bluuebunny/crossref_metadata_2025_split huggingface dataset:
Foliar uptake of peroxyacetyl nitrate (PAN) by herbaceous species varying in susceptibility to this pollutant
Authors: OKANO K. , TOBE K. , FURUKAWA A. 
Published: April 2006

SummaryFoliar uptake of peroxyacetyl nitrate (PAN) was measured by the gas exchange method on nine herbaceous species. Susceptibility to PAN was also examined in the tested species in order to seek correlations with the uptake rate of PAN. PAN was synthesized by the nitration of peracetic acid in n‐tridecane.Uptake rate of PAN by the leaves was kept at a steady level during the 90 min light period, while in the dark it declined rapidly and reached almost zero within 30–45 min. This suggests that adsorption of PAN on to the surface of the leaves is very small and most of it enters the leaf through open stomata.Among the species tested, sunflower showed the highest rate of PAN uptake, followed by radish, tomato and spinach. Maize and soyabean exhibited the lowest rate. A highly significant correlation was observed between the rate ol PAN uptake and stomatal conductance among the tested species.Petunia was most susceptible to PAN, followed by radish and tobacco, but maize and peanut were tolerant. There was no significant correlation between the uptake rate of PAN and susceptibility to it among the species. A higher susceptibility of petunia to PAN was not characterized by a higher rate of pollutant uptake. These results show that the main factor determining the differences between species in susceptibility to PAN is not the amount that gains access to the tissues, but some internal metabolic processes.
The history of the endemic flora of St Helena: late Miocene:‘Trochetiopsis‐like’ pollen from St Helena and the origin ofTrochetiopsis
Authors: CRONK Q. C. B. 
Published: April 2006

SummaryRe‐examination of a fossiliferous sediment from St Helena has revealed the presence in the late Miocene of pollen grains very similar to modernTrochetiopsispollen.Trochetiopsisis found only in St Helena and is assumed to be a palaeoendemic genus. The late Miocene material provides striking confirmation of this view.The two extantTrochetiopsisspecies are compared with other species in the Sterculiaceae: Dombeyeae, using multivariate methods. It is suggested that the two extantTrochetiopsisspecies diverged on St Helena comparatively recently, probably as a result of disruptive selection followed by ecological isolation caused by environmental change at the beginning of the Quaternary.It is also suggested that the ancestor of the extantTrochetiopsisspecies arrived in St Helena by long distance dispersal from African or Madagascar Dombeyeae stock at least 9 million years ago. However, since this time the pollen morphology of theTrochetiopsislineage has changed little. The taxonomic isolation ofTrochetiopsiscan thus be explained partly by evolution on St Helena, but mainly by evolution and extinction in the Dombeyeae elsewhere (reliction).
Oligosaccharides in foliage of Agropyron, Bromus, Dactylis, Festuca, Lolium and Phleum*
Authors: CHATTERTON N. J. , HARRISON P. A. , THORNLEY W. R. , DRAPER E. A. 
Published: April 2006

SUMMARYTemperatures are frequently too cool on rangelands of the western United States for plant growth to occur during much of the time when soil moisture is most readily available. Altering plant metabolism to facilitate growth under cool temperatures holds considerable potential for improving forage production on these ranges. Sucrosyloligosaccharides in representative grasses were characterized. Sucrosyloligosaccharides facilitate the partitioning of carbohydrates outside the chloroplasts during growth at cool temperatures. Eight grasses (Bromus inermis Leys., B. tectorum L., Dactylis glomerata L., Lolium perenne L., Festuca arnndinacea Schreb., Phleum pratense L., and two accessions of ‘Hycrest’ a cross between Agropyron desertorum (Fischer ex. Link) Schultes and A. cristatum L. Gaertner were grown in controlled environments at 10/5 ± 1 °C day/night temperatures. Oligosaccharides extracted from lyophilized leaves were separated using anion exchange chromatography. The relative amounts and kinds of trisaccharides varied among species. All grass contained both raffinose and 1‐ketose. Neoketose was the dominant trisaccharide in Lolium and Festuca but was absent from both Agropyron hybrids. 6‐Kestose was present in all species except L. perenne. Extracts of L. perenne and F. arundinacea contained a trisaccharide containing glucose, fructose and galactose (1:1:1), tentatively given the trivial name ‘loliose’. The oligosaccharide pattern in L. perenne, both Bromus species, D. glomerata and P. pratense suggest the presence of simple polymeric fructan series. However, the series are different from the inulin series in Jerusalem artichoke tubers. In contrast, chromatograms of leaf extracts of F. arundinacea and both Agropyron accessions have complicated profiles which may reflect the presence of both linear and branched polymers in those species. The oligosaccharide profiles determined by anion exchange chromatography may have useful chemotaxonomic applications.
Lodging of winter barley (Hordeum vulgare L.) in relation to its degree of exposure to sulphur dioxide
Authors: BAKER C. K. , FULLWOOD A. E. , COLLS J. J. 
Published: April 2006

