Parts Of Thallus Research Articles

Water‐ and temperature‐dependence of DNA damage and repair in the fruticose lichen Cladonia arbuscula ssp. mitis exposed to UV‐B radiation

The induction of cyclobutane pyrimidine dimers (CPDs) by ultraviolet‐B radiation (UV‐B, 280–315 nm) and repair mechanisms were studied in the lichen Cladonia arbuscula ssp. mitis exposed to different temperatures and water status conditions. In addition, the development and repair of CPDs were studied in relation to the different developmental stages of the lichen thallus podetial branches. Air‐dried lichen thalli exposed to UV‐B radiation combined with relatively high visible light (HL, 800 μmol m−2 s−1; 400–700 nm) for 7 days showed a progressive increase of CPDs with no substantial repair, although HL was present during and after irradiation with UV‐B. Fully hydrated lichen thalli, that had not been previously exposed to UV‐B radiation for 7 days, were given short‐term UV‐B radiation treatment at 25°C, and accumulated DNA lesions in the form of CPDs, with repair occurring when they were exposed to photoreactivating conditions (2 h of 300 μmol m−2 s−1, 400–700 nm). A different pattern was observed when fully hydrated thalli were exposed to short‐term UV‐B radiation at 2°C, in comparison with exposure at 25°C. High levels of CPDs were induced at 2°C under UV‐B irradiation, without significant repair under subsequent photoreactivating light. Likewise, when PAR (300 μmol m−2 s−1) and UV‐B radiation were given simultaneously, the CPD levels were not lowered. Throughout all experiments the youngest, less differentiated parts of the lichen thallus – namely ‘tips’, according to our arbitrary subdivision – were the parts showing the highest levels of CPD accumulation and the lowest levels of repair in comparison with the older thallus tissue (‘stems’). Thus the experiments showed that Cladonia arbuscula ssp. mitis is sensitive to UV‐B irradiation in the air‐dried state and is not able to completely repair the damage caused by the radiation. Furthermore, temperature plays a role in the DNA damage repairing capacity of this lichen, since even when fully hydrated, C. arbuscula ssp. mitis did not repair DNA damage at the low temperatures.

Importance of structure and density of macroalgae communities (Fucus serratus) for photosynthetic production and light utilisation

Determination of photosynthetic production in plant communities is essential for evaluating plant growth rates and carbon fluxes in ecosystems, but it cannot easily be derived from the photosynthetic response of individual leaves or thalli, which has been the focus of virtually all previous aquatic studies. To evaluate the regulation of aquatic community production, we measured the photosynthetic production of thallus parts and entire communities of Fucus serratus (L.) of differ- ent density and spatial structure exposed to varying photon flux density and dissolved CO2 concen- tration. Photosynthetic production in relation to photon flux density differed considerably between entire communities and individual thallus parts. No light saturation occurred in the communities, and all photosynthetic variables such as light compensation point, efficiency of light utilisation at low light and maximum production at high light depended on community density. Therefore, while the determination of the production of individual algal thalli is useful for evaluating differences in accli- matisation and adaptation between species and stands, it is not useful for evaluating production rates for entire plants and communities. Maximum gross production of F. serratus followed a hyperbolic curve at increasing community density, reaching a maximum of 30 µmol O2 (m 2 ground area) � 1 s � 1 at a leaf area index (LAI) of 8 to 10. Maximum net community production in the light was attained at an LAI of 6 to 8, while the maximum in a natural day-night cycle is attained at an LAI of 5 to 6. Maximum gross production was about 3-fold lower in F. serratus communities than in terrestrial communities in forests, grasslands and crops. Manipulating F. serratus communities to a more vertical structure increased light penetration and gross production in the communities, implying that canopy structure had a profound influence on community production and that a non-optimal distribution of light is likely to be the main reason for the lower maximum gross production rates in aquatic than terrestrial plant communities.

