bluuebunny/crossref_metadata_2025_split huggingface dataset:
The sensitivity of pollen from various coniferous and broad–leaved trees to combinations of acidity and trace metals
Authors: COX R. M. 
Published: April 2006

SUMMARYThe effects of acidic and trace element components of polluted rain on pollen germination and tube growth in vitro are described. The sensitivity of pollen to pH in vitro was related to the species' position in canopy and was different for conifers and broad‐leaved trees. Most pollen assayed revealed significant inhibition of germination and germ tube growth in response to pHs currently observed in rain samples in eastern Canada. Acer saccharum Marsh and Betula alleghaniensis Britt. pollen in vitro showed a high sensitivity to pH in combination with copper. The pollen of Populus tremuloides L, was shown to be highly sensitive to pH, and a synergism between pH and copper on pollen function in this species was also demonstrated. This was in contrast to the general antagonistic interaction of pH and copper noted in the other species tested in which copper by it self either did not affect pollen function or was stimulatory. Zinc has little or no effect, whereas lead at the concentrations used significantly inhibited both germination of Pinus strobus L. pollen at pH 5.6–3.6 and tube growth of both P. strobus and Pinus resinosa Ait. The increase in pollen mortality in response to air pollution at the time of pollination raises certain implications for reproduction and breeding. These implications are also discussed in the light of the significant genetic overlap between pollen and sporophytes of higher plants.
Absorption of atmospheric NO2 by several herbaceous species: estimation by the 15N dilution method
Authors: OKANO K. , MACHIDA T. , TOTSUKA T. 
Published: April 2006

SUMMARYAbsorption of nitrogen dioxide (NO2,) by eight herbaceous species was determined by the 15N dilution method. The plants were continuously exposed to NO2, at 0.5 μll−1 for 2 weeks. Susceptibility to NO2, was simultaneously examined in the tested species to see if this was correlated with the rate of absorption.The total amount of NO2‐nitrogen absorbed by a plant during the 2‐week exposure period primarily depended on the size of the plant. Among the tested species, sunflower showed the highest rate of NO2, absorption per unit leaf area, reaching as much as 0.55 mg N dm −2 d−1, which was about four times greater than that for sorghum which had the lowest rate. A highly significant correlation was observed between the rate of absorption and the stomatal conductance among the species. A proportion of the NO2‐nitrogen accumulated in the plant might be absorbed via the air‐soil‐root route.Sunflower and radish which had higher rates of NO2 absorption than the other species were more susceptible to NO2. On the contrary, sorghum and maize which showed a lower rate of NO2, absorption were tolerant. Consequently, the higher susceptibility to NO2 of radish and sunflower is considered to be directly related to their superior ability to absorb NO2.
Genetic variation for tolerance to copper and zinc within and among populations of the moss, Funaria hygrometrica Hedw.
Authors: SHAW JONATHAN 
Published: April 2006

SUMMARYTen individuals from each of lour populations of the moss, Funaria hygrometrica Hedw., were grown on two copper and two zinc treatments and a control in order to assess tolerance to these metals. Tolerances of two life‐history stages (protonemal growth and stem production) showed significant variation among populations, and among individuals within all populations. Heritabilities for tolerance were high within three populations, but were close to zero within a population that originated on a copper mine. Phenotypic correlations among growth responses to the five experimental treatments were similar in the four populations, but this reflected a greater similarity among the environmental correlations than among the genotypic correlations. There was evidence of positive genetic correlations between growth on control medium and growth on media enriched with copper or zinc. This is in contrast to data from flowering plants and fungi, and raises the question of why tolerant individuals are restricted to contaminated sites in nature.
Vegetational history and land use: a radiocarbon‐dated pollen diagram from Machrie Moor, Arran, Scotland
Authors: ROBINSON DAVID E. , DICKSON JAMES H. 
Published: April 2006