SUMMARYPlots in a field crop of winter barley (Hordeum vulgare L. ev.‘Igri’) were exposed to SO2 concentrations of 50, 100 and 200 nl l−1 above ambient. During May 1984 the crop lodged owing to wind and heavy rain, and the severity of lodging was clearly related to the gas concentrations that the plants had experienced.Samples of stems from the experimental plots were tested to find how much force was needed to bend the basal internode. Stems of plants that had experienced SO2 elevations of 100 and 200 nl l−1 were weaker than those from control plots; stems of the plants exposed to 50 nl l−1 were the strongest of all. Investigation of stem anatomy showed that lodging resistance was correlated with stem anatomical attributes, and particularly with the thickness of pairs of contiguous walls of sclerenchyma cells.The differences in stem strength in the SO2 treatments probably arose from the effects of SO2 on plant growth earlier in the season.
Morphogenetic modifications induced by the mycorrhizal fungus Glomus strain E3 in the root system of Allium porrum L
Authors: BERTA G. , FUSCONI A. , TROTTA A. , SCANNERINI S. 
Published: April 2006

SUMMARYMorphometric analysis, modelling and histological techniques were used to study root morphogenesis in nonmycorrhizal and mycorrhizal plants of Allium porrum infected by a Glomus sp., strain E3, during the first 105 days after sowing. They showed that morphogenetic changes were induced by the fungus in the root system of the host.Adventitious roots of mycorrhizal plants became more numerous and shorter than those of controls, as mycorrhizal infection proceeded. Increase in number was fitted by logistic curves in mycorrhizal and control plants; increase in length was fitted in both cases by logistic curves. Mycorrhizal roots became progressively more branched than controls: branching increased linearly with time in mycorrhizas, whereas in the controls it showed an almost constant frequency from day 49 onwards and was fitted by a logistic curve. There was a significant depression of mitotic index demonstrated in the apical meristems of vesicular‐arbuscular mycorrhizas.
Effect of nitrate and ammonium nutrition on the metabolism of the ectomycorrhizal basidiomycete, Hebeloma cylindrosporum Romagn
Authors: SCHEROMM P. , PLASSARD C. , SALSAC L. 
Published: April 2006

SUMMARY Hebeloma cylindrosporum Romagn. grown on a nitrate medium exhibits a growth rate ten times greater than that on an ammonium medium lacking organic acids. Nitrate reduction is accompanied by a low rate of synthesis of organic anions and an elevated excretion of OH− ions into the external medium. The addition of a Krebs cycle organic acid, e.g., malate, citrate, succinate or pyruvate to the ammonium medium induces a strong increase in the growth of the thalli which then equals that obtained on a nitrate medium. The absorption of such precursors to 2‐oxoglutarate could permit the recharging of the Krebs cycle, otherwise inhibited because the assimilation of ammonium causes an important re‐routing of 2‐oxoglutarate. In these thalli, the soluble nitrogen content shows a clear reduction compared with the thalli cultured on ammonium medium lacking organic acids. The poor growth observed on an ammonium medium may be due in part to insufficient CO2 fixation by anaplerotic reactions which, in Hebeloma cylindrosporum Romagn., is carried out by phosphoenolpyruvate carboxykinase.
Helianthemum—Terfezia relations in different growth media
Authors: ROTH‐BEJERANO N. , LIVNE D. , KAGAN‐ZUR V. 
Published: April 2006

SUMMARYThe Israeli desert truffle, Terfezia leonis Tul., failed to enter into association with its plant symbiont, Helianthemum sessiliflorum (Defs.) Pers., when cultivated together on an agar medium consisting of inorganic salts. Addition of activated charcoal to the growth medium brought about rapid and extensive association. Activated charcoal did not enhance fungal growth in the absence of the plant seedling. The stimulating effect of the charcoal is probably related to its adsorption characteristics and may not be due to contact or abrasion between seedling roots and charcoal particles.
Leaf polymorphism in Ranunculus nanus Hook. (Ranunculaceae)
Authors: MENADUE Y. , CROWDEN R. K. 
Published: April 2006

