Field measurement of net photosynthesis of mosses at Langhovde,East Antarctica

Net photosynthesis and dark respiration (CO₂ flux) of Antarctic mosses were measured at Langhovde, East Antarctica, from 9 to 17 January 1988. Moss blocks were taken from communities in the Yukidori Valley (69°14′30″S, 39°46′00″E) at Langhovde. Each block was composed ofCeratodon purpureus andBryum pseudotriquetrum, orB. pseudotriquetrum. The upper part of the block was used to measure net photosynthesis and dark respiration. The net photosynthesis of each sample was measured in the field for one or three days with two infrared CO₂ gas analyzers and an assimilation chamber. The relationships of net photosynthetic rate and dark respiration rate, to the water content of the sample, the intensity of solar radiation and the moss temperature were estimated from the field data. The maximum rate of net photosynthesis was about 4 μmol CO₂ m⁻²s⁻¹ at saturating radiation intensity and at optimum temperature, about 10°C. Environmental features of moss habitats in the Yukidori Valley are discussed in relation to these results.     

Measurement of moss growth in continental Antarctica

Using steel pins inserted into growing moss colonies near Casey Station, Wilkes Land, continental Antarctica, we have measured the growth rate of three moss species: Bryum pseudotriquetrum and Schistidium antarctici over 20 years and Ceratodon purpureus over 10 years. This has provided the first long-term growth measurements for plants in Antarctica, confirming that moss shoots grow extremely slowly in Antarctica, elongating between 1 and 5 mm per year. Moss growth rates are dependent on availability of water. Antheridia were observed on some stems of B. pseudotriquetrum; no archegonia or sporophytes were observed. Stems bearing antheridia elongated much more slowly than vegetative stems in the same habitat. Two other methods of growth rate measurement were tested, and gave similar rates of elongation over shorter periods of time. However, for long-term measurements, the steel pin measurements proved remarkably reproducible and reliable.     

Ultraviolet B screening potential is higher in two cosmopolitan moss species than in a co-occurring Antarctic endemic moss: implications of continuing ozone depletion

Concentrations of UVB (ultraviolet B) absorbing pigments and anthocyanins were measured in three moss species, over a summer growing season in Antarctica. Pigment concentrations were compared with a range of climatic variables to determine if there was evidence that pigments were induced by UVB radiation, or other environmental parameters, and secondly if there were differences between species in their pigment responses. Significant seasonal differences in the potential UVB screening pigments were found, with the two cosmopolitan species Bryum pseudotriquetrum and Ceratodon purpureus appearing better protected from the potentially damaging effects of ozone depletion than the Antarctic endemic Schistidium antarctici. B. pseudotriquetrum accumulated the highest concentration of UVB screening pigments and showed positive associations between UVB radiation and both UVB absorbing and anthocyanin pigments. The negative associations between water availability measures and UVB absorbing and anthocyanin pigments also suggest that B. pseudotriquetrum is well protected in the desiccated state. This could offer B. pseudotriquetrum an advantage over the other species when high UVB radiation coincides with low temperatures and low water availability, thus limiting physiological activity and consequently, active photoprotective and repair mechanisms. As these pigments could act as either direct UVB screens or antioxidants, the results suggest that B. pseudotriquetrum is best equipped to deal with the negative effects of increased exposure to UVB radiation due to ozone depletion. The most exposed species, C. purpureus, has intermediate and stable concentrations of UVB absorbing pigments suggesting it may rely on constitutive UVB screens. Anthocyanin pigments were more responsive in this species and could offer increased antioxidant protection during periods of high UVB radiation. S. antarctici appears poorly protected and showed no evidence of any UV photoprotective response, providing additional evidence that this endemic is more vulnerable to climate change.     