The Relationships between Fertility and Contents of Gibberellic Acid, Sugars and Dry Mass in Apical Parts of Chara Vulgaris Thalli

The contents of endogenous gibberellic acid (GA3), sugars, and dry mass in apical parts of fertile and sterile thalli of Chara vulgaris were estimated. The GA3 concentration in the first node of fertile thallus, determined by capillary electrophoresis, was about 70.0 mg kg−1 of fresh mass (f.m.). Pisum sativum-bioassay showed GA3 concentration of 80.0 mg kg−1 (f.m.) which was about 3 times higher than in the first node of sterile thallus. The higher amount of GA3, glucose, and the lower starch content and dry mass in fertile plants than in sterile ones suggest the interdependence between fertility and contents of studied components.

PRELIMINARY RESULTS ON SECONDARY METABOLITES FROM ANTARCTIC BROWN ALGAE AND THEIR ECOLOGICAL RELEVANCE

Iken, K. 1, Amsler, C. D.1, Hubbard, J. M.2, McClintock, J. B.1, Baker, B. J.3 1University of Alabama at Birmingham, Dept. of Biology, Birmingham, AL 35294‐1170 USA 2Hanshew Middle School, 10121 Lake Otis Pkwy., Anchorage, AK 99507 USA; 3Dept. of Chemistry, Florida Institute of Technology, Melbourne, FL 32901 USABrown algae (Phaeophyceae) are often dominant members in abundance and biomass of Antarctic macroalgal communities. They are ecologically important in providing habitat structure and shelter to many invertebrates and fish. However, as live algae they often appear to be of little importance as food for herbivores. Palatability of thalli of eight abundant Antarctic brown algae was tested against two sympatric algal grazers, the fish Notothenia coriiceps and the sea star Odontaster validus. Polar and non‐polar organic extracts of six brown algae were also tested against these grazers and against the omnivorous amphipod Gondogeneia antarctica. Almost all thalli and at least one of the extract types per algal species were unpalatable to the grazers, suggesting that chemical defenses are probably present in Antarctic brown algae. We further tested biological activity of brown algal extracts in antimicrobial assays as well as antifouling assays with sympatric bacteria and diatoms, respectively. We chemically screened organic brown algal extracts for the occurrence of secondary metabolites. Acetogeno‐terpenes were detected in Desmarestia menziesii and D. anceps. Phlorotannins were present in all brown algal species analyzed, but at different concentrations between species as well as between different thallus parts within individuals. Phlorotannin extracts were size fractionated to examine distribution and abundance of various size classes between species as well as between different thallus parts within individuals.

The effect of nitrogen on growth and key thallus components in the two tripartite lichens, Nephroma arcticum and Peltigera aphthosa

ABSTRACTRelationships between growth, nitrogen and concentration of unique biont components were investigated for the tripartite lichens Nephroma arcticum (L.) Torss. and Peltigera aphthosa (L.) Willd. Nitrogen availability was manipulated during 4 summer months by removing cephalodia and their associated N2 fixation activity, or by weekly irrigation with NH4NO3. Chlorophyll and ribulose 1·5‐biphosphate carboxylase/oxygenase (Rubisco), and chitin and ergosterol were used as photobiont and mycobiont markers, respectively. Nitrogen concentrations were similar in older and newer parts of the same thallus, varying between 2 and 5 g m−2, with P. aphthosa having higher concentrations than N. arcticum. Both chlorophyll (Chl a) and chitin were linearly correlated with thallus N, but N. arcticum invested more in fungal biomass and had lower Chl a concentrations in comparison with P. aphthosa at equal thallus N. During the 4 months, control and N‐fertilized thalli of N. arcticum increased in area by 0·2 m2 m−2 and P. aphthosa by 0·4 m2 m−2. Thallus expansion was significantly inhibited in samples without cephalodia, but there was no effect on lichen weight gain. Mean relative growth rate (RGR; mg g−1 d−1) was 3·8 for N. arcticum and 8·4 for P. aphthosa, when time (d) reflected the lichen wet periods. RGR was 2–3 times lower when based on the whole time, i.e. when including dry periods. The efficiency (e) of converting incident irradiance into lichen biomass was positively and linearly correlated with thallus Chl a concentration to the same extent in both species. The slower growth rates of N. arcticum, in comparison with P. aphthosa, could then be explained by their lower nitrogen and Chl a concentrations and a subsequently lower light energy conversion efficiency. Functional and dynamic aspects of resource allocation patterns of the two lichens are discussed in relation to the above findings.

