The weathering action of saxicolous lichens in maritime Antarctica

Summary Xanthoria elegans (Link) Th Fr. and Lecidea lapicida (Ach.) were studied on volcanic andesite, and Rhizocarpon geographicum (L.) DC. and Bacidia stipata Lamb on a volcanigenic sediment, using light microscopy, infrared spectroscopy, X-ray diffraction and transmission electron microscopy. Feldspars were present in the rocklichen interface to a lesser extent than in the underlying rock. R. geographicum was found to alter the minerals in the rock on which it grew without producing any new minerals in the rock/lichen interface, in contrast to the observations for this species on granite in temperate regions. Beneath of the thallus of L. lapicida there was calcium oxalate and some micas of the illite type, which may have been degradation products of various phyllosilicates in the rock. B. stipata, an endemic Antarctic lichen, had the greatest capacity to weather the rock and had weddellite (dihydrate calcium oxalate) and calcite in the contact area as well as many bacteria. The presence of crystalline oxalate, imogolite, allophane, carbonates (calcite) and amorphous material not found in the parent rock indicates biomineralization processes attributable to the lichens.     

Growth and vitality of epiphytic lichens

 We tested the hypothesis that changed microclimate at induced forest edges causes reduced growth of epiphytic lichens. Two foliose, green algal lichens were transplanted to the lower canopy of a mature Picea abies forest at six distances (2, 6.25, 12.5, 25, 50 and 100 m) from a clearcut. The biomass growth in Platismatia glauca (6.2% in 16 months) was 41% higher than in Lobaria pulmonaria (4.4%). We found no growth reduction near the forest edge. In contrast, the highest growth in both species occurred within 12 m from the edge. Further, fluorescence and chlorophyll measurements showed that lichen vitality was unaffected by distance from edge. The light intensity was 4.3 times higher at the edge than in the interior during the growing season, but there were only minor differences in air temperature and relative humidity. Monitoring of thallus water content revealed clear differences in both number and length of wetting and drying cycles. However, the total time with water content sufficient for photosynthetic activity was only slightly higher at the edge. The data thus indicate that our gradient in microclimate was too small to significantly affect lichen growth, and that lichens are largely metabolically inactive when large edge-interior contrasts in microclimate occur. Lichen response to forest edge microclimate results from intricate interactions among several biotic and abiotic factors. Linking data on lichen growth, microclimate and thallus water content with physiological measurements provides a framework for future studies of the mechanisms behind abiotic edge effects. Received: 15 April 1996 / Accepted: 21 June 1996     

Introduction of saxicolous lichens distributed in coastal rocks of U-do islet in Jeju, Korea

This study reports, for the first time, the investigation of the distribution of Korean saxicolous lichens in the coastal rocks of U-do islet, which is known as an unpolluted zone in Jeju. More than thirty lichens were obtained and investigated from the coastal rocks frequently contacted by seawater. A molecular analysis using PCR amplification of the rRNA ITS regions revealed the coastal rock lichens could be placed into 8 families and 14 genera, Ramalinaceae (Bacidia, Ramalina), Physciaceae (Buellia, Dirinaria, Phaeophyscia, Physcia, Pyxine), Lecanoraceae (Candelaria, Lecanora), Parmeliaceae (Xanthoparmelia), Graphidaceae (Graphis), Pertusariaceae (Pertusaria), Rhizocarpaceae (Rhizocarpon), and Teloschistaceae (Caloplaca), showing a diversity of lichens, with foliose (flat leaf-like), crustose (crust-like), and fruticose (miniature shrub-like) life forms might be distributed in the coastal rocks. These findings suggested the possibility that the lichens identified in the present work might be resistant to a salty environment.     

