bluuebunny/crossref_metadata_2025_split huggingface dataset:
THE IDENTITY AND ORIGINS OF PICEA ABIES (L.) KARSTEN FROM THE CHELFORD INTERSTADIAL (LATE PLEISTOCENE) OF ENGLAND
Authors: HOLYOAK D. T. 
Published: May 2006

SummaryPollen and macrofossils of Picea from the Chelford Interstadial (Early Devensian) of England are described. All leaves and cones were referred to P. abies (L.) Karsten, and the unimodal size distribution of pollen also suggests only this species was present. The fossil leaves are mostly similar to those of P. abies subspecies obovata (Ledeb.) Hultén, but the cones are intermediate between subspecies obovata and abies. Occurrence of forms approaching the north‐east European subspecies obovata does not necessarily imply immigration of Picea into England from the east or north‐east during the Early Devensian because similar intermediate forms also occur in the Alps.
TWO POSTGLACIAL POLLEN PROFILES FROM THE UPLANDS OF SNOWDONIA, GWYNEDD, NORTH WALES
Authors: INCE J. 
Published: May 2006

SummaryPollen diagrams are presented from two upland cwms in Gwynedd, North Wales. The profiles provide a detailed record of vegetational and environmental changes in the uplands of Snowdonia during the early and later postglacial (Flandrian) periods. Radiocarbon dates indicate that at both sites organic sedimentation commenced at around 10000 B.P., and support geomorphological evidence of cwm glaciation during the Loch Lomond (Younger Dryas) Stadial. Pollen analysis of basal minerogenic sediments, deposited sometime before 10000 B.P., reveal the colonization of the recently deglaciated uplands by grassland communities rich in Rumex and other open habitat taxa. Early herbaceous communities were invaded by Juniperus and Betula, and then replaced by Betula—Corylus woodland, and later by forests of birch, pine, oak, elm and alder. Altitudinal factors ensured the survival of many open habitat taxa in the uplands throughout the Flandrian period. Deteriorating environmental conditions and human interference during mid‐ to late‐Flandrian times resulted in the gradual decline of forests in the uplands and the development of open grassland and heathland communities characteristic of Snowdonia today.
LOCALIZATION OF POLYPHENOLOXIDASES DURING THE ESTABLISHMENT OF OPHRYS LUTEA ENDOMYCORRHIZAS
Authors: PAIS M. SALOMÉ S. , BARROSO J. 
Published: May 2006

SUMMARYThe cytochemical location of polyphenoloxidases in Ophrys lutea during invasion by Rhizoctonia repens suggests that the fungus is able to synthesize or activate polyphenoloxidases.The dense product of its reaction is observable in the fungal cytoplasm during the first stages of fungal invasion. Later on, it is located in small quantities in the hyphal cytoplasm and great amounts are seen at the interface.Our results suggest that the enzymes, synthesized in the fungal cytoplasm, are translocated across the plasmalemma and the cell wall of the fungus. These enzymes are accumulated in the interface close to the host plasmalemma, where they are likely to promote the oxidation of phenols from the host.
ULTRASTRUCTURE OF INTRAHYPHAL HYPHAE OF GLOMUS FASCICULA TUM (THAXTER) GERDEMANN AND TRAPPE IN ROOTS OF WHITE CLOVER (TRIFOLIUM REPENS L.)
Authors: LIM L. L. , FINERAN B. A. , COLE A. L. J. 
Published: May 2006

SUMMARYIntrahyphal hyphae are reported in roots of white clover (Trifolium repens) infected with Glomus fasciculatum, this being the first unequivocal description of the phenomenon in coarse vesicular–arbuscular mycorrhizal associations. Various configurations of the hyphae are illustrated by transmission electron micrographs. The simplest situation is where the intercellular hypha contains a single intrahyphal hypha that may be either thin‐ or thick‐walled and which may also show different degrees of association with the enclosing hypha, the relationship often varying along the length of the two hyphae. The wall of the surrounding hypha may also be either thin‐or thick‐walled. Degenerate remnants of protoplasm frequently persist between the walls of the two hyphae. Compound intrahyphal hyphae also occur which may represent either branches of a single hypha or successive re‐invasion of a hypha with close adposition of walls so that in transverse section the wall appears to be concentrically layered.
INTERPRETING THE EVOLUTION OF A TRIAZINE‐RESISTANT POPULATION OF POA ANNUA L.
Authors: DARMENCY H. , GASQUEZ J. 
Published: May 2006

