bluuebunny/crossref_metadata_2025_split huggingface dataset:
Vegetational history of Carbury Bog (Co. Kildare, Ireland) during the last 850 years and a test of the temperature indicator value of 2H/1H measurements of peat samples in relation to historical sources and meteorological data
Authors: van GEEL B. , MIDDELDORP A. A. 
Published: April 2006

SUMMARYA palynological study of contiguous samples of the upper 128 cm of Carbury Bog, Co. Kildare, Ireland, showed details of the fluctuating human impact on the vegetation during the last c. 850 years. During the period of c. 1130–1440 A.D. the landscape around Carbury Bog was still dominated by forest. During the second half of the 15th century there was a considerable reduction of the forested area, reflected in the pollen diagram. The commercial exploitation of the forest during the 17th century resulted in almost complete deforestation. The pollen records for the 18th century vegetation show a rise in the curves of Pinus, Fraxinus and Fagus as a consequence of planting of these trees.Apart from pollen many other palynomorphs (‘Types’, a.o. fungal spores and rhizopods) were recorded. The spectrum of Types appeared to be comparable with the Type spectrum of continental raised bogs. The results of the macrofossil analysis in combination with the indicator values of some Types were used in a detailed reconstruction of the local vegetation succession and the changes in hydrological and trophic conditions. The disappearance of Sphagnum imbricatum during the late medieval period possibly was caused by the increased influx of dust, as a consequence of man's impact on the environment around the bog. The recent importance of S. magellanicum as a peat forming species is possibly the effect of an increased atmospheric deposition of nitrate.Parallel to the analysis of micro‐ and macrofossils a sample series from the same monolith was analysed for the ratio of the stable isotopes 2H and 1H. Theoretically the 2H/1H ratio in cellulose of peat‐forming plants should be indicative for palaeotemperatures, but, apart from a temperature dependent signal, this ratio is also strongly related to specific characteristics in the isotopic behaviour of different peat forming species. The overall fractionation is a complex function of climatic and plant‐physiological parameters.In the present study the results of the 2H/1H measurements were compared with Lamb's palaeoclimatic data derived from historical sources and meteorology. The 2H/1H ratios of Carbury Bog appeared to be negatively correlated with the medieval climatic optimum, the Little Ice Age and the subsequent phase of warming climate. There is an obvious relationship between the 2H/1H ratio and the local succession of peat forming taxa and, as a consequence, with strictly local hydrological and trophic conditions. The present study shows that a climatic signal in the 2H/1H ratio of peat samples is completely dominated by the direct effects of the spectrum of plants. In addition, the variation in the duration of the growing season in different climatic periods may have had a considerable influence on the 2H/1H ratio of the peat‐forming plants.
The accumulation and the effect of heavy metals on the water fern Azolla filiculoides
Authors: SELA MORDECHAI , GARTY JACOB , TEL‐OR ELISHA 
Published: April 2006

SUMMARY Azolla filiculoides Lamarck grown for 3‐7 days in nutrient media containing 8‐15 ppm of different heavy metals was found to contain about 10000 ppm cadmium, 1990 ppm chromium, 9000 ppm copper, 9000 ppm nickel and 6500 ppm zinc. The content of heavy metal in the roots was two‐ to five‐fold higher than in the shoots, and 98% of the heavy metals were bound to the insoluble fraction of the Azolla. The content of heavy metals in dead dried Azolla was 3–7 times higher than in the living plants. Zinc and cadmium were more readily transferred from the roots to the shoots than nickel, copper and chromium. Growth in the presence of the heavy metals resulted in severe leakage of K+, Mg2+ and Na+ ions from the roots with less leakage of Ca2+. The effect of heavy metals on the loss of K+, Na+ and Mg2+ from the shoots was more limited. Nitrogenase activity was almost completely inhibited by cadmium, nickel and zinc, while copper and chromium had less effect. Azolla may prove useful in the detoxification of industrial effluents.
Interactions between ozone and plant cuticles
Authors: KERSTIENS GERHARD , LENDZIAN KLAUS J. 
Published: April 2006

SUMMARYThe flux of ozone to plant surfaces results in its decomposition at the surface and its uptake through the cuticle. Ozone deposition velocity and ozone permeance were determined for a variety of isolated plant cuticles. Ozone deposition velocity was lower than determined with whole plants kept in darkness. It declined continuously during exposure to the gas and showed a‘recovery’effect after an interruption of the fumigation. It increased with the moisture content of the cuticles and decreased when the ozone concentration in the surrounding air was raised. The deposition velocity was much higher than cuticular ozone permeance at equivalent ozone concentrations. Due to the ozone decay in the cuticle, ozone permeance was much lower in thick than in thin cuticles. Even with the most permeable cuticles, ozone uptake under natural conditions is smaller than the flux through open stomata by a factor of at least 10000.
Reproductive traits and accumulation of nitrogen and phosphorus during the development of fruits of Protea compacta R. Br. (Calcifuge) and Protea obtusifolia Buek. ex Meisn. (Calcicole)
Authors: ESLER K. J. , COWLING R. M. , WITKOWSKI E. T. F. , MUSTART P. J. 
Published: April 2006

SUMMARY Protea compacta R. Br. and P. obtusifolia Buek. ex Meisn. are closely related, non‐sprouting serotinous shrubs occurring on the Agulhas Plain, South Africa. The former grows in highly infertile acidic sands and the latter in more fertile alkaline sands. These species were used in a comparative study designed to explore the role of soil type as a selective factor in the evolution of seed size, number and nutrient content. The calcifuge P. compacta had larger seeds with higher N and P content but a lower annual seed production than the calcicole P. obtusifolia. It is proposed that P. compacta exhibits a trade‐off between seed and crop size since it requires larger, more nutritious seeds to establish in the infertile soils. In both species the accumulation of high concentrations of nitrogen and phosphorus in developing infructescenes (cones) was delayed until seed ripening. The significance of this for ecosystem losses of N and P, associated with flower and cone harvesting, are discussed.
Factors controlling the distribution of Tilia cordata Mill at the northern limits of its geographical range
Authors: PIGOTT C. D. 
Published: April 2006

SUMMARYThe ages of trees of Tilia cordata Mill in the Lake District, which is close to the northern limit of the species in Britain, have been estimated by three methods. Estimates for the few old maiden trees are based on extrapolation of the relation between the diameter of the stem at 1‐3 m above the ground and the known age of planted trees. The diameter of young coppice‐stools is shown to be 1.8 times the diameter at 1.3 m above the ground of trees at the same age; this ratio is applied to large circular stools and their age then estimated. The age of stools with exposed roots has been estimated from measurements of the depth of exposure and of the recent rate of erosion. All three methods show that the age of many trees is of the order of 1000 years. There is therefore the possibility that they became established during earlier periods which were warmer than at present, such as that between A.D, 1 150 and 1300.
A succession to ombrotrophic bog in the Gwent Levels, and its demise: a Welsh parallel to the peats of the Somerset Levels
Authors: SMITH A. G. , MORGAN LORRAINE A. 
Published: April 2006

SUMMARYVegetational history in the period 7000–3000 years ago is described at two adjacent locations in the intertidal zone of the Gwent Levels. The evidence, which bears mainly on the succession of peat‐forming communities, is taken from stratigraphy, lithology, pollen, and plant macro‐remains. The sequences are dated by means of calibrated radiocarbon dates.At about 6900 B. P. (before present), Phragmites swamp was established on estuarine clay, probably succeeding salt marsh at the higher of the two sites. By about 6700 B. P., after a pioneer phase involving colonization by willows, alder carr was coming into existence. This persisted as a stable community for some 600 years. During its existence there was a minor marine incursion which had little overall effect. There was then a retrogressive succession to reedswamp, probably brought about by an increase of water level, possibly related to changes of tide levels in the Bristol Channel. Phragmites was succeeded by Cladium mariscus (L.) Pohl. as the water became shallower. This was in turn succeeded by a drier fen‐meadow or fen‐grassland but no recolonization by willows or alder ensued. The lack of renewed carr development may have been due to depletion of mineral nutrients. The reedswamp and fen stages lasted for some 300 years overall. The role of oak remains problematic and requires further investigation. The fen gave way to ombrotrophic bog at about 5750 B. P. Via a‘transition bog’stage . The raised bog, which was the culmination of the succession, was annihilated by renewed deposition of estuarine sediments at about 3400 B. p.The discussion sets the succession on the Gwent Levels in the context of general considerations about postglacial hydroseres and makes a comparison with the history of the Somerset Levels. A Neolithic farming phase is compared with those previously described from the north‐east of Ireland (Pilcher et al., 1971). The Goldcliff phase has three stages of comparable age and duration, but differs in having cereal type pollen in the second stage following the elm decline rather than the first.
Reproductive biology of wild and cultivated carrot (Daucus carota L.)
Authors: KOUL PUSHPA , KOUL A. K. , HAMAL I.A. 
Published: April 2006

