Thallus initiation and development in the lichen Rhizocarpon lecanorinum

Ascospore germination, thallus initiation, and areole and prothallus development in the lichen Rhizocarpon lecanorinum Anders were examined using light, fluorescence and scanning electron microscopy. The ascospore germ hyphae remain very short and do not form a prothallus-like mycelium. Instead, a compact soredium-like granule develops directly from sporeling contact with a compatible species of Trebouxia . Diffuse initial stages involving non-trebouxioid algae are lacking. The onset of thallus differentiation is marked by the deposition of rhizocarpic acid in an incipient cortical layer within the apical part of the granule. As pigmentation and cortex-formation transform this structure into a typical areole, radiating prothallus hyphae are simultaneously initiated from its basal margin. Most areoles formed subsequently in the marginal prothallus lack subtending melanized hyphae and apparently stem from overgrowth by the prothallus of photobiont cells on, or in, the substratum. Apothecia reach maturity in thalli as small as 2 mm in diameter. It is proposed that the lack of diffuse hyphal growth in sporelings and telescoped morphogenesis of R. lecanorinum are part of a life history strategy geared to precocious, heavy investment in ascospore production. The R. lecanorinum – Trebouxia symbiosis has a number of features which make it well-suited for further studies of the life history and development of prothallus-forming crustose lichens with sexually reproducing mycobionts.     

Development of areolae and growth of the peripheral prothallus in the crustose lichen Rhizocarpon geographicum: an image analysis study

Areolae of the crustose lichen Rhizocarpon geographicum (L.) DC., are present on the peripheral prothallus (marginal areolae) and also aggregate to form confluent masses in the centre of the thallus (central areolae). To determine the relationships between these areolae and whether growth of the peripheral prothallus is dependent on the marginal areolae, the density, morphology, and size frequency distributions of marginal areolae were measured in 23 thalli of R. geographicum in north Wales, UK using image analysis (Image J). Size and morphology of central areolae were also studied across the thallus. Marginal areolae were small, punctate, and occurred in clusters scattered over the peripheral prothallus while central areolae were larger and had a lobed structure. The size-class frequency distributions of the marginal and central areolae were fitted by power-law and log-normal models respectively. In 16 out of 23 thalli, central areolae close to the outer edge were larger and had a more complex lobed morphology than those towards the thallus centre. Neither mean width nor radial growth rate (RaGR) of the peripheral prothallus were correlated with density, diameter, or area fraction of marginal areolae. The data suggest central areolae may develop from marginal areolae as follows: (1) marginal areolae develop in clusters at the periphery and fuse to form central areolae, (2) central areolae grow exponentially, and (3) crowding of central areolae results in constriction and fragmentation. In addition, growth of the peripheral prothallus may be unrelated to the marginal areolae.     

Experimental studies on the growth and usnic acid production in "lichen"Usnea ghattensis in vitro

The study was aimed to optimize the culture conditions for the production of usnic acid in the cultured cell aggregates composed of symbionts in lichen Usnea ghattensis in vitro. The cultured lichen tissue composed of symbionts appeared after about 2-3 weeks of inoculation in water-agar and malt-yeast extract (MYE) media and shown the production of usnic acid after 2-3 months of inoculation. However, the growth of symbionts was strongly affected by different culture conditions. The addition of excess carbon and nitrogen sources in the media has significantly enhanced the growth as well as usnic acid content. The cultured symbionts in MYE medium having 4% sucrose, 4% polyethyl glycol (PEG) gave 7.63 g dry biomass with 3.9 microg usnic acid/g dry biomass. In water-agar medium having 4% sucrose and 4% PEG gave 3.08 g dry biomass with 1.11 microg usnic acid/g dry biomass. The positive effects of medium on the growth of symbionts and the production of usnic acid are seemed to be due to nutritional factors.     

Accurate lifespan estimates cannot be obtained from14C profiles in the crustose lichen Rhizocarpon geographicum (L.) DC.

Abstract:Radial¹⁴C/C profiles across three individuals of the crustose lichenRhizocarpon geographicum (L.) DC. have been determined using accelerator mass spectrometry. These data were used to assess whether lifespan estimates can be determined in this species using¹⁴C/C isotope ratio measurements.¹⁴C/C profiles are relatively flat with Δ¹⁴C values (deviations from the modern radiocarbon standard) for the radial samples displaying a small spread ranging from 130 to 200 per mil. The data are consistent with carbon cycling based on growth patterns involving replacement and fusion of areoles within the thallus as well as or instead of cellular or molecular replacement. Consequently, lifespan estimates cannot be obtained from¹⁴C/C measurements of this species and the Δ¹⁴C profiles provide no insights into whether the relationship between size and age is linear or curvilinear in this species.     