SUMMARYThe frequency of esterase isozyme genotypes was analysed both in a triazine‐resistant population and in susceptible populations. The main findings were (i) a low polymorphism, (ii) a high rate of heterozygotes at one particular locus; this polymorphism being related to the growth form, (iii) a higher proportion of prostrate plants then would usually be expected in an open habitat. This genetic structure could result from a recent founder event in a triazine‐treated area followed by an increase of polymorphism through gene migration from adjacent populations. The importance of environmental conditions (other than triazine treatments) on the evolution of populations is discussed.
THE SIGNIFICANCE OF INTERSPECIFIC DIFFERENCES IN SPECIFIC LEAF AREA TO THE GROWTH OF SELECTED HERBACEOUS SPECIES FROM DIFFERENT ALTITUDES
Authors: WOODWARD F. I. 
Published: May 2006

SUMMARYField measurements of selected upland and lowland species have demonstrated a decline in specific leaf area with altitude, probably due to changes in both air temperature and wind‐speed.Both field and controlled environment experiments have demonstrated that the upland species have lower specific leaf areas than the lowland species, under similar environmental conditions.Leaf growth and turgor of the upland species, Phleum alpinum, are insensitive to changes in wind‐speed in the range of 0.2 to 3 m s−1, while both growth and turgor decline with wind‐speed for the lowland P. pratense. Leaf turgor of P. pratense declined with increasing specific leaf area but no such relationship was found for P. alpinum.
THE ECOLOGY OF SHORT‐LIVED FORBS IN CHALK GRASSLANDS: DISPERSAL OF SEEDS
Authors: VERKAAR H. J. , SCHENKEVELD A. J. , Van de KLASHORST M. P. 
Published: May 2006

SUMMARYWind dispersal of some characteristic short‐lived species in Dutch chalk grasslands was studied. Field observations were in agreement with a model and indicated a rather limited dispersal of seeds (0.3 to 3.5 m).Species with inherently short inflorescences have more extensive and less concentrated dispersal in open vegetation than in dense turf despite the fact that they are slightly taller in dense turf. In dense turf the slight increase in plant height does not sufficiently compensate for the reduced wind velocity in that habitat. In contrast, in species which have inherently longer inflorescences, dispersal is usually more extensive and less concentrated in dense turf. Apparently, in this case additional height more than counterbalances the reduced wind velocity in such turf. In all cases dispersal seems to be more affected by the interaction of stem height and wind profile at each site, and by the terminal vertical movement of seeds, than by other factors.Heterogeneity in the seed bank in the soil is partly explained by limited dispersal of seeds but may also be due to variation in seed production and to the pattern of distribution of fruiting individuals.
THE INFLUENCE OF SOIL AERATION ON THE EFFICIENCY OF VESICULAR‐ARBUSCULAR MYCORRHIZAS
Authors: SAIF S. R. 
Published: May 2006

SUMMARYOxygen concentrations in the soil atmosphere influenced growth and mineral uptake in Eupatorium odoratum L., Sorghum bicolor (L.) Moench and Guizotia abyssinica (L.f.) Cass. inoculated with Glomus macrocarpus, Glomus mosseae and ‘white reticulate’. Shoot and root dry weights of mycorrhizal plants increased with O2 concentration up to 16%. Dry weights of roots and shoots of non‐mycorrhizal plants were lower than those of mycorrhizal plants at all O2 concentrations except at 2 %. Mycorrhizal and non‐mycorrhizal plants at 21 % O2, or non‐aerated controls, were smaller than those at 16%. Generally, mycorrhizal plants contained higher quantities of mineral elements than did non‐mycorrhizal plants and took up more nutrients as soil O2 concentrations increased. Phosphorus concentrations of mycorrhizal plants were mostly significantly higher than those in non‐mycorrhizal plants. Soil O2 generally did not influence the P concentrations of plants. Inoculation increased the concentrations of K and Mg in E. odoratum, but only the concentration of Mg in S. bicolor and the concentrations of Ca and Mg in Guizotia abyssinica. Only the concentrations of K and Mg in E. ordoratum, the concentrations of Ca and Mg in S, bicolor and the concentration of Mg in Guizotia aybssinica showed positive responses to increase in soil O2. The development of Glomus macrocarpus, Glomus mosseae and ‘white reticulate’ exhibited quantitative and qualitative responses to different soil O2 concentrations.
TRIMORPHIC INCOMPATIBILITY IN MEXICAN POPULATIONS OF PONTEDERIA SAGITTATA PRESL. (PONTEDERIACEAE)
Authors: GLOVER D. E. , BARRETT S. C. H. 
Published: May 2006

