bluuebunny/crossref_metadata_2025_split huggingface dataset:
The physical and biochemical condition of Modiolus modiolus (L.) in selected Shetland voes
Authors: Comely C. A. 
Published: March 2014

Synopsis1. A general survey of the sub-tidal populations of Modiolus modiolus (L.) to a depth of 18 or 21 m was carried out in five Shetland voes, with particular emphasis in Sullom Voe. Estimations of density distribution and growth rate were made.2. Commencing in June 1976 samples were collected at three-monthly intervals from two sites in Sullom Voe, and from one site in Cat Firth in 1977, to investigate seasonal variations in flesh and biochemical content. The data indicate that Shetland Modiolus are generally similar in their biology to those from Scottish lochs, and are liable to considerable variation between and within populations, with groups responding to environmental variations of very local extent.3. A list of animals found associated with Modiolus and their byssus complexes is given. As no effort was made to collect the fauna systematically or quantitatively, the list is not comprehensive.
Genetics of gametophyte development
Authors: Hickok Leslie G. 
Published: March 2014

SynopsisFern gametophytes provide unique opportunities for the investigation of various aspects of physiology, genetics and development. Past genetic studies of gametophytes have primarily involved investigations of variegation and radiation-induced plastid aberrations. Two studies have utilised the gametophyte generation to develop screens for specific types of mutations. The considerable natural variation that exists in gametophyte development has not been investigated genetically. Genetic studies can provide needed information regarding basic aspects of development. A selection system with broad applicability has been developed to isolate gametophyte mutations that confer resistance to growth regulators. An example of the use of the screen with abscisic acid is given and preliminary characterisations of some of the mutants are presented.
Gametogenesis: the playground of the developmental cytologist
Authors: Miller C. C. J. , Duckett J. G. , Kirkham B. 
Published: March 2014

SynopsisDevelopmental ultrastructural studies have led to major advances in our understanding of key questions ranging from the causal basis for the alternation of generations and the role of the cytoskeleton in cellshaping processes to the phylogeny of archegoniate plants. Oogenesis is characterised by profound nuclearcytoplasmic interactions accompanied by striking changes in the egg mitochondria and plastids. At fertilization, egg penetration is a physical process and the plastids from the spermatozoids are excluded from the egg. Considerable dissimilarity between the shapes of the biflagellate spermatozoids ofLycopodiumandSelaginellaunderlines their ancient separation. Equally striking differences in spermatozoid architecture argue against any direct phyletic link between heterosporous and homosporous ferns. Taxonomic variations between the spermatozoids of homosporous ferns suggests blepharoplast morphology to be a potentially rich source of new systematic data. Whilst there is general agreement that the multilayered structure is a cytoskeletal alignment system, a proposed shape-generating system situated near the nuclear envelope, which provides the force necessary for spermatozoid morphogensis, has not yet been identified. New fixation procedures have revealed hitherto overlooked filamentous elements associated with the nucleus. Whereas tests for actin were negative, immunoblotting suggests that these contain the intermediate filament protein antigens.
Physiology and biochemistry of pteridophytes
Authors: Raven John A. 
Published: March 2014

SynopsisThe biochemical characteristics of pteridophytes firmly ally them with other Tracheophyta, with Bryophyta and with the class Charophyceae of the algal division Chlorophyta. Pteridophyte sporophytes, like the sporophytes of other terrestrial Tracheophyta, generally have the attributes of homoiohydric plants. All gametophytes are poikilohydric. Many gametophytes, and some sporophytes, are desiccation tolerant.Quantitative comparisons between pteridophyte sporophytes and the sporophytes of other tracheophytes show that there are probably no systematic differences between the efficiency of important processes: examples are the quantum yield of photosynthesis, and the water use efficiency of organic matter accumulation, in the (mainly) C3 pteridophytes relative to other C3 tracheophytes. By contrast, the potential rales of physiological processes, as indicated by the conductance of photosynthetic (C3) carbon assimilation, and of water movement in the xylem, are generally towards the low end of the range for terrestrial tracheophytes. These low conductances restrict the maximum specific growth rate of pteridophyte sporophytes to rates lower than those found in annual angiosperms. Constraints imposed by the pteridophyte life cycle may have limited the capacity of pteridophytes to function in nature as annuals, and thus have reduced the selection pressure for high conductances (e.g. by a more widespread occurrence of vesseles in xylem of pteridophytes).
Action and phylogeny of antheridiogens
Authors: Schraudolf H. 
Published: March 2014

