Identification of crystalline material found in the thallus of the lichen, Myelochroa leucotyliza

Lichens are symbiotic associations of fungi and algae (or cyanobacteria). Fungal cells produce large amounts of lipid, assisted by algae, and secrete them out of the cells. Some of the secreted lipids crystallize in the thallus of the lichen. The crystalline materials sometimes occupy 30% of total dry weight of the thallus. This unusual amount of lipid crystal led to our interest in investigating the mechanism of lipid secretion. To begin the cell biological study of lipid secretion and to know the significance of the existence of such crystals in the thallus, it is essential to identify the crystal. The lipid crystal extracted from the thallus of a lichen, Myelochroa leucotyliza, was studied by EM observations, TLC analysis, and EM and X-ray diffraction methods. Atranorin is the predominant component of the crystalline materials in the lipids extracted.     

Influence of management on the species composition of epiphytic cryptogams in Danish Fagus forests

Abstract. The purpose of this study is to evaluate and to quantify the influence of management on the epiphytic species composition in Danish Fagus sylvatica forests. Trunks were chosen at random within selected blocks in both managed and unmanaged Fagus stands.117 trunks in 43 sample plots in three forests were investigated. Cover was estimated for 72 lichens, 29 bryophytes and two fungi on vertical trunks 0.3 ‐2 m above ground. 18 explanatory variables were recorded and arranged in three groups: eight management‐related variables, six micro‐climatic‐ and soil variables, and four geographical‐ and geological variables. Canonical Correspondence Analysis was used to test and to quantify the explaining power of the three groups of variables applying the variation partitioning approach. Detrended Correspondence Analysis was used to evaluate whether important gradients were ignored. It was concluded that the traditional ‘shelterwood uniform system’ used in Fagus forests has a marked influence on the epiphytic species composition. Thus, management‐related variables explained more than one third of the total variation explained, which equals 10.9% of the total variation. Microclimatic and soil variables explained 9.0%, and geographical and geological variables explained 6.0%. The following three recommendations are suggested to reduce the significant influence of management on the epiphytic species composition. First, it should be attempted to ensure a continuous occurrence of some big trees per ha to be left for natural death and decomposition. Second, regular thinning is necessary, especially in the first part of rotation. Third, a multi‐layered forest, where wind and desiccation effects are minimized, is recommended.     

两种地衣植物的化合物分析

本文报道石蕊科石蕊属的两种地衣植物的化学成分,我们从软石蕊(Cladonia mitis),石蕊(Cladonia rangiferina)中分离鉴定了五个化合物,它们分别是左旋和右旋松萝酸、黑茶浸素、原地衣硬酸、环萝酸、蛋氨酸乙酯;上述资料对开发利用该植物资源提供了科学依据。     

In situ studies of water relations and CO2 exchange of the tropical macrolichen, Sticta tomentosa

Diel (24-h) time courses of CO₂ exchange, water relations, and microclimate of the foliose lichen, Sticta tomentosa (Swartz) Ach., and responses to experimentally manipulated conditions were measured at a forest edge in a lower montane rainforest in Panama.
Similar to earlier observations on two other rain forest lichens, daily desiccation suppressed net photosynthesis (NP) during the period when irradiation was highest. Not surprisingly, the light response curves of NP showed saturation at rather low light levels. Rehydration was associated with an initial resaturation burst of short duration, which could be demonstrated both under natural conditions and experimentally. This additional loss of CO₂ seems too low to be ecologically relevant. Moreover, high thallus hydration was also detrimental to NP: at maximum water content net CO₂ uptake was depressed by >50%. Although NP was well adapted to the prevailing high temperatures, the latter also stimulated dark respiration. On average, almost 60% of the diurnal carbon gain was lost during the night.
In spite of these limitations, the integrated 24-h C gain was quite high, on average 0·5% of the thallus C content. Whilst these figures were determined for horizontally exposed samples, we also assessed the role of different exposures on photosynthetic performance. Diel C gain was highest under conditions of semi-shade (westerly exposure), which allowed long periods of activity, whilst much higher irradiance at other exposures could not be utilized for photosynthetic production: easterly exposed thalli dried out even faster than horizontally exposed samples.     