SUMMARYThe wild and cultivated forms of Daucus carota L. are andromonoecious and protandrous. The separation of male and female phases is complete at the level of the Mower and the umbel, but the two phases overlap at the level of the full plant, Creating conditions for geitonogamy. At the same time, insect visits between umbels of adjacent plants lead to xenogamy. The extent of overlap between the male and female phases of various umbel orders varies between wild and cultivated carrot. Consequently, there is probably more outbreeding in wild carrot. The chiasma frequency is higher in cultivated carrot. These findings indicate that the meiotic system generates more variability in cultivated carrot whereas the breeding system has the potential to generate greater variability in the wild plant.
Inter‐and intraspecific variation in seed mass in seven species of umbellifer
Authors: HENDRIX STEPHEN D. , SUN I‐FANG 
Published: April 2006

SUMMARYPatterns and causes of inter‐and intraspecific variation in individual seed mass were‐investigated in three prairie and four woodland species of perennial umbellifer. Except for Cryptotaenia canadensis, seeds from woodland species were significantly heavier than those from prairie species. Within species, the magnitude of variation in individual seed mass ranged from three‐to 16‐fold. All the distributions of individual seed masses for the seven species were significantly leptokurtotic and except for Osmorhiza longistylis, all were significantly skewed. Variation between plants was significant in one prairie species (Oxypolis rigidior) and all woodland species. Mean seed mass in a plant was significantly correlated with plant size in three species. Within plant variation in seed mass accounted for 52‐98% of total variation. No one factor consistently affected intraspecific variation in seed mass, although seed number per umbel, timing of umbel production and location of umbel were all important for at least one species. It is postulated that intraspecific variation in seed mass is the rule rather than the exception because of the influence of developmental factors such as seed number, timing of inflorescence production and location of different inflorescences. However, these factors may act in conflicting directions, making it difficult to assign causality to within plant variation in seed mass.
Longitudinal and transverse profiles of K+ and Cl− concentration in ‘low‐’ and ‘high‐salt’ barley roots
Authors: HUANG CHENG X. , Van STEVENINCK REINHARD F.M. 
Published: April 2006

summaryThe concentrations of K+ and Cl− in meristematic and differentiated cells of barley (Hordeum Vulgare. L. ev. California Mariout) roots were determined by means of quantitative X‐ray microanalysis. In roots of seedlings grown in 0.5 mM CaSO4 (‘low‐salt’ roots), the mean cytoplasmic K+ concentration of meristematic cells was 194 mM, while the average vacuolar concentrations at 10, 50 and 100 mm from the root tip were 62,25 and 22 mM, respectively. Such marked differences in vacuolar K+ concentration of differentiated cells were not found in roots of seedlings grown in full strength Johnson solution (‘high‐salt’ roots). Thus the maintenance of K+ at a relatively high concentration in the cytoplasm of meristematic cells of ‘low‐salt’ roots appears to be a priority requirement. The mean Cl− concentration in the cytoplasm of meristematic cells of ‘low‐salt’ roots was 4.6 mM, and the vacuolar Cl− concentration declined towards the root base. These measured concentrations are compatible with previous data, indicating that X‐ray microanalysis of fully‐hydrated samples, used together with colloidal graphite mixtures as standards, provides a reliable means of measuring ion concentrations at the subcellular level.
Effects of nutrients on the distribution of dry mass, nitrogen and phosphorus in seedlings of Protea repens (L.) L. (Proteaceae)
Authors: WITKOWSKI E. T. F. 
Published: April 2006