SynopsisEvolution of new forms of organisms must be accompanied by evolution of the informational processes which regulate the development of these new forms. During plant phylogeny, products of metabolism have become phytohormones through the evolution of receptor molecules. Although nothing is known about these receptor molecules, it is suggested that the schizaeaceous ferns are the most primitive group in which a gibberellin-like substance acts as a signal for morphogenesis, and that their antheridiogen pheromones, which stimulate antheridium formation and spore germination, are the ancestors of the gibberellin hormones which influence seed plant development. Chemical and biological evidence for this suggestion is discussed.
Spore filaments in the ant-fern Lecanopteris mirabilis—an alternative viewpoint
Authors: Walker Trevor G. 
Published: March 2014

SynopsisSpores of the ant-fern Lecanopteris mirabilis (C.Chr.) Ching are discharged in groups of 16 spores per sporangium and are held together by long filamentous outgrowths of their surface. It is contended that the filaments are not primarily an adaptation to ant-dispersal, as has been suggested, but maintain genetic variability by promoting intergametophytic mating of the prothallial populations produced as an outcome of the spores being held together in clusters.
Rusts and other fungal parasites as aids to pteridophyte taxonomy
Authors: Bennell Alan P. , Henderson Douglas M. 
Published: March 2014

SynopsisThe fungal parasites of ferns and their allies have been largely neglected, both by pteridologists and mycologists. Greater interest is advocated in the light of recent studies of patterns of host specificity of such fungi on angiosperms, which have provided valuable insights into the systematics of these hosts. Our knowledge of the major groups of fungi reported as parasites of pteridophytes is reviewed, and their potential contribution to host classification and phylogeny discussed. The relationship of the Uredinales (rust fungi) and their fern hosts is examined in detail.
Interaction between bracken and its insect herbivores
Authors: Lawton J. H. , MacGarvin M. 
Published: March 2014

SynopsisBracken in Britain is a host for 27 species of insect herbivores, with a further 11 species that either feed below ground (and are poorly studied), or appear to be only rarely associated with the plant. A typical site in northern England has an average of 15–16 of these species in any one year. Compared with perennial herbaceous angiosperms with similar wide distributions, bracken is not noticeably depauperate in the number of insect species that feed upon it. Bracken in others parts of the world is attacked by a wide variety of insects, with more species present in the geographical areas where bracken is most common.The ‘feeding niches’ of some of these insects are reviewed. Most are very rare relative to the biomass of their host plants, probably because of the impact of natural enemies; the effect of most of the insects upon their host-plant is consequently negligible.Reverse effects, of host-plant upon the insects, are subtle but poorly understood. Experiments to elucidate these effects are briefly outlined.
Studies on the physiology and propagation of the ostrich fern, Matteuccia struthiopteris
Authors: Prange Robert K. 
Published: March 2014

SynopsisThe effect of photosynthetic photon flux density (PPFD), water, temperature and nutrition on frond emergence, vegetative frond production, fertile frond production, vegetative propagation and dormancy is examined. Ostrich fern plants will not break winter dormancy until they have received a minimum amount of cold exposure below a base temperature which is above 5.8°C and may be as high as 20°C. After the plants have received their chilling requirement, vegetative frond emergence does not occur until temperatures at or above ca. 9.3°C are reached. Percent germination and rate of emergence increases up to ca. 24°C. Photosynthetic photon flux density, water availability and mineral nutrition can affect both vegetative and fertile frond production but water availability appears to be the most critical. A mild water stress of −0.15MPa can have significant effects on water status and gas exchange in fronds. Sporophyte plants for field production have been produced vegetatively from detached meristems occurring naturally on the rhizomes, and through fertilization of axenic gametophytes.
Photoresponses in cell cycle regulation
Authors: Wada Masamitsu 
Published: March 2014

