Lobe growth variation and the maintenance of symmetry in foliose lichen thalli

The aim of this study was to determine how thallus symmetry could be maintained in foliose lichens when variation in the growth of individual lobes may be high. Hence, the radial growth of a sample of lobes was studied monthly, over 22 months, in 7 thalli of Parmelia conspersa (Ehrh. Ex Ach.) Ach. And 5 thalli of P. glabratula ssp fuliginosa (fr. ex Duby) Laund. The degree of variation in the total radial growth of different lobes within a thallus over 22 months varied between thalli. Individual lobes showed a fluctuating pattern of radial growth from month to month with alternating periods of fast and slow growth. Monthly variations in radial growth of different lobes were synchronized in some but not in all thalli. Few significant correlations were found between the radial growth of individual lobes and total monthly rainfall or shortwave radiation. The levels of ribitol, arabitol and mannitol were measured in individual lobes. All three polyols varied significantly between lobes within a thallus suggesting that variations in algal phostosynthesis and in the partitioning of fungal polyols may contribute to lobe growth variation. The effect on thallus symmetry of lobes which grew radially either consistently faster or slower than average was studied. Slow growing lobes were overgrown, and gaps in the perimeter were eliminated by the growth of neighbouring lobes, in approximately 7 to 9 months. However, a rapidly growing lobe, with its neighbours removed on either side, continued to grow radially at the same rate as rapidly growing control lobes. The results suggested that lobe growth variation results from a combination of factors which may include the origin of the lobes, lobe morphology and the patterns of algal cell division and hyphal elongation in different lobes. No convincing evidence was found to suggest that exchange of carbohydrate occurred between lobes which would tend to equalize their radial growth. Hence, the fluctuating pattern of lobe growth observed may be sufficient to maintain a degree of symmetry in most thalli. In addition, slow growing lobes would tend to be overgrown by faster growing neighbours thus preventing the formation of indentations in the thallus perimeter.

Development and growth of the lichen Rhizocarpon geographicum

The development of new areolae on the marginal hypothallus of the lichen Rhizocarpon geographicum (L.) DC was studied after complete or partial removal of the central areolae. New areolae developed slowly on the isolated hypothalli over two years. Development was similar when the areolae were completely removed and when the central areolae were separated from the marginal hypothallus by ‘moats’ 2 to 5 mm in width. However, in intact thalli, the marginal areolae developed rapidly during Jan. – June 1986 but showed periods of retreat from the margin during Oct. - Dec. 1985 and July – Sept. 1986. These results suggested that primary areolae may develop from free-living algal cells trapped by the hypothallus while secondary areolae may develop from zoospores produced by the thallus. Complete removal of the areolae resulted in no measurable radial growth of the marginal hypothallus over 18 months. Removal of the central areolae to within 1 and 2 mm of the hypothallus significantly reduced growth. These results suggest that the areolae may supply the hypothallus with carbon for growth. When the marginal hypothallus was experimentally removed a new hypothallus developed within one year. Regeneration occurred initially by retreat of the marginal areolae and later by new hyphal growth. The concentration of ribitol, arabitol and mannitol was measured in the areolae and marginal hypothallus on four occasions in 1985/6 in a population growing on a steep south facing rock surface. The three carbohydrates were present in significantly higher concentration in the areolae than in the hypothallus. Hence, the slow growth of this species may result from inhibited transport of carbohydrate from areolae to hypothallus.

