Numbers of myxomycetes and associated microorganisms in the root zones of cabbage (Brassica oleracea) and broad bean (Vicia faba) in field plots

Amewowor, D.H.A.K.; Madelin, M.F.

Numbers of myxomycetes and associated microorganisms in the root zones of cabbage (Brassica oleracea) and broad bean (Vicia faba) in field plots

1991

Amewowor, D.H.A.K. | Madelin, M.F.

Myxomycetes, dictyostelids, naked amoebae, ciliates, nematodes, bacteria, rhizobia and fungi in the root zones of cabbage (Brassica oleracea) and broad bean (Vicia faba) growing in agricultural soil in field plots have been studied quantitatively throughout a growing season, and the populations compared with those in soil 30 cm distant from the stem bases. All the organisms were more abundant in the root zones than in non-root-zone soil. Myxomycetes were enumerated both as plasmodium-forming units (PFUs) and myxoflagellate-forming units (MFUs). Counts of MFUs were consistently higher (up to 500 times larger) than corresponding counts of PFUs. Possible reasons for this are discussed. The increases of myxomycetes near roots were proportionately greater with cabbage than with broad bean, and more pronounced when myxomycetes were enumerated as PFUs than as MFUs. Particularly high numbers were present near cabbage roots from August to December and abundant myxomycete sporangia and plasmodia were then seen on the plants and on nearby soil. None were seen on broad bean plants. A large proportion of myxomycete PFUs near roots of both plants were in a freezing-resistant dormant state, presumably as microcysts. Myxomycetes identified in the enumeration plates were species of Didymium and Physarum. Dictyostelid slime moulds were particularly abundant near the roots of broad bean. Myxomycetes and dictyostelids constituted significant and possibly substantial proportions of the total naked amoebal populations in the soils studied.

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