Cellular injuries in epiphytic lichens transplanted to air polluted areas

The epiphytic lichens Hypogymnia physodes (L.) W. Wats, and Bryoria capillaris (Ach.) Brodo & D. Hawksw. growing on spruce branches were transplanted from a clean rural area to the environment of a fertilizer plant and a pulp mill in central Finland. The common major pollutants in these environments are SO₂, NO_x and ammonia but the fertilizer plant also emits fluorides. In the transmission electron microscope two main types of cellular injuries were observed both in algal and fungal cells in both species and in both environments. The first type, characterized by rapid degeneration of cell organelles, was an apparently acute injury leading to plasmolysis and rapid death of the cells. The second type was considered chronic injury and involved changes in chloroplast shape, swelling of mitochondria and increased density of cytoplasm in algal cells, and increased vacuolization and appearance of dark vacuolar accumulations in fungal cells. The cytoplasmic storage droplets decreased gradually in size both in algae and fungi. The acute injury was mainly seen in the lichens transplanted to sites with higher pollution levels near the sources, and was more usual in algal than in fungal cells. B. capillaris was more susceptible to acute injury than H. physodes. An additional injury type was detected in algal cells of both lichen species in the vicinity of the fertilizer plant. This type was characterized by severe swelling of thylakoids and their interspaces and granulation of thylakoid membranes, and was suspected to be related to the effects of fluorides. The injuries as seen in light microscope, and expressed as increased proportion of dead algae and visible bleaching of thallus, were usually observable simultaneously. The injuries as seen in the electron microscope always preceded other injuries; they were clearly observable already after one week of transplantation in the more polluted sites but developed more slowly in the less polluted ones. The time lack between these injuries and the visible ones was 2–3 weeks in the more polluted sites, but several months or even years in the less polluted ones.     

Organic and inorganic nitrogen uptake in lichens

In order to learn more about nitrogen (N) acquisition in lichens, and to see whether different lichens differ in their affinity to various N sources, N uptake was measured in 14 various lichen associations (species). These species represented various morphologies (fruticose or foliose), contrasting microhabitat preferences (epiphytic or terricolous), and had green algal, cyanobacterial or both forms of photobionts. N was supplied under non-limiting conditions as an amino acid mixture, ammonium, or nitrate, using ¹⁵N to quantify uptake. Carbonyl cyanide m-chlorophenylhydrazone (CCCP) was used to separate active and passive uptake. Thallus N, amino acids, soluble polyol concentrations, and the biont-specific markers chlorophyll a and ergosterol were quantified, aiming to test if these metabolites or markers were correlated with N uptake capacity. Ammonium uptake was significantly greater and to a higher extent passive, relative to the other two N sources. Nitrate uptake differed among lichen photobiont groups, cyanobacterial lichens having a lower uptake rate. All lichens had the capacity to assimilate amino acids, in many species at rates equal to nitrate uptake or even higher, suggesting that organic N compounds could potentially have an important role in the N nutrition of these organisms. There were no clear correlations between N uptake rates and any of the measured metabolites or markers. The relative uptake rates of ammonium, nitrate and amino acids were not related to morphology or microhabitat.Abbreviations CCCP Carbonyl cyanide m-chlorophenylhydrazone - Chl Chlorophyll - N Nitrogen     

Stand characteristics in colour-infrared aerial photographs as indicators of epiphytic lichens

Information about forest biodiversity has so far been collected mostly by using field inventories, but it is desirable to find other methods that can cover large areas at a lower cost. In a forest landscape covering 2000 ha in southern Sweden we tested if colour-infrared (CIR) aerial photographs on the scale of 1:30000 can be used to interpret forest stand characteristics correlated to the occurrence of epiphytic lichens that are Red-listed or otherwise indicate high nature conservation value (signal species). Using logistic regression we found that the interpreted stand variables tree height and crown structure class were significantly correlated to the occurrence of Red-listed species. For signal species, the variables tree height, percentage of southern deciduous trees and crown structure class were significantly correlated to the occurrence. The logistic regression models successfully predicted a significantly higher probability to find Red-listed species in the stands that actually contained such species compared to stands without Red-listed species. The same was true for stands with signal species. We conclude that interpretation of CIR aerial photographs could be a useful method to find certain groups of epiphytic lichens in surveys covering large areas.     

Water relations and carbon dioxide exchange of epiphytic lichens in the Namib fog desert