summaryThe response of seedlings of the sclerophyllous shrub, Protea repens (L.) 1., to increasing concentrations of phosphorus (P), nitrogen (N) and a mixture of all essential nutrients excluding N and P (M) was determined in potted Clovelly soil collected Irotn a lowland fynbos site at pella, south‐western Cape, South Africa. Pot culture resulted in increased soil mineral nitrogen, in particular nitrate, and decreased available (resin‐extractable) phosphorus concentrations compared to field soil. High amounts of N (4–64 g m2 N) and M addition resulted in seedling mortality. Plant dry mass, leaf area and phosphorus and nitrogen contents increased in response to increasing application of N, but no significant differences were found in response to M. Increasing applications of N resulted in reduced plant dry mass, leaf area and phosphorus content. These patterns of mortality and growth are interpreted as a response to an imbalance between nitrogen and phosphorus availability. These results are compared to the response of mature fynbos shrubs to fertilizer additions in the field and the responses of pot‐sclerophyllous plants from other Mediterranean‐type ecosystems.
Carbon partitioning patterns of mycorrhizal versus non‐mycorrhizal plants: real‐time dynamic measurements using 11CO2
Authors: WANG G. M. , COLEMAN D. C. , FRECKMAN D. W. , DYER M. I. , McNAUGHTON S. J. , AGRA M. A. , GOESCHL J. D. 
Published: April 2006

summaryGas exchange and carbon allocation patterns were studied in two populations of Panicum coloratum, an Africa C‐4 grass. The plants were grown in split‐root pots, containing partially sterilized soil, with one side either inoculated (I) or not inoculated (NI) with a vesicular arbuscular (VA) mycorrhizal Fungus, Gigaspora margarita. Net carbon exchange rates (CER) and stomatal conductances were measured with conventional gas exchange apparatus, and carbon assimilation, translocation, and allocation were measured using photosynthetically‐fixed 11CO2.Mycorrhizal infection on one half of the split‐root system caused a 20%, increase in CER. The effect on CER was less in tillers on the opposite side of the plants from the infected half of the roots. The rate at which photosynthates were stored in the leaves was 45% higher. Sink activity (concentration of labelled photosynthates in stem phloem tissue) more than doubled in 1 versus NI plants. CER and stomatal conductances, along with most of the carbon allocation patterns, were nearly identical between the NI (control) high grazing and low grazing ecotypes. However, VA mycorrhizal fungi caused a greater storage of photosynthates in the low grazing ecotype.
Ectomycorrhizal mediation of competition between coniferous tree species
Authors: PERRY D. A. , MARGOLIS H. , CHOQUETTE C. , MOLINA R. , TRAPPE J. M. 
Published: April 2006

summaryTo test the effect of ectomycorrhizal fungi (EMF) on interactions between host plants, Pseudotsuga menziesii (Mirb.) Franco and Pinus ponderosa Dougl. ex. Laws., seedlings were grown in replacement series in pasteurized soil with (a) no EMF added, (A) two EMF species added ‐ Rhizopogon vinicolor Smith (specific to Douglas‐fir) and R. ochraceorubens Smith (specific to pine), and (c) tour EMF species added ‐ the two Rhizopogon species plus two host generalists, Laccaria laccata (Scop, ex Fr.) Bk. & Br, and Hebeloma crustuliniforme (Bull.) Quel. A replacement series in unpasteurized forest soil also was included. Seedlings without added EMF were colonized by the greenhouse contaminant, Thelephora terrestris. Without added EMF (but with T. terrestris), the tree species mutually inhibited one another, producing Relative Yield Totals significantly < 1; with EMF added, mutual inhibition disappeared. With four EMF species added, Pseudotsuga menziesii seedlings were significantly larger in mixture than in monoculture, with no corresponding decrease in the size of Pinus ponderoso seedlings; this was due solely to seedlings with L. laccata, which apparently enhanced nitrogen (N) and phosphorus (P) uptake by Pseudotsuga menziesii at the expense of luxury consumption by Pinus ponderosa. Graphical analysis suggested that better growth of Pseudotosuga menziesii in mixture with EMF added was related to improved P nitrogen. Both N and P nutrition of Pinus ponderosa was better in mixture with two than no EMF species added; there was no clear nutrient effect with four EMF species added. Results indicate that EMF can reduce competition between plant species and perhaps increase overall community P uptake. However, patterns were specific to both EMF and tree species and were quite different in unpasteurized soils. Hence generalizations about the effects of EMF on plant‐plant interactions must be made cautiously.
Ultrastructural evidence for the identity of some multinucleate rhizoctonias
Authors: WILLIAMS P. G. , THILO E. 
Published: April 2006

