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Contamination by atmospheric mercury has been assessed in two different areas from Spain (Las Cuevas, Ciudad Real and Flix, Tarragona) using lichens as biomonitors. The relationship established between mercury contents in the soils and the gaseous mercury (GM) was also observed. It was found that the GM is highest in the vicinity of the source and it is dispersed depending on of the distance to the source and the wind directions. The mercury concentration in the gas phase in Flix was higher than that found in Las Cuevas and also higher than the value that the US EPA recommended. The mercury bioaccumulation in the native lichens from genders Ramalina and Xanthoria were used as biomonitors for absorbing mercury in Las Cuevas and Flix, respectively. The mercury uptake by Ramalina was higher than the amount accumulated by Xanthoria, a difference that was mainly due to the lichen characteristics. The content of mercury in lichens in relation to the mercury in gas was fitted by a Freundlich type equation, indicating that the equilibrium between both phases was established. Besides, transplanted Ramalina lichen in Las Cuevas allowed to obtain the kinetic of mercury uptake. A kinetic model of first order based on the equilibrium was proposed and the mass transfer constants for each sampling station were estimated. As it was expected, these values increased with the predominant wind flow direction., (Copyright © 2016 Elsevier Ltd. All rights reserved.)

The accumulating ability of the atmospheric Metal Trace Elements (MTE) of two lichenic species thalli; Xanthoria parietina and Ramalina farinacea were evaluated in the region of Megres. The recorded concentrations of MTE (Fe, Cu, Mn, Cd, and Pb) were determined by atomic absorption spectrophotometry (AASF). The ability to accumulate MTE in X. parietina thalli is considerably greater than that of the fruticulous lichen R. farinacea in all stations studied. The general pattern of the elements accumulated in the thalli of the two species in decreasing order of their concentrations was Fe> Mn> Pb> Cu> Cd. The Fe values are very high in X. parietina thalli with an average of 35237.5 ± 3394.2 mg/kg dry wt. In contrast, the Pb concentrations are high, especially in the southern station of the Megres region. The results showed that X. parietina is a hyper-accumulating species of MTE, compared to R. farinacea. This work highlights the ecological importance of this species as a stable and resistant pioneer in this fragile region. [ABSTRACT FROM AUTHOR]

Molecular analyses of the recently described Xanthoria polessica collected from the type locality and of the Australian species X. coomae were used to determine whether these taxa are distinct species or fall within the wide phenotypic variation of the wellknown and cosmopolitan X. parietina. Our results clearly indicate that both taxa should be considered as synonyms of X. parietina since the infraspecific morphological range is accommodated by the observed variation in the thallus and lobe size, their color, position of apothecia, the shape of ascospores, and width of ascospore septum. [ABSTRACT FROM AUTHOR]

Eight species, new for science, i.e.: Lobothallia gangwondoana S. Y. Kondr., J.-J. Woo et J.-S. Hur and Phyllopsora dodongensis S. Y. Kondr. et J.-S. Hur from South Korea, Eastern Asia, Ioplaca rinodinoides S. Y. Kondr., K. K. Ingle, D. K. Upreti et S. Nayaka, Letrouitia assamana S. Y. Kondr., G. K. Mishra et D. K. Upreti, and Rusavskia indochinensis S. Y. Kondr., D. K. Upreti et S. Nayaka from India and China, South Asia, Caloplaca orloviana S. Y. Kondr. and Rusavskia drevlyanica S. Y. Kondr. et O. O. Orlov from Ukraine, Eastern Europe, as well as Xanthoria ibizaensis S. Y. Kondr. et A. S. Kondr. from Ibiza Island, Spain, Mediterranean Europe, are described, illustrated and compared with closely related taxa. Fominiella tenerifensis S. Y. Kondr., Kärnefelt, A. Thell et Feuerer is for the first time recorded from Mediterranean Europe, Huriella loekoesiana S. Y. Kondr. et Upreti is provided from Russia for the first time, and H. pohangensis S. Y. Kondr., L. Lőkös et J.-S. Hur for the first time from China, Phoma candelariellae Z. Kocakaya et Halıcı is new to Ukraine, and Staurothele frustulenta Vain. is recorded from the Forest Zone of Ukraine for the first time. Twelve new combinations, i.e.: Bryostigma apotheciorum (for Sphaeria apotheciorum A. Massal.), Bryostigma biatoricola (for Arthonia biatoricola Ihlen et Owe-Larss.), Bryostigma dokdoense (for Arthonia dokdoensis S. Y. Kondr., L. Lőkös, B. G. Lee, J.-J. Woo et J.-S. Hur), Bryostigma epiphyscium (for Arthonia epiphyscia Nyl.), Bryostigma lobariellae (for Arthonia lobariellae Etayo), Bryostigma lapidicola (for Lecidea lapidicola Taylor), Bryostigma molendoi (for Tichothecium molendoi Heufl. ex Arnold), Bryostigma neglectulum (for Arthonia neglectula Nyl.), Bryostigma parietinarium (for Arthonia parietinaria Hafellner et Fleischhacker), Bryostigma peltigerinum (for Arthonia vagans var. peltigerina Almq.), Bryostigma phaeophysciae (for Arthonia phaeophysciae Grube et Matzer), Bryostigma stereocaulinum (for Arthonia nephromiaria var. stereocaulina Ohlert), are proposed based on results of combined phylogenetic analysis based on mtSSU and RPB2 gene sequences. Thirty-one new combinations for members of the genus Polyozosia (i.e.: Polyozosia actophila (for Lecanora actophila Wedd.), Polyozosia agardhiana (for Lecanora agardhiana Ach.), Polyozosia altunica (for Myriolecis altunica R. Mamut et A. Abbas), Polyozosia antiqua (for Lecanora antiqua J. R. Laundon), Polyozosia bandolensis (for Lecanora bandolensis B. de Lesd.), Polyozosia behringii (for Lecanora behringii Nyl.), Polyozosia caesioalutacea (for Lecanora caesioalutacea H. Magn.), Polyozosia carlottiana (for Lecanora carlottiana C. J. Lewis et Śliwa), Polyozosia congesta (for Lecanora congesta Clauzade et Vězda), Polyozosia eurycarpa (for Lecanora eurycarpa Poelt, Leuckert et Cl. Roux), Polyozosia expectans (Lecanora expectans Darb.), Polyozosia flowersiana (Lecanora flowersiana H. Magn.), Polyozosia fugiens (for Lecanora fugiens Nyl.), Polyozosia invadens (for Lecanora invadens H. Magn.), Polyozosia juniperina (for Lecanora juniperina Śliwa), Polyozosia latzelii (for Lecanora latzelii Zahlbr.), Polyozosia liguriensis (for Lecanora liguriensis B. de Lesd.), Polyozosia massei (for Myriolecis massei M. Bertrand et J.-Y. Monnat), Polyozosia mons-nivis (for Lecanora mons-nivis Darb.), Polyozosia oyensis (for Lecanora oyensis M.-P. Bertrand et Cl. Roux), Polyozosia percrenata (for Lecanora percrenata H. Magn.), Polyozosia persimilis (for Lecanora hagenii subsp. persimilis Th. Fr.), Polyozosia poeltiana (for Lecanora poeltiana Clauzade et Cl. Roux), Polyozosia prominens (for Lecanora prominens Clauzade et Vězda), Polyozosia prophetae-eliae (for Lecanora prophetae-eliae Sipman), Polyozosia salina (for Lecanora salina H. Magn.), Polyozosia schofieldii (for Lecanora schofieldii Brodo), Polyozosia sverdrupiana (for Lecanora sverdrupiana Øvstedal), Polyozosia torrida (for Lecanora torrida Vain.), Polyozosia wetmorei (for Lecanora wetmorei Śliwa), Polyozosia zosterae (for Lecanora subfusca? zosterae Ach.)) are proposed. [ABSTRACT FROM AUTHOR]

This paper aims to summarize the main characteristics of lichens that make them excellent bioindicators of air pollution with heavy metals. Also, the paper shows other possible uses of lichen species in the future. [ABSTRACT FROM AUTHOR]

The protocols commonly applied in surveys with lichens as biomonitors of airborne trace elements require analyses of samples derived from thalli or parts of thalli grown in the last year before sampling, under the postulation that samples of the same size are of the same age. Unfortunately, the influence of ecological site-specific factors on lichen growth is still largely ignored, so that samples of the same size collected in environmentally and climatically diverse sites might actually differ in age. This work aims at quantifying the influence of climatic conditions on the radial growth rates (RaGRs) of Xanthoria parietina, one of the most popular lichen biomonitors. RaGR was monitored in seven populations distributed along an altitudinal transect of 30 km in the Classical Karst (NE Italy), from 20 to 500 m above sea level. For c. 17 months, lobe growth was measured seasonally with a digital calliper, and site-specific climatic variables were monitored by means of thermo-hygrometric sensors and implemented by meteorological data. Finally, the lobe growth of X. parietina was modelled as a function of 18 environmental variables. Results revealed that thalli of relatively dry sites had significantly lower seasonal RaGR with respect to moister ones. Considering that cumulative precipitations were equally distributed along the transect, it was concluded that RaGR of X. parietina is affected negatively by high air temperatures and positively by high relative humidity. The importance of RaGR variation in lichen bioaccumulation studies is critically discussed. [ABSTRACT FROM AUTHOR]

The mechanisms of nitrogen (N) tolerance in lichens are not yet fully understood. Here, we investigated how the increase of chitin content is related with N excess at inter- and intra-specific levels, by using species with differing ecological N tolerances (the tolerant Xanthoria parietina and Parmotrema hypoleucinum and the sensitive Evernia prunastri and Usnea sp.) and thalli of X. parietina and P. hypoleucinum from sites with different availabilities of N of agricultural origin (livestock), as confirmed by lichen N content and δN. Nitrogen, chitin (N-containing compound), and ergosterol contents were measured in lichen thalli. Nitrogen and chitin contents were higher in tolerant species than those in sensitive ones (inter-specific level) and in thalli collected from the N-polluted site than in thalli from the clean site (intra-specific level). We suggest that chitin contributes to N stress tolerance in lichens, and that excess N can be partially stored as chitin (non-toxic form) in the cell walls of tolerant species. [ABSTRACT FROM AUTHOR]

The paramagnetic properties of lichens were investigated using EPR spectroscopy and Xanthoria parietina (L.) Th. Fr. as a case study. It was found that the concentration of paramagnetic centers in lichen thalli increased as the air-pollution level increased. Possible formation mechanisms of the paramagnetic centers in lichens were discussed. The efficiency of using EPR spectroscopy to study lichens as environmental quality indicators was demonstrated. [ABSTRACT FROM AUTHOR]

The Trebouxia photobiont freshly isolated from Xanthoria parietina (L.) Th. Fr. was used to develop a live cell chondriome (mitochondrial DNA) labelling method. In the initial phase six candidate dyes were tested and compared for mitochondrial labelling utility as assessed by the signal to noise ratio (SNR) of the mitochondrial signal to the adjacent cellular background in standardized confocal images of 30 labelled cells. DIOC7, JC-1 and MitoTracker orange (MTO) dyes showed some labelling ability. MTO had significantly higher utility than the other dyes. In a second phase, MTO concentration was optimized. The final labelling protocol was a 30 minute incubation with 1 μM of MTO. The resultant labelling was suitable for both widefield and confocal microscopy. Both 2D thresholding and 3D volume construction are demonstrated using the resultant data. The protocol can therefore be utilized for both qualitative research and for quantitative measurement of the chondriome in Trebouxia photobionts. This will facilitate a wide range of mitochondrial investigations in lichenology. [ABSTRACT FROM AUTHOR]

The present study aimed to evaluate the antimicrobial activity of methanol and chloroform extracts of five lichen species, Melanohalea exasperata, Physcia aipolia, Usnea florida, U. subfloridana and Xanthoria parietina. Antimicrobial activity in culture assays of these foliose and fruticose lichen extracts were examined against two Gram-negative bacteria (Pseudomonas aeruginosa and Escherichia coli), two Gram-positive bacteria (Enterococcus faecalis and Staphylococcus aureus), and the yeast Candida albicans using the paper disc method through determination of minimal inhibitory concentrations (MICs). The obtained results indicated the existence of different levels of antibiotic substances in the chloroform and the methanol extracts of the examined lichen species. The chloroform extracts of Usnea subfloridana showed the highest activity against Escherichia coli and Pseudomonas aeruginosa while the methanol extracts of this species were not active against these microorganisms. The chloroform extracts of the examined species exhibited more significant antimicrobial activity than the methanol extracts. None of the species were active against Enterococcus faecalis and Staphylococcus aureus. Most of the lichen extracts indicated a moderate antifungal activity against Candida albicans, except for Physcia aipolia, which was not active. [ABSTRACT FROM AUTHOR]

Lichens are sensitive to the presence of ammonia (NH 3 ) in the environment. However, in order to use them as reliable indicators in biomonitoring studies, it is necessary to establish unequivocally the occurrence of certain symptoms following the exposure to NH 3 in the environment. In this paper, we simulated an episode of acute air pollution due to the release of NH 3 . The biological effects of acute air pollution by atmospheric NH 3 have been investigated using N-sensitive ( Flavoparmelia caperata ) and N-tolerant ( Xanthoria parietina ) species. Lichen samples were exposed to ecologically relevant NH 3 concentrations for 8 weeks, simulating three areas of impact: a control area (2 μg/m 3 ), an area of intermediate impact (2–35 μg/m 3 ) and an area of high impact (10–315 μg/m 3 ), with a peak of pollution reached between the fourth and fifth week. Ammonia affected both the photobiont and the mycobiont in F. caperata , while in X. parietina only the photosynthetic performance of the photobiont was altered after exposure to the highest concentration. In the photobiont of F. caperata we recorded chlorophyll degradation as indicated by OD 435/415 ratio, decrease of the photosynthetic performance (as reflected by the maximum quantum yield of primary photochemistry F V / F M and the performance index PI ABS ); in the mycobiont, ergosterol reduction, membrane lipid peroxidation (as reflected by the increase of thiobarbituric acid reactive substances), alteration (decrease) of the secondary metabolite usnic acid. No effects were detected on caperatic acid and dehydrogenase activity. In X. parietina , the only signal determined by NH 3 was the alteration of F V / F M and the performance index PI ABS . The results suggest that physiological parameters in N-sensitive lichens well reflect the effects of NH 3 exposure and can be applied as early indicators in monitoring studies. [ABSTRACT FROM AUTHOR]