Although there is only negligible rainfall, frequent nocturnal fog, dew and high air humidity support a luxurious lichen vegetation in the coastal zone of the central Namib Desert (Namibia). In earlier publications, we have studied ecophysiological performance of a series of epilithic and terrestrial lichens. Here, we have extended this work to three epiphytic species (Heterodermia namaquana, Ramalina lacera, and Xanthoria turbinata) that inhabit the sparse perennial shrubs growing in this area. Our intention, monitoring lichen CO₂ exchange, their water relations and microclimate conditions, was to determine the functional mechanisms that allow these epiphytes to exist under the special conditions of a fog desert. Measurements were conducted mainly during the spring season.The epiphytic lichens showed response patterns very similar to the epilithic and epigaeic species at the same site. Their metabolism was activated through moistening by dew and/or fog during the night and, in the very early morning, they exhibited the typical brief peak of net photosynthesis (NP) between sunrise and desiccation. The thalli were almost completely dry for the remainder of the day. Average duration of the positive NP during the morning peak was about 3 h. Dew condensation, alone, resulted in activation that provided 58–63% of integrated carbon income (ΣNP) as compared to fog (plus dew). In the late afternoon, there was a tendency for hydration to increase again, due to water vapour uptake at higher air humidity, and this allowed on some days a brief additional period of very low rates of photosynthesis shortly before sunset.Light response of photosynthesis showed “sun-plant” characteristics with saturation around 1000 μmol m⁻² s⁻¹ photosynthetically active photon flux density (PPFD). Light compensation point (LCP) of CO₂ exchange after sunrise was highly dependent on actual water content (WC) for X. turbinata: at low hydration it was ca. 10 μmol m⁻² s⁻¹ PPFD whilst, at high WC, it was almost 80 μmol m⁻² s⁻¹ PPFD. In contrast, LCP of R. lacera was almost independent of WC. This phenomenon was probably due to differences in thallus structure.Maximal attained NP and daily ΣNP both showed a saturation-type response to previous maximal nocturnal WC. Neither parameter was increased substantially when higher maximal thallus WCs were produced by experimental moistening in the night. All three species, despite their different morphologies, performed optimally at the highest nocturnal moistening achieved by natural fog and were not able to make use of higher hydration.The three studied epiphytes were similar in their chlorophyll-related rates of NP. Due to lower chlorophyll content, dry weight and carbon-related NP of X. turbinata was only about one-third of that of the other two species. The average carbon income on days with fog and/or dew hydration during the spring season amounted to 2.4 and 2.1 mgC (gC)⁻¹ day⁻¹ (related to thallus carbon content) for H. namaquana and R. lacera, respectively. This primary production was of similar magnitude to those found for the terrestrial species at the same site.     

Highly efficient uptake of phosphorus in epiphytic bromeliads

Background and Aims

Vascular epiphytes which can be abundant in tree crowns of tropical forests have to cope with low and highly intermittent water and nutrient supply from rainwater, throughfall and stem flow. Phosphorus rather than nitrogen has been suggested as the most limiting nutrient element, but, unlike nitrogen, this element has received little attention in physiological studies. This motivated the present report, in which phosphate uptake kinetics by leaves and roots, the subsequent distribution within plants and the metabolic fate of phosphate were studied as a step towards an improved understanding of physiological adaptations to the conditions of tree canopies.

Methods

Radioactively labelled [³²P]phosphate was used to study uptake kinetics and plant distribution of phosphorus absorbed from bromeliad tanks. The metabolism of low molecular phosphorus metabolites was analysed by thin-layer chromatography followed by autoradiography.

Key Results

Uptake of phosphate from tanks is an ATP-dependent process. The kinetics of phosphorus uptake suggest that epiphytes possess effective phosphate transporters. The K_m value of 1·05 µm determined for leaves of the bromeliad Aechmea fasciata is comparable with values obtained for the high affinity phosphate transporters in roots of terrestrial plants. In this species, young leaves are the main sink for phosphate absorbed from tank water. Within these leaves, phosphate is then allocated from the basal uptake zone into distal sections of the leaves. More than 80 % of the phosphate incorporated into leaves is not used in metabolism but stored as phytin.

Conclusions

Tank epiphytes are adapted to low and intermittent nutrient supply by different mechanisms. They possess an effective mechanism to take up phosphate, minimizing dilution and loss of phosphorus captured in the tank. Available phosphorus is taken up from the tank solution almost quantitatively, and the surplus not needed for current metabolism is accumulated in reserves, i.e. plants show luxury consumption. Young, developing leaves are preferentially supplied with this nutrient element. Taken together, these features allow epiphytes the efficient use of scarce and variable nutrient supplies.Key words: Epiphytic bromeliads, phosphorus uptake, forest canopies, luxury consumption, phytotelms, plant nutrition, Aechmea fasciata     

High cyanobiont selectivity of epiphytic lichens in old growth boreal forest of Finland