SUMMARYThe Tasmanian endemic species Ranunculus nanus Hook, has variable leaf morphology, the range of which frequently overlaps that of other co‐occurring Ranunculus species. Thus, identification of vegetative material is difficult and often there is taxonomic confusion.Transplant and controlled‐environment experiments have shown that the variations in leaf form are largely plastic growth responses to localised environmental conditions.In general, the morphological variation is greater between populations than within populations, suggesting that selection pressures at different sites have produced a range of genotypically different populations, each with a varying phenotypic response to their particular environment.These findings have taxonomic implications. Because of phenotypic plasticity, the characters, leaf size, leaflet number, hairiness and petiole length, are of little value in diagnostic keys.
Holocene vegetational and environmental history at Loch Lang, South Uist, Western Isles, Scotland
Authors: BENNETT K. D. , FOSSITT J. A. , SHARP M. J. , SWITSUR V. R. 
Published: April 2006

SUMMARYA Holocene record of pollen, charcoal, magnetic susceptibility and sediment chemistry from South Uist, Western Isles, is described and discussed. The vegetation of eastern South Uist included areas of woodland over as much as half of the available landscape during the early postglacial. This woodland was dominated by Betula and Corylus, but Quercus, Ulmus, Alum glutinosa and Fraxinus excelsior were also present. The status of Pinus sylvestris is uncertain. Quercus, Ulmus and A. glutinosa are now extinct as native trees in the Western Isles. During the later half of the Holocene (from about 4000 BP), woodland declined, possibly as a result of the use of hill land as grazing. Blanket peat vegetation, which had begun to spread from about 5500 BP, became the dominant feature of the landscape as the woodland areas decreased. The physical and chemical data from Loch Lang sediments suggest that little erosion of soils took place until about 550 years ago, when there was a marked increase, possibly attributable to increasing grazing pressure.
Photosynthetic acclimation in a terrestrial CAM bromeliad, Bromelia humilis Jacq
Authors: FETENE M. , LEE H. S. J. , LÜTTGE U. 
Published: April 2006

SUMMARYPhotosynthetic acclimation of a terrestrial CAM bromeliad –Bromelia humilis Jacq. to irradiance and nitrogen supply during growth was investigated under controlled conditions. Considerable acclimation to shade was realized through an increase in total chlorophyll, accessory pigments, an increase in chloroplast size and appressed to non‐appressed thylakoid membrane ratio, and a reduction in chlorophyll a/b ratio. A relatively high apparent photon yield in shade was associated with a low light‐compensation point and low dark‐respiration rate.Light saturation of integrated dark CO2 uptake occurred at a relatively low total daily photosynthetic photon flux density (PPFD) and was not influenced by growth PPFD level. Maximum photosynthetic capacity expressed per unit chlorophyll and nitrogen use efficiency were significantly higher in high‐PPFD‐grown plants. In addition, apparent photon yield was only slightly reduced in high‐PPFD‐grown plants with nitrogen, while maximum photosynthetic rate remained the same indicating radiationless dissipation of excess light.Very high levels of recycling of respiratory carbon were observed under nitrogen deficiency in plants grown in both high and low PPFD. The extensive photosynthetic acclimation of B. humilis is discussed in terms of contrasting exposure and limitations of its natural environment.
Transport and assimilation of inorganic carbon byLichina pygmaeaunder emersed and submersed conditions
Authors: RAVEN JOHN A. , JOHNSTON ANDREW M. , HANDLEY LINDA L. , McINROY SHONA G. 
Published: April 2006

