摘要:

AbstractSphagnum isoviitae(sect.Cuspidata; theS. recurvumcomplex)sp. nov. is known by the brown and flat capitulum with a regularly 5-radiate appearance of the outer branches and the inner branches somewhat laterally curved and forming a delimited part, and a visible terminal bud; the acute-apiculate stem leaves longer than broad; the fairly narrow and usually 5-ranked divergent branch leaves which are nonrecurved or indistinctly recurved above when dry; the differentiated stem cortex; and the pale yellow spores. The new species is most closely related toS. fallax(Klinggr.) Klinggr. It grows in transitional poor and intermediate fens, and is reported from north-western Europe and eastern North America.

ISSN:0373-6687    

DOI:10.1179/jbr.1992.17.1.1

出版商:Taylor&Francis    

年代:1992

数据来源: Taylor

摘要:

AbstractAxenic culture conditions which supported adequate to relatively rapid growth and development ofSphagnumspecies were used to conduct common garden experiments with two taxa in SectionIsocladusand four in SectionCuspidata. Our main objective was to determine if certain variable taxonomic characters (e.g. hemi-isophylly vs hetrophylly) are‘genetically fixed’or environmentally induced. We found that heterophylly and toothing of branch leaf margins were not‘genetically fixed’in the taxa we investigated. All taxa were isophyllous under uniform growing conditions. Characters that appeared least subject to environmental modulation were general growth habit and histological characters of branch leaves. Under common garden conditions, both taxa in SectionIsocladusremained distinct, but only three of the four taxa in SectionCuspidatadid.

ISSN:0373-6687    

DOI:10.1179/jbr.1992.17.1.15

出版商:Taylor&Francis    

年代:1992

数据来源: Taylor

ISSN:0373-6687    

DOI:10.1179/jbr.1992.17.1.27

出版商:Taylor&Francis    

年代:1992

数据来源: Taylor

摘要:

AbstractAxenically cultured shoots of fourSphagnumspecies were grown in aqueous solutions in which the concentrations of ions and of dissolved carbon dioxide were varied. Hyaline cell length was related directly to carbon dioxide concentration, and related inversely to the concentrations of nitrogen and phosphorus. The lengths of hyaline and chlorophyllose cells were closely correlated with each other and with leaf length. Short leaves contained very few hyaline cells, and those present were poorly differentiated. It is proposed that the open network of chlorophyllose cells which results from hyaline cell differentiation is a scavenging system for certain inorganic ions present at low concentrations in the surrounding aqueous environment.

ISSN:0373-6687    

DOI:10.1179/jbr.1992.17.1.35

出版商:Taylor&Francis    

年代:1992

数据来源: Taylor

摘要:

AbstractThe classic explanation of the low pH in bogs attributes this phenomenon to the H+exchange capacity ofSphagnum. However, recent researchers have challenged this theory, arguing instead that such exchange could not account for the ions measured and that organic acids were a more likely explanation. We have attempted to determine ifSphagnumcan exchange sufficient hydrogen to account for the low pH of the bog surface zone. To determine cation exchange capability ofSphagnum magellanicumin relation to the common cations of natural habitats, distilled and deionized water and different concentrations of Mg2+, Ca2+, K+, and Rudolph's Sphagnum nutrient medium were tested. In these experiments Sphagnum changes the pH of a surrounding liquid medium in the pH range of 3 to 7. The cation exchange capacity of Sphagnum magellanicum follows the series K+

ISSN:0373-6687    

DOI:10.1179/jbr.1992.17.1.47

出版商:Taylor&Francis    

年代:1992

数据来源: Taylor

ISSN:0373-6687    

DOI:10.1179/jbr.1992.17.1.59

出版商:Taylor&Francis    

年代:1992

数据来源: Taylor

摘要:

AbstractSphagnum magellanicumBrid. andSphagnum fallax(Klinggr.) Klinggr. react differently to several nutrient applications.S. fallaxis significantly promoted by additional nitrate and ammonium in the hollows and partly in the lawns while no positive effects of these treatments onS. magellanicumcould be detected. On the hummocks nitrate and to a lesser extent ammonium reduces the growth of both species. Under lower than recent input levels the growth rates of both species decrease, indicating that the growth of theseSphagnumspecies used to be N limited in bogs.S. fallaxcan be characterized as a competitive species whileS. magellanicumexhibits a stress-tolerant strategy. Under increased N deposition levelsS. fallaxis able to outcompeteS. magellanicumin the hollows and if the water supply is sufficient also at lawn level. The atmospheric nitrogen supply may therefore be responsible for the present-day success of this species in the bog vegetation of central and north-eastern Europe.

ISSN:0373-6687    

DOI:10.1179/jbr.1992.17.1.71

出版商:Taylor&Francis    

年代:1992

数据来源: Taylor

摘要:

AbstractThree species ofSphagnum (S. magellanicum, S. flexuosumandS. rubellum) were exposed to an artificial ozone regime in open-top chambers. Exposure levels consisted of a modified twice ambient (2X) treatment and a charcoal-filtered treatment. Additionally, an open plot treatment was established. The total ozone exposures during the experimental period were 80, 40 and 0.4 ppm in the 2X, open plot and charcoal-filtered treatments, respectively. Ozone level, temperature, humidity, light intensity and NOxlevel were constantly monitored during the experimental period. After ten weeks of exposure the growth (length and dry weight), photosynthesis and chlorophyll content were measured. The study showed that ozone exposure had a significant influence on growth in length, photosynthesis and chlorophyll content. There were also significantdifferences in reaction to ozone among species. Differences in light intensity, humidity, temperature and ozone level between open plots and charcoal-filtered chambers revealed differences in growth in length, biomass, photosynthesis and chlorophyll content between plants in open plots and plants in charcoal-filtered chambers.

ISSN:0373-6687    

DOI:10.1179/jbr.1992.17.1.81

出版商:Taylor&Francis    

年代:1992

数据来源: Taylor

ISSN:0373-6687    

DOI:10.1179/jbr.1992.17.1.93

出版商:Taylor&Francis    

年代:1992

数据来源: Taylor

摘要:

AbstractHygrohypnum styriacum(Limpr.) Broth. is reported for the first time in the British Isles.

ISSN:0373-6687    

DOI:10.1179/jbr.1992.17.1.107

出版商:Taylor&Francis    

年代:1992

数据来源: Taylor