SynopsisThe cell cycle of a protonema of Adiantum capillus-veneris L. cultured under continous red light is controlled by two photoreceptors: phytochrome and a blue and near-ultraviolet light-absorbing pigment (Pb−nuv). Irradiation with blue light, which is absorbed by Pb−nuv located in the nuclear region, shortens the duration of the G1 phase, but does not affect other phases. On the other hand, phytochrome has two roles in cell cycle regulation. Irradiation at the beginning of the G1 phase with far-red light, which is absorbed by phytochrome located throughout the entire protonema, lengthens the duration of the G2 phase. Phytochrome also arrests the cell cycle at the G0 phase under continuous red light, and, after red light irradiation, returns to the G0 phase any cell cycle which has already been started by dark incubation, unless the cell cycle has progressed to a ‘point of no return’ which coincides with the beginning of the S phase. Photoregulation of the cell cycle is summarised in Figure 4.
Geography and ecology of Indian clubmosses
Authors: Pandey P. S. 
Published: March 2014

SynopsisObservations are made on the geographical and ecological distribution of the clubmosses (Lycopodiuni) in India, and their habitats and reproductive abilities.The requirements of clubmosses in India for conditions of good illumination plus habitats of low vegetational competition pressure are probably the most important factors in restricting the species to either well lit forest canopies in the tropics or to open, treeless hillsides in the temperate zone. In the former, the epiphytic habit has become important. In the latter, the terrestrial habit has been exploited. Reproduction in the epiphytes is by spores, which establish in mossy epiphytic cushions. Reproduction in the terrestrial species is either by spores which establish in mosses or in areas opened by erosion and landslides, or by bulbils. The latter achieve a useful, local, additional means of reproduction in climates where, because of low temperatures, the rates of growth can be very slow.
Speciation and hybridisation in North American quillworts
Authors: Taylor W. Carl , Luebke Neil T. , Smith Mary B. 
Published: March 2014

SynopsisSpecies of Isoetes in northeastern North America may have evolved through hybridisation and allopolyploidy. Evidence for natural hybridisation was obtained from overlapping distribution patterns, abortive and polymorphic spore formation, chromosome numbers ranging from diploid to decaploid, and additive enzyme electrophoresis profiles. The ease with which hybrids form in culture supports the hypothesis that natural hybrids occur and that hybridisation could be involved in the evolution of new species.
Ecology and geography of hybridisation in British and Irish horsetails
Authors: Page C. N. , Barker Marian A. 
Published: March 2014

SynopsisHybridisation inEquisetumin Britain and Ireland is examined in respect of the exceptional numbers of hybrids present, their geographic and ecological distribution, their formation and subsequent spread.It is concluded that the moist oceanic climate and relative paucity of competing species in the British and Irish floras in post-glacial time have created uniquely favourable conditions for the formation and subsequent success of hybrid horsetails, promoting both the short-term persistence of weaker hybrids, and the extremly long-term persistence of others.The taxonomic inter-relations of parental combinations which have formed ecologically successful hybrids are discussed.
Nucleic acid comparisons as a tool in understanding species interrelationships and phylogeny
Authors: Stein Diana B. 
Published: March 2014

SynopsisStudies comparing nucleic acids of some pteridophytes with others or with angiosperms are briefly reviewed. Amongst the pteridophytes, the fern genus Osmunda has been most thoroughly investigated by DNA sequence comparisons. O. cinnamomea, O. claytoniana, and O. regalis have equally diverged DNA sequences suggesting that evolutionary lines leading to these three species separated at about the same time; taxonomic placements that link any two of the three species closely together are, therefore, inappropriate. DNAs of the hybrid fern, O. × ruggii, were examined by analysis of restriction fragments of chloroplast DNA and by nuclear DNA hybridisation. The results support the previously proposed parentage.
Diversification of early ferns
Authors: Galtier Jean , Scott Andrew C. 
Published: March 2014