Sterols of the lichen Pseudevernia furfuracea

A mixture of C₂₇, C₂₈ and C₂₉ sterols was isolated from the lichen Pseudevernia furfuracea and characterized by means of GLC and MS. Mono-, di- and tri-unsaturated sterols were identified as well as a small amount of fully saturated sterols (stanols). Only a part of the total sterols present in the lichen tissue was easily extractable with organic solvents. Another portion was only obtained after saponification of the lichen residue remaining after extraction with organic solvents. The composition of these two fractions difrered considerably, the former contained predominantly 5a,8a-epidioxy-5a-ergosta-6,22-dien-3β-ol (ergosterol peroxide) and 24-ethylcholesta-5,22-dien-3β-ol while in the latter 24-ethylcholesta-5,22-dien- 3β-ol and C₂₈ triene sterols were the main components.     

Lichenizing Rhizomorphs and Thallus Development in the Squamulose Lichen Aspicilia crespiana Rico ined. (Lecanorales,Ascomycetes)

This work describes the rhizomorphs and their relation to thallus development in the squamulose lichen Aspicilia crespiana Rico ined. The rhizomorphs capture algal cells, giving rise to new squamules terminally or laterally. The thallus thus consists of a network of lichenized squamules interlinked by mycobiontic rhizomorphs. A previously proposed comparison of lichen rhizomorphs to the prothallus (hypothallus) of crustose lichens is applied and expanded upon. Other less organized prothallic structures sometimes produced by A. crespiana are also described. The importance of lichenizing rhizomorphs as an essential feature of thallus growth in this species is emphasized and a competitive role in substrate occupation and thallus expansion is suggested.     

Carbohydrates in the hypothallus and areolae of the crustose lichen <Emphasis Type="Italic">Rhizocarpon geographicum</Emphasis> (L.) DC.

Carbohydrate concentrations in the marginal hypothallus and areolae of the crustose lichen Rhizocarpon geographicum (L.) DC. were measured in north Wales, U.K. using gas chromatography. Ribitol, arabitol, and mannitol were the most abundant carbohydrates while α- glucose β-glucose, fructose, sucrose, and trehalose were present in smaller amounts. The concentrations of arabitol, ribitol, mannitol, fructose, and α-glucose were greater in the areolae while the concentration of trehalose was greater in the hypothallus. Concentrations of carbohydrates varied little between sample days. Concentrations of polyols in the hypothallus were not correlated with those in the areolae. These results suggest: 1) the hypothallus has a lower demand for carbohydrates than the areolae or there is limited transport from areolae to hypothallus, 2) increased trehalose in the non-lichenised hypothallus may be an adaptation to withstand stress and desiccation, and 3) polyols are partitioned differently in the hypothallus and areolae.     

Slowest to fastest: Extreme range in lichen growth rates supports their use as an indicator of climate change in Antarctica

Global temperature rise is suggested to be greater and more rapid in polar regions. There has been a clear temperature rise of 0.056 °C y⁻¹ in the Antarctic Peninsula and this has led to changes in higher plant extent and range. In the more extreme environments of the main continent the vegetation is scattered and composed of lichens and mosses. There is interest in the possible effects of global climate change on these communities acting through changes in temperature and precipitation. Lichens have been extensively used to date the substrates on which they are growing using the techniques of lichenometry. The slow growth and longevity of lichens particularly suites them for this use. We present evidence that there appears to be a substantial (two orders of magnitude) cline in lichen growth rate from the warmer, wetter and more productive Peninsula to the cold Dry Valleys at 77°S latitude. The differences in growth rate reflect the precipitation and temperature regimes at the different sites. The large range in growth rates coupled with the simplicity of measuring lichen growth using modern techniques suggests that this could be an excellent tool for the detection of climate change in continental Antarctica.     

Epiphytic lichen vegetation on Larix in the Italian Alps

Abstract

A synthesis of the epiphytic lichen vegetation on larch in the Italian Alps is presented. Vegetation types are described on the basis of a numerical classification of 291 relevés. They can be compared to a few well-known phytosociological unions found in other parts of the Alps. Some communities are restricted to subalpine areas with continental climate. Despite the homogeneity of the substrate, the flora is rich, with 98 species, several of which are rare, and hence of interest from a conservational point of view.     