This study investigated if treatment of the lichen Xanthoria parietina (L.) Th. Fr. with glyphosate caused uptake of this herbicide as well as physiological alterations. Samples were treated with Glifene SL®, a common commercial glyphosate-based herbicide, at the lowest recommended doses (3.6 g/L) as well as with doses slightly higher than the highest suggested (36 g/L). The results clearly showed glyphosate uptake in X. parietina proportionally to the dose provided. Adverse physiological effects were evident on the photosynthetic apparatus (photosynthetic efficiency, chlorophyll a content, chlorophyll degradation) as well as on the fungal respiration rates and cell membrane integrity (ergosterol content, dehydrogenase activity) already after 24 h from treatment, also at the low application dose. It is concluded that lichens are suitable organisms for monitoring unwanted biological effects from the application of glyphosate-based herbicides, as well as for detecting the accumulation of this compound in the biota, thus screening for its environmental fate. [ABSTRACT FROM AUTHOR]

In this paper we investigated whether a different accuracy in sample cleaning prior to the analysis may affect the elemental composition of unwashed samples of the lichen Xanthoria parietina. To this purpose, samples of this lichen were collected from a remote area of Sardinia (Italy) and randomly divided into two aliquots, one cleaned very carefully (ca. 3-4 h to obtain ca. 200 mg of material for analysis) and the other cleaned with a lower efficiency (ca. 1-2 h). Samples were analysed by ICP-MS for the content of Al, As, Ba, Ca, Cd, Co, Cr, Cu, Fe, K, Mg, Mn, Ni, Pb, V and Zn. The results indicated that an accurate cleaning is effective for reducing the content of Al and Fe, i.e. soil-related elements, but that it has no effect on the concentrations of other elements less represented in the soil. [ABSTRACT FROM AUTHOR]

In this study, we investigated whether ammonia emissions from industrial composting of organic waste may influence the surrounding environment, using lichens as bioindicators. To this purpose, samples of N-tolerant and N-sensitive lichens, namely Xanthoria parietina and Evernia prunastri, were transplanted for 1-3 months along transects at increasing distance (0-400 m) from a composting facility in Tuscany, Italy. Atmospheric concentrations of ammonia were measured using passive samplers. The physiological response of lichen transplants was investigated by means of the photosynthetic efficiency (measured as chlorophyll a fluorescence emission), the integrity of cell membranes (measured as electrolyte leakage), and sample viability (measured as enzymatic activity of dehydrogenase). Epiphytic lichen communities were investigated using biodiversity indices. The results showed decreasing concentrations of ammonia, from 48.7 μg/m at the composting facility to 2.7 μg/m at 400 m. The N-tolerant X. parietina was not affected and some physiological parameters even showed a higher performance, while the N-sensitive E. prunastri showed a reduced performance with increasing atmospheric concentrations approaching the source. A shift from lichen communities composed by meso-acidophilous species (actual condition) to more nitrophilous communities in the near future, approaching the composting facility is suggested. It is concluded that lichens can provide useful data for decision-makers to establish correct science-based environmentally sustainable waste management policies. [ABSTRACT FROM AUTHOR]

We studied group I introns in sterile cultures of selected groups of lichen photobionts, focusing on Trebouxia species associated with Xanthoria s. lat. (including Xanthomendoza spp.; lichen-forming ascomycetes). Group I introns were found inserted after position 798 ( Escherichia coli numbering) in the large subunit ( LSU) r RNA in representatives of the green algal genera Trebouxia and Asterochloris. The 798 intron was found in about 25% of Xanthoria photobionts including several reference strains obtained from algal culture collections. An alignment of LSU-encoded r DNA intron sequences revealed high similarity of these sequences allowing their phylogenetic analysis. The 798 group I intron phylogeny was largely congruent with a phylogeny of the internal transcribed spacer region, indicating that the insertion of the intron most likely occurred in the common ancestor of the genera Trebouxia and Asterochloris. The intron was vertically inherited in some taxa, but lost in others. The high-sequence similarity of this intron to one found in Chlorella angustoellipsoidea suggests that the 798 intron was either present in the common ancestor of Trebouxiophyceae, or that its present distribution results from more recent horizontal transfers, followed by vertical inheritance and loss. Analysis of another group I intron shared by these photobionts at small subunit position 1512 supports the hypothesis of repeated lateral transfers of this intron among some taxa, but loss among others. Our data confirm that the history of group I introns is characterized by repeated horizontal transfers, and suggests that some of these introns have ancient origins within Chlorophyta. [ABSTRACT FROM AUTHOR]

To investigate the mechanisms of nitrogen (N) tolerance in lichens, we examined the physiological responses to increased N availability in different functional groups. Thalli of the nitrophytic Xanthoria parietina (L.) Th.Fr. previously grown both in an N-poor environment (~2kgNha[sup -1] year[sup -1]) and in an N-rich environment (~52 kg Nha[sup -1] year[sup -1]) were compared with the oligotrophic species Evernia prunastri (L.) Ach. and Usnea sp. Lichens were submitted to ammonium treatments. Maximum PSII efficiency, redistribution of the ions between the intra- and extracellular compartments and potassium and magnesium concentrations were the parameters used to check for the effects of N supply. The buffering capacity of the lichen extracts was also determined in untreated lichen thalli to check if different lichen behaviours were due to their ability to maintain the pH. The results showed a more similar response between X. parietina from the N-poor environment and the N-sensitive species than between X. parietina from the N-poor and N-rich environments, suggesting that X. parietina achieved N-tolerance after long-term exposure to N-rich environment. These results are important in understanding the effects of chronic ammonium pollution on one of the most sensitive components of the ecosystem, linking physiological response and ecological consequences. [ABSTRACT FROM AUTHOR]

Abstract: Airborne metal deposition in the major urban and the industrial districts of Kocaeli was monitored using Xanthoria parietina lichen specimen as a biomonitoring organism. Lichen samples were analyzed for Al, As, Co, Cd, Cu, Fe, Hg, Mn, Ni, Pb, Ti, Tl, V and Zn contents to determine the relationship between the potential pollutant sources in the region and the degree of airborne metal deposition. Results showed that airborne metal deposition in the Kocaeli province was widespread and environmental alteration was serious near the industrial facilities. Mean metal concentrations of lichen samples in the industrial district (Dilovası) of Kocaeli were two to seven folds higher than those in the urban districts of Kocaeli: Mn (7), Pb–Cd–Zn (6), Fe–Ni–Cu (3) and Al–Co–Ti–Hg–As–V (2). Environmental alteration in Dilovası region was severe in terms of all metals analyzed. Cluster analysis showed that metal industry (iron–steel, aluminum, zinc) in Dilovası, fossil fuel combustion processes related to the industry and power plant and heavy traffic contributed significantly to the metal emission in Dilovası region. Airborne metal deposition in the urban districts of Kocaeli was high especially around the coal-fired cement plant in Hereke and petroleum refinery in Körfez. Fossil fuel combustion and traffic emission were among the important sources of airborne metals in the urban–suburban districts. [Copyright &y& Elsevier]