Here, cyanobiont selectivity of epiphytic lichen species was examined in an old growth forest area in Finland. Samples of the eight lichen species were collected from the same aspen (Populus tremula) and adjacent aspens in the same stand. The cyanobionts of these samples were compared with free and symbiotic Nostoc obtained from other habitats and geographic regions. Our results, based on the phylogenetic analysis of a partial small subunit of the ribosomal DNA (16S rDNA) and the rbcLX gene complex did not show any correlation with the geographic origin of the samples at any spatial scale. Instead, there was a correlation between the cyanobionts and the alleged taxonomy of their mycobionts. The results indicate that the lichen species examined are highly selective towards their cyanobiont partners. Only Lobaria pulmonaria proved to be more flexible, being able to associate with a wide range of Nostoc. A same Nostoc strain was found to form associations with taxonomically unrelated lichens indicating that the cyanobiont-mycobiont associations as a whole were not highly specific in the examined species.     

Enhanced phosphate uptake and polyphosphate accumulation in Burkholderia cepacia grown under low pH conditions

Of bacterial cells in a sample of activated sludge, 34% contained detectable intracellular polyphosphate inclusions following Neisser staining, when grown on glucose/mineral salts medium at pH 5.5; at pH 7.5 only 7% of cells visibly accumulated polyphosphate. In a sludge isolate of Burkholderia cepacia chosen for further study, maximal removal of phosphate and accumulation of polyphosphate occurred at pH 5.5; levels were up to 220% and 330% higher, respectively, than in cells grown at pH 7.5. During the early stationary phase of growth at pH 5.5 a maximum level of intracellular polyphosphate that comprised 13.6% of cellular dry weight was reached. Polyphosphate kinase activity was detected in actively growing cells only when cultured at pH 5.5. The phenomenon of acid-stimulated phosphate uptake and polyphosphate accumulation in this environmental bacterial population parallels observations previously made by us in the yeast Candida humicola and may thus represent a widespread microbial response to low external pH values.     

Distribution pattern of air pollution and epiphytic lichens in the Osaka Plain (Japan)

The geographic distributions of two common species of epiphytic lichens,Phaeophyscia limbata (Poelt) Kashiw. andLecanora pulverulenta Müll. Arg., on city park trees in the Osaka Plain and their relation to the distribution of SO₂ and NO₂ was examined. The concentrations of SO₂ and NO₂ are greater in the central area of this plain, and decrease with distance from the center. The frequency ofL. pulverulenta is lowest in the central area, and increases gradually toward the periphery. In contrast, the frequency ofP. limbata is highest in the intermediate area, and lower in the central and peripheral areas, i.e. at intermediate SO₂ and NO₂ concentrations. We conclude thatL. pulverulenta is more useful thanP. limbata as a bioindicator of air pollutants such as SO₂ and NO₂.     

Habitat type and primary colonisation of annual shoots of conifer saplings by epiphytic lichens

The ability of single lichen species to colonise annual shoots of Scots pine ( Pinus sylvestris ) and Norway spruce ( Picea abies ) under a variety of microclimatic conditions was assessed. Lichens were found to colonise the annual shoots of conifer saplings relatively slowly. Hypogymnia physodes is almost invariably the first sorediate species to attach to the bark whereas the other sorediate species appear only exceptionally on shoots in their first couple of years. The age of the substrate seems to be less important to pendulous species, however, probably due to their ability to reproduce also by thallus fragmentation and not only by soredia or spores as most other species do. The majority of the species colonise the annual shoots of spruce faster than those of pine, which suggests that bark exfoliation can effectively hinder colonisation. The colonisation rate of most of the species is clearly reduced under open canopy emphasising the importance of diaspore supply from lichens growing on mature trees.     

Bacterial symbionts on green hydra and their effect on phosphate uptake

Gram-negative rod-shaped bacteria (1.5–2m long and 0.5m wide) have been found associated with green hydra. They are always present on the hydra surface delineating the ectodermal cells, on animals in culture, and also on those sampled from a natural habitat. The bacteria could be removed by a 30-min treatment with antibiotics (50/ml polymyxin B and 50/ml streptomycin). Antibiotic-treated hydra took up 55% less phosphate from the medium than control hydra. The nutritional relationship between the bacteria and green hydra and possible routes of infection of the hydra by these prokaryotic symbionts are discussed. Their importance in interpreting results of certain types of physiological experiments using aquatic organisms is emphasized.     