SUMMARYPollen, plant macrofossil and charcoal analyses are presented from a radiocarbon‐dated sequence of peat deposits from Machrie Moor, Arran. The deposits began forming at the close of the late glacial and the sequence continued unbroken into recent times. During this period there was a transition at the site from rich to poor fen and finally to blanket mire communities. The major deciduous forest tree species were late in migrating to the island, probably as a consequence of the sea acting as a harrier to fruit dispersal. The development of the local terrestrial vegetation during the Flandrian period was also heavily influenced by human activity. There is evidence for mesolithic disturbances as early as 8500 B.P. and these almost certainly played a role in depressing tree pollen values. The first cereal pollen grain (ef. Hordeum) was found at a level dated to an estimated 5375 B.P. Later, agriculture was apparently of such an intensity that there were periods during the late Neolithic and at the transition between the Bronze and Iron Ages when it could no longer he sustained with the resources available. I he latter period coincided with the onset of blanket peat formation. A similar episode of reduced agricultural activity is evident in the Dark Ages. It was followed by a clear resurgence in Viking and early medieval times which apparently coincided with the improvement of the climate during the so‐called ‘little optimum’
Holocene pollen stratigraphy of central East Anglia, England, and comparison of pollen zones across the British Isles
Authors: BENNETT K. D. 
Published: April 2006

SUMMARYTwo new Holocene pollen diagrams are presented from central East Anglia. Using these sites and others from the same area, regional pollen assemblage‐zones for the area are formally defined. The regional pollen assemblage‐zones are then combined with zones from other well‐dated sequences in the British Isles to produce time/space diagrams for vegetation history along three transects across the islands. It is shown that pollen assemblage‐zones have only a limited extent in time and space. Forest vegetation has varied almost continually in time and space throughout the Holocene and over the whole of the British Isles.
Fructan biosynthesis in excised leaves of Lolium temulentum L.
Authors: CAIRNS A. J. , POLLOCK C. J. 
Published: April 2006

SUMMARYFructan oligosaccharides with degree of polymerization of 3–12 extracted from leaves of Lolium temulemtum L. were analyzed by normal‐phase thin‐layer chromatography. The pattern of oligosaccharides was more complex than that observed in tubers of Helianthus tuberosus L. and stem internodes of Hordeum vulgare L., indicating that fructans of multiple linkage types were present in this tissue.On the basis of co‐chromatography with known standards and constituent hexose analysis, two trisaccharides, neokestose (6‐G fructosyl sucrose) and isokestose (1‐F fructosyl sucrose) were found to accumulate to high concentrations. A third trisaccharide, thought to be kestose (6‐F fructosyl sucrose) was present at much lower tissue concentrations. An abundant tetrasaccharide with a chromatographic mobility similar to that of nystose (1‐F difructosyl sucrose) also accumulated.When carbohydrate‐depleted leaves were excised and continuously illuminated, total water‐soluble carbohydrate accumulation was linear with respect to time at a rate of 1–8 mg g‐1 fresh mass over a 30 h period. In the first 6h sucrose accumulated to lOmgg1, at which time fructan biosynthesis was detected. Isokestose appeared first, followed by neokestose and subsequently kestose and longer oligo‐ and polyfructosides. Changes in the concentrations of these compounds, and their radioactivity following feeding of 14CO2, was consistent with precursor‐product relationships between sucrose and trisaccharides, and between trisaccharides and oligo‐ and polyfructans.
Enzymology of ammonium assimilation in three green flagellates
Authors: AHMAD IFTIKHAR , HELLEBUST JOHAN A. 
Published: April 2006

SUMMARYThe relationship between assimilation of nitrogen and animating activities of glutamine synthetase (GS), NADH‐glutamate dehydrogenase (GDH) and NADPH‐GDH in ammonium‐grown Chlamydomonas pulsatilla Wollen‐weber and ammonium‐ and nitrate‐grown Brachiomonas submarina Bohlin and Tetraselmis succica (Kylin) Butcher was investigated. The three flagellates show minor changes (15–60%) in enzyme activities when ammonium is replaced by nitrate as the nitrogen source or the concentration of nitrogen is lowered from 2 to 0·2 mM. The activities of NADH‐GDH and NADPH‐GDH in the three flagellates do not appear to be high enough to make a significant contribution to ammonium assimilation in the presence of a highly active GS. Fast protein liquid chromatography (FPLC) of GS revealed the presence of two distinct molecular forms, designated as GS1 and GS2, in C. pulsatilla and T. suecica, whereas only a single GS peak designated as GS2 was detected in B. submarina. Both GS1 and GS2 are stabilized by sorbitol and glycinebetaine in media employed for enzyme extraction and FPLC fractionation. The presence of thiol reagents is essential for GS2 stability, but inhibits GS1 activity. GS2 is by far the more active of the two isoenzymes in C. pulsatilla and T. suecica. This isoenzyme, therefore, appears to be the major port of entry of ammonium in all three flagellates.
Ectomycorrhizal rain‐forest legumes and soil phosphorus in Korup National Park, Cameroon
Authors: NEWBERY D. M. , ALEXANDER I. J. , THOMAS D. W. , GARTLAN J. S. 
Published: April 2006