南极地衣提取物抗氧化能力的初步研究

本文讨论4种南极地衣簇花石萝Usnea aurantiacoatra,南极石萝Usnea antarctica,粉球衣Sphaerophorus globosus及一种石蕊Cladonia sp.甲醇提取物的体外抗氧化能力;采用亚油酸氧化体系、二苯代苦味酰自由基体系、还原力实验对其抗氧化活性进行测定,并同维生素C、丁基甲氧基苯酚进行比较。结果显示供试南极地衣均具有较高的抗氧化活性,且呈剂量依赖关系;其中,簇花石萝的脂质过氧化抑制率最高,还原力最大;石蕊的二苯代苦味酰自由基清除能力最大。此外,从簇花石萝中提取的松萝酸具有一定的抗氧化活性,但明显低于簇花石萝粗提物。     

中国石蕊科地衣多样性与区系研究

通过实地调查我国华北、 西南等地区的石蕊科地衣多样性,结合前人的研究资料,从物种多样性、 生境、区系成分等多方面对我国石蕊科地衣进行研究.结果显示,我国石蕊科地衣共有5属107种,其中石蕊属(Cladonia)占优势,有94种,占石蕊科地衣总种数的87.9％.共鉴定出山西省新记录8种,云南省新记录种3种.石蕊科地衣生境...     

Ecological investigations on lichen fields of the Central Namib

Number, geographic location, extent and characteristics of lichen fields were recorded within the Central Namib fog desert. Their occurrence is restricted to stable surfaces in the near coastal belt, while percentage cover changes with exposure, elevation and distance from the coastline. Maximum coverage of 70% was found at a distance of 5 km from the coast near Wlotzkas Baken. The highest biomass rate of 400 mg/m² was measured here at a distance of 1 km from the coast, where Teloschistes capensis appears as cushion growth type. Distribution patterns on hills, riverbeds and polygon structures are described. In general, fruticose and foliose lichens dominate on SW-exposed, ocean-facing habitats. Crustose species dominate on NE-E-exposed plots.Species composition and distribution, particularly the distribution of the fruticose species T. capensis (L. f.) Vain. ex Müll. Arg., were investigated in seventysix plots along twenty W-E transects in one lichen field near Wlotzkas Baken. T. capensis occurs in three different growth types: tuft, cushion and mat. Four zones are distinguished within the above lichen field, each dominated by a growth form indicating various influences of different climatic, geomorphic or biogenic parameters.     

Bioaccumulation capacity of two chemical varieties of the lichen Pseudevernia furfuracea

The concentrations of 18 trace elements (Al, Ba, Ca, Cd, Co, Cr, Cu, Fe, K, Mg, Mn, Na, Ni, P, Pb, Sr, V, and Zn) were measured in two varieties of the epiphytic lichen Pseudevernia furfuracea in order to compare their bioaccumulation capacity. Var. ceratea and var. furfuracea have identical morphology, substrate requirements and ecophysiology, but produce different secondary metabolites (lichen substances). Lichen substances may influence the processes of bioaccumulation of trace elements. We tested the hypothesis that the different metabolic chemical composition of the two varieties may influence the elements uptake. Lichen thalli were collected in a remote area of north-west Italy and transplanted, for one month in two seasons, to the urban-industrial area of Genoa (NW Italy). Lichen material was analysed by means of ICP-AES and bioaccumulation data were interpreted in terms of EC ratio (the ratio of each element after the exposure and, in control samples, prior to exposure). There were significant differences between the two varieties, which could be possibly related to their chemistry: var. ceratea has a higher accumulation capacity for all elements, except for Ca and Cu (which were lower in var. ceratea transplanted in Summer). Particularly, 10 out of 18 elements (Al, Cd, Co, Cr, Fe, Mg, Ni, Sr, and V) showed ‘severe accumulation’ in var. ceratea in both seasons. Thus, in order to enhance data quality in biomonitoring studies, it is suggested to avoid the joint use of the two varieties.     

采自甘肃白龙江流域中国茶渍属地衣的三个新记录种

在对甘肃白龙江流域的茶渍属(Lecanora)地衣进行调查采集和鉴定的基础上,报道三个中国新记录种:暗灰茶渍(L.cinereofusca H.Magn),暗黄茶渍(L.flavidofusca Mll.Arg.)和颗粒茶渍(L.perplexa Brodo)。对每种给出了详尽的形态、解剖和化学特征描述,并提供了每种的外部形态照片。