summaryThe ultrastructure of the pore cap in ten multinucleate rhizoctonias, endophytes of non‐orchids and of Microtis (Orchidaceae), was compared with that in isolates of four Sebacina species. The pore cap in all the rhizoctonias was an imperforate, disc‐like structure, Slightly smaller in diameter than the flange forming the septal pore canal. The cap was formed by two Bat lamellae continuous with, but more electron‐dense than, the membranes of the endoplasmic reticulum. The lamellae enclosed a lumen containing a deposit of electron‐dense material. The pore cap in the rhizoctonias was indistinguishable from that in an isolate of Sebacina vermifera Oberwinkler. In contrast, the pore caps in isolates of S. calcea (Pers.: Fr.) Bres., S. umbrina Rogers and S. grisea (Pets.: Fr.) Bres., which were also imperforate and contained a band of electron dense material, were strongly dome‐shaped and extended from one side of the flange to the other.
Electrophoretic variation in a population of the lichen Peltigera rufescens (Weis.) Mudd
Authors: BROWN D. , CURETON‐BROWN M. M. , KERSHAW K. A. 
Published: April 2006

summaryIsoelectric focusing was used to investigate the distribution of enzymes exhibiting phosphoglucose isomerase, phosphoglucose mutase, malate dehydrogenase, esterase, hexokinase, glucose‐6‐phosphate dehydrogenase, peroxidase and fructose‐1,6‐bisphosphatase activities in a central Ontario population of the lichen Peltigera rufescens (Weis) Mudd. Samples of thalli were collected in order to estimate enzymatic variation in thalli collected within a site (separated by distances of 1–10 m) and between sites (separated by 5–15 km). A total of 85 different enzyme bands were identified in the 27 samples analysed. The results indicated that, at some locations, within site variation was as large as between site variation. The importance of this variation in the design of physiological studies of lichens is discussed.
Investigation of genetic transfer between strains of the basidiomycete, Stereum hirsutum, using molecular and morphological criteria
Authors: BEECHING JOHN R. , AINSWIRTH A. MARTYN , BROXHOLME S. JOHN , PRYKE JANET A. , RAYNER ALAN D. M. 
Published: April 2006

SummaryPairings between strains of Stereum hirsutum (Willd. ex Fr.) S. F. Gray pp 2% malt agar were analysed using changes in mycelial morphology and non‐self recognition properties as evidence of genetic transfer between the participants. In some combinations the morphological evidence suggested the‐ uniform emergence of a heterokaryon following mating and reciprocal nuclear migration between two compatible homokaryons. In other combinations there was evidence of strongly selective invasion by one of two nuclear types from a heterokaryon into a homokaryon, and in a third type of pairing there was evidence for acquisition by a homokaryon of a second mating type but not an entire nuclear genome.Combinations representing each of these three apparent classes of genetic transfer were selected, and mycelia grown from single hyphal tips and/or basidiospores taken either from pure cultures of the progenitor strains or from subcultures from interacting colonies. The DNA from each of these mycelia was extracted and analysed using restriction fragment length polymorphisms to detect genomic differences between strains. The results were consistent with the interpretation of events based on morphological criteria. The combination of morphological and molecular approaches holds considerable potential for rapid, yet precise investigation of genetic exchange between fungal strains isolated from natural populations which have not been the subject of extensive genetic analysis by classical means.
Ericoid mycorrhizal fungi in the Myxotrichaceae and Gymnoascaceae
Authors: DALPÉ Y. 
Published: April 2006

SummaryTen species of Byssoascus, Myxotrichum and Pseudogymtioascus (Myxotrichaceae) and (Gymnascella (Gymnoascaceae) were tested for their ability to form ericoid mycorrhizas with axenically grown Vaccinium angmtifolium seedlings. Positive results were obtained with Myxotriclium setasmn and Gymnascella dankalienst's, both of which form Oidiodendron anamorphs and with PseudogypmoOSCUS roseus, a species with a Geomyces anamorph.