Abstract: Atmospheric mercury (Hg) deposition around a mercury cell chlor-alkali plant located near Grenoble, south-east France, was assessed using Hg concentrations in lichens and soils. Hg content in the epiphytic Xanthoria parietina lichen ranged from ∼0.07 to ∼2.51μgg−1, and concentrations decreased with increasing distance to the plant, with a contamination radius of ∼2km. Soil Hg concentration profiles were consistent with an atmospheric origin, with higher concentrations in the upper part of the profiles. Concentration of Hg in lichens and top soils (0–10cm depth) as a function of the distance to the chlor-alkali plant exhibited highly similar variations. Using a simple first-order deposition model, mean Hg fallouts for the whole history of chlor-alkali plant are estimated to ∼36gHgday−1 in this area, compatible with values reported for reactive gaseous mercury (RGM) emissions of similar industrial plants. Using literature data on RGM to total Hg emission ratio, we estimate that the plant emitted ∼650kgHgyear−1. Two kilometres away from the plant, Hg content in top soils falls to values of (0.13±0.07)μgg−1 Hg, which is the local anthropogenic geochemical background level, but higher than unperturbed geochemical background found at the bottom of soil profiles (below 40cm depth) estimated to (0.04±0.01)μgg−1 Hg. The present study evidences that lichens are a pertinent proxy for soil Hg contamination around chlor-alkali plants. They are attractive biomonitoring tools since sampling and preparations protocols for lichens are less time consuming than those used for soils. [Copyright &y& Elsevier]

Abstract: The sensitivity of three foliose lichen species to urban environments with different air pollution loads and climatic conditions was tested using chlorophyll a fluorescence (Chl a F) PAM measurements. Transplants of Xanthoria parietina (L.) Th. Fr., Flavoparmelia caperata (L.) Hale and Parmotrema perlatum (Huds.) M. Choisy collected in a pristine site of the Classic Karst (Trieste, NE Italy) were exposed for 12 weeks (August–December 2008) at that site (control, A), and in two urban sites with heavy traffic in Trieste (B) and Udine (C). Concentrations of the main gaseous pollutants were monitored by passive samplers in A (NO2, O3), and by pollution monitoring stations in B and C (NOX, NO2, SO2, O3). In the laboratory, Kautsky curves were induced under standardized conditions at species-specific PPFD values before exposure, after 6 weeks and at the end of the exposure. Significant decrease in F v/F m was only observed in P. perlatum transplants exposed in B, possibly as a consequence of the dry conditions of that site. Non-photochemical quenching (NPQ) was negatively affected in all three species, although with different intensity, in both urban sites, but more intensively in C than in B. Chl a F data shows clearly that (i) the decrease of NPQ was modulated by time exposure to NOX as well as by NOX concentration, and (ii) the species response to pollutants was related to species ecology: X. parietina, which is more nitro- and xerophytic than the other two species, tolerated better the transplant environmental conditions, confirming recent floristic observations carried out in several urban areas of Central Europe. [Copyright &y& Elsevier]

Abstract: Effects of methyl jasmonate (MeJA), salicylic acid (SA) or 2-aminoindane-2-phosphonic acid (AIP) pre-treatments on the sensitivity of Xanthoria parietina exposed to UV-A were studied. UV decreased chlorophylls and stimulated increase in hydrogen peroxide and superoxide level. Accumulation of soluble phenols and flavonoids increased in response to UV treatment. Metabolic modulators had negligible impact on these UV-induced changes. Within free amino acids, AIP (−UV variant) and SA and MeJA (+UV variants) altered their accumulation. AIP had no effect on the amount of phenylalanine. Benzoic and cinnamic acids were elevated by UV and mainly MeJA influenced their accumulations. Among lichen specific metabolites, vulpinic acid and ergosterol increased while usnic acid and atranorin decreased after exposure to UV; accumulation of parietin was not affected. Applied modulators showed a different effect on these lichen metabolites but biosynthetic pathway-specific trend of alteration was visible. Overall, MeJA showed the most pronounced effect among studied parameters. Accumulation of selected phenolics in response to UV-A seems to be an important feature of Xanthoria tolerance. Present finding in the context of phenolic metabolism in non-vascular plants and with respect to limited data about effect of studied modulators on non-vascular plants are discussed. [Copyright &y& Elsevier]

Abstract: The aim of this study was to test in a short term laboratory experiment the accumulation and physiological effects of As in the epiphytic lichen Xanthoria parietina. Arsenic content in treated samples increased progressively with increasing concentration in treatment solutions. Treatment of X. parietina thalli with 0.1, 1, 10ppm As solutions caused significant decrease of viability, measured as intensity of respiratory activity, and damages to cell membranes, assessed by increase of electric conductivity of rinsing water and lipid peroxidation products. Soluble proteins content decreased and H2O2 content increased already at the lowest As concentration tested (0.01ppm). Photosynthetic efficiency, measured in terms of FV /FM ratio, decreased significantly only at the highest As concentration (10ppm). It was concluded that As exposure causes physiological stress both on the mycobiont and the photobiont and that cell membrane damage, expressed in terms of electric conductivity of rinsing water, is the parameter most affected by As treatment. [ABSTRACT FROM AUTHOR]

This study aimed to deepen the knowledge about intraspecific mechanisms regulating nitrogen tolerance in lichens to wet nitrogen deposition. Thalli of the nitrophilous lichen Xanthoria parietina were collected from environments with different nitrogen availabilities and immersed in 80 mL of ammonium sulphate (NH)SO solutions with distinct concentrations (0, 0.025, 0.05 and 0.25 M) for 5 h per day during 3 days in a week. After each soaking event, lichens were air dried. After each treatment, maximal PSII efficiency, localization of ammonium ions, concentrations of K and Mg and thalli buffer capacity were determined. Our results show that lichens are marked by their native nitrogen environment, since there were important differences between the physiological responses of X. parietina thalli previously grown in an area with high nitrogen deposition (nitrogen emissions of ca. 13,000 t/year) and those previously grown in an unpolluted area (nitrogen emissions of ca. 500 t/year). Greater N availability seems to enable X. parietina to cope better with the effects of nitrogen pollution. [ABSTRACT FROM AUTHOR]

Host use by herbivores is largely determined by host properties such as nutrient content and chemical defence against foragers. The impacts of these attributes on a herbivore may largely depend on its life cycle stage. Lichen species are known to differ in nutritional quality and level of chemical defence and, consequently, vary as fodder for herbivores. The aim of this study was to explore the impact of several lichen species and the presence of their secondary metabolites on their use as hosts by a specialist lichen-feeder, Cleorodes lichenaria. This study also addressed, for the first time, how a specialist lichen-feeder deals with different lichen secondary metabolites. In the beginning of their development, larvae grew better on Xanthoria parietina than on the other host lichens, whereas older larvae grew best on Ramalina fraxinea. Lichen secondary chemicals in R. fraxinea and Parmelia sulcata hindered larval growth in the beginning but after 75 days lichen secondary chemicals had no impact on the mass of larvae. Physodic acids in Hypogymnia physodes were lethal to larvae. In general, larvae metabolized 70–95% of ingested lichen secondary chemicals and the rest of these were excreted in frass. Lichen secondary metabolites in P. sulcata restrict and in H. physodes prevent their use as a host for C. lichenaria larvae. Our main finding, the ability of larvae to metabolize several lichen secondary metabolites, indicates digestive adaptation to these chemicals. No signs of sequestration of these chemicals were found. [ABSTRACT FROM AUTHOR]

The present work aims at testing if exposure time and dose play a role in the response of lichen species to nitrogen (N) pollution. To this purpose, samples of the N-sensitive Evernia prunastri and the N-tolerant Xanthoria parietina were treated for 5 weeks either with solutions of NH4NO3 0.05 and 1M, or (NH4)2SO4 0.025 and 0.5M. Photosynthetic efficiency was measured as an indicator of sample vitality. The results showed that the lowest concentrations were ineffective at the beginning, but after several supplies both compounds inhibited photosynthetic activity of E. prunastri. The highest concentrations had a deleterious effect, but with a temporal trend. For X. parietina no effect was found for the lowest concentrations, while the same trend shown by E. prunastri was instead observed following treatments with the highest concentrations. It was concluded that the response of lichens to N supply is not only species-specific, but also time- and dose-dependent. The results give a clue on field studies on the relationships between lichens and N pollution. [Copyright &y& Elsevier]

Lichens, representing mutualistic symbioses between photobionts and mycobionts, often accumulate high concentrations of secondary compounds synthesized by the fungal partner. Light screening is one function for cortical compounds being deposited as crystals outside fungal hyphae. These compounds can non-destructively be extracted by 100% acetone from air-dry living thalli. Extraction of atranorin from Physcia aipolia changed the lichen colour from pale grey to green in the hydrated state, whereas acetone-rinsed and control thalli were all pale grey when dry. Removal of parietin from Xanthoria parietina changed the colour of desiccated thalli from orange to grey. Colour changes were quantified by reflectance measurements. By a new chlorophyll fluorescence method, screening was assessed as the decrease in incident irradiance (PAR) necessary to reach identical effective quantum yields of PSII (ΦPSII) in acetone-rinsed and control thalli. Thereby, we estimated a screening efficiency due to cortical atranorin crystals at 61, 38, and 40% of blue, green and red light, respectively, whereas parietin screened 81, 27 and 1% of these wavelength ranges. Removal of atranorin caused similar levels of increased photoinhibition for P. aipolia in blue, green and red light, whereas parietin-deficient thalli of X. parietina exhibited increased photoinhibition with decreasing wavelengths. Atranorin possibly prevents water from entering the spaces between the hyphae in the cortex. The air-filled cavities with white atranorin crystals reflect excess light, whereas the yellow compound parietin absorbs excess light. Thereby, both atranorin and parietin play significant photoprotective roles for symbiotic green algae, but with compound-specific screening mechanisms. [ABSTRACT FROM AUTHOR]

The aim of this study was to compare the performance of two lichen species--Xanthoria parietina and Ramalina canariensis--as biomonitors of the toxic organic compounds dioxins and furans (PCDD/Fs). For that purpose, the concentrations and profiles of PCDD/Fs found in samples of these two lichen species were compared. Results showed that R. canariensis presented higher concentrations than X. parietina and that the PCDD/F homologue profiles were substantially different between these species. Xanthoria parietina appeared to be a more efficient interceptor of more chlorinated PCDD/Fs and also of particles, whereas R. canariensis mainly reflected less chlorinated PCDD/Fs. Results also showed that the PCDD/F profile of X. parietina differed from the one found in other foliose and fruticose lichen species. Despite the differences observed between the profiles of R. canariensis and X. parietina, the calibration of PCDD/F concentrations between the two species was achieved, allowing the biomonitoring of PCDD/Fs at a regional scale using both species simultaneously. [ABSTRACT FROM AUTHOR]

The fine-scale genetic variation and population structure of lichen-forming fungi is little known and sampling strategies are rarely recommended or discussed. I tested if the sample sizes of molecular data sets used in recent population studies of Xanthoria parietina revealed all haplotypes potentially present and, accordingly, quantified how many haplotypes were potentially missing in the samples. Data sets were concatenated from two geographical regions in Scandinavia and investigated if the sampling reached saturation at two levels: 1) individual-based using rarefaction curves and 2) population-based using species accumulation curves. At both levels, the matrices of two molecular markers (IGS and ITS) were analysed separately. The molecular markers show similar and parallel patterns in all analyses. Rarefaction analyses did not reveal different patterns for populations in different habitats, i.e., bark and rock. Species accumulation curves estimated with the Chao 1 richness estimator indicated that 23% of the IGS and 8% of the ITS haplotypes were not detected. Corresponding figures from an abundance-based coverage estimator (ACE) were 37% and 18%. Pilot studies are recommended to determine appropriate sample sizes for genetic-based population studies of lichen-forming fungi. [ABSTRACT FROM AUTHOR]

Abstract: The results of a study aimed at investigating the effects of boron excess on a set of ecophysiological parameters in the lichen Xanthoria parietina, to set up a monitoring system to trace early biological effects of boron pollution in geothermal areas, are reported. To this purpose, lichen thalli have been incubated for 24h in solutions at boron concentrations of 0.1, 1, 10 and 100ppm, which were within the range in bulk deposition and geothermal fluids. The results showed a general trend of decreasing sample viability and increasing cell membrane damage and membrane lipid peroxidation under increasing boron concentrations, while photosynthetic efficiency, chlorophyll degradation and the contents of H2O2 and water-soluble proteins were not affected. It was argued that the fungal partner, that represents the large majority of the lichen biomass, is more sensitive to boron excess than the algal partner. [Copyright &y& Elsevier]

The sensitivity of lichens measuring photosynthetic efficiency and polyamines as modulator of nitrogen stress tolerance was investigated. Two lichen species with a markedly different tolerance to nitrogen compounds, namely Evernia prunastri (L.) Ach. and Xanthoria parietina (L.) Th.Fr., were incubated with deionized water (control) and solutions of KNO3, NH4NO3 and (NH4)2SO4 and then exposed to different light conditions. The F v/F m parameter (maximum quantum efficiency of photosystem II) was used as stress indicator. The results showed that F v/F m values, in the produced experimental conditions, were independent from the light gradient. Photosynthetic efficiency of E. prunastri was impaired by high ammonium concentrations, while nitrate had no effect; X. parietina was hardly influenced by nitrogen compounds. External supply of polyamines reduced the sensitivity of E. prunastri, while polyamine inhibitors reduced the tolerance of X. parietina to NH4 +, suggesting that polyamines play an important role in modulating the sensitivity/tolerance to nitrogen stress. [Copyright &y& Elsevier]

Abstract: This study investigated if some nitrogen (N) compounds commonly used as fertilizers (KNO3, NH4NO3, (NH4)2SO4) cause chlorophyll degradation in the N-tolerant lichen Xanthoria parietina and if polyamines are responsible for the N-tolerance of this species. The results showed that N excess does not cause chlorophyll degradation and suggested the absence of kinetics in the mode of action of the N compounds tested. External supply of inhibitors of polyamine biosynthesis prior to N treatments did not cause any change in the response of chlorophyll integrity, suggesting that at least chlorophyll integrity is not controlled by polyamines. [Copyright &y& Elsevier]