Heterogeneity of Chlorophyll Fluorescence over Thalli of Several Foliose Macrolichens Exposed to Adverse Environmental Factors: Interspecific Differences as Related to Thallus Hydration and High Irradiance

Spatial heterogeneity of chlorophyll (Chl) fluorescence over thalli of three foliose lichen species was studied using Chl fluorescence imaging (CFI) and slow Chl fluorescence kinetics supplemented with quenching analysis. CFI values indicated species-specific differences in location of the most physiologically active zones within fully hydrated thalli: marginal thallus parts (Hypogymnia physodes), central part and close-to-umbilicus spots (Lasallia pustulata), and irregulary-distributed zones within thallus (Umbilicaria hirsuta). During gradual desiccation of lichen thalli, decrease in Chl fluorescence parameters (FO - minimum Chl fluorescence at point O, FP - maximum Chl fluorescence at P point, Φ2 - effective quantum yield of photochemical energy conversion in photosystem 2) was observed. Under severe desiccation (>85 % of water saturation deficit), substantial thalli parts lost their apparent physiological activity and the resting parts exhibited only a small Chl fluorescence. Distribution of these active patches was identical with the most active areas found under full hydration. Thus spatial heterogeneity of Chl fluorescence in foliose lichens may reflect location of growth zones (pseudomeristems) within thalli and adjacent newly produced biomass. When exposed to high irradiance, fully-hydrated thalli of L. pustulata and U. hirsuta showed either an increase or no change in FO, and a decrease in FP. Distribution of Chl fluorescence after the high irradiance treatment, however, remained the same as before the treatment. After 60 min of recovery in the dark, FO and FP did not recover to initial values, which may indicate that the lichen used underwent a photoinhibition. The CFI method is an effective tool in assessing spatial heterogeneity of physiological activity over lichen thalli exposed to a variety of environmental factors. It may be also used to select a representative area at a lichen thallus before application of single-spot fluorometric techniques in lichens.

Content of Gibberellic Acid in Apical Parts of Male and Female Thalli of Chara Tomentosa in Relation to the Content of Sugars and Dry Mass

The contents of gibberellic acid (GA3), glucose and starch, and dry mass in four nodes of apical parts of male and female thalli of Chara tomentosa were measured. The GA3 concentration was about 4 times higher in male than in female thallus and about 10 times higher in the first node than in the next three nodes of both thalli. The apical part of male thallus contains 2.5 times less glucose and 1.7 times less starch than female one. The average amount of dry mass of male and female thallus was similar: 9.9 and 9.8 % of fresh mass. The findings of this investigation demonstrate the interdependence of gibberellic acid and sugars in development of male and female Chara tomentosa thalli.

Copper and iron concentrations in Ascophyllum nodosum (Fucales, Phaeophyta) from different sites in Ireland and after culture experiments in relation to thallus age and epiphytism.

In laboratory experiments, copper concentrations in plants of Ascophyllum nodosum (L.) Le Jolis (Fucales, Phaeophyta) increased with the concentrations in the culture media and were highest in younger, meristematic thallus parts. After initial accumulation in high-copper medium and subsequent transfer to clean seawater for 5 days, no release of copper could be detected. Iron concentrations in A. nodosum tissue were not related to concentrations in the culture medium. Differences between copper concentrations in plants from different sites in areas with high yachting activity in Strangford Lough, Northern Ireland, could be explained by differences in water motion and human activity, in particular the application of copper-releasing antifouling paints to leisure boats. Iron concentrations were also highest in plants from the sheltered, polluted site but did not differ significantly between the other two sites. No differences in copper nor iron concentrations were found between different-aged thallus parts of plants from any site. X-ray microanalysis revealed that most of the iron detected was located in epiphytic pennate diatoms on the A. nodosum surface. In thallus areas without diatoms, iron levels were below the detection limit for X-ray microanalysis. Mapping for copper indicated that most of the accumulated copper was located in cells near and immediately below the thallus surface. "Epidermis"-shedding occurred in plants from the culture experiments and also in freshly-collected material and may have resulted in a loss of metal ions accumulated by surface cells and by epiphytic diatoms. The results suggest that A. nodosum could be used as a biological indicator for copper but not for iron, and that young, apical plant parts are most sensitive to changes in metal concentrations in the water.