SynopsisA review of current knowledge of early fern evolution is presented including new data on age, morphology and anatomy with two diagrams summarising the early diversification of cauline and foliar anatomy and of the reproductive structures. The relationships and even the attribution of some Devonian taxa to the ferns is questioned whilst most of the Carboniferous coenopterids are considered indisputable ferns, some of them being related to modern filicaleans. The discovery, in the Lower Carboniferous of Scotland, of diverse annulate filicalean sporangia suggests an earlier (Tournaisian) radiation of true ferns than was previously assumed.
Population dynamics of woodland Dryopteris in Britain
Authors: Willmot A. 
Published: March 2014

SynopsisFive mixed populations of Dryopteris dilatata and D. filix-mas have been studied in deciduous woods near Derby, England. It has been shown that in selected populations of each species, the plants were significantly clumped. It has also been shown that small plants of each species in all populations tended to grow amongst bryophytes, whilst larger ones grew in a wider range of habitats. All populations of D. dilatata showed an excess of small, sterile plants over larger, fertile ones. All but one of the D. filix-mas populations showed an excess of large, fertile plants over small, sterile ones, while the remaining one showed roughly equal numbers of large, fertile plants and small sterile ones. The population dynamics of two populations of each species have been studied so far over two seasons. This has shown that plants may increase or decrease in size or remain the same size between years. Mortality has been shown to be very size-specific in that smaller plants have a much lower chance of survival. Colonisation by new plants was mostly in bryophytes near established plants. The significance of these observations for the population dynamics of the species is discussed.
Hybridisation in Costa Rican Polystichum
Authors: Barrington David S. 
Published: March 2014

SynopsisPolystichum muricatum hybridises with both P. polyphyllum and P. speciosissimum on the Cerro de la Muerte in Costa Rica. Both hybrids are intermediate between their two parents in most of the assessed characters. True indusia, which are fully developed in P. muricatum, vestigial in P. polyphyllum, and absent in P. speciosissimum, are intermediate in mean development in both hybrids. However, one sorus is likely to have either a fully-developed indusium or a vestigial indusium. False indusia are characteristic of P. speciosissimum, but are vestigial to absent in its hybrid with P. muricatum. False-indusium development appears to behave as a recessive trait in the interaction of P. speciosissimum with P. muricatum.Environmental disturbance has played a major role in the development of hybrids in Costa Rica. Mixed populations of the parent species are more common in disturbed terrain than in pristine areas, and hybrids are found only in disturbed terrain; this suggesting that disturbance promotes hybridisation.
Ecological aspects of distribution and speciation in Old World tropical ferns
Authors: Parris B. S. 
Published: March 2014

SynopsisThe number of fern species in various countries in the Old World tropics is examined and explanations for very rich and very poor fern floras are given. Borneo and New Guinea are the two richest areas, with an estimated 1000 and 2000 species respectively; the difference in number is probably due to the much greater area of land at high altitudes in the latter. Aspects of geographical and ecological speciation in the genusGrammitiswithin New Guinea are discussed, and the means by which such speciation may have been promoted are outlined.
Adaptive strategies of African pteridophytes to extreme environments
Authors: Kornás Jan 
Published: March 2014