SUMMARYThe mycorrhizal status of a group of caesalpinioid legumes in lowland rain‐forest in Korup National Park, SW Cameroon, was examined. Species in ten genera, Anthonotha, Aphanocalyx, Berlinia, Didelotia, Gilbertiodendron, Julbernardia, Microberlinia, Monopetalanthus, Tetraberlinia(tribe Amherstieae) and Afzelia(tribe Detarieae) were ectomycorrhizal. These species were not uniformly distributed in the forest, and three large emergent species Microberlinia bisulcata A. Chev., Tetraberlinia bifoliolata(Harms) Hauman, and T. moreliana Aubr. in particular appear to form groves c. 600 m across. This type of distribution may be related to the ectomycorrhizal habit.A previous large scale enumeration and soil survey on four 5 km transects of plots in the forest, carried out during the wet season, had revealed an association between these ectomycorrhizal legumes and low concentrations ( 5 μg g‐1) of extractable phosphorus in the mineral soil. In the current study part of one of the original transects in a low phosphorus area of the forest, where ectomycorrhizal trees comprise 29 % of the basal area, was resampled at the subplot level during the dry season. Whereas in the wet season soil phosphorus had been lower (2·8 μg g‐1) within the ectomycorrhizal groves than without (3·8 μg g‐1), in the dry season the situation was reversed and the overall concentrations were higher (12·3 and 7·9 μg g‐1 respectively). Ordination analysis re‐affirmed the association of the three Microberlina/Tetraberlinia species with relatively low concentrations of extractable phosphorus in the wet season but relatively high ones in the dry season. The groves are characterized by high inputs of leaf litter in the dry season, extensive colonization of surface organic matter by ectomycorrhizas and hyphal strands, and high carbon: extractable inorganic phosphorus ratios in the mineral soil in the wet season. These features are discussed in relation to the presumed ability of ectomycorrhizas to utilize organic phosphorus.
Growth response to and morphology of mycorrhizas of Thysanotus (Anthericaceae Monocotyledonae)
Authors: McGee P. A. 
Published: April 2006

SUMMARYSeedlings of Thysanotus were inoculated in pot culture with fungi that form vesicular‐arbuscular or ectomycorrhizas on other hosts. Mycorrhizas formed by both fungi were similar in morphology to each other and to mycorrhizas observed in field‐collected plants. Hyphae of mycorrhizal fungi penetrated between epidermal cells and ramified between the cortex and epidermis. Spread of mycorrhizas in pot‐cultured T. tenellus Endl. occurred only in the presence of a companion plant. In soils with low levels of nutrients, mycorrhizal plants of T. tenellus grew faster than non‐mycorrhizal plants, with roots of infected plants growing relatively faster than shoots.
The effect of shoot spacing on the growth and branch development of the moss Rhytidiadelphus triquetrus
Authors: BATES J. W. 
Published: April 2006

SUMMARYThe effects of a range of shoot spacings (5, 10, 20, 50 mm) on the growth and development of the moss Rhytidiadelphus triquetrus (Hedw.) Warnst. within artificial colonies were studied under conditions of intermittent moisture supply. Growth of the main axis was promoted by decreased spacings of the shoots, probably due to increased resistance to evaporation and prolongation of the period of metabolic activity. Etiolation of shoots occurred at close spacings but no self‐thinning was observed. The growth of determinate lateral branches was also stimulated by decreasing shoot spacings but the closest plantings led to inhibited branch growth for shoots in the centres of the colonies. Marginal shoots generally showed less growth of the main axis and branches than central shoots except at the 5 mm spacing.The numbers of offshoots of indeterminate growth produced at each shoot spacing were low and only a slight trend of increasing offshoot production with increasing spacing was observed over the range 5–20 mm.Overall growth of shoots was optimal at or near to the closest spacing. Calculated productivity was, therefore, greatest for the densest colonies (1000 shoots dm a) indicating that the advantage of reduced water loss, conferred by dense packing of shoots, greatly outweighs the disadvantage of reduced irradiance.
Modelling of the root cap of Zea mays L in relation to temperature
Authors: CLOWES F. A. L. , WADEKAR R. 
Published: April 2006

