Mauro Tretiach

Classification Framework for Graphene‐Based Materials

Graphing graphene: Because the naming of graphene-based materials (GBMs) has led to confusion and inconsistency, a classification approach is necessary. Three physical-chemical properties of GBMs have been defined by the GRAPHENE Flagship Project of the European Union for the unequivocal classification of these materials (see grid).

Genetic diversity and photobiont associations in selected taxa of the Tephromela atra group (Lecanorales, lichenised Ascomycota)

Mycobiont and photobiont genetic diversity was investigated in four taxa of the Tephromela atra complex, which differ in ecology and substratum preference (from siliceous rocks, limestone to bark), and are differently interpreted by taxonomists. Phylogenetic analyses were performed using mycobiont nuclear ITS, beta tubulin and homologous polyketide synthase gene (PKS) sequences obtained from freshly collected material sampled from the Mediterranean region to the Southern Alps. The silicicolous samples from the Alps form a basal lineage of the entire complex, and despite the morphological similarity, they do not form a monophyletic group with the Mediterranean samples. No resolution was found among the calcicolous and the silicicolous taxa from Mediterranean habitats, which are traditionally segregated at variety or species level. The epiphytic taxon, although nested with the other ecotypes, splits in two well-supported lineages. Among the four taxa, Tephromela grumosa is the only morphologically, chemically and genetically distinct taxon. However, it is also nested in the large T. atra complex. Phylogenetic analysis of photobionts ITS sequences revealed that thalli from the Mediterranean region are associated with two distinct lineages of Trebouxia, but the lineages are not correlated with substrate or mycobiont phenotype. The thalli from the Alps are exclusively associated with T. simplex, suggesting a protracted isolation from the other lineages.

Determinant factors for the formation of the calcium oxalate minerals, weddellite and whewellite, on the surface of foliose lichens

The factors influencing the predominance of one of the two mineral forms of calcium oxalate (CO), the monohydrated whewellite (COM) and the di-hydrated weddellite (COD), forming the pruina of the upper cortex of lichens, have been investigated through a simple, sensitive histochemical assay: toluidine blue O (TBO), a metachromatic staining test. The differential reactivity of 43 thalli of 17 pruinose foliose species, supplemented by X-ray diffraction analysis and observations with polarizing and scanning electron microscopy, suggests that the histochemical reactivity of hyphal walls and cementing substances of the upper cortex are related to the density of anionic charges. These factors are probably due to the occurrence of polyuronic acid substances that strongly affects the mineralization of CO. Di-hydrated wedellite is always associated with TBO metachromatic reactivity, and COM with orthochromatic reactivity. When the material has an ambiguous ortho/metachromatic reactivity, COD and COM may occur together. This study presents the first experimental evidence that in lichens CO biomineralization is at least partially biologically controlled.

Accumulation of airborne trace elements in mosses, lichens and synthetic materials exposed at urban monitoring stations: towards a harmonisation of the moss-bag technique.

Mosses, lichens and cellulose filters were exposed for 17 weeks at four urban monitoring stations in Naples (S Italy) to assess the accumulation of airborne Al, As, Ba, Ca, Cd, Co, Cr, Cu, Fe, Hg, K, Mg, Mn, Mo, Ni, Pb, Ti, V, and Zn. In each site, the element accumulation was significantly higher in the moss Hypnum cupressiforme than in the lichen Pseudevernia furfuracea. Acid washed mosses accumulated the highest amount of trace elements, but the differences in element concentrations among the moss samples exposed after water washing and different devitalisation treatments (acid washing, oven drying and water boiling) and between the lichen samples exposed with and without the nylon bag were not statistically significant. The cellulose filters showed the lowest accumulation capability. The reciprocal ordination of sites and exposed materials showed an increasing contamination gradient (especially for Pb, Cu and Zn) from the background site to the trafficked city streets; this pattern was undetectable from PM(10) data recorded by the automatic monitoring devices operating in the four exposure sites. The element profile in exposed materials did not change substantially throughout the urban area and particles of polluted urban soils seem the main source of airborne metals in Naples. Through a comprehensive evaluation of the results from this and previous studies, a protocol is suggested for the moss-bag monitoring of trace element deposition in urban environments.

Bags with oven-dried moss for the active monitoring of airborne trace elements in urban areas.

To define a harmonized methodology for the use of moss and lichen bags as active monitoring devices of airborne trace elements in urban areas, we evaluated the element accumulation in bags exposed in Naples in different spring weather conditions for 6- and 12-weeks. Three different pre-exposure treatments were applied to moss and lichen materials: water-washing, acid-washing and oven-drying. During the different exposure periods in the Naples urban environment the moss accumulated always higher amounts of elements (except Hg) than lichens and the element accumulation increased during wetter weather and higher PM(10) conditions. The oven pre-treatment did not substantially modify the morphology and element composition of moss and the exposure in bags of this material for 6-weeks was sufficient to detect the pattern of airborne trace elements.

