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Selectivity of photobiont choice in a defined lichen community: inferences from cultural and molecular studies 总被引:10,自引:5,他引:5
Axenic cultures of lichen photobionts isolated from bark-inhabiting lichen thalli of the Physcietum adscendentis Ochsner were identified by light microscopy and sequence comparisons of internal transcribed spacer rDNAs to investigate principles of lichenization within a defined lichen sociological unit. The photobiont identity of eight lichen species is reported for the first time (photobiont species in square brackets): Lecania cyrtella (Ach.) Th. Fr. [ Trebouxia arboricola Puym.], Lecania naegelii (Hepp) Diederich & v. d. Boom [ Dictyochloropsis symbiontica Tscherm.-Woess], Candelaria concolor (Dicks) B. Stein [ Trebouxia jamesii (Hildreth & Ahmadjian) Gärtner], Candelariella cf. reflexa (Nyl.) Lettau [ T. jamesii ], Lecanora spec. [ T. arboricola ], Phaeophyscia orbicularis (Neck.) Moberg [ T. impressa Ahmadjian], Physcia adscendens (Fr.) H. Olivier [ T. impressa ] and Lecidella elaeochroma (Ach.) M. Choisy [ T. arboricola ] and could be confirmed for another two species, Physcia stellaris (L.) Nyl. [ Trebouxia impressa ] and Xanthoria parietina (L.) Th. Fr. [ Trebouxia arboricola ]. The observation that pioneer lichens without vegetative propagules, growing on smooth bark, had Trebouxia arboricola as photobiont can be explained by the assumption of a free-living population of Trebouxia arboricola . Species of photobionts from Xanthoria parietina were morphologically and genetically different from those of Physcia adscendens and Phaeophyscia orbicularis , respectively; a finding that does not support the previous assumption that Xanthoria parietina takes over its algal partner from a Physcia species, at least at the sites investigated. 相似文献
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The effect of pH on growth, metal uptake and toxicity in four isolates of ericoid mycobionts (two Hymenoscyphus ericae from unpolluted heathland sites and two H. ericae-type mycobionts from metal-contaminated mine spoil) was assessed in vitro. These isolates were incubated in liquid medium (10% Rorisons medium, glucose at 10 g l–1) containing either 0.25 mM Cu or 2.0 mM Zn and adjusted to pH 2, 3, 4, 5 or 6. After 30 days incubation, dry mass and mycelial metal content were determined and growth was expressed as tolerance index, i.e. dry mass in the presence of metal as a percentage of dry mass in the absence of metal. Initial medium pH had a significant effect on both tolerance index and metal accumulation. Tolerance indices were highest at pH 2, with several isolates showing a stimulation of growth (i.e. tolerance index >100%) at this pH. Tolerance index decreased at higher initial pH values and growth of two mycobionts was completely inhibited (tolerance index=0) in the Cu-supplemented media at pH 6. Reduction in tolerance index coincided with an increase in mycelial accumulation of Cu and Zn. Practical and environmental implications of these results are discussed. 相似文献
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