Abstract: We characterize the transcript of a polyketide synthase gene (PKS) from the cultured mycobiont of Xanthoria elegans (XePKS1) using SMART-rapid amplification of cDNA ends (RACE) cDNA synthesis. Sequence analysis of the cloned cDNA reveals an open reading frame of 2144 amino acid residues. It contains features of a non-reducing fungal type I PKS with an N-terminal starter unit: acyl carrier protein (ACP) transacetylase domain, ketosynthase, acyltransferase, two acyl carrier protein domains, and a thioesterase domain. XePKS1 was the only paralogue detected in the cDNA and the genomic DNA of the cultured X. elegans mycobiont by using a degenerate PCR approach targeted at the conserved regions of non-reducing type I PKS genes. The hypothetical protein is phylogenetically related to genes that are basal to a clade of dihydroxynaphthalene synthases (non-reducing clade II) and anthraquinone type synthases of non-lichenized fungi (non-reducing clade I). According to hplc and tlc analyses, the cultured mycobiont exclusively produced anthraquinones and its precursors. Therefore, we discuss whether the characterized paralogue is involved in anthraquinone production, which raises the possibility of a paraphyletic origin of lichen anthraquinone biosynthesis. The cDNA of XePKS1 was the first full-length coding sequence of a lichen PKS to be published. This proves SMART RACE to be a suitable tool for obtaining full-length coding sequences of genes from environmental samples and organisms, which are hardly amenable to standard molecular approaches or genomic sequencing. [Copyright &y& Elsevier]

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Samples of lichen species ( Xanthoria parietina) collected from Aegean Region of Turkey were analyzed by instrumental neutron activation analysis to determine the concentrations of 31 elements. The elements (Au, Rb, Zn, Hg, Sb, Cd, As, Cl, Br, and Se) showed enrichment with respect to the crustal composition. It has been hypothesized that lichen data can be examined more meaningfully without the inclusion of elements K, Mg, Ca, and Mn in the factor analysis. Four factors explaning 77.2% of the total variance were identified. The first factor represented the crustal elements Al, Na, Sc, Cr, Fe, La, and Sm along with contaminated soil with loadings of As, V, and Sb. The second factor was associated with mixed emissions including iron works (Cr, Zn, and Sb) and coal burning (As and Sb). The source profile of factor 3 was a strong marine component characterized by the elements Na, Cl, and Br. The factor 4, identified as regional background, contained the high loadings of As, Se, and Sb due to long-range transport of pariculate matter. These findings were supported by the geographical distribution of factor score maps. [ABSTRACT FROM AUTHOR]

The objective of this work was to evaluate the spatial and temporal impact of dust-pollution in the vicinity of a cement industry, located in an area with dry climate. The spatial impact integrated over time was evaluated from the concentrations of Ca, Fe and Mg in in-situ Xanthoria parietina. The temporal pattern was assessed through one-month transplants of the lichen Ramalina canariensis. Four potential sources of atmospheric dust were evaluated: the limestone-quarry; the unpaved roads, the deposit area and the cement mill. Calcium concentration in lichens was considered the best cement-dust indicator. Different types of dust (clinker and grinded-limestone-dust) resulted in different time-patterns of Ca accumulation, which was also related with the different influence that wet and dry periods have in the lichen accumulation process. The dust pollution was found to be deposited locally and dependent on: the nature of dust particles and the volume and frequency of precipitation. [Copyright &y& Elsevier]

To survive in high mountain environments lichens must adapt themselves to alternating periods of desiccation and hydration. Respiration and photosynthesis of the foliaceous lichen, Xanthoria elegans, in the dehydrated state were below the threshold of CO2-detection by infrared gas analysis. Following hydration, respiration totally recovered within seconds and photosynthesis within minutes. In order to identify metabolic processes that may contribute to the quick and efficient reactivation of lichen physiological processes, we analysed the metabolite profile of lichen thalli step by step during hydration/dehydration cycles, using 31P- and 13C-NMR. It appeared that the recovery of respiration was prepared during dehydration by the accumulation of a reserve of gluconate 6-P (glcn-6-P) and by the preservation of nucleotide pools, whereas glycolytic and photosynthetic intermediates like glucose 6-P and ribulose 1,5-diphosphate were absent. The large pools of polyols present in both X. elegans photo- and mycobiont are likely to contribute to the protection of cell constituents like nucleotides, proteins, and membrane lipids, and to preserve the integrity of intracellular structures during desiccation. Our data indicate that glcn-6-P accumulated due to activation of the oxidative pentose phosphate pathway, in response to a need for reducing power (NADPH) during the dehydration-triggered down-regulation of cell metabolism. On the contrary, glcn-6-P was metabolised immediately after hydration, supplying respiration with substrates during the replenishment of pools of glycolytic and photosynthetic intermediates. Finally, the high net photosynthetic activity of wet X. elegans thalli at low temperature may help this alpine lichen to take advantage of brief hydration opportunities such as ice melting, thus favouring its growth in harsh high mountain climates. [ABSTRACT FROM AUTHOR]

Xanthoria parietina, a conspicuous orange foliose lichen, has been doubtfully recorded as part of the Ontario lichen flora because the previous documented reports were very old (1868 and 1917) and it had never been reported since. Here, we document a number of new sightings, all in southern Ontario. A previous report of this lichen from "Longulac" that was interpreted as Long Lake in Frontenac County is corrected to Longlac in the Thunder Bay District, and the specimen proved to be Xanthomendoza hasseana. A search lot the lichen around Belleville, one of the original localities, proved fruitless. It is still not clear whether the new sightings of Xanthoria parietitla represent a reintroduction of this coastal species to the inland sites, or whether the lichen has persisted in southern Ontario for almost 140 years, but was never reported. Substrate enrichment (eutrophication due to agricultural activity) in the region is one explanation for the spread of the lichen in southern Ontario. [ABSTRACT FROM AUTHOR]

In order to examine genetic variation and population structure of the widespread lichen-forming ascomycete Xanthoria parietina from similar habitats, but different sites in Scandinavia, we investigated seven populations in Scania, southernmost Sweden, and compared the results with a corresponding study on Storfosna, central Norway. Sequence variations of the nuclear ribosomal DNA were used as molecular markers, for both a part of the IGS region and the complete ITS1-5.8S-ITS2 region. The amount of genetic variability observed was comparable in the two investigations. Divergence between populations in different habitats found in the previous study was also present in this study. Xanthoria parietina is genetically differentiated between habitats with no evidence of restricted gene flow between populations in the same habitat at the present spatial scale, at least at sites along the coast of Scandinavia. Differentiation between habitats is considerable at both study sites, which we attribute to restricted gene flow between habitats, i.e. habitat isolation. [ABSTRACT FROM AUTHOR]

Effects of high ammonia emissions and nitrogen deposition were investigated on lichens around a pig stockfarm (ca. 7,000 animals) in central Italy. Four sites were selected along a transect at 200, 400, 1000 and 2500m from the stockfarm, the diversity of epiphytic lichens was measured and transplanted thalli of Xanthoria parietina and Flavoparmelia caperata exposed, together with passive NH3 (diffusion tubes) samplers. Ammonia dramatically decreased from the centre of the stockfarm to the sampled sites, where it was correlated with bark pH. Total lichen diversity was not associated with either NH3 concentrations or bark pH, but the diversity of strictly nitrophytic species was highly correlated with both parameters. Physconia grisea was the best indicator species for NH3 pollution. Total N accumulated in X. Parietina and F. Caperata was correlated with NH3 concentrations. [Copyright &y& Elsevier]