The biology of the crustose lichen Rhizocarpon geographicum

The crustose lichen Rhizocarpon geographicum (L.) DC. comprises yellow-green lichenized areolae which develop and grow on the surface of a non-lichenized fungal hypothallus, the latter extending beyond the edge of the areolae to form a marginal ring. The hypothallus advances very slowly and the considerable longevity of R. geographicum, especially in Arctic and Alpine environments, has been exploited by geologists in dating the exposure age of rock surfaces (lichenometry). This review explores various aspects of the biology of R. geographicum including: (1) structure and symbionts, (2) lichenization, (3) development of areolae, (4) radial growth rates (RaGR), (5) growth physiology, (6) changes in RaGR with thallus size (growth ratesize curve), (7) maturity and senescence, and (8) aspects of ecology. Lichenization occurs when fungal hyphae become associated with a compatible species of the alga Trebouxia, commonly found free-living on the substratum. Similarly, 'primary' areolae develop from free-living algal cells trapped by the advancing hypothallus. The shape of the growth rate-size curve of R. geographicum is controversial but may exhibit a phase of decreasing growth in larger thalli. Low rates of translocation of carbohydrate to the hypothallus together with allocation for stress resistance results in very slow RaGR, a low demand for nutrients, hence, the ability of R. geographicum to colonize more extreme environments. Several aspects of the biology of R. geographicum have implications for lichenometry including early development, mortality rates, the shape of the growth-rate size curve, and competition. © The Author(s) 2012.

Factors associated with lobe division in the lichen Parmelia conspersa (Ehrh. ex. Ach.)Ach.

The factors associated with lobe division were studied in thalli of the lichen Parmelia conspersa (Ehrh. ex Ach.)Ach. Lobe division was studied in sequences of adjacent lobes using spatial pattern analysis. In five large thalli, lobe division within the thallus margin was randomly distributed. Correlations between the degree of lobe division, the radial growth of the lobe and lobe morphology were studied in six thalli. Lobe division was positively correlated with either lobe width or area in four thalli. Correlations were observed with radial growth or morphology of the adjacent lobes in two thalli. Dividing and non-dividing lobes were removed from large thalli and glued to pieces of slate with their tips either at the same level or in front of neighbouring lobes. Dividing lobes divided more rapidly when their tips were glued in front of their neighbours. The levels of ribitol, arabitol and mannitol were measured within a 2 mm region of the tip in dividing and non-dividing lobes on four occasions in 1994. Carbohydrate levels were significantly increased in dividing compared with non-dividing lobes. In addition, the mean size of the algal cells was greater in non-dividing compared with dividing lobes especially at the lobe base. However, the percentage of zoosporangia and aplanosporangia did not vary significantly in dividing and non-dividing lobes. These results suggest that: 1) the pattern of lobe division within the thallus margin may be random, 2) lobe division may be determined by lobe size and the location of the lobe tip relative to the neighbouring lobes and 3) there may be an increase in the productivity of lobes associated with lobe division.

Polyols in the crustose lichen Rhizocarpon geographicum

A lichen is an intimate association between an alga and a fungus and is regarded as one of the best examples of ‘mutualism’ or ‘symbiosis’ involving microorganisms. In lichens which have Trebouxia as the algal partner, photosynthesis by the algae results in the production of the soluble polyol ribitol which is then transported to the fungus where it is converted to arabitol and mannitol. Within the fungus, arabitol may act as a short-term carbohydrate reserve while mannitol may be involved in stress resistance. The crustose lichen Rhizocarpon geographicum (L.) DC., has an unusual thallus structure consisting of discrete granules (areolae) containing the algal component growing in association with a non-lichenised fungal hypothallus that extends beyond the areolae to form a marginal ring. The concentrations of ribitol, arabitol, and mannitol were measured, using gas chromatography, in the central areolae and marginal hypothallus of the crustose lichen Rhizocarpon geographicum (L.) DC. growing on slate rocks in north Wales, UK. The concentrations of all three polyols were greater in the central areolae than in the marginal hypothallus. In addition, the ratios of polyols in the marginal hypothallus to that in the central areolae varied through the year. The concentration of an individual poyol in the hypothallus was correlated primarily with the concentrations of the other polyols in the hypothallus and not to their concentrations in the areolae. Low concentration of ribitol, arabitol, and mannitol in the marginal hypothallus compared with the central areolae suggests either a lower demand for carbohydrate by the hypothallus or limited transport of polyols from areolae to hypothallus, and may explain the low growth rates of this species. In addition, polyols appear to be partitioned differently through the year with an increase in mannitol compared with arabitol in more stressful periods.

