Efeito do cobre sobre fungos micorrÃzicos e trevo vermelho (Trifolium pratense L.)

AUTOR(ES)
DATA DE PUBLICAÇÃO

2006

RESUMO

The effects of copper on arbuscular mycorrhizal (AMF) and ectomycorrhizal fungi (EMF) and on the symbiosis between AMF and plants of Trifolium pratense L were evaluated. Species diversity, most probable number (MPN) of propagules and production of glomalin by AMF were estimated in a copper mining area (a- waste product area; b- interface between the waste product area and a cultivated area; c- cultivated with Eucalyptus) in CamaquÃ, State of Rio Grande do Sul. The symbiosis of Trifolium pratense L with the AMF Glomus etunicatum Becker &Gerd. was observed in sand irrigated with nutrient solution. The EMF Pisolithus microcarpus UFSCâPt116, Chondrogaster angustisporus UFSCâCh163 and Suillus sp. UFSCâSu168 were cultivated in Melin Norkrans modified medium (MNM) with Cu (31 to 7869 μM) and two levels of P (0,1 and 1,9 mM). The phosphatase activity of Suillus sp. in medium with Cu and P was also estimated. This fungus was more tolerant than the other EMF in medium with concentration 123 μM Cu. The supplement of P decreased significantly the toxicity of Cu over the EMF. Mycelial growth in liquid medium was strongly inhibited by phosphorus (1.9 mM) and Cu (123 μM). However, there was an increase of 50% on the activity of phosphatases produced by Suillus sp. For this fungus, concentrations of 40 and 160 μM of Cu inhibit 50% of growth (CI50), respectively in solid and liquid media. Twelve taxa of AMF were identified in the studied areas. Glomus was the most common genus and Paraglomus brasilianum (Spain &Miranda) Morton &Redecker the only species found in the three areas. Lower diversity of AMF occurred in the interface between the two other areas (waste product and cultivated). Higher number of spores, MPN of propagules and production of glomalin were registered in the area with Eucalyptus. Deleterious effect of copper was observed in plants maintained in substrate with 1967 μM de Cu. The mycorrhization, evaluated by root colonization, was inhibited in substrate with 123 μM Cu; however, in this same level, the addition of phosphate decreased the toxicity of the metal. In the treatment with G. etunicatum and 1,9 mM P, the toxicity of Cu on growth and nutrient accumulation (P, K, Cu e Fe) of Trifolium plants also decreased. Inoculation with AMF and supplementation of phosphate can increase the host tolerance to high levels of Cu in the substrate. Thus, application of both, mycorrhizal fungi and phosphate may constitute a useful practice on reforestation of mining areas

ASSUNTO(S)

toxicity micorriza arbuscular mining arbuscular mycorrhiza heavy metals toxicidade mineraÃÃo micologia ectomycorrhiza ectomicorriza metais pesados

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