Spectral properties of Antarctic and Alpine vegetation monitored by multispectral camera: Case studies from James Ross Island and Jeseníky Mts.

In this study, we investigated the utility of spectral remote sensing data gathered by a multispectral camera for estimating of vegetation cover in Antarctic vegetation oasis and Arcto-Alpine tundra. The surveys exploiting unmanned aerial vehicles (UAV) and multispectral camera were done in an Antarctic vegetation oasis located at the Northern shore of James Ross Island (Antarctica), and arcto-alpine tundra located in the Jeseníky Mts. (NE Czech Republic, 1 420 m a.s.l.). For the two locations, false colour images of spectral indices (VARI, NGRDI, GLI, RGVI, ExG, NDVI, PRI) were taken and analysis of vegetation types and components of vegetation cover done. Additionally, field research was performed by handheld instruments measuring NDVI, PRI and of selected vegetation components: Bryum pseudotriquetrum, Nostoc commune colonies (Antarctica), lichens grown on flat stones and boulders (the Jeseníky Mts.). The results show UAV photo surveys and imaging of spectral reflectance indices can be used to monitor vegetation types forming Antarctic vegetation oases and arcto-alpine tundra.

Bryophytes of the Larsemann Hills (Princess Elizabeth Land, Antarctica)

The bryoflora of Larsemann Hills oasis (Princess Elizabeth Land, Antarctica) was investigated. Six moss species and one liverwort, Cephaloziella varians, were recorded during field studies over the period 2009–2014. Bryum archangelicum Bruch et Schimp. is new for Princess Elizabeth Land and three species [B. archangelicum, Bryoerythrophyllum antarcticum (L. I. Saviz et Smirnova) P. Sollman and Syntrichia sarconeurum Ochyra et R. H. Zander] are new for Larsemann Hills. Representative specimens are listed and data on habitats and associated species provided. The most common mosses in the area are Bryum pseudotriquetrum and Coscinodon lawianus. Bryum pseudotriquetrum was found for the first time in Larsemann Hills at the bottom of lakes.

Light-triggered action potentials in plants

Special attention is paid in this paper to the criteria of the light-triggered action potential, namely the all-or-none law, propagation, the occurrence of refractory periods. Such action potentials have been recorded in <em>Acetabularia mediterranea, Asplenium trichomanes, Bryum pseudotriquetrum, Eremosphaera viridis </em>and <em>Concephalum conicum. </em>In <em>Acetabularia, </em>action potentials are generated after sudden cessation of light stimuli of sufficient intensity. The depolarization phase of the action potential develops as a result of a transient reversal of the action of the electrogenic Cl- pump. This is a principle of the "metabolic" action potential hypothesis proposed by Gradmann. In the gametophytes of <em>Aspleniam trichoma­nes </em>and <em>Bryum pseudo triquetrum, </em>action potentials are triggered on illumination. Gutation starts 1.5-2 seconds after the passage of an action potential. The active water secretion facilitates fertilization. In the unicellular fresh water alga, <em>Eremosphaera viridis, </em>action potential-like responses are evoked after light termination. The process responsible for its appearance is the opening of potassium channels in the plasmalemma. The liverwort, <em>Conocephalum conicum, </em>generates action potentials in response to light, electrical, chemical and mechanical stimuli. Calcium and potassium channels as well as proton pumps are involved in electrogenesis of action impulses in the species. Excitation causes a significant increase in the respiration rate. The role of action impluses as mediators in a system of a metabolism control is discussed.

Bryophytes of the oasis Molodyoznyi (Enderby Land, Antarctica)

For the first time the bryoflora of oasis Molodyoznyi (Enderby Land, Antarctica) was investigated in details. Detailed field studies in 2010–2013, generalization of literature data and study of collections from Bryological Herbarium of Komarov Botanical Institute (LE) resulted in records of eight moss species. Four species (Bryum archangelicum Bruch et Schimp., B. argenteum Bruch et Schimp., Coscinodon lawianus (J. H. Willis) Ochyra и Schistidium antarctici (Card.) L. I. Savicz et Smirnova) are new for oasis Molodyoznyi. Coscinodon lawianus and Schistidium antarctici are new for Enderby Land. Representative specimens and data on habitats and associated species are provided. The moss vegetation of oasis Molodyoznyi is very poor and typical for continental coastal oases of Antarctica. The most common mosses are Ceratodon purpureus and Bryum pseudotriquetrum. Bryum argenteum, Coscinodon lawianus and Schistidium antarctici are rare in oasis Molodyoznyi and Hennediella heimii (Hedw.) R. H. Zander and Orthogrimmia sessitana (De Not.) Ochyra et Żarnowiec are known for oasis Molodyoznyi from the literature only.