SUMMARYRates of mitosis in each of the four tiers of the cap meristem of primary roots of Zea mays L. were measured at uniform root length by a stathmokinetic method and compared with rates for other regions of the apices in seedlings growing at between 15 and 35 °C. The highest elemental rate of cap cell production in the proximal tier and in the cap meristem as a whole occurs at 26 °C and the proportion of cells supplied by the proximal tier rises from 48%, at 15 °C to 90% at 35 °C. The number of cells in the whole cap and in its meristem decreases with increasing temperature. This is due to the general reduction in the width of root apices with age and growth in length being faster at the higher temperatures. The slimming of the apex is effected by a decline in the proportion of divisions that are longitudinal to the files of cells at the quiescent centre. This is enhanced by a slight but continuous increase in the rate of mitosis in the quiescent centre the higher the temperature (in contrast with the rest of the root whose maximal rate is at 2S °C). The decline results in an increase in the elemental rate for longitudinal divisions in the cap initials from 0.02 to 0.17 cells per cell per day between 15 and 35 °C and a consequent change in the cell pattern in the cap.
Different strategies of drought resistance in three Mediterranean sclerophyllous trees growing in the same environmental conditions
Authors: LO GULLO M. A. , SALLEO S. 
Published: April 2006

SUMMARYMeasurements have been made of leaf conductance to water vapour, relative water content and water potential inOlea oleasterHoffmgg et Link,Ceratonia siliquaL. andLaurus nobilisL., three evergreen sclerophyllous trees growing in Sicily at sea level. Measurements were made hourly in May and September 1986. Although all the three species are regarded as components of a homogeneous group (sclerophylls) and they all showed a high degree of sclerophylly, the strategies they adopted to withstand drought were completely different.Olea oleasterbehaved as a ‘drought‐tolerating’ species. Drought was ‘avoided’ byCeratonia siliquaby a ‘water‐spending’ strategy and byLaurus nobilisby a ‘water‐saving’ strategy combined with the capability of recovering even minimal water losses by dropping leaf water potential drastically. Such differences in drought resistance are discussed in terms of differences in the bulk elastic modulus of leaf cells and wood anatomy.
A comparative study of Geum rivale L. and G. urbanum L. to determine those factors controlling their altitudinal distribution II. Photosynthesis and respiration
Authors: GRAVES J. D. , TAYLOR K. 
Published: April 2006

SUMMARY Geum urbanum and G. rivale are a sympatric interfertile pair of species with contrasting distributions. Geum rivale occurs at higher altitudes and more northerly latitudes than G. urbanum. As part of a study to determine the factors responsible for this difference in distribution, a comparison of the carbon economy of the two species was made. The light and temperature dependence of photosynthesis was assessed for plants of both species grown in contrasting light and temperature regimes. Acclimation to the prevailing environmental conditions was more pronounced in G. urbanum. Amongst populations of the two species originating from different altitudes the temperature optimum for photosynthesis was similar. When grown at 25/16 °C, higher rates of respiration were measured he roots of G. rivale at all temperatures, when pretreated at 8/5 °C there was a smaller increase in the rate of respiration in the roots of G. rivale. It is proposed that these differences in root respiration account for observed higher root growth rates at low temperatures in G. rivale. It is concluded that whilst carbon assimilation is not a critical factor determining the upper altitudinal limit of G. urbanum, the pattern of carbon utilization may be important. The greater phenotypic plasticity observed in G. urbanum, may be of value for survival in the herb layer of deciduous woodland where it is most commonly found.
Mycorrhizal growth responses: interactions between photon irradiance and phosphorus nutrition
Authors: SON C. L. , SMITH S. E. 
Published: April 2006