Assays for Evaluating Seaweed Attachment Using Isolated Utricles of Codium fragile(Codiales, Chlorophyceae). I. Selection of Suitable Utricles for Assays.

The present paper deals with growth and attachment of isolated utricles from various parts of thalli in Codium fragile (Suringar) Hariot, with utricles from different stages being studied in laboratory culture in order to select suitable utricles for conducting assays on seaweed attachment. Clavate utricles were observed in the thalli at three stages: utricles without a gametangium, those with a gametangium before and after gamete release, and slender utricles without a gametangium. The clavate utricles were abundant except for the basal parts of the thalli, so that these utricles were used in the present study. The utricles isolated from six parts of the thalli and those at three different stages had the ability to form medullary filaments and attach to the substratum by their elongated filaments. However, the ability of the isolated utricles to elongate their filaments differed among the parts of the thalli used for isolating the utricles, and the ability of the utricles to form and elongate their filaments differed among the stages of the utricles. Furthermore, utricles with a gametangium were obtained only in a certain period when the thalli were fertile. Therefore, the clavate utricles without a gametangium isolated from the higher orders of axes are more suitable for use in assays on seaweed attachment.

Determination of GA3 in Chara vulgaris by capillary electrophoresis system

Method for simultaneous measurement of gibberellic acid was applied using capillary zone electrophoresis. Gibberellic acid was identified in extracts of apical part of thallus of Chara vulgaris L. The amount of gibberellins measured on the basis of activity determined by the micro-drop bioassay (59.8 mg·kg−1; with gibberellic acid as a standard) was comparable with that estimated by capillary electrophoresis (54.9 mg·kg−1).

Biomechanical and biochemical weathering of lichen-encrusted granite: textural controls on organic–mineral interactions and deposition of silica-rich layers

The crustose lichen Rhizocarpon geographicum weathers the Lower Devonian Shap Granite by both biomechanical and biochemical means. Biomechanical weathering is mediated by fungal hyphae that penetrate into the rock via intergranular boundaries at ≥0.002–0.003 mm year −1. Once inside the granite, hyphae exploit intragranular pores along cleavage and fracture planes in biotite, alkali and plagioclase feldspar. Grains of biotite exposed at the lichen–granite interface have been fragmented by biomechanical action in <122 years. After an extended period of biomechanical weathering of <10 kyr outcrop surfaces, sub-mm sized fragments of biotite and plagioclase feldspar abound in lower parts of the lichen's thallus. Grains of biomechanically weathered biotite show the clearest evidence for biochemical weathering. Typically, K and Fe are leached from the biotite, but other cations may also be removed, leaving a silica-dominated relic. The silica-rich remains of biotite and possibly also feldspar have been redistributed along the lichen–granite interface forming a silica-rich layer. This silica-rich material also cements fractures and pores beneath the interface. Alkali feldspars from outcrop surfaces have been weathered chemically, as indicated by etch pits on cleavage surfaces and fractures, but it is not obvious that lichen was involved in the dissolution. The etch pits were probably formed during earlier phases of non-biochemical weathering that widened intergranular and intragranular pores, facilitating subsequent access of fungal hyphae into the granite. Despite evidence for biomechanical and biochemical weathering, it is unlikely that colonisation of granite surfaces by R. geographicum at Shap significantly enhances their weathering rate relative to bare rock surfaces. The lichen may actually retard weathering by protecting the surface from frost action, binding fragmented mineral grains and depositing `protective' silica-rich layers.