Multiple colonization and dispersal events hide the early origin and induce a lack of genetic structure of the moss Bryum argenteum in Antarctica

The dispersal routes of taxa with transoceanic disjunctions remain poorly understood, with the potential roles of Antarctica not yet demonstrated. Mosses are suitable organisms to test direct intra‐Antarctic dispersal, as major component of the extant Antarctic flora, with the cosmopolitan moss Bryum argenteum as ideal target species. We analyzed the genetic structure of B. argenteum to provide an evolutionary time frame for its radiation and shed light into its historical biogeography in the Antarctic region. We tested two alternative scenarios: (a) intra‐Antarctic panmixia and (b) intra‐Antarctic genetic differentiation. Furthermore, we tested for evidence of the existence of specific intra‐Antarctic dispersal routes. Sixty‐seven new samples (40 collected in Antarctica) were sequenced for ITS nrDNA and rps4 cpDNA regions, and phylogenetic trees of B. argenteum were constructed, with a focus on its Southern Hemisphere. Combining our new nrDNA dataset with previously published datasets, we estimated time‐calibrated phylogenies based on two different substitution rates (derived from angiosperms and bryophytes) along with ancestral area estimations. Minimum spanning network and pairwise genetic distances were also calculated. B. argenteum was potentially distributed across Africa and Antarctica soon after its origin. Its earliest intra‐Antarctic dispersal and diversification occurred during a warming period in the Pliocene. On the same timescale, a radiation took place involving a dispersal event from Antarctica to the sub‐Antarctic islands. A more recent event of dispersal and diversification within Antarctica occurred during a warm period in the Pleistocene, creating favorable conditions also for its colonization outside the Antarctic continent worldwide. We provide evidence supporting the hypothesis that contemporary populations of B. argenteum in Antarctica integrate a history of both multiple long‐range dispersal events and local persistence combined with in situ diversification. Our data support the hypothesis that B. argenteum has been characterized by strong connectivity within Antarctica, suggesting the existence of intra‐Antarctic dispersal routes.     

Phenological studies on British mosses

Abstract

Seasonal patterns of reproductive development are reported for the five British mosses Atrichum undulatum, Bryum argenteum, Grimmiapulvinata, Polytrichum alpestre and Tortula muralis, and vegetative phenology is also described for B. argenteum and P. alpestre. Clearly defined seasonal cycles of gametangial and sporophytic development characterize P. alpestre, and the cycles in Britain resemble those previously reported for polar populations of this species. The seasonal timing of the later stages of sporophytic development, and of spore release, was shown to be relatively constant within each species but the gametangial cycles and fertilization periods appear to be more variable than in P. alpestre in the weedy colonist, B. argenteum, and particularly in the lithophytes, G. pulvinata and T. muralis.     

Delayed fluorescence as a new screening method of plant species for urban greening: an experimental study using four bryophytes

Selecting suitable plant species is important in urban greening because urban environments often provide unfavorable conditions for plant growth. We focused on delayed fluorescence (DF), i.e., light emitted from plants immediately following light exposure as a result of back electron transfer in photosynthesis, as an indicator of photosynthetic activity. Moss greening, urban greening using bryophytes, has attracted attention as a new domain of greening that does not require soil. Therefore, tolerance to drying, which is a characteristic environmental factor in cities, of four bryophytes—Bryum argenteum Hedw., Racomitrium japonicum Dozy et Molk., Hypnum plumaeforme Wilson, and Polytrichum commune Hedw.—was evaluated in the laboratory using DF. Assuming an urban environment, experiments were performed to measure the transition of DF following the cessation of irrigation and re-watering. The recovery of accumulated DF values (0–200 s) by rehydration 8 days after irrigation cessation was increased in the order H. plumaeforme ≈ P. commune?<?R. japonicum?<?B. argenteum. B. argenteum presented an increase in the accumulated amount of DF 8 h after irrigation cessation, and presented a significantly higher DF when compared with the other three species at 16 h. Together with results of previous studies, these findings of desiccation tolerance in the studied species indicate that DF is a useful method for characterizing desiccation tolerance in plants and selecting potentially useful plants for urban greening.