An anatomical investigation of calcicolous endolithic lichens from the Trieste karst (NE Italy)

ABSTRACT The anatomy of five endolithic lichens (Acrocordia conoidea, Petractis clausa, Rinodina immersa, Verrucaria baldensis, and V. marmorea) from the Trieste Karst (north-eastern Italy) was thoroughly investigated. Samples already used in previous ecophysiological studies were examined by histological and mineralogical techniques, and by SEM. Biomineralisation products were searched for by X-ray diffractometry, X-ray microdiffractometry, and Fourier Transformed Infrared spectrophotometry. The results confirm that the photobiont layer is located approximately at the same depth in the substratum, although the species occur in habitats with strongly different light regimes; the thallus development is relatively constant within populations of a single species, but differs considerably among species. Several peculiarities of each species were revealed, such as the presence of large clews of hyphae in the inner layer of P. clausa, forming large voids in the substratum, or the development of morphologically ...

A combined molecular and morphological approach to species delimitation in black-fruited, endolithic Caloplaca: high genetic and low morphological diversity

A revision based on the morphological and genetic analyses of 133 specimens of black-fruited, endolithic Caloplaca belonging to subgenus Pyrenodesmia is presented. The material was collected in 16 sites distributed along a transept from Gargano (Central Italy) to the southeastern Alps, from sea level to ca 1500m. The nuclear ITS was sequenced for all the mycobionts and selected representatives of photobionts. Except for the sorediate C. erodens, all species share the same algal lineage of Trebouxia as photobiont. The haplotype analysis of the mycobionts revealed an unexpected, high genetic heterogeneity. Three main morphotypic clusters were recognized among five species: C. albopruinosa (syn. C. agardhiana auct.), C. alociza, C. badioreagens, C. erodens, and C. variabilis. A phylogenetic analysis, including already available Caloplaca sequence data, revealed that these lichens form a monophyletic group within the genus. For each species, notes on ecology, distribution in Italy, and nomenclature are given.

FT-Raman spectroscopy of lichens on dolomitic rocks: an assessment of metal oxalate formation

The FT-Raman spectra of five epilithic lichen taxa growing on dolomite and magnesium-rich carbonate rocks have been analysed and interpreted for the key molecular marker bands associated with calcium oxalate monohydrate (whewellite), calcium oxalate dihydrate (weddelite) and magnesium oxalate dihydrate. From the results, it can be concluded that the biomineral product of lichen biodeterioration involves the calcareous part of the substratum only; no trace of magnesium oxalate has been found in the Raman spectra. Two of the species, Lecanora sulfurea and Aspicilia calcarea, produce calcium oxalate monohydrate exclusively, but Dirina massiliensis f. sorediata, D. massiliensis f. massiliensis and Tephromela atra produce significant quantities of the dihydrate. An explanation is advanced for the exclusive accumulation of calcium oxalate into the lichen thallus despite the significant presence of magnesium ions.

Photosynthetic activity of Quercus ilex at the extremes of a transect between Mediterranean and submediterranean vegetation (Trieste - NE Italy)

Summary Microclimatic data and CO2 gas exchange rates were measured in the coastal area near Trieste (NE Italy) in two groups of plants growing at the extremes of a floristic-vegetational gradient between an evergreen Mediterranean maquis on the coast and a winter deciduous submediterranean woodland on the Karst plateau, where Q. ilex persists only sporadically but is still a co-dominant tree. Field data were recorded from sunrise to sunset during the periods of highest productivity and of maximum physiological stress. i.e. high temperatures and water deficit in summer, and low temperatures and strong, dry winds in winter. Photosynthesis was measured with a portable Infrared Gas Analyzer. Microclimatic data showed that summer and winter stress were more intense on the Karst plateau. Assimilation of the coastal population was higher because a positive CO2 balance was maintained during both stress periods. During summer drought stress diurnal assimilation of the inland population was just in balance with nocturnal leaf respiration. In winter, on the contrary, photosynthetic activity ceased almost completely for almost a week, due to the lower temperature regime and to strong, dry winter winds that caused severe mechanical damages and, more generally, a drastic shortening of the leaf life span. The competition ability of Q. ilex in ecotonal areas is briefly discussed onthe basis of these results. Winter stress seems to be the main factor limiting the distribution of Q. ilex northwards.

Drought-induced xylem cavitation and hydraulic deterioration: risk factors for urban trees under climate change?

Urban trees help towns to cope with climate warming by cooling both air and surfaces. The challenges imposed by the urban environment, with special reference to low water availability due to the presence of extensive pavements, result in high rates of mortality of street trees, that can be increased by climatic extremes. We investigated the water relations and xylem hydraulic safety/efficiency of Quercus ilex trees growing at urban sites with different percentages of surrounding impervious pavements. Seasonal changes of plant water potential and gas exchange, vulnerability to cavitation and embolism level, and morpho-anatomical traits were measured. We found patterns of increasing water stress and vulnerability to drought at increasing percentages of impervious pavement cover, with a consequent reduction in gas exchange rates, decreased safety margins toward embolism development, and increased vulnerability to cavitation, suggesting the occurrence of stress-induced hydraulic deterioration. The amount of impermeable surface and chronic exposure to water stress influence the site-specific risk of drought-induced dieback of urban trees under extreme drought. Besides providing directions for management of green spaces in towns, our data suggest that xylem hydraulics is key to a full understanding of the responses of urban trees to global change.