Abstract: HPLC analyses of Xanthoria elegans cultivated on different media and either aposymbiontically or with its photobiont revealed that the carbon source and the presence of the algal partner have an impact on the secondary metabolism of the mycobiont. The aposymbiotically (without photobiont) grown mycobiont contained up to 70% more of the main compounds in its thallus than in resynthesis stage. Although this is speculative, the induction of the polyketide pathway may be a feedback mechanism to the absence of the photobiont. All cultures produce a variety of substances which were not detectable in the voucher specimen. Besides physcion (the major substance), we were able to identify emodin as well as physcion-bisanthrone, teloschistin monoacetate and derivatives. A strong inducible effect on the production of physcion, physcion-bisanthrone and on their precursors and derivatives was found for mannitol. By contrast, supplementation of ribitol had negligible effects, if any, on polyketide quantities although it is the main carbon source for the mycobiont in free-living lichens with Trebouxia photobiont. [Copyright &y& Elsevier]

Optimal oviposition theory predicts that females prefer a host that assures the highest offspring fitness. I compared the host preference of females and larvae of a lichenivorous moth, Cleorodes lichenaria, and subsequent larval performance on host lichens with laboratory experiments and field observations. Both females and larvae preferred Ramalinafraxinea and Ramalinafarinacea over Xanthoria parietina and Pannelia sulcata. Larvae reached the pupal stage faster on Ramalina species than on other lichens, whereas other fitness parameters including larval survival and pupal size did not differ between the lichen species. Interestingly, growth rates before overwintering were higher on P. sulcata and X. parietina than on Ramalina species, whereas after overwintering, the situation was reversed. The results of this study support the preference-performance hypothesis. Females clearly preferred host lichens that ensure the shortest developmental period at the expense of higher growth rates at the beginning of the larval period. Moreover, ecological and/or evolutionary factors in addition to females' oviposition in host selection of C. lichenaria seem to be important. Because more larvae were found on Ramalina species than expected according to the oviposition pattern of females, final host selection is at least partially determined by larval behavior. It is also suggested that the physical and chemical properties of the hosts may provide a basis for enemy-free space for larvae. [ABSTRACT FROM AUTHOR]

Despite numerous investigations on substrate-inhabiting microflora, especially lichens, very little is known about the colonization of coastal escarpments by lithobiontic micro-organisms, inland of a retreating coastline in Africa. Reported herein are the results of a combined field observation and microscopy study focusing on the connection between microrelief of the substrate, colonies of lithobiontic micro-organisms (in particular the lichen Xanthoria parietina) and microstructures of putative bacterial origin. The occurrence of weathering pits in which the early stages of the biotic development occurs, and the subsequent disintegration of the rock indicate that lichens, mosses and fungi act synergistically by alternating chemical and mechanical weathering. Penetration of grains by expansion and contraction of the hyphae depletes the rock matrix and contributes to the mechanical breakdown of the rock. Calcite rhombs on the weathered surfaces of the calcite-cemented sandstones are severely etched with well-developed rhomb-shaped etch pits ('spiky calcite'), holes, or has one or more of the faces removed, and their cores exposed and leached. Nanofilaments (c. 100-700 nm) and 'nanomicrobial' fruiting bodies (c. 250 nm) emanating from micropores appear to be common on affected crystalline structures. Weddellite present immediately below the thallus is a strong indicator of biomineralization. Quartz responds differently to chemical weathering by producing peeling structures and microbrecciation features. The dissolution of these crystals appears to be a surface reaction. controlled process mediated by microbial microfilaments and nanofilaments. A model is proposed, firstly indicating early-stage biochemical weathering, followed by biophysical weathering. Disintegration of the rock outcrops in due to a complex interplay of several events, probably beginning at the nanoscale with penetration of sites on crystal faces. [ABSTRACT FROM AUTHOR]

Genetic diversity and fine-scale population structure in the lichen-forming ascomycete Xanthoria parietina was investigated using sequence variation in part of the intergenic spacer (IGS) and the complete internal transcribed spacer (ITS) regions of the nuclear ribosomal DNA. Sampling included 213 and 225 individuals, respectively, from seven populations in two different habitats, bark and rock, on the island Storfosna off the central west coast of Norway. Both markers revealed significant variation and a total of 10 IGS and 16 ITS haplotypes were found. There were no signs of significant positive spatial autocorrelation at any spatial size class down to 10% of transect length, nor did we find significant deviations from neutrality or signs of historical population expansion. Analysis of molecular variance (amova) indicated that most of the genetic variance observed was within populations, but when populations were grouped according to habitat, more than a quarter of the variance was explained among groups. Pairwise comparisons of populations ( FST, exact tests of population differentiation) revealed significant differentiation between populations in different habitats (on bark or rock), but not between populations in the same habitat. Haplotype networks show that internal and presumably old haplotypes are shared between habitats, whereas terminal haplotypes tend to be unique to a habitat, mostly bark. We interpret the observed pattern to mean that there is no evidence of restricted gene flow between populations in the same habitat at the present spatial scale (interpopulation distances one or a few kilometres). On the other hand, differentiation between habitats is considerable, which we attribute to restricted gene flow between habitats (habitat isolation). Evidence suggests that the observed differentiation did not evolve locally. Estimates of divergence time between populations in the respective habitats indicate that an ancestral population started to diverge at least 34 000 years ago but probably much further back in time. [ABSTRACT FROM AUTHOR]

Diurnal courses of photosystem II (PS II) activity of Xanthoria elegans were continuously monitored using a novel technique of chlorophyll fluorescence imaging in the field (maritime Antarctica) over a period of 7 days. The lichen specimens grew on rock surfaces in a north-facing coastal area of Galindez Island (Argentine Islands). A portable fluorometer FluorCam equipped with a CCD camera and image analysis software was placed over a thallus so that false colour images of FV/FM and quantum yield of photochemical processes in PS II (ΦII) distribution over the thallus could be taken over the course of a day. Simultaneously, microclimatic parameters of the habitat were recorded: air and thallus temperatures, relative air humidity, PPFR (photosynthetic photon fluence rate) and global radiation. Photosynthetic processes in X. elegans were activated by rainfall or water from melting snow. After thallus hydration, FV/FM and ΦII gradually decreased from their maximum values due to evaporation and progressive loss of water from the thallus. Chlorophyll fluorescence imaging showed that the thallus dehydration started from the margins and moved towards the central thicker thallus zones. These zones exhibited higher activity of PS II than the margins throughout the day. The rate of inhibition of photosynthetic processes in PS II was faster at the margins than in the centre of the thallus. Dependence of ΦII on thallus water potential (WP) was investigated during gradual dehydration under laboratory conditions. After a decrease in WP from zero to -7 MPa, X. elegans exhibited only a 13.8% decrease in ΦII from its maximal value. Within the range of WP of from -8 to -20 MPa, the ΦII decrease was more rapid reaching the critical point (ΦII = 0) at WP of approximately -25 MPa. Chlorophyll fluorescence imaging and WP measurements showed that X. elegans is capable of maintaining detectable photosynthetic activity even at extremely low WP. Based on our microclimatological data, X. elegans may be photosynthetically active under field conditions for several hours after being wetted by rain or snowfall. It is suggested that chlorophyll fluorescence imaging is a powerful technique, transferable to field conditions and capable of visualizing heterogeneity of photosyntetic processes over a lichen thallus subjected to periodic dehydration. [ABSTRACT FROM AUTHOR]