Desiccation protects two Antarctic mosses from ultraviolet-B induced DNA damage

Antarctic mosses live in a frozen desert, and are characterised by the ability to survive desiccation. They can tolerate multiple desiccation-rehydration events over the summer growing season. As a result of recent ozone depletion, such mosses may also be exposed to ultraviolet-B radiation while desiccated. The ultraviolet-B susceptibility of Antarctic moss species was examined in a laboratory experiment that tested whether desiccated or hydrated mosses accumulated more DNA damage under enhanced ultraviolet-B radiation. Accumulation of cyclobutane pyrimidine dimers and pyrimidine (6–4) pyrimidone dimers was measured in moss samples collected from the field and then exposed to ultraviolet-B radiation in either a desiccated or hydrated state. Two cosmopolitan species, Ceratodon purpureus (Hedw.) Brid. and Bryum pseudotriquetrum (Hedw.) Gaertn., B.Mey. & Scherb, were protected from DNA damage when desiccated, with accumulation of cyclobutane pyrimidine dimers reduced by at least 60% relative to hydrated moss. The endemic Schistidium antarctici (Cardot) L.I. Savicz & Smirnova accumulated more DNA damage than the other species and desiccation was not protective in this species. The cosmopolitan species remarkable ability to tolerate high ultraviolet-B exposure, especially in the desiccated state, suggests they may be better able to tolerate continued elevated ultraviolet-B radiation than the endemic species.

Additions to the bryophyte flora of Réunion (East African Islands)

Nineteen species of bryophytes are reported for the first time for Réunion. Especially remarkable are the first African record of Anastrophyllum leucocephalum (Tayl.) Steph. and the first records for the East African Islands of Cephaloziella cf. vaginans Steph., Fossombronia foveolata Lindb., Riccia huebeneriana Lindenb., Barbula unguiculata Hedw., Bryum pseudotriquetrum (Hedw.) Schwägr., Chenia leptophylla (Müll.Hal.) R.H.Zander, Dicranella subsubulata (Hampe ex Müll.Hal.) A.Jaeger, Ditrichum punctulatum Mitt., Physcomitrium spathulatum (Hornsch.) Müll.Hal. var. spathulatum and Trichostomum crispulum Bruch var. crispulum. Brachymenium gemmiferum A.J.Shaw & W.R.Buck is regarded as synonymous with Brachymenium exile (Dozy & Molk.) Bosch & Sande Lac.

Desiccation tolerance of three moss species from continental Antarctica

Tolerance of desiccation was examined in three species of moss, Grimmia antarctici Card., Ceratodon purpureus (Hedw.) Brid. and Bryum pseudotriquetrum (Hedw.) Gaertn., Meyer et Scherb. collected from two sites of contrasting water availability in the Windmill Islands, continental Antarctica. Physiological tolerance to desiccation was measured using chlorophyll fluorescence in plugs of moss during natural drying in the laboratory. Differences in relative water content, rate of drying and the response of photosynthesis to desiccation were observed among the three species and between sites. Of the three species studied, G. antarctici showed the lowest capacity to sustain photosynthetic processes during desiccation, B. pseudotriquetrum had an intermediate response and showed the greatest plasticity and C. purpureus showed the greatest capacity to sustain photosynthesis during desiccation. These results fit well with the known distribution of the three species with G. antarctici being limited to relatively wet sites, C. purpureus being common in the driest sites and B. pseudotriquetrum showing a wide distribution between these two extremes. Levels of soluble carbohydrates were also measured in these samples following desiccation and these indicate the presence of stachyose, an oligosaccharide known to be important in desiccation tolerance in seeds, in B. pseudotriquetrum. Both gross morphology and carbohydrate content are likely to contribute to differences in desiccation tolerance of the moss species. These results indicate that if the Casey region continues to dry out, as a result of local geological uplifting or global climate change, we would expect to see not only reductions in the moss community but also changes in community composition. G. antarctici is likely to become more limited in distribution as C. purpureus and B. pseudotriquetrum expand into drying areas.