Seasonal variation in the pigment content and photosynthesis of different thallus regions of Ascophyllum nodosum (Fucales, Phaeophyta) in relation to position in the canopy

Pigment contents and photosynthetic parameters of different regions of thalli of Ascophyllum nodosum (L.) Le Jolis collected from Strangford Lough, Irish Sea, and Helgoland, North Sea, were examined on a seasonal basis and after exposure to various irradiance and nutrient treatments in the laboratory. In culture, pigment contents of young plant parts acclimated rapidly to changes in irradiance and increased after nutrient enrichment in all irradiances. Chlorophyll a levels in plant tips in situ increased during autumn and winter and were reduced by 50% during summer. In older plant parts, which were subject to less seasonal variation in irradiance and were more shaded at both high and low tide, chlorophyll a levels were higher than in the tips at all times of the year. Older plant material from the lower shore contained higher pigment levels than corresponding material from the upper shore. Fucoxanthin : chlorophyll a ratios peaked during summer in apical plant parts from the upper shore and increased in culture with irradiance and with length of daily exposure to high irradiance. Variations of pigment concentration within plants and between shore levels were probably due to differences in irradiance between microhabitats caused by water depth and self-shading and enhanced by nutrient limitation in summer. Maximum net photosynthesis (Pmax) of young plant parts was higher than that of older plant parts and increased with temperature to a maximum at 20°C, in contrast to older plant parts which had low rates at all temperatures. Pmax was highest in tips in all seasons and decreased with distance from the tip along the thallus. Older, basal thallus parts exhibited shade acclimation with high pigment content and high photosynthetic rates at low irradiances, in contrast to apical tips, which were acclimated to high light. The observed decrease in Pmax of plants tips collected in summer from the upper shore may have been caused by photoinhibition.

Ultraviolet-absorbing scytonemin and mycosporine-like amino acid derivatives in exposed, rock-inhabiting cyanobacterial lichens

The occurrence of ultraviolet (UV)-absorbing substances like scytonemin and mycosporine-glycine is reported for the first time from cyanobacterial lichens of the genera Collema, Gonohymenia and Peltula, all coming from high-light-intensity habitats. Except for Collema with the filamentous Nostoc, all other cyanobionts belong to the unicellular genera Chroococcidiopsis, Cyanosarcina, Gloeocapsa or Myxosarcina. From transmission electron microscope studies it is evident that the pigmentation (scytonemin) is located extracellularly in the sheath of the outer thallus parts. Fluorescence microscopy and microprobe measurements clearly show UV radiation into the lichen thallus and hence the relevance of UV sunscreens for the protection of the organism.

VEGETATIVE ESTABLISHMENT AND EXPANSION BY THE MYCOBIONT OFCLADINA SUBTENUIS

Cladina subtenuisestablishes and expands by mechanisms of the thallus mycobiont. Vegetative reproduction occurs through thallus fragmentation, branch ‘de-differentiation’, and the extension of the underground prothallus. Establishment hyphae can be considered as any hyphae that provide the mechanism for these modes of clonal thallus extension. They may originate in various parts of the thallus, laterally on branch surfaces, at the growing tips of branches, or from the inner fungal layers of the podetium. The thallus ofC. subtenuisis structurally and functionally plastic. Parts of the photosynthetic lichen thallus can transform into non-photosynthetic fungal aggregations, and non-photosynthetic aggregations may re-establish as a photosynthetic lichen thallus. These activities expand the area occupied by the clone, and potentially increase its photosynthetic surface.

Vegetative Establishment and Expansion By the Mycobiont of Cladina Subtenuis

Cladina subtenuis establishes and expands by mechanisms of the thallus mycobiont. Vegetative reproduction occurs through thallus fragmentation, branch ‘ de-differentiation ’, and the extension of the underground prothallus. Establishment hyphae can be considered as any hyphae that provide the mechanism for these modes of clonal thallus extension. They may originate in various parts of the thallus, laterally on branch surfaces, at the growing tips of branches, or from the inner fungal layers of the podetium. The thallus of C. subtenuis is structurally and functionally plastic. Parts of the photosynthetic lichen thallus can transform into nonphotosynthetic fungal aggregations, and non-photosynthetic aggregations may re-establish as a photosynthetic lichen thallus. These activities expand the area occupied by the clone, and potentially increase its photosynthetic surface.