SUMMARYThe effects of photon irradiance, phosphorus (P) supply and mycorrhizal infection [Glomus mosseae (Nicol. and Gerd) Gerdemann and Trappe] on growth and P uptake by Allium cepa L. were measured. Two experiments were carried out, one in a naturally‐lit glasshouse and the other in a growth cabinet. Shade cloth was used to provide ‘high’ irradiance (600 and 550 μmol m−2s−1 in glasshouse and growth cabinet respectively) and ‘low’ irradiance (250 μmol m−2s−1). Growth at high irradiance was associated with increases in total dry weight, root: shoot dry weight ratio and total root length and with decreases in shoot fresh weight: dry weight ratio. Mycorrhizal growth responses were lower at low irradiance and depressions were observed at high P supply and high irradiance, as well as at low irradiance. Mycorrhizal plants generally had higher shoot fresh weight: dry weight ratios than those of equivalent non‐mycorrhizal plants. Mycorrhizal infection was lower in the presence of additional P in both experiments. In the glasshouse there was an interaction between low irradiance and high P, leading to very low values of fractional infection. This effect was not apparent in the growth cabinet. At high irradiance mycorrhizal plants had higher inflows than those of equivalent non‐mycorrhizal plants at all levels of P, regardless of the growth response. Low irradiance had little effect on inflow into non‐mycorrhizal plants, but depressed inflow into mycorrhizal plants. This reduction in inflow can be attributed in part to lower levels of infection, but an effect on P uptake by hyphae or on transport between the symbionts is also likely.
Ultrastructural localization of ATPase activity in the Pinus sylvestris/Laccaria laccata ectomycorrhizal association
Authors: LEI J. , DEXHEIMER J. 
Published: April 2006

SUMMARYUltrastructural localization of the plasmalemmal ATPase activity has been studied in basidiomycete ectomycorrhizas synthesized between Pinus sylvestris L, and Laccaria laccata Scop, ex Fries.The cortical cells showed a strong plasmalemma‐bound ATPase activity. The activity was also associated with the fungal plasmalemma in the external hyphae, sheath and Hartig net. The plasmalemmal ATPase activity disappeared in degenerating cortical cells. In the Hartig net, only the parts of the plasmalemma adjacent to other hyphae were active. When the Hartig net hyphae adjoined on one side a living cortical cell and, on the other side, a dead cortical cell, the ATPase activity of fungus plasmalemma was asymmetrically distributed. These observations are discussed in relation to the possible function of ATPase in ectomycorrhizas.
Reflectance of blue, green, red and near infrared radiation from wetland vegetation used in a model discriminating live and dead above ground biomass
Authors: LORENZEN BENT , JENSEN ARNE 
Published: April 2006

SUMMARYField measurements of canopy reflectance of wetland vegetation in the blue (450 ran), green (548 nm), red (655 nm) and NIR (805 nm) wavebands were correlated with plant biomass variables. Negative relationships, asymptotic in nature, were observed between visible wavebands, canopy reflectance and total live biomass as well as green biomass, with correlation coefficients r between −0·52 and −0·93. Curvilinear relations were observed between NIR canopy reflectance and total live biomass as well as green biomass, with r between 0·39 and 0·88. Different normalization indices (NIR blue−1, NIR red−1, VI, PI and NIRlbio) were tested and positive relations between these indices and total live biomass and green biomass were observed, with r between 0·69 and 0·96. Inverse relations of an asymptotic nature were observed between dead biomass as a percentage of total biomass and of green biomass, with r between 0·90 and 0·91. A model discriminating live and dead above‐ground biomass was developed to improve correlations between canopy reflectance and biomass variables. The model nearly doubled the correlation coefficient between reflectance and green biomass for a canopy containing large amounts of interfering dead biomass, but did not change this correlation for a canopy containing small amounts of dead biomass.
Effects of auxin and boron on nucleic acid metabolism and cell division during adventitious root regeneration
Authors: ALI A. H. N. , JARVIS B. C. 
Published: April 2006

SUMMARYTreatment with indolebutyric acid (IBA) enhances root regeneration in stem cuttings of mung bean (Phaseolus aureus Roxb.) provided cuttings are supplied with borate. Treatment also increases the content of RNA in hypocotyls although RNA synthesis is inhibited by such treatment. Cell division in phloem parenchyma cells is evident 24 h after cuttings are prepared, irrespective of treatment with, or without, IBA. Following the preparation of cuttings, synthesis of RNA increases in the hypocotyl prior to the earliest mitoses in these cells and continues to increase in the presence of supplied borate. Autoradiographic investigation shows that, in the absence of supplied borate, synthesis of RNA within the nucleus decreases markedly in IBA‐treated cuttings 40 h after cuttings are made. Moreover, RNA synthesis is totally inhibited 24 h later whereas cell division does not cease until 60 h. Witholding supply of boron For up to 72 h after cuttings are made has no effect on DNA synthesis.