SUMMARYPhotosynthetic O2evolution by the upper littoral lichen,Lichina pygmaea(Lightf.) C.Ag., under light‐saturated conditions at 5 °C is saturated by the 2 mol m−3inorganic C found in seawater at pH 8.0. Photosynthesis is not reduced when pH is increased to pH 9.4, and is slightly reduced at pH 10.0, when submersed in seawater with 2 mol m−3inorganic C. The rate of photosynthesis at pH 10 greatly exceeds the rate of uncatalysed conversion of HCO3−. It is concluded that HCO3−is used in photosynthesis. Since extracellular carbonic anhydrase is present, it is possible that CO2enters the photobiont (Calothrix) cells even during HCO3use. pH drift experiments support the notion of HCO3−use. Emersed photosynthesis at 5 °C is more than half‐saturated by 35 Pa (normal atmospheric) CO2; the light‐ and CO2‐saturated emersed photosynthetic rate is not significantly different from the light and inorganic C‐saturated photosynthetic rate when submersed. Inorganic C diffusion from the thallus surface to the photobiont needs, at least under some conditions, carbonic anhydrase activity which permits HCO3−fluxes to supplement CO2movement. The CO2compensation partial pressure at 5 °C is 0.83 Pa, i.e. at the low range of values found for terrestrial cyanobacterial lichens. Dark14C‐inorganic C assimilation when submersed is a small fraction of the dark respiratory rate, consistent with the observed absence of diel CAM‐like variation in intracellular titratable acidity. The high value (−11.5%) of δ13C, the low CO2compensation partial pressure, and the relatively high affinity for inorganic C., are consistent with the operation of an inorganic C concentrating mechanism such as occurs in free‐living cyanobacteria and probably occurs in terrestrial cyanobacterial lichens and in most intertidal algae.
Ammonium assimilation by the nitrate‐utilizing yeast, Candida nitratophila
Authors: HIPKIN C. R. , FLYNN K. J. , MARJOT E. , HAMOUDI Z. S. , CANNONS A. C. 
Published: April 2006

SUMMARYAmmonium‐nitrogen was assimilated rapidly by nitrogen‐replete cultures of the nitrate‐utilizing yeast, Candida nitratophila as long as a suitable source of carbon was available. These cultures contained high activities of an NADPH‐dependent glutamate dehydrogenase with a relatively high affinity for ammonium (Km= 0.27 mM) and high glutamine synthetase activity. Both enzyme activities were apparently derepressed when glutamine‐grown cultures were starved of nitrogen or transferred to nitrate medium. Nitrogen‐deficient cultures also contained NADH‐dependent glutamate synthase activity that was inhibited by azaserine in vitro. Ammonium assimilation in vivo, was inhibited by methionine sulphoximine whilst addition of azaserine resulted in an accumulation of intracellular glutamine and an inhibition of glutamate production. Our results suggest that, in C. nitratophila, there is a potential for ammonium assimilation via both the glutamate dehydrogenase pathway and the glutamine synthetase/glutamate synthase pathway with the latter pathway predominating in nitrogen‐deficient cells.
Suberization and bud formation in tobacco explants
Authors: WILMS F. H. A. , NEELISSEN J. A. M. , KROH M. 
Published: April 2006

SUMMARYWound‐healing and floral bud formation were studied in explants of Nicotiana tabacum L. Examination of sectioned material by conventional light microscopy, fluorescence microscopy and electron microscopy showed that suberin is formed in cells at the cut surface in close contact with the medium, after 4–7 days of culture.The number of cells depositing suberin depended on the agar concentration in the medium. In explants cultured on a medium with low agar concentration (0‐2 % agar), fewer cells showed suberin deposition and more callus cells without suberin were found. Explants cultured on a medium with high agar concentration (5 % agar) formed a complete layer of cells with suberin deposition.In tobacco explants floral determination occurred within 4 days after explantation. The inability of the explants to form floral buds after this period is probably due to barrier formation by suberin.
Effects of interactions between nutrient supply and rust infection of Senecio vulgaris L. on competition with Capsella bursa‐pastoris (L.) Medic.
Authors: PAUL N. D. , AYRES P. G. 
Published: April 2006

SUMMARY Senecio vulgaris L., either healthy or inoculated with rust (Puccinia lagenophorae Cooke), was grown in monoculture or in mixture with Capsella bursa‐pastoris (L.) Medic, under high or low nutrient conditions. At harvests made 7, 9, and 11 weeks after sowing, uninfected S. vulgaris progressively outcompeted C. bursa‐pastoris under nutrient‐rich conditions. Rust infection eliminated the competitive advantage of S. vulgaris over C. bursa‐pastoris under high nutrient conditions. In contrast, under low nutrient conditions C. bursa‐pastoris outcompeted uninfected S. vulgaris and infection with P. lagenophorae resulted in no additional competitive disadvantage to its host. The reduced competitiveness of rusted S. vulgaris under high nutrient conditions was associated with reductions in root growth in mixtures that were greater than those caused by rust in monocultures.The effects of nutrient supply, rust infection and competition on tissue concentrations of nitrogen, phosphorus and potassium were complex and often influenced by interactions between these factors. Increasing the nutrient supply increased nitrogen concentrations ([N]) in S. vulgaris, as did rust infection, but the effects of infection were confined to monocultures. In general [N] in C. bursa‐pastoris showed rather less variation. Phosphorus concentrations ([P]) in C. bursa‐pastoris increased with nutrient supply but under nutrient‐rich conditions were reduced by competition. In S. vulgaris [P] increased with increasing nutrient supply and with infection but in both cases responses were confined to monoculture. Potassium concentration ([K]) in S. vulgaris was increased by rust, especially in mixtures. In C. bursa‐pastoris [K] under high nutrient levels was higher in mixtures than in monoculture.The mechanisms by which the effects of rust on host competitiveness differed under high and low nutrient conditions are considered and the implications for our understanding of the role of rusts in natural vegetation are discussed.
Salt tolerance in the halophytic wild rice, Porteresia coarctata Tateoka
Authors: FLOWERS T. J. , FLOWERS S. A. , HAJIBAGHERI M. A. , YEO A. R. 
Published: April 2006