Regeneration and mechanisms of secondary attachment in Solieria filiformis (Gigartinales, Rhodophyta)

As in most red algae, thallus regeneration in Solieria filiformis (Kützing) Gabrielson provides a means of wound repair in both naturally and experimentally damaged thalli. In cultured explants, regeneration is a polar phenomenon that is characterized by production of endogenous normal buds on the distal cut surfaces and exogenous callus-pads of cortical tissue on the proximal ones. Rhizoid production can occur from both cut surfaces after prolonged forced contact with a substratum. In addition, undamaged apices are able to attach to the substratum by means of internal rhizoidal filaments protruding through the cuticle near the apical cells. Favorable conditions for formation of S. filiformis rhizoids are obtained in contact with penetrable calcareous substrata. Rhizoids outside the thallus behave differently from those inside; their apical cells divide repeatedly and are enclosed in a sheath composed of three layers, the outermost remaining attached to the substratum when the haptera are experimentally removed. After 30–40 d in culture, both haptera and parts of thallus in contact with a substratum become filled with floridean starch granules.

Accumulation of Trace Elements in the Peripheral and Central Parts of a Foliose Lichen Thallus

Accumulation of Trace Elements in the Peripheral and Central Parts of a Foliose Lichen Thallus

The Lichenicolous Genus Lettauia in North America

The genus Lettauia is reported in North America from Tennessee, with the species L. santessonii Ihlen & Tensberg sp. nov. and L. cladoniicola D. Hawksw. & R. Sant. The new species Lettauia santessonii, lichenicolous on Loxospora pustulata, is distinct from L. cladoniicola by the shorter and broader ascospores and larger apothecia. During a field trip to eastern North America in 1992, the junior author collected a lichenicolous fungus on Loxosporapustulata (Brodo & W. L. Culb.) R. C. Harris, which proved to represent an undescribed species of Lettauia D. Hawksw. & R. Sant., a recently described genus based on the single species L. cladoniicola (Hawksworth & Santesson 1990). The aim of the present paper is to describe this new species, and to report on the occurrence of L. cladoniicola in North America. Lettauia was recently reported new to North America by Esslinger and Egan (1995). MATERIALS AND METHODS Fungal hyphae were stained blue with lactoglycerol-aniline-blue (LGAB). Amyloid reactions were carried out, after pretreatment with 10% KOH, by a modified Lugol's solution in which H20 was replaced by lactic acid. The scatter diagram is based on the length and width of 40 spores from four apothecia of each of the type specimens of Lettauia cladoniicola and L. santessonii, and plotted in 0.5 Mm increments (i.e., rounded to the nearest 0.5 Mm). Lettauia D. Hawksw. & R. Sant. Bibliotheca Lichenologica 38: 136 (1990). Type species: L. cladoniicola D. Hawksw. & R. Sant. The asci and ascospores ofLettauia suggest affinites with the Fuscidaceae Hafellner (Hawksworth & Santesson 1990), which, with a question mark, has been assigned to the Teloschistales (Eriksson & Hawksworth 1993). LETTAUIA SANTESSONII Ihlen & Tonsberg sp. nov. (FIG. 1-2) Ascomycetes lichenicola. Lettauiae cladoniicolae D. Hawksw. & R. Sant. similis, sed ascosporis brevioribus (14-20 pm versus 18-25 Mm) et latioribus (3-5 ~m versus 2.5-3.0 Mm) et apotheciis majoribus (0.2-0.4 mm diam. versus 0.15-0.20 mm). Ascomata apothecia, 0.2-0.4 mm in diameter, slightly immersed in host thallus, scattered or in groups; disc more or less flat, pale brownish; exciple d stinct, uneven, paler than disc, consisting of radiating hyphae. Hypothecium hyaline. Hymenium hyaline, 37-54 tm high, K/I+ blue; epithecium hyaline to pale orange. Hamathecium formed by paraphyses; paraphyses slightly branched or unbranch d, not anastomosed, up to 2 pm in diameter, with slightly swollen apices; apices up to 2.5 pm. A ci elongate-clavate to broadly clavate, 42-52 x 10-12 pm, upper part of innermost layer and periascal gel K/I+ blue, 6-8 spored. Ascospores + distichously arranged, narrowly ellipsoid to ? cylindric-fusiform, with rounded ends, hyaline, (1-)2-3 septate, (12.5-)14.5-18.7(-20) x (2-)2.9-4.5(-5) pm (length: mean = 16.6, SD = 2.1; width: mean = 3.7, SD = 0.8). TYPE: U.S.A. TENNESSEE. Monroe Co., Cherokee Nat. Forest, E of Tellico, S of Road FR 210, Bald River Falls, on Loxospora pustulata growing on Betula lenta, 16 September 1992, Tensberg 18085 (holotype, BG; isotypes, DUKE, UPS). Lettauia santessonii was found lichenicolous on the thallus of Loxospora pustulata growing corticolous on Betula lenta. The new species clearly belongs in Lettauia, as circumscribed by Hawksworth and Santesson (1990), based on apothecioid ascomata, persistent exciple, simple or branched paraphyses, elongate-clavate ascus with an amyloid reaction in the periascal gel and upper part of the innermost layer, and 1-3 septate, cylindric-fusiform, hyaline ascospores (see Hawksworth & Santesson 1990 for further details). Lettauia santessonii differs from L. cladoniicola by the shorter and broader ascospores (Fig. 2), in L. cladoniicola they are (-17)18.8-24.2(-30) x (1.5-) 2.1-3.3(-4) pm (length: mean = 21.5, SD = 2.7; width: mean = 2.7, SD = 0.6). The new species is further distinct from L. cladoniicola by the broader apothecia (0.15-0.20 mm in diameter in L. cladoniicola) and its host choice (the hosts of L. cladoniicola are given below). The color of the infected parts of the host thallus 0007-2745/96/32-33$0.35/0 This content downloaded from 157.55.39.59 on Sat, 15 Oct 2016 04:35:14 UTC All use subject to http://about.jstor.org/terms 1996] IHLEN & TONSBERG: LETTAUIA IN NORTH AMERICA 33