云南玉龙雪山地衣资源的评价

本文讨论了玉龙山的自然环境对地衣植物生长的影响;列举了15种玉龙山常见地衣并分别讨论了各种的分布、生境、已知化学物质及其利用。其中还推出了三种在国内化学及应用方面研究较少,而在该山分布量较大的地衣种。     

Classification and ordination of cryptogamic communities in Wilkes Land,Continental Antarctica

The entirely cryptogamic vegetation of Bailey and Clark Peninsulas, Windmill Islands, Budd Coast, Wilkes Land, Antarctica, is described for the first time. The vegetation of this area is exceptionally well developed and diverse and represents one of the most important botanical sites on the continent. The macroflora comprises three species of moss, one liverwort, three fruticose lichens, four foliose and over 20 crustose lichens; several macroalgae also occur. Seventy stands of relatively homogeneous vegetation were analysed and the percentage cover afforded by every species within 20 quadrats per site was recorded. A subjective classification was developed by visual ordering of the data sets and a hierarchical system erected which incorporates one moss- and one lichen-dominated sub-formation; the former includes two associations and seven sociations, while the latter comprises one association which includes four sociations. The data were then arranged by centroid linkage analysis to produce and objective classification, and subsequently ordinated by principal components analysis to generate groups of stands, the inter-relations of which were interpreted in ecological and environmental terms. The objective classification and ordination strongly support the subjectively derived groupings or sociations. Examples of plant interactions are qualitatively described.     

A new depside and two new diphenyl ether compounds from the lichen Ramalina farinacea (L.) Ach

The chemical investigation of the Vietnamese lichen Ramalina farinacea (L.) Ach. led to the isolation and the structure elucidation of eight compounds (1–8), including one new depside, formulated as methyl homosekikate (1) and two new diphenyl ethers, 3-(2-carboxy-5-methoxy-3-propylphenoxy)-2-hydroxy-4-methoxy-6-propylbenzoic acid, namely ramalinic acid A (2), and 3-(2-carboxy-5-methoxy-3-propylphenoxy)-2-hydroxy-4-methoxy-6-pentylbenzoic acid, namely ramalinic acid B (3). Their chemical structures were unambiguously determined by analysis of 1D and 2D NMR and high resolution ESI mass spectroscopic data, as well as by comparison with literature data. We also proposed a possible biosynthetic route for the formation of the two new diphenyl ethers (2) and (3) via an enzymatically induced intramolecular Smiles rearrangement of the depsides sekikaic acid and homosekikaic acid, respectively.     

Water relation parameters of six Peltigera species correlate with their habitat preferences

Water relation parameters were measured in six congeneric lichen species with different requirements for water availability and with green algae (Peltigera aphthosa, Peltigera leucophlebia, Peltigera venosa) or cyanobacteria (Peltigera horizontalis, Peltigera praetextata, Peltigera rufescens) as main photobionts. Pressure–volume analysis was performed with a dewpoint hygrometer and integrated with anatomical analyses. The Peltigera species typical of arid environments were characterized by relatively lower osmotic potential (π₀) and turgor loss point (Ψ_TLP), and higher values of bulk modulus of elasticity (?). Both π₀ and Ψ_TLP were correlated with the size of medullary cells, while ? was negatively correlated with cell dimensions. The adaptive value of low Ψ_TLP might reside in the capability to maintain cell turgor for longer time intervals under dry conditions. High ? might allow xerophilous lichens to regain cell turgor more promptly even for small amounts of water uptake, thus enlarging the cumulative period of positive carbon balance in environments with fluctuating water availability. The influence of the photobiont type is also discussed.