Polyols in the crustose lichen rhizocarpon geographicum

A lichen is an intimate association between an alga and a fungus and is regarded as one of the best examples of ‘mutualism’ or ‘symbiosis’ involving microorganisms. In lichens which have Trebouxia as the algal partner, photosynthesis by the algae results in the production of the soluble polyol ribitol which is then transported to the fungus where it is converted to arabitol and mannitol. Within the fungus, arabitol may act as a short-term carbohydrate reserve while mannitol may be involved in stress resistance. The crustose lichen Rhizocarpon geographicum (L.) DC., has an unusual thallus structure consisting of discrete granules (areolae) containing the algal component growing in association with a non-lichenised fungal hypothallus that extends beyond the areolae to form a marginal ring. The concentrations of ribitol, arabitol, and mannitol were measured, using gas chromatography, in the central areolae and marginal hypothallus of the crustose lichen Rhizocarpon geographicum (L.) DC. growing on slate rocks in north Wales, UK. The concentrations of all three polyols were greater in the central areolae than in the marginal hypothallus. In addition, the ratios of polyols in the marginal hypothallus to that in the central areolae varied through the year. The concentration of an individual poyol in the hypothallus was correlated primarily with the concentrations of the other polyols in the hypothallus and not to their concentrations in the areolae. Low concentration of ribitol, arabitol, and mannitol in the marginal hypothallus compared with the central areolae suggests either a lower demand for carbohydrate by the hypothallus or limited transport of polyols from areolae to hypothallus, and may explain the low growth rates of this species. In addition, polyols appear to be partitioned differently through the year with an increase in mannitol compared with arabitol in more stressful periods.

LEAPS:a semantic web and linked data framework for the Algal biomass domain

In this paper we present, LEAPS, a Semantic Web and Linked data framework for searching and visualising datasets from the domain of Algal biomass. LEAPS provides tailored interfaces to explore algal biomass datasets via REST services and a SPARQL endpoint for stakeholders in the domain of algal biomass. The rich suite of datasets include data about potential algal biomass cultivation sites, sources of CO2, the pipelines connecting the cultivation sites to the CO2 sources and a subset of the biological taxonomy of algae derived from the world's largest online information source on algae.

Effect of Cu and Sn promotion on the catalytic deoxygenation of model and algal lipids to fuel-like hydrocarbons over supported Ni catalysts

The ability of Cu and Sn to promote the performance of a 20% Ni/Al2O3 catalyst in the deoxygenation of lipids to fuel-like hydrocarbons was investigated using model triglyceride and fatty acid feeds, as well as algal lipids. In the semi-batch deoxygenation of tristearin at 260 °C a pronounced promotional effect was observed, a 20% Ni-5% Cu/Al2O3 catalyst affording both higher conversion (97%) and selectivity to C10-C17 alkanes (99%) in comparison with unpromoted 20% Ni/Al2O3 (27% conversion and 87% selectivity to C10-C17). In the same reaction at 350 °C, a 20% Ni-1% Sn/Al2O3 catalyst afforded the best results, giving yields of C10-C17 and C17 of 97% and 55%, respectively, which contrasts with the corresponding values of 87 and 21% obtained over 20% Ni/Al2O3. Equally encouraging results were obtained in the semi-batch deoxygenation of stearic acid at 300 °C, in which the 20% Ni-5% Cu/Al2O3 catalyst afforded the highest yields of C10-C17 and C17. Experiments were also conducted at 260 °C in a fixed bed reactor using triolein − a model unsaturated triglyceride − as the feed. While both 20% Ni/Al2O3 and 20% Ni-5% Cu/Al2O3 achieved quantitative yields of diesel-like hydrocarbons at all reaction times sampled, the Cu-promoted catalyst exhibited higher selectivity to longer chain hydrocarbons, a phenomenon which was also observed in experiments involving algal lipids as the feed. Characterization of fresh and spent catalysts indicates that Cu enhances the reducibility of Ni and suppresses both cracking reactions and coke-induced deactivation.