The responses of the nitrophytic green algal lichen Xanthoria parietina to varying nitrogen CN) concentrations were investigated by collecting 67 X. parietina thalli from clay roof tiles from 13 sites in Portugal with different exposures to N. Concentrations of total N, chlorophyll α (a marker for the photobiont), ergosterol (a marker for the mycobiont), and thallus specific weight (TSW; thallus dry weight in relation to surface area) were quantified for each thallus to see how biont investments were related to thallus N concentrations. Thallus N ranged from 11 to 43 mg g-1 DW revealing a wider N concentration range in this lichen compared to other green algal lichen species. Both chlorophyll α and ergosterol concentrations increased with increasing thallus N, with a steeper increase of the photobiont marker. TSW was similar in all thalli without any significant effect of thallus N concentration, suggesting that thallus developmental patterns are similar in low and high thallus N concentrations. The relatively higher resource allocation to the photobiont in relation to the mycobiont with increasing thallus N concentrations is an indication of the capacity of X. parietina to meet the C demands associated with N assimilation. This result is also in agreement with the inter-specific resource allocation pattern for green algal lichens across the same N concentration range. [ABSTRACT FROM AUTHOR]

The aim of this study was to compare the physiological responses to increased nitrogen (N) supply between the nitrophytic lichenXanthoria parietina(L.) Th. Fr. and the acidophytic lichenEvernia prunastri(L.) Ach. The two lichens were exposed to a weekly dosage of 0.05, 0.1, 0.2, 0.6 or 2.4 g N m-2 for 2 months, administered as NH4NO3 dissolved in artificial rainwater (1 l m-2). After the treatments, in vivo chlorophyllafluorescence was determined to assess vitality; concentrations of total N, ammonium, nitrate and dominant amino acids, including glutamate, glutamine and arginine, were quantified in order to follow changes in N status; and the polyols ribitol, arabitol and mannitol were quantified to follow changes in the lichens’ carbon (C) status. The uptake of N was quantified by labelling the fertiliser with15N in the ammonium position; chlorophyllawas used as an indirect marker for algal activity, and ergosterol as an indirect marker of fungal activity. Nitrogen uptake was higher inE. prunastrithan inX. parietina, although the latter species may have used the mannitol reserves to obtain C skeletons and energy for N assimilation. Chlorophyllaand ergosterol concentrations remained unaltered inX. parietinairrespective of N dosage while ergosterol decreased with increasing N uptake inE. prunastri. The latter species had accumulated a large pool of ammonium at the highest N dosage, whilst inX. parietinaa significant nitrate pool was instead observed. Taken together, these short-term responses to high N supply observed in the two lichens, and the differences between them, can partly explain the higher tolerance ofX. parietinatowards increased atmospheric N levels. [ABSTRACT FROM AUTHOR]

Specimens of Xanthoria parietina were collected from worldwide locations and ascospore discharge used to establish axenic cultures of the mycobiont. DNA was extracted and RAPD-PCR fingerprinting of 59 isolates was successfully achieved, resulting in 58 unique fingerprints. 110 multilocus RAPD markers were generated and used to construct a dendrogram. Two main groups were distinguished (75% bootstrap support): the first comprising samples from the Iberian Peninsula, the Balearic and Canary Islands; the second comprising all other worldwide samples including isolates from throughout Europe and North America. Samples from Australia and New Zealand clustered with the second group except one additional, phenotypically distinct specimen, not belonging to X. parietina, which formed an outgroup. However, comparative DNA sequence analyses are required to verify this interpretation. [ABSTRACT FROM AUTHOR]

Seven highly-coloured lichen species belonging to the genera Caloplaca, Candelariella, Aspicilia and Xanthoria from ecclesiastical buildings in northern Spain have been analysed non-destructively by FT-Raman spectroscopy. The vibrational band assignments in the spectra of the specimens, which were still attached to their limestone or sandstone substrata, were accomplished with the assistance of the chemical compositions obtained from wet chemical extraction methods. β-Carotene was found in all specimens as the major pigment, and the characteristic spectral signatures of calcium oxalate monohydrate (whewellite) and dihydrate (weddelite) could be identified; chemical signatures were found for these materials even in lichen thalli growing the non-calcareous substrata, indicating, probably, that the calcium was provided here from wind-or-rain-borne sources. The Raman spectral biomarkers found in the lichens broadly agreed with the chemical extraction profiles as expected, but the present study indicates that some form of non-destructive taxonomic identification based on Raman spectroscopy was possible. [Copyright &y& Elsevier]

The aim of this investigation was to determine the NH4Cl concentration threshold, above which negative physiological effects would occur in the nitrophytic lichen Xanthoria parietina. Over a 10 month period, X. parietina thalli growing on roof tiles were exposed weekly to NH4Cl concentrations of 0.04, 0.17, 0.34 or 0.69 M. Nitrogen (N) uptake from ammonium and the concentrations of total thallus N and biont markers (chlorophyll a, ergosterol and chitin) were measured on four occasions, over the experimental period. Xanthoria parietina was able to assimilate a significant quantity of the applied ammonium. However, lichens exposed to the two higher concentrations suffered damage to both the photobiont and the mycobiont, as evidenced by reduced chlorophyll a and ergosterol concentrations, while lichens exposed to the two lower concentrations showed no significant changes in either chlorophyll a or ergosterol that could be related to the ammonium inputs. Xanthoria parietina tolerated a weekly irrigation of at least 0.17 M NH4Cl, corresponding to an N deposition of c. 1000 kg ha-1 yr-1, suggesting that this species has a very high tolerance to N pollution. [ABSTRACT FROM AUTHOR]

Synthesis of the cortical anthraquinone pigment parietin (= physcion) was studied in acetone-rinsed, parietin-free Xanthoria parietina thalli. UV-B induced the synthesis, which increased linearly with UV-B (log-transformed) to the highest applied UV-B level (1.8 W m−2). At natural UV-B levels (0.75 W m−2), parietin resynthesis occurred at a constant pace (106 mg m−2 d−1) during a 14-d period at 220 µmol m−2 s−1 PAR. Under these conditions, 56% of the natural parietin content prior to extraction was resumed, accounting for 10% of total net carbon gain. In the presence of UV-B, the remaining results were consistent with the hypothesis assuming that photosynthates regulate the pace at which parietin is synthesized by the mycobiont. Resynthesis was rapid when photosynthesis was activated by light, or when certain carbohydrates were added exogenously. Additions of ribitol, the carbohydrate delivered from the photobiont, increased the parietin resynthesis substantially. Mannitol, the main fungal polyol, was significantly less effective. Furthermore, parietin resynthesis in X. parietina was depressed at high and low hydration when net photosynthesis is depressed. Therefore, the photobiont regulates the parietin resynthesis pace in its mycobiont partner by the delivery of photosynthates. In conclusion, both lichen bionts play important roles in the synthesis of parietin, which probably acts as a PAR- rather than a UV-B-screen. [ABSTRACT FROM AUTHOR]

Instrumental neutron activation analysis and ICP-OES were used to determine 38 elements in two lichen species namely Xanthoria parietina (L.) Th. Fr. and Parmelia tiliacea (Hoffm) Ach. which were collected in Aegean Region of Turkey. It was found that the accumulation capacities of two species differed only for the elements Ca, Cl, Cu and Pb by using ANOVA at 95% confidence level. Average concentrations of all elements except for Ba, Mn and Hg were higher in Parmelia tiliacea. For the elements Ba, Br, Co, Cr, Cs, Fe, K, Mg, Mn, Mo, Rb, Sb and Ti, the equation y = ax+b could be used to make interchangeability possible between two species. [ABSTRACT FROM AUTHOR]