SUMMARYPopulations of Pontederia sagittata from the northern coastal plain of Mexico possess a tristylous breeding system. Styles and stamens are reciprocally arranged in the three floral morphs. Differences in anther size, pollen size and pollen production are associated with the three anther levels. Controlled pollinations performed in the glasshouse indicate that physiological self‐incompatibility accompanies floral trimorphism. Pollinations between morphs with anthers and stigmas at equivalent heights are highly productive of seed in comparison with self‐ or intra‐morph pollinations. In each floral morph, substantial differences in seed production result from self‐pollination with alternate anther levels. Overall, the mid‐styled morph exhibits weak self‐incompatibility whereas the long‐ and short‐styled morphs are more strongly self‐incompatible. In all pollen‐stigma combinations pollen germinated readily and pollen tubes penetrated stigmatic tissue. Inhibition of pollen tubes occurs in the style and possibly the ovary. The rate of pollen tube growth differs between anther levels following self‐pollination.The three floral morphs were represented in eight populations examined although there was a tendency for the long‐styled morph to be under‐represented. Strong pollen trimorphism allows the origin of pollen deposited on naturally pollinated stigmas to be determined. Considerable variation in the amount and composition of pollen deposited on stigmas by syrphid flies was recorded. The likelihood of legitimate pollination appears to be highest in the long‐styled morph, intermediate in the mid‐styled morph and lowest in the short‐styled morph. Tristyly in P. sagittata is compared with the closely related P. cor data and P. rotundifolia. Implications of weak self‐incompatibility in the mid‐styled morph for the breakdown of tristylous breeding systems in the Pontederiaceae are discussed.
AUXIN AND BORON IN RELATION TO THE ROOTING RESPONSE AND AGEING OF MUNG BEAN CUTTINGS
Authors: JARVIS B. C. , ALI A. H. N. , SHAHEED A. I. 
Published: May 2006

SUMMARYBoron is required for development of root primordia on stem cuttings of mung bean seedlings. Although exogenous boron is not required until more than 48 h after stem cuttings are placed in auxin, it may be supplied at any previous time, including during growth of the seedlings. There is a progressive loss of rooting response to auxin and boron when cuttings are aged in water prior to rooting treatment. This ageing effect is not influenced by the presence of boron but is considerably reduced by application of dilute solutions of auxin, which are themselves without effect on rooting. Cuttings prepared from seedlings grown in the presence of boron initiate fewer roots in response to low concentrations of auxin than do cuttings taken from seedlings raised in the absence of boron. Despite being required for development of root primordia, boron is antagonistic to the influence of low concentrations of supplied auxin on rooting. The possibility that boron regulates endogenous auxin levels during root development is discussed.
ALLOCATION OF PHOTOSYNTHETICALLY FIXED CARBON INFESTUCA OVINAL. ANDNARDUS STRICT AL.
Authors: ATKINSON C. J. , FARRAR J. F. 
Published: May 2006

SUMMARYThe allocation of carbon in two montane grasses was followed using14C labelling and gas exchange measurements. Both grasses showed similar total non‐structural carbohydrate contents and net allocation of carbon. A six‐compartmental model (with root and shoot each composed of soluble, storage and structural material) was used to summarize the data, to provide estimates of carbohydrate turnover rates, and to produce complete carbon budgets. Storage carbohydrate was heavily labelled and turned over rapidly, with half‐times of 25 h inFestuca ovinaand 15 h inNardus stricta.This does not support the idea that storage carbohydrates are deposited only to be mobilized in response to environmental perturbations. It is suggested that the small relative growth rates in these species are not the result of inefficient use of fixed carbon, but of slow rates of photosynthesis; the respiratory costs of growth are similar to those for barley. The large flux of carbon through storage carbohydrate is suggested to ensure a readily available supply of sugars for metabolism, independent of environmental conditions.
PHOTOSYNTHESIS AND RESPIRATION IN THE SUB‐ANTARCTIC TUSSOCK GRASS POA COOKII
Authors: BATE G. C. , SMITH V. R. 
Published: May 2006

