Anatomy of the endolithic Sonoran Desert lichen Verrucaria rubrocincta Breuss: implications for biodeterioration and biomineralization (original) (raw)
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Naturwissenschaften, 2008
Verrucaria rubrocincta Breuss is an endolithic lichen that inhabits caliche plates exposed on the surface of the Sonoran Desert. Caliche surface temperatures are regularly in excess of 60°C during the summer and approach 0°C in the winter. Incident light intensities are high, with photosynthetically active radiation levels typically to 2,600 μmol/m 2 s −1 during the summer. A crosssection of rock inhabited by V. rubrocincta shows an anatomical zonation comprising an upper micrite layer, a photobiont layer containing clusters of algal cells, and a pseudomedulla embedded in the caliche. Hyphae of the pseudomedulla become less numerous with depth below the rock surface. Stable carbon and oxygen isotopic data for the caliche and micrite fall into two sloping, well-separated arrays on a δ 13 C-δ 18 O plot. The δ 13 C PDB of the micrite ranges from 2.1 to 8.1 and δ 18 O SMOW from 25.4 to 28.9, whereas δ 13 C PDB of the caliche ranges from −4.7 to 0.7 and δ 18 O SMOW from 23.7 to 29.2. The isotopic data of the micrite can be explained by preferential fixing of 12 C into the alga, leaving local 13 C enrichment and evaporative enrichment of 18 O in the water. The 14 C dates of the micrite range from recent to 884 years b.p., indicating that "dead" carbon from the caliche is not a significant source for the lichen-precipitated micrite. The endolithic growth is an adaptation to the environmental extremes of exposed rock surfaces in the hot desert. The micrite layer is highly reflective and reduces light intensity to the algae below and acts as an efficient sunscreen that blocks harmful UV radiation. The micrite also acts as a cap to the lichen and helps trap moisture. The lichen survives by the combined effects of biodeterioration and biomineralization. Biodeterioration of the caliche concomitant with biomineralization of a protective surface coating of micrite results in the distinctive anatomy of V. rubrocincta.
Flora, 1982
In comparison to the Negev Desert environment, where extensive desert lichen photosynthetic and productivity studies have been conducted, the environment of the interior Sonoran Desert at Phoenix, Arizona, is shown to be much less favorable for lichen photosynthetic •activity. Lack of dewfall events is inferred to be the major difference, as the estimated dewfall frequency of 12 d per year is only 6 % of the number of days when dewfall occurs at Avdat, Israel. Favorable moi• sture periods for lichen photosynthesis are shown to be largely restricted to the winter period when temperatures are cool. The occurrence of dewfall and periods with low vapor pressure deficits is generally coupled with the occurrence of winter rainfall periods. Fog, a factor responsible for luxuriant lichen communities in some maritime, arid environments, is shown to be almost non•-existent at Phoenix. Preliminary photosynthetic measurements over 28 d confirmed that days with photosynthetic activity are tightly coupled with precipitation events. Moisture conditions favorable for photosynthetic activity may persist for a day or two after precipitation events. Because of the marked differences in moisture conditions and in lichen biomass estimates between the Negev and the interior Sonoran Desert, it is inferred that lichen productivity must be much lower at the Sonoran Desert site.
Lichenologist, 2002
The chemical and ultrastructural features of the interface formed by different biotypes of saxicolous lichen species with their rock substrata were investigated in the semiarid habitat of the SE Iberian Peninsula and the relationships between the bioweathering patterns observed and lichen colonization selectivity towards the different rock substrata evaluated. Xanthoria parietina was able to fix to the rock substratum by the adherence of single cell walls from the lower cortex. Neofuscelia pulla used rhizines and loose groups of hyphae for attachment of the thallus to the rock. Colonization by the foliose lichen species was confined to the rock surface, while Diploschistes diacapsis was also able to grow below the surface showing two types of hyphal growth. Minerals in close contact with cell walls were biochemically and biophysically weathered, but hyphae showing calcium oxalate crystals did not appear to be directly involved in the patterns observed. The textural characteristics of the substratum seemed to be related to the type of microorganism colonization: sedimentary rocks were more deeply colonized by lichens and other chasmolithic microorganisms than volcanic material. Calcium oxalate crystals were found in the medulla of N. pulla but not at the lichen-substratum interface. Crustose lichens such as D. diacapsis showed calcium oxalate crystals in the upper cortex and over the outside of fungal medullary hyphae but not in direct contact with the rock surface. Calcium oxalate precipitation seems to be related to the different metabolic activities of the mycobiont within the lichen thallus and to different species. D. diacapsis inhibits the growth of other microorganisms in close proximity to the thallus, whereas foliose species were associated with several communities of microorganisms.
New Phytologist, 2004
• Through the combined use of molecular and microscopy techniques, the endolithic lichens Lecidea cancriformis and Lecidea sp. were identified, even in the absence of fruiting bodies, and positioned under epilithic lichens. Cells of both algal and fungal symbionts were observed in fissures and cracks of the lithic substrate with no clear heteromerous structure. At the ultrastructural level, the two lichens differed in terms of their algal–fungal relationships.• Only one genotype of Trebouxia ITS sequence was identified from specimens of Lecidea sp., Umbilicaria aprina and Buellia frigida from the same zone, which could be mainly determined by low availability of alga in these extreme environments.• These lichens showed features typical of both chasmoendolithic and euendolithic microorganisms. Signs of biogeophysical and biogeochemical action on the substrate were detected close to fungal cells. This action seemed to be mainly conditioned by the local physico-chemical features of the substrate. Evidence for the biomobilization of elements by these endolithic lichens was found. L. cancriformis was observed to accumulate substantial amounts of calcium-rich biominerals.• The combined approach proposed is useful for mapping the distribution of endolithic lichens and analysing the processes that occur in their microscopic environment.Through the combined use of molecular and microscopy techniques, the endolithic lichens Lecidea cancriformis and Lecidea sp. were identified, even in the absence of fruiting bodies, and positioned under epilithic lichens. Cells of both algal and fungal symbionts were observed in fissures and cracks of the lithic substrate with no clear heteromerous structure. At the ultrastructural level, the two lichens differed in terms of their algal–fungal relationships.Only one genotype of Trebouxia ITS sequence was identified from specimens of Lecidea sp., Umbilicaria aprina and Buellia frigida from the same zone, which could be mainly determined by low availability of alga in these extreme environments.These lichens showed features typical of both chasmoendolithic and euendolithic microorganisms. Signs of biogeophysical and biogeochemical action on the substrate were detected close to fungal cells. This action seemed to be mainly conditioned by the local physico-chemical features of the substrate. Evidence for the biomobilization of elements by these endolithic lichens was found. L. cancriformis was observed to accumulate substantial amounts of calcium-rich biominerals.The combined approach proposed is useful for mapping the distribution of endolithic lichens and analysing the processes that occur in their microscopic environment.
46 Acosta Hospitaleche et al 2011, lichen bioerosion PDF
Sarcogyne orbicularis Körber, Verrucaria sp. Schrad, and Buellia aff. punctiformis (Hoff.) Massal. The lichen Aspicilia aff. aquatica produced rounded holes on an Antarctic tooth (Type 2). On the same tooth, the epilithic lichen Caloplaca sp. Th. Fries did not leave any kind of mark on the enameloid.
Appl Surf Sci_ Lichens_2017.pdf
Laser irradiation of lichen thalli on heritage stones serves for the control of epilithic and endolithic biological colonizations. In this work we investigate rock samples from two quarries traditionally used as source of monumental stone, sandstone from Valonsadero (Soria, Spain) and granite from Alpedrete (Madrid, Spain), in order to find conditions for efficient laser removal of lichen thalli that ensure preservation of the lithic substrate. The samples presented superficial areas colonized by different types of crustose lichens, i.e. Candelariella vitellina, Aspicilia viridescens, Rhizocarpon disporum and Protoparmeliopsis muralis in Valonsadero samples and P. cf. bolcana and A. cf. contorta in Alpedrete samples. A comparative laser cleaning study was carried out on the mentioned samples with ns Q-switched Nd:YAG laser pulses of 1064 nm (fundamental radiation), 355 nm (3rd harmonic) and 266 nm (4th harmonic) and sequences of IR-UV pulses. A number of techniques such as UV-Vis absorption spectroscopy, stereomicroscopy, scanning electron microscopy (SEM) at low vacuum, SEM with backscattered electron imaging (SEM-BSE), electron dispersive spectroscopy (EDS) and FT-Raman spectroscopy were employed to determine the best laser irradiation conditions and to detect possible structural, morphological and chemical changes on the irradiated surfaces.
Investigation of Calcium Forms in Lichens from Travertine Sites
Plants
Lichens are symbiotic organisms with an extraordinary capability to colonise areas of extreme climate and heavily contaminated sites, such as metal-rich habitats. Lichens have developed several mechanisms to overcome the toxicity of metals, including the ability to bind metal cations to extracellular sites of symbiotic partners and to subsequently form oxalates. Calcium is an essential alkaline earth element that is important in various cell processes. Calcium can serve as a metal ligand but can be toxic at elevated concentrations. This study investigated calcium-rich and calcium-poor sites and the lichen species that inhabit them (Cladonia sp.). The calcium content of these lichen species were analyzed, along with localized calcium oxalate formed in thalli collected from each site. The highest concentration of calcium was found in the lichen squamules, which can serve as a final deposit for detoxification. Interestingly, the highest content of calcium in Cladonia furcata was locali...