     

降雪对荒漠地区藓类结皮中真藓生理生化的影响

生物土壤结皮的生存环境是地球上自养生物生存最为极端的生境之一,真藓是荒漠结皮中最为重要的组分之一。很少有研究涉及冬季降雪对结皮层生物体的影响。以宁夏沙坡头人工植被区内发育良好、长势均匀的真藓结皮为研究对象,系统研究降雪影响下荒漠地区藓类结皮层真藓的光合色素含量、可溶性糖含量、可溶性蛋白含量、丙二醛(MDA)含量以及脯氨酸含量的变化,并探讨其对降雪的生理生化响应。采用了4个降雪处理,分别是无降雪、0.5倍降雪、1倍降雪、2倍降雪。结果表明:随着降雪量的增加,其光合色素含量和可溶性蛋白含量显著增加;而可溶性糖含量、游离脯氨酸含量以及MDA含量均呈下降趋势。研究结果表明,作为生物土壤结皮重要水源之一的冬季降雪,能够为结皮层生物体提供适宜的水分条件以激发其生理生化活性,对维持荒漠生态系统的稳定性具有重要作用。     

Improved,scalable techniques to cultivate fire mosses for rehabilitation

As wildfires increase in extent and severity in the western United States, land managers need new tools to stabilize and rehabilitate impacted hillslopes. One potential tool is the use of three disturbance‐adapted mosses Ceratodon purpureus (Redshank), Funaria hygrometrica (Cord moss), and Bryum argenteum (Silvergreen moss), collectively known as fire mosses. By growing and adding vegetative propagules in the form of gametophyte fragments to burned hillslopes, land managers could potentially increase the rate of moss colonization and stabilize soils. A first step in developing a native plant materials rehabilitation technique is overcoming propagule limitations using ex situ cultivation. We focused on greenhouse cultivation of moss gametophyte fragments allowing us to grow vegetative propagules with control over atmospheric, edaphic, and hydrologic conditions. In this experiment, we grew fire mosses using an easily scalable technique and commercially available materials. We demonstrated repeated success growing these species in the greenhouse and fine‐tuned harvesting techniques to increase productivity. We found that fire moss achieved high cover in 2 months when grown on organic substrate with constant wicking hydration and a protective shade covering, but growth was not favored by addition of burned materials. We successfully upscaled our growing technique, and developed efficient harvest methods. This success overcomes an initial barrier to testing and developing fire mosses as a novel rehabilitation technique.     

Filamentous fungi of the Windmill Islands, continental Antarctica. Effect of water content in moss turves on fungal diversity

This study presents the effect of water content in moss turves from the Windmill Islands, Wilkes Land, continental Antarctica on the composition of associated filamentous fungi. The two most prevalent mosses were sampled: Grimmia antarctici and Bryum pseudotriquetrum. Results were expressed as dry weights. No relationship was found between water content of the mosses or the surrounding soil and fungal diversity. Ten species of fungi were recovered and all species belong to cosmopolitan taxa. Accepted: 21 June 1999     

An assessment of the relationship between chlorophyll a fluorescence and CO2 gas exchange from field measurements on a moss and lichen

The relationship between CO₂ exchange and relative electron-transport rate through photosystem II (ETR, measured using chlorophyll a fluorescence) was determined for a moss and a green algal lichen, photobiont probably Trebouxia sp., in the field in Antarctica. Net photosynthesis (NP) and dark respiration (DR) were measured over temperatures from zero to 25 °C and gross photosynthesis (GP) calculated (GP = NP + DR). The strong response of DR to temperature in these organisms resulted in substantial changes in CO₂ exchange rates. The moss Bryum argenteum Hedw. showed a strong, linear relationship between GP and ETR. This was an unexpected result since mosses are C₃ plants and, in higher plants, this group normally has a curvilinear GP versus ETR relationship. It is suggested that suppression of DR in the light might be involved. The lichen, Umbilicaria aprina Nyl., had nonlinear relationships between ETR and GP that were different at each measurement temperature. In some cases the lowest ETR was at the higher CO₂ exchange rates. It is suggested that these relationships are the result of strong quenching mechanisms that are inversely proportional to GP. The results support a growing impression that the relationships between ETR and CO₂ exchange are complex in these organisms and different from those found for higher plants. Received: 24 November 1997 / Accepted 2 May 1998     

Benthic moss pillars in Antarctic lakes

Unique pillar-like colonies of aquatic mosses, rising from cyanobacterial and algal mats, have been discovered in some freshwater lakes in the vicinity of Syowa Station (69°00′S, 39°35′E), continental Antarctica. These moss pillars are about 40 cm in diameter and up to 60 cm high and occur at the lake bottoms mainly between 3 and 5 m depth. The primary component is a species of Leptobryum, a genus unknown in the continental Antarctic terrestrial bryoflora and as an aquatic genus elsewhere in the world. Bryum pseudotriquetrum is often an associated species. In longitudinal section the pillars reveal several whitish layers formed by mineral sediment and dead cyanobacteria. It is speculated that the biomass of aquatic mosses at the bottom of many Antarctic lakes is considerably greater than that previously estimated. Accepted: 11 April 1999     

Thermal tolerance of dried shoots of the moss Bryum argenteum

We conducted laboratory experiments to determine the lethal temperatures of the shoots of dried Bryum argenteum and to determine how this restoration species responds to extreme environments. We specifically assessed changes in gene expression levels in the shoots of dried B. argenteum plants that were subjected to sudden heat shock (control (20 ± 2°C), 80°C, 100°C, 110°C or 120°C) followed by exposure to heat for an additional 10, 20, 30 or 60 min. After they were exposed to heat, the samples were placed in wet sand medium, and their survival and regeneration abilities were evaluated daily for 56 days. The results showed that lethal temperatures significantly reduced the shoot regeneration potential, delayed both shoot and protonemal emergence times and reduced the protonemal emergence area. In addition, the expression of nine genes (HSF3, HSP70, ERF, LEA, ELIP, LHCA, LHCB, Tr288 and DHN) was induced by temperature stress, as assessed after 30 min of exposure. Additionally, a new thermal tolerance level for dried B. argenteum – 120°C for 20 min – was determined, which was the highest temperature recorded for this moss; this tolerance exceeded the previous record of 110°C for 10 min. These findings help elucidate the survival mechanism of this species under heat shock stress and facilitate the recovery and restoration of destroyed ecosystems.     

N- and P-addition inhibits growth of rich fen bryophytes

A greenhouse experiment was set up to investigate if infrequently and frequently occurring species respond differently to simulated habitat changes. Two frequently occurring (Bryum pseudotriquetrum and Calliergonella cuspidata) and two infrequently occurring (Hamatocaulis vernicosus and Paludella squarrosa) rich fen bryophytes were grown in mixed culture and subjected to rainwater or groundwater and three levels of N, ammonium nitrate (0, 1 and 3?mg?N?L^–1) and P, potassium phosphate (0, 0.05 and 0.1?mg?P/L). All species responded negatively to higher N-levels and three of the four species responded negatively to rainwater and higher P-levels. C. cuspidata had highest relative growth rate (RGR) in all treatments, and the infrequently occurring species had lower RGR and were more negatively affected by high levels of N than the frequently occurring species. A negative effect of rainwater seemed to be caused by higher background levels of N in rainwater compared to groundwater. We found a negative effect of high initial bryophyte density in three of the four species indicating density-dependent inhibition between species. We suggest that maintenance of oligotrophic conditions by recharge of nutrient-poor groundwater is vital for conservation of infrequently as well as frequently occurring rich fen bryophytes.     

Diversity within two serogroups of Rhizobium leguminosamm native to soils in the Palouse of eastern Washington*

The effect of plant genotype, soil temperature, and moisture on recovery of Rhizobium leguminosamm serogroups WA01 and WA02 from soil, was evaluated in the greenhouse using three plant genotypes (Pisum sativum cv. Alaska, Pisum sativum cv. Paloma and Lens culinaris cv. Rechief), three temperatures (12, 20 and 24°C) and soil from two different slope positions. The impact of moisture was followed by assessing pea nodulation after incubation of soil at different preplanting moisture levels. Isolates were also evaluated for serogroup, response to low levels of antibiotics and efficacy of symbiotic characters. Of the 33 antibiotic-strain combinations showing growth, 10 permitted 50% or more of the isolates to grow. Of the 24 clusters obtained, all except one were dominated by isolates in either serogroup. WA01 or WA02. There was no relation between either serogroup or cluster groupings and N₂ fixation. Serogroup recovery was influenced by plant genotype and temperature. At root temperatures of 12 and 24°C, serogroup WA02 occurred in a significantly lower fraction of the lentil nodules as compared to the pea species. At 12°C, recovery of WA02 was higher for the Paloma than Alaska pea. Recovery of WA02 in pea nodules generally increased as the soil moisture was preconditioned to drier levels of -0.5 and -1.5 MPa water potential.     

Terrestrial vegetation at Canada Glacier,Southern Victoria Land,Antarctica

Summary Bryophyte flushes in the vicinity of Canada Glacier in S.S.S.I. No. 12, Taylor Valley, Southern Victoria Land, were investigated in order to describe the vegetation present and to investigate factors affecting vegetation distribution. Biomass values from 950 to 1,250 g m^–2 (dry weight) and vegetated areas up to 14,450 m² indicate this is a significant area of bryophyte growth in Southern Victoria Land. The pattern of plant species in relation to water flow was investigated through detailed mapping. This is the first confirmed identification of Bryum argenteum, and Pottia heimii, and the first report of Bryum pseudotriquetrum from this area. Tissue nitrogen values for plants at this site are lower than other reported data, but it seems unlikely this would be a limiting factor for growth. It is concluded that, in this area, summer water flow in conjunction with microtopography has the greatest influence in determining where mosses, cyanobacteria and algae grow.     

Distribution of carbon,nitrogen and phosphorus in a moss community-soil system developed on a cold desert in Antarctica

The distributions of carbon, nitrogen and phosphorus in a moss community-soil system developed on a naked region in Rundvågskollane (69⁰50'S, 39⁰09'E), East Antarctica, were investigated in order to analyze the flow of matter in an Antarctic terrestrial ecosystem.

1. The moss community was formed from many moss blocks of different sizes and was composed ofBryum pseudotriquetrum (Hedw.) Gaertn., Meyer et Scherb.,Ceratodon purpureus (Hedw.) Brid. andGrimmia lawiana J. H. Willis. The surface of the community was covered with cyanobacteria.
2. It was estimated that nitrogen fixed by cyanobacteria flowed from these organisms to the moss and that little nitrogen was transported within the moss body.
3. A large amount of phosphorus existed in the soil. The moss community had a high phosphorus content although the amount itself was relatively little due to the small phytomass.
4. It seems that absorption of phosphorus from soil is difficult for moss, because of the paucity of water necessary for the movement of phosphorus and the suppressed growth of moss due to the arid conditions.

     

Growth temperature preferences of fungal strains from Victoria Land,Antarctica

Thirty-five strains of microfungi, isolated from various sites in Victoria Land, Antarctica, were grown at eight temperatures ranging from 0 to 45°C. Only 1 strain (Chaetomium sp. from hot soil) was a thermotolerant mesophile; other strains were psychrophilic (2 strains) or psychrotrophic (32 strains). The fitness of different species to thermal instability is discussed, based on the width of the growth rate curves.     

Air humidity as key determinant of morphogenesis and productivity of the rare temperate woodland fern Polystichum braunii

(1) Most ferns are restricted to moist and shady habitats, but it is not known whether soil moisture or atmospheric water status are decisive limiting factors, or if both are equally important. (2) Using the rare temperate woodland fern Polystichum braunii, we conducted a three‐factorial climate chamber experiment (soil moisture (SM) × air humidity (RH) × air temperature (T)) to test the hypotheses that: (i) atmospheric water status (RH) exerts a similarly large influence on the fern's biology as soil moisture, and (ii) both a reduction in RH and an increase in air temperature reduce vigour and growth. (3) Nine of 11 morphological, physiological and growth‐related traits were significantly influenced by an increase in RH from 65% to 95%, leading to higher leaf conductance, increased above‐ and belowground productivity, higher fertility, more epidermal trichomes and fewer leaf deformities under high air humidity. In contrast, soil moisture variation (from 66% to 70% in the moist to ca. 42% in the dry treatment) influenced only one trait (specific leaf area), and temperature variation (15 °C versus 19 °C during daytime) only three traits (leaf conductance, root/shoot ratio, specific leaf area); RH was the only factor affecting productivity. (4) This study is the first experimental proof for a soil moisture‐independent air humidity effect on the growth of terrestrial woodland ferns. P. braunii appears to be an air humidity hygrophyte that, whithin the range of realistic environmental conditions set in this study, suffers more from a reduction in RH than in soil moisture. A climate warming‐related increase in summer temperatures, however, seems not to directly threaten this endangered species.     

Response surface optimization of mixed substrate solid state fermentation for the production of lovastatin by Monascus purpureus

The objective of this work is to enhance the production of lovastatin using Monascus purpureus MTCC 369 in mixed substrate solid state fermentation using various solid substrates and to optimize the combination of the solid substrates by response surface methodology. Solid state fermentation was conducted in a 250 mL Erlenmeyer flask at 30°C for 14 days with initial moisture content of 40% and inoculum size of 10% active culture. Barley, long grain rice and sago starch were found to be the suitable substrates producing maximum lovastatin of 193.7 mg, 190.2 mg and 180.9 mg/g of dry solids. These substrates were further used in various combinations as designed by the central composite design for enhancing the lovastatin production using Monascus purpureus. To the best of our knowledge this is the first report on the production of lovastatin using a mixed substrate solid state fermentation using Monascus purpureus.     

A Study on the Spore Morphology of Bryum Hedw. in China

Spore morphology of thirteen species of the genus Bryum Hedw. were observed by LM and SEM. The results show that the ornamentation of spore exine could be divided into three types: Type I , blunt at the top of baculate processes, to which four species belong: Bryum argenteum, B. lonchocaulon , B. uliginosum and B. arcticum. Type Ⅱ, sharp or with small processes at the top of baculate processes, represented by seven species: B. pallescens, B. caespiticium, B. pallens, B. pseudotriquetrum, B. paradoxum, B. alpinum and B. thomsoii. Type Ⅲ, expanded into hemispherical-shaped at the top of baculate processes, represented by two species: B.coronatum and B.sauteri. The Bryum species may also be divided into three groups according to the variation of spore diameter. Group I , with spore diameter under 10 μm, including one species, B. uliginosum. Group Ⅱ, with spore diameter 11～20 μm, including seven species: B. argenteum, B. alpinum, B. coronatum, B. pallens, B.paradoxum, B.sauteri, B.thomsonii. Group Ⅲ, spore diameter 21～30 μm, with five species: B. pallescens, B. caespiticium, B. pseudotriquetrum, B. lonchocaulon, B. arcticum. There are resemblances of spore morphology and exine ornamentation among the thirteen species. In the view of palynology, the genus Bryum is a natural taxon which is more advanced than the genus Pohlia Hedw. But spores of thirteen species are different at some characters such as diameter, shape ofproximal leptoma, etc., which indicates the genetic differentiation in the genus Bryum.