SynopsisWater deficiency is the key factor limiting the occurrence of pteridophytes in seasonally dry tropical areas and shaping their adaptive strategies in respect of habitat preferences, life-forms, phenological patterns, and reproductive biology. In Zambia, which is situated in the savanna woodland zone, a total of 146 pteridophyte species occur mainly in special habitats: extrazonal evergreen forest patches and initial successional stages of lithoseres and hydroseres. Life-forms with perennating buds well protected against desiccation (hemicryptophytes and geophytes) dominate, while those with more exposed buds (epiphytes, chamaephytes and phanerophytes) are much less numerous and restricted mainly to the higher-rainfall areas. Selaginella tenerrima represents the life form of a therophyte, unknown in any other pteridophyte genus. Three major seasonal patterns of growth and dormancy may be distinguished: the evergreen type (ca. 40% of species), the poikilohydrous type (ca. 20%) and the deciduous (‘summer-green’) type (ca. 40%). No less than 20% of species are able to survive recurrent bush-fires, and some of them possess the features of advanced pyrophytes. In the driest parts of the savanna zone in Africa, e.g. in the Lake Chad Basin of northeastern Nigeria, seasonal pools are remarkably rich in water ferns, especially of the genus Marsilea which has undergone an intensive adaptive radiation in this environment.
The topography, climate and chemical nature of the mammalian skin surface
Authors: Jenkinson D. McEwan 
Published: March 2014

SynopsisComparative evidence on the topography, climate and chemical nature of the mammalian skin surface ecosystem is reviewed. Potential and established surface defence systems have been identified and their significance and interactions discussed in an attempt to provide a basis for further multidisciplinary study of the protective role of the skin surface, a function which is more extensive than hitherto recognised.
The inhabitants of the mammalian skin surface
Authors: Lloyd D. H. 
Published: March 2014

SynopsisThe wide variety of metazoan and microbial species frequenting the mammalian skin surface is described. The damage which they cause to the superficial barrier mechanisms and the host factors which modify their activity are examined. Predatory and inhibitory reactions between the skin inhabitants are discussed in relation to their ability to inhibit the activities of pathogenic organisms.
Experimental chronic dermatophilosis
Authors: Davis D. , Philpott M. 
Published: March 2014

SynopsisThe effect of artificially induced climatic changes or arthropod bites on the development of experimental dermatophilosis lesions was examined. The lesions were produced following application ofDermatophilus congolensiszoospores to the skin of goats.When zoospores were applied to skin which had been treated with methanol, the resulting lesion healed rapidly. This observation contrasts with the disease under natural conditions, where lesions become chronic. There was no increase in the time for lesions to heal if the goats were sprayed with water to simulate rainfall. However, if a delayed hypersensitivity reaction to chlorodinitrobenzene was induced at the site of zoospore application (to simulate the host's response to an arthropod bite), the resulting lesion was morphologically similar to natural lesions and failed to heal so long as applications of the chemical were repeated.It is suggested that arthropods play a primary role in producing chronic lesions by inducing an immune reaction at the site of infection withD. congolensis.
The avian skin in relation to surface ecology
Authors: Spearman R. I. C. 
Published: March 2014

SynopsisBirds have a layer of plumage over most of the body which provides thermal insulation. The vane-shaped feathers are more efficient than fur in decreasing air movement between the skin microclimate and the ambient environment. Around the feathers is a layer of air, the depth of which for optimum insulation is determined by their angles to the skin surface maintained by the follicular musculature. The mean avian core temperature is 41°C which is higher than in mammals, but skin surface temperature is several degrees lower. Over the exposed skin the microclimate is more variable, but the skin is warmed by the dermal blood vessels and so the feet do not freeze even at sub-zero temperatures. Transpiration occurs through the skin and helps cool the body. Some water vapour is absorbed by the feather keratin, which prevents the feathers from becoming brittle in dry ambient air. Maintenance of the feather vane arrangement requires a more rigid keratin than in hairs. Birds have only one skin gland, the secretion of which contains wax and lipids, but the epidermis is also strongly lipogenic. The sebaceous secretion probably waterproofs the skin, prevents the feathers from becoming too dry, and is anti-microbial. The avian skin surface provides habitats for many commensal micro-organisms and a few bacterial, fungal and arthropod parasites. Pathogenic microorganisms can penetrate the epidermal barrier in wounds or indirectly through the bites of animal parasites. Once in the dermis micro-organisms are combated by immune responses.