SUMMARY Poa cookii dominates the tussock grasslands at islands of the Kerguelen Province of the sub‐Antarctic. In common with other sub‐Antarctic Poa species it is highly productive. Infra‐red gas analysis studies at Marion Island (46° S, 37° E) showed that P. cookii is a C3 photosynthetic type plant, possessing a high CO2 compensation concentration (c. 100 p.p.m.) and apparently high rates of photorespiration. However, photosynthetic light saturation was not attained at a photosynthetic photon flux density (PPFD) of 2000μmol m−2s−1, possibly due to leaf anatomical features causing shading of the chlorophyllous mesophyll. Compensating irradiance values were 5 to 11 μmol m−2s−1. Net photosynthesis occurred below 0 °C and increased with temperature up to 10 to 12 °C, remaining constant up to 19 to 23 °C, depending in PPFD. Dark respiration increased exponentially with temperature and at 32 °C the temperature optimum had not been reached. Photorespiration also increased with temperature but rates were lower than those of dark respiration. Increasing the wind velocity over a leaf immediately decreased the net assimilation rate, which then slowly recovered to almost the original level. It appears that the grass is well‐adapted to sub‐Antarctic conditions of low light, low (seldom freezing) temperatures and high wind.
PHOTOSYNTHESIS BY ISOLATED CODIUM FRAGILE CHLOROPLASTS OF VARYING INTERNAL PHOSPHATE STATUS
Authors: RUTTER J. C. , COBB A. H. 
Published: May 2006

SUMMARYPhotosynthesis by isolated Codium fragile frond‐tip chloroplasts appeared to be inversely related to stromal orthophosphate (Pi) and polyphosphate content. Thus, exogenous 10 mM Pi inhibited photosynthesis by chloroplasts with a relatively high internal phosphate status but stimulated it when internal phosphate status was low. Inhibition of 14CO2 fixation by 5 mM Pi was not accompanied by any significant release of photosynthetically‐reduced 14C and may therefore be mediated by processes other than, or in addition to, stromal depletion of metabolites as a result of translocator action. In chloroplasts where photosynthesis was stimulated by exogenous Pi, phosphoglyceric acid or glucose‐6‐phosphate this effect was reversed by the addition of a second test substrate suggesting translocator involvement in this reversal.
TRANSLOCATION OF ORTHOPHOSPHATE AND GLUCOSE‐6‐phosphate IN CODIUM FRAGILE CHLOROPLASTS
Authors: RUTTER J. C. , COBB A. H. 
Published: May 2006

SUMMARYUptake of 32Pi (orthophosphate) by isolated frond‐tip chloroplasts of Codium fragile (Suringar) Hariot was light‐stimulated, strongly inhibited by 50 μM p‐chloromercuriphenyl sulphonic acid (pCMS) and showed an exponential increase with exogenous Pi concentrations above 1 mM, However, [14C] glucose‐6‐phosphate (G‐6‐P) uptake showed saturation kinetics, was not light‐stimulated, was less sensitive to pCMS and was slower than Pi uptake.Exogenous Pi stimulated the release of radioactivity from chloroplasts preloaded with [14C]G‐6‐P and vice versa. 3‐Phosphoglycerate (PGA) readily stimulated label release from 32Pi‐preloaded chloroplasts, but only slightly stimulated the release of label from [14C]G‐6‐P‐preloaded chloroplasts. The apparent PGA‐stimulated release of Pi was inhibited by 50μM pCMS but the exchange of Pi with G‐6‐P, as indicated by back‐exchange studies, showed no consistent sensitivity to pCMS.The presence of two separate and distinct phosphate translocators in the envelopes of C. fragile frond‐tip chloroplasts is postulated: (a) one facilitating the exchange of PGA with Pi, which is relatively fast, light‐stimulated and sensitive to inhibition by 50 μM pCMS; (b) another facilitating the relatively slower exchange of Pi with G‐6‐P which is not light‐stimulated and shows little sensitivity to pCMS.
PIGMENT/PROTEIN COMPLEXES OF THE INTERTIDAL ALGACODIUM FRAGILE(SURINGAR) HARIOT
Authors: BENSON ERICA E. , COBB A. H. 
Published: May 2006

SUMMARYSix pigment‐containing bands were isolated fromCodium fragilethylakoids using sodium dodecyl sulphate/polyacrylamide gel electrophoresis. Two, designated CPla and CP1, were associated with Photosystem I and enriched in chlorophyllaand a‐carotene, and two light‐harvesting complexes (dimer LHCP1 and monomer LHCP2) were enriched in chlorophyllb, siphonoxanthin, siphonein and neoxanthin. A fifth pigment/protein (CPa) was not successfully characterized. Undissociated free pigment contained almost all the violaxanthin recovered from gel eluates and a high concentration of siphonoxanthin.Several high (100 ± 3.0 to 62 ± 7.7 kilodaltons) and two low molecular weight proteins (15.2 ± 1.2 to 16.5 plusmn; 1.2 and 18.0 kilodaltons) were thought to be associated with CPla and CP1. LