摘要:

AbstractThe major soluble carbohydrate in shoots of the mossesDicranum majus, Hookeria lucens, Polytrichum commune, Racomitrium lanuginosum, Thuidium tamariscinumandTortula ruraliformisis sucrose, whose content varied between 100 and 500 f.Lmolg dry weight−1. Sucrose content was unaffected by desiccation. Glucose and fructose are present at less than one-tenth the sucrose cop.tent in each species and, inT. ruraliformis, desiccation causes a decrease in their concentration. Comparison with published data suggests that the above features, along with low levels of starch, are characteristic of mosses. It is suggested that high sucrose content, allied with low levels of reducing sugars, contributes to the desiccation tolerance of mosses.

ISSN:0373-6687    

DOI:10.1179/jbr.1992.17.2.185

出版商:Taylor&Francis    

年代:1992

数据来源: Taylor

摘要:

AbstractMeasurements are presented ofδ13C values from nineSphagnumspecies and associated vascular plants and peat from a wet heath in East Devon, fromSphagnum trinitenseC. Müll. at different sites and heights above water level in a North Carolina lake, and from two Marchantialean and two Metzgerialean liverworts from various habitats. The terrestrialSphagnumspecies show broadly similarδ13C values. Species with photosynthetic cells enclosed by the hyaline cells on both surfaces have significantlylowerδ13C values (mean -27.12) than the other terrestrial species (mean - 28.91).S. cuspidatumfrom a bog pool has aδ13C of -34.70, very significantly more negative than the other sphagna, probably from a proportion of recycled CO2in its source carbon.S. trinitenseshows significant between-site and within-site variation inδ13C in relation to height above water level. Samples at 6 cm give the most negativeδ13C values (mean -26.10), with progressively less negative values at lower levels (mean at 3 cm, -23.98; submerged, -22.55), implying increasing limitation of carbon uptake by diffusion resistance with increasing saturation and submersion.The four liverworts give similarδ13C values. The slightlymore negative figure forAneura pinguismay reflect some uptake of recycled CO2; the figure forPellia epiphyllais close to that for the two Marchantiales.Bryophytes have generally similarδ13C values to C3 vascular plants, suggesting that their photosynthetic structures are functionally comparable to those of vascular plants, with similar relations between diffusive and biochemical limitations on the rate of carbon uptake. This probably results from similar selection pressures operating in the two groups. Relationships between structure, diffusion resistances and inorganic carbon acquisition inSphagnumare discussed.

ISSN:0373-6687    

DOI:10.1179/jbr.1992.17.2.193

出版商:Taylor&Francis    

年代:1992

数据来源: Taylor

摘要:

AbstractThe pattern of apparent curvature of cellulose microfibrils in TEM photographs of the multilayered intine ofArchidium alternifoliumshowed variation between sections compatible with models suggesting regular rotation of the microfibrils in successively deposited sheets of wall materials. The intine extended inwards as a conspicuous ridge around the aperture on the proximal face of the spore ofA. alternifolium, a feature not previously reported in mosses. Germination was uniformly through the proximal aperture. Little protonema was produced. The first shoot either emerged through the aperture, arose from a colourless protruberance developing immediately outside the aperture, or grew from a bud on protonema close to the spore. On agar, germination continued over a period of several months. Percentage germination was consistently less than 65%, and increased with the age of the spores up to four years in freshly collected material.The origin of young shoots in a population ofA. alternifoliumat Stocks Reservoir was primarily by vegetative propagation, and shoot fragments predominated in the propagule bank in soil cores taken outside established colonies. Most spores produced in dense colonies ofA. alternifoliumat Stocks Reservoir appeared to be retained in the colonies, many of them in the parent perichaetia. The spores typically failed to germinate in that situation, but occasional sporelings with welldeveloped shoots were recorded in open colonies.