Changes in the distributions of epiphytic lichens in southern Sweden using a new statistical method

Past studies on changes in species distribution have mainly been based on analysis of range boundaries. In contrast, the method used here evaluates shifts in species' geographic centroids within a predefined area. We used presence/absence data on epiphytic lichens collected 1986 and 2003 from 64 sites in southern Sweden. A centroid was calculated each year, for each lichen species and substrate. The distance of centroid movement was evaluated in a permutation procedure. In total, 56 lichen species on 22 tree species were involved in the analyses, yielding 30 cases that had sufficient sample sizes both years to be evaluated. Out of these, three exhibited a significant movement of their centroid. The shift of lichen centroids of Hypogymnia physodes (L.) Nyl. and Vulpicida pinastri (Scop.) J.-E. Mattsson & M. J. Lai on the tree species Juniperus communis L. was 50 and 151 km with the direction 27° and 48°, respectively. For Hypogymnia physodes on Pinus sylvestris L., corresponding values were 41 km and 30°. The northnortheast shifts of these species in Sweden could be a response to a warming climate.     

Effect of the medium pH and the cell pH upon the kinetical parameters of phosphate uptake by yeast.

1. Both the maximum rate of phosphate uptake and the Km depend upon the pH of the medium in a complex way. 2. The effect of medium pH upon the maximum rate of uptake is mainly indirect and is correlated with changes in cell pH. 3. The Km is affected by the medium pH both directly via an apparent competitive inhibition by hydroxyl anions and indirectly in a similar way as the maximum rate of uptake.     

Development of secondary woodland in oak wood pastures reduces the richness of rare epiphytic lichens

Wooded pastures with ancient trees were formerly abundant throughout Europe, but during the last century, grazing has largely been abandoned often resulting in dense forests. Ancient trees constitute habitat for many declining and threatened species, but the effects of secondary woodland on the biodiversity associated with these trees are largely unknown. We tested for difference in species richness, occurrence, and abundance of a set of nationally and regionally red-listed epiphytic lichens between ancient oaks located in secondary woodland and ancient oaks located in open conditions. We refined the test of the effect of secondary woodland by also including other explanatory variables. Species occurrence and abundance were modelled jointly using overdispersed zero-inflated Poisson models. The richness of the red-listed lichens on ancient oaks in secondary woodland was half of that compared with oaks growing in open conditions. The species-level analyses revealed that this was mainly the result of lower occupancy of two of the study species. The tree-level abundance of one species was also lower in secondary woodland. Potential explanations for this pattern are that the study lichens are adapted to desiccating conditions enhancing their population persistence by low competition or that open, windy conditions enhance their colonisation rate. This means that the development of secondary woodland is a threat to red-listed epiphytic lichens. We therefore suggest that woody vegetation is cleared and grazing resumed in abandoned oak pastures. Importantly, this will also benefit the vitality of the oaks.     

Interaction of arsenic and phosphate on their uptake and accumulation in Chinese brake fern

Interactive effects of arsenate (As (V)) and phosphate (Pi) were investigated under hydroponic culture. Arsenic concentrations in fronds and roots of Chinese brake fern (Pteris vittata L.) significantly (p < 0.05) increased with increasing As (V), but decreased (p < 0.05) with increasing Pi in nutrient solution. Phosphate uptake was significantly (p < 0.05) inhibited by 1000 micromol L(-1) As (V). Under 100 micromol L(-1) As (V), frond phosphorus (P) increased at 100 and 1000 micromol L(-1) Pi, and root P increased at 250 micromol L(-1) Pi exposures. Arsenic and P concentrations in fronds and roots of Chinese brake fern were negatively correlated (p < 0.05). Arsenate treatments enhanced As and P transport to fronds, while increasing Pi inhibited their transportation, with highest frond P and As (%) obtained under 100 micromol L(-1) treatment. pH values in nutrient solution increased with increasing exposure time, but decreased with increasing Pi levels. Dissolved organic carbon (DOC) contents (dry weight) in nutrient solution decreased with increasing Pi levels, both for treatments with and without As (V). Arsenate at 1000 micromol L(-1) significantly (p < 0.05) increased DOC contents, especially for treatment without Pi. Six organic acids were detected in root exudates of Chinese brake fern, with oxalic and malic acids being most dominant.