Cytological Investigations of Lithobiontic Microorganisms in Granitic Rocks

AbstractThis paper shows the ultrastructure of lithobiontic organisms in a granitic rock from the exterior to the interior, where fissures are found 1–2 mm from the surface. There is clear differentiation at cell level between mycobiont and photobiont cells located on the rock surface which forms part of the lichen thallus and prokaryotic and eukaryotic cells (algae and fungi) found in the fissures. As well as the observations at the ultrastructural level of the microorganisms which live in fissures and cavities, immunolabelling techniques with colloidal gold have been applied to obtain an immunolocalization of Rubisco enzyme in some of the cells. The technique applied here permits Rubisco enzyme to be identified in algae‐like cells belonging to fissures where it is difficult to identify the pyrenoid. The mineral environment of the cells situated inside the fissures is investigated by Energy Dispersive Spectrometry (EDS). The biotite particles present in the fissure walls, as well as some lithobiont microorganisms, show a depletion of potassium from interlayer positions.

Trace Element Patterns in Lichens Following Uranium Mine Closures

Instrumental neutron activation analysis was used to determine trace elements in Cladina mitis (Sandst.) Hale & Culb. along transects extendingfrom uranium mines at Elliot Lake and Agnew Lake in central Ontario, Canada. Levels of 11 elements were reported and the presence of uranium (U) was confirmed, although U concentrations were much less than in Cladina rangiferina 10 years earlier. Among the elements identified in lichen thalli was Th, which occurred in higher concentrations than U. All trace elements, including the two radionuclides, were found in deterio- rating thallus parts as well as living podetia, and five of these seem to have originated as airborne particulates from minesites. In spite of mine closures, levels of Th and U remained higher near sources of ore dust and there was little relationship between radionuclide concentrations in thallus