Growth rate of Usnea aurantiacoatra (Jacq.) Bory on Fildes Peninsula, Antarctica and its climatic background.

The ages of a fruticose lichen of Usnea aurantiacoatra (Jacq.) Bory, from Fildes Peninsula, King George Island, Southwest Antarctic, were determined by radiocarbon (14C), and it is 1993-1996 at bottom and 2006-2007 at top of the lichen branch. The growth rates of U. aurantiacoatra calculated are 4.3 to 5.5 mm year(-1) based on its length and ages. The comparisons show that the growth rates of U. aurantiacoatra are higher than those of U. antarctica (0.4 to 1.1 mm year(-1)). The growth rates of fruticose lichens are always higher, usually >2 mm year(-1), than those of crustose ones, usually <1 mm year(-1), in polar areas. A warming trend on Fildes Peninsula is recorded in the period from 1969 to 2010 obviously: the mean annual temperature rose from -2.75 to -1.9°C and the average temperature of summer months from 0.95 to 1.4°C, as well as the average temperature of winter months from -6.75 to -5.5°C. The alteration of lichen growth rates in polar areas may respond to the climatic and environmental changes, and the lichens may act as bio-monitor of natural condition.

Antioxidative and cardiovascular-protective activities of metabolite usnic acid and psoromic acid produced by lichen species Usnea complanata under submerged fermentation.

CONTEXT: Lichens have been used for various purposes such as dyes, perfumes and remedies in folk medicine indicating the pharmaceutical potential of lichens. OBJECTIVE: Lichen growth in nature is very slow. To overcome this major drawback, we standardized the culture media to culture the lichen Usnea complanata (Müll.Arg.) Motyka (Parmeliaceae) for (1) in vitro synthesis of natural lichen substances, and (2) determination of antioxidative and cardiovascular-protective activity of usnic acid and psoromic acid. MATERIALS AND METHODS: Lichen U. complanata has been cultured in fermentor under submerged condition. Antioxidative and cardiovascular-protective activity of the extract and the purified lichen substances usnic and psoromic acid have been determined. RESULTS: Except methanol, all other extracts exhibited antioxidative action in terms of free radical scavenging activity (FRSA) with a half-inhibiting concentration (IC50) value of 22.86 to 25.0 µg/mL, nitric oxide radical scavenging activity (NORSA) 141.3 to 149.1 µg/mL and for lipid peroxidation inhibition (LPI) 125 to 157.9 µg/mL. Usnic acid or psoromic acid showed antioxidative action with IC50 values ranging from 0.174 to 0.271 mg/mL. Methanol and ethyl acetate extract showed hydroxy-3-methyl-glutaryl-CoA reductase (HMGR) inhibition of 65.18 to 74.81%. Only 43.47% inhibition of angiotensin converting enzyme (ACE) was shown by methanol extract. Usnic acid showed noncompetitive type of HMGR inhibition and uncompetitive type of ACE inhibition. Psoromic acid exhibited competitive type of HMGR inhibition and mixed type of ACE inhibition. DISCUSSION: U. complanata showed both cardiovascular-protective and antioxidant properties. The lichen species U. complanata may be a natural bioresource for possible pharmaceutical applications.

Development of thallus axes in Usnea longissima (Parmeliaceae, Ascomycota), a fruticose lichen showing diffuse growth.

PREMISE OF THE STUDY: While cell wall thickening in plants is generally associated with tissue maturation, fungal tissues in at least two lichens continue to grow extensively while accumulating massively thickened cell walls. We examined Usnea longissima to determine how diffuse growth shapes morphological and anatomical development of thallus axes and how the highly thickened cell walls of the central cord behave in diffuse growth. METHODS: Fresh material was examined with light and epifluorescence microscopy and conventional and low-temperature SEM. Fixed material was embedded in Spurr's resin, microtome-sectioned, and examined with TEM and light microscopy. KEY RESULTS: Main axes consisted essentially of bare medullary cord tissue; their characteristic morphology developed by destruction of the overlying cortex and consequent stimulation of lateral branch formation. Fungal cells of the cord tissue continually deposited wall layers of electron-transparent substances and layered, electron-dense materials that include UV-epifluorescent components. Discontinuities were evident in the outermost layers; new branch cells grew through wall materials accumulated by older neighboring cells. CONCLUSIONS: Sustained diffuse growth of cord tissue in U. longissima underlies the structural transformation of a corticated thallus branch into a long axis. In the cord tissue, diffuse growth may be responsible for the increasingly disrupted appearance of the older, electron-dense cell wall layers, while new wall materials are laid down adjacent to the protoplast. Cell and tissue development appeared comparable to that observed previously in Ramalina menziesii, although accumulation of wall material was somewhat less extensive and with a greater proportion of electron-dense/UV-epifluorescent components.

[Ontogeny and morphogenesis of the fruticose lichen Usnea florida (L.) Weber ex F.H. Wigg].

The development of the fruticose lichen Usnea florida was described in accordance with the concept of a discrete approach to the description of higher plant ontogeny proposed by T.A. Rabotnov and A.A. Uranov. The ontogeny of the U. florida thallus, represented by 4 periods and 11 ontogenetic states, includes the development of fungal mycelium from a spore, its association with alga into a rudimentary thallus, thallus morphogenesis (the life form formation and decay of the thallus), and all related morphological changes in the apothecia and other structures generated by the thallus. Based on an analysis of morphogenetic processes during thallus formation, we proposed morphological criteria for the separation of ontogenetic states. The formation of the main frame of the thallus and its intensive branching occur before the development of the apothecia because of the switching to the reproductive function. Thallus aging and decay start even before carposome formation (v2 state); later, these processes become more intensive and reach a maximum at the g3 and ss states. Changes in thallus morphogenesis can include both delay and acceleration of morphogenetic processes, representing the manifestation of adaptation mechanisms in response to different environmental factors.

Epiphytic lichen growth abnormalities and element concentrations as early indicators of forest decline.

Thallus morphology and element concentrations (S, Al, Fe, Sr, Mn, Ni, Zn, Cu, Pb, As, F, and Cl) were compared in samples of the fruticose lichen genus Usnea at two heights of the Abies sibirica canopy in the East Sayan Mountains (Krasnoyarsk District, Russia) sampled from three stations at 15, 25 and 35 km from Krasnoyark. Usnea species with an abnormal morphology dominated on branches in the upper canopy, 15-22 m above ground level, and normal thalli on lower tree branches, 2-5 m above ground. Abnormal thalli at the tree-top level contained higher Al, Fe, Zn, F, Sr and Pb concentrations compared with normal thalli growing below, confirming a dust impact. No such clear trend was observed between sampling stations. Crown canopy architecture, surface microtopography and the balance between the processes of deposition and the movement and loss of particles play a major role in particle interception and in pollutant delivery to Usnea.

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.