SUMMARYWhile members of the genus Oryza are very sensitive to salinity, salt concentrations as high as 20% of that of seawater had no adverse effect on the growth of the tropical wild rice (Porteresia coarctata Tateoka) in experiments undertaken in a greenhouse in the UK. P. coarctata plants accumulated sodium and chloride ions in the leaves, but maintained a Na: K ratio as low as 0.7, even after 6 weeks of growth in 25% artificial seawater (ASW) where the Na: K ratio was 34. This ability to maintain a high K: Na ratio in the leaves is in part a consequence of the secretion of ions from the leaves. The ratio of Na: K in the secreted salt (more than 5 for plants growing in 25% ASW) is similar to that measured by X‐ray microanalysis in the vacuoies of hairs found in folds of the adaxial surface of the leaf lamina, suggesting that the secretions emanate from these hairs. The salt secreted by the hairs is an important factor in the salt‐balance of the leaves: the consequences of these findings for the transfer of salt‐tolerance from this species into cultivated rice are discussed.
Kinetics of exchange of ions between artificial precipitation and maple leaf surfaces
Authors: SCHERBATSKOY TIMOTHY , TYREE MELVIN T. 
Published: April 2006

SUMMARYExperiments were conducted to test the hypothesis that ion exchange between precipitation and leaves does not involve rapid transcuticular ion permeation. The kinetics of exchange of ions between artificial precipitation and sugar maple (Acer sacckarum Marsh.) leaf surfaces were evaluated by measuring ion concentrations in individual drops at pH 5.4 or 3.8 after time periods on the leaf ranging from 4 to 128 min. Similar experiments were conducted in which leaves, were immersed in artificial precipitation solutions. These experiments indicated that (1) mechanisms of exchange differed with ion species, (2) solution pH had significant effects on the rate of exchange, and (3) rates of ion diffusion through cuticles were small. Cu2+and Pb2+were rapidly adsorbed to the leaf surface at pH 5.4, but not at pH 3.8. Zn2−concentrations were unchanged by any treatment. K+, Ca2+, and Mg2+were released from the leaf surface, and this effect was greater at pH 3.8 than pH 5.4. Apparent permeability coefficients calculated from the kinetics of these experiments indicated net exchange was dominated by cuticle surface adsorption for Cu2+and Pb2+, and cuticular permeation for K+, Ca2+, and Mg2+. The magnitude of cuticular permeation, however, was small; calculated half‐times for cation efflux from foliage were of the order of 10 days, assuming continuous precipitation. These experiments support the hypothesis that permeation of ions through cuticles during precipitation events may not occur at biologically significant rates.
The cause of peat erosion: a palaeolimnological approach
Authors: STEVENSON A. C. , JONES V. J. , BATTARBEE R. W. 
Published: April 2006

SUMMARYPalaeoecological analyses of two lake sediment cores from the Round Loch of Glenhead, Galloway, S.W. Scotland and Loch Laidon, Ratinoch Moor, Central Scotland have been conducted to elucidate the cause of the observed blanket peat erosion in their catchments. Both simple physical measurements such as percentage loss on ignition and the pollen and diatom record reveal clearly the onset of peat erosion in these catchments. Accurate dating of erosion is still problematical. Nevertheless, some of the competing hypotheses that have been advanced to explain blanket peat erosion are evaluated. Acid deposition cannot be responsible for the peat erosion in these two catchments since the combined use of 211Pb and 14C dating suggests that erosion was initiated between c. AD 1500 and AD 1700, an age well before the effects of atmospheric deposition are documented by the core. However, it remains to he resolved what the effects have been of land‐management changes such as grazing, burning and climatic effects, such as the Little Ice Age.