ISSN:0373-6687    

DOI:10.1179/jbr.1992.17.2.203

出版商:Taylor&Francis    

年代:1992

数据来源: Taylor

摘要:

AbstractRecent information on mineral nutrient acquisition and retention is reviewed in relation to the suspected importance of bryophytes in mineral relations of ecosystems. Nutrient inputs from various sources are discussed and the importance of determining the cellular locations of elements in experimental studies is emphasized. Mineral inputs from the substratum appear to be particularly important in rapidly growing species, e.g.Brachythecium rutabuium, which exploit seasonally deposited vascular plant litter. Slower-growing feather mosses, e.g.Pseudoscieropodium purum, may depend largely on wet deposition for minerals, although phosphate, which is present at low concentration in precipitation, is probably obtained principally from the substratum. The ecophysiological bases for the contrasting growth responses of different species to nutrient applications are poorly understood. Elevated cell wall cation exchange capacities (CEC) in bryophyte tissues in comparison to tracheophyte roots may be of significance in the sequestration and protoplasmic uptake of essential cations like Mg. In epilithic and woodland soil bryophytes the CEC decreases with decreasing Ca content and pH of the preferred substratum. It is possible that lowered CEC prevents excessive adsorption of the phytotoxic cation AI, which becomes increasingly available in acidic conditions, but this hypothesis has not yet been fully substantiated.

ISSN:0373-6687    

DOI:10.1179/jbr.1992.17.2.223

出版商:Taylor&Francis    

年代:1992

数据来源: Taylor

摘要:

AbstractGrimmia antarcticiis abundant on the Bailey and Clark Peninsulas, Wilkes Land, East Antarctica. It grows as a turf in wet locations and as cushions at relatively dry sites. This paper documents substantial differences in the internal CO2concentration of cushion and turf communities during the growing season. In November, CO2levels in the rhizo/phylloplane of both growth forms were close to ambient (around 350 ppm). Over the next two months the levels increased tenfold in turf but remained essentially constant in cushions. This means that the actively growing shoot tips of turf would be photosynthesizing at optimal CO2concentration (i.e. close to CO2saturation) for most of the summer. Photosynthesis in cushions, on the other hand, would be severely limited by CO2. These findings may account for the observations of Kappenet al.(1989), made at the same field sites in January 1986, that turf photosynthesizes at higher rates than cushions under simulated field conditions and is more resistant to photoinhibition.

ISSN:0373-6687    

DOI:10.1179/jbr.1992.17.2.241

出版商:Taylor&Francis    

年代:1992

数据来源: Taylor

摘要:

AbstractThamnobryum cataractarum sp. nov.is described from Yorkshire, England. It is most closely related toT. fernandesiifrom Madeira and is also similar toT. angustifoliumfrom Derbyshire, England. The three species are compared, and the habitat of the new species is described.T. fernandesiiandT. cataractarumare retained inThamnobryumrather than inCrassiphyllumOchyra.

ISSN:0373-6687    

DOI:10.1179/jbr.1992.17.2.251

出版商:Taylor&Francis    

年代:1992

数据来源: Taylor

摘要:

AbstractBryum demaretianum Arts sp. nov.is described from Belgium. The plant belongs to theB. erythrocarpumcomplex and is characterized by the occurrence of dense clusters of bright orange pyriform rhizoidal tubers.

ISSN:0373-6687    

DOI:10.1179/jbr.1992.17.2.263

出版商:Taylor&Francis    

年代:1992

数据来源: Taylor

摘要:

AbstractGrimmia subsquarrosaWils. andG. stirtonii Schimp. are reduced to synonymy withG. trichophyllaGrev.G. trichophyllavar.tenuis(Wahlenb.) Wijk&Marg. isrestored to specific status (asG. muehlenbeckiiSchimp.) and deleted from the list of British species. Var.robusta(Ferg.) A. J. E. Smith is restored to specific status asG. britannicaA. J. E. Smithnom. nov.and shown to be endemic to the British Isles.

ISSN:0373-6687    

DOI:10.1179/jbr.1992.17.2.269

出版商:Taylor&Francis    

年代:1992

数据来源: Taylor

摘要:

AbstractTortula muralisvar.obcordataandT. muralisvar.baetica, two taxa described from samples collected in Spain, were compared withT. muralisvar.muralisin order to establish their taxonomic status. The results obtained from a biometric study support maintenance of varietal status for var.obcordataand recognition of var.baeticaas a species,T. baetica(Casas&Oliva) Guerra&Ros.stat. nov.

ISSN:0373-6687    

DOI:10.1179/jbr.1992.17.2.275

出版商:Taylor&Francis    

年代:1992

数据来源: Taylor

ISSN:0373-6687    

DOI:10.1179/jbr.1992.17.2.285

出版商:Taylor&Francis    

年代:1992

数据来源: Taylor