatanus, A. glutinosa or S. purpurea seedlings can be colonised from the ERM network radiating from quickly growing grasses, which can act as important agents for AMF distribution and facilitate mycorrhization of planted trees. In particular for willow, grass seems to be an essential nurse plant to achieve successful root colonisation.

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The distribution and biological half-life of radiocaesium (137Cs) in broiler chickens after three oral applications (in course of 1 day at the age of 14 days) of artificially contaminated feed mixture were studied. There was a rapid uptake of the orally administered 137Cs (within a few hours) and also a rapid loss of 137Cs which varied in the different organs (the initial biological half-life was: liver 0.6 day, intestine 0.6 day, breast meat 2 days, leg meat 1.2 days). More than one-half of the total administered 137Cs activity (55%) was excreted from the body within the 1st day after dosage, and after 14 days more than 90% had been excreted. The highest accumulation of 137Cs occurred in meat (50%-90%), and the proportion of total activity in breast and leg meat varied during decontamination. The transfer of radiocaesium from feed into the chicken body (measured as ratios of the 137Cs activity concentrations in the organ to the 137Cs activity concentration in the applied dose) 1 day after application was: 0.0220, 0.0294, 0.0216 and 0.0195 for breast meat, leg meat, intestine and liver, respectively. Significant differences between the values were demonstrated (P < 0.05) except between those of breast meat and intestine. For the first 3 days there was a higher proportion of 137Cs activity in leg meat, whereas from the 4th day a greater part of total activity was found in breast meat. The latter results were confirmed in a subsequent study. Data from this study suggest that if broiler chickens are contaminated by radiocaesium to a level of 5 kBq/chicken in the course of 1 day at the age of 14 days, then immediate feeding with uncontaminated feed mixture for 18 days should be effective in decontaminating the chicken's meat below the intervention levels for radiocaesium in animal products, i.e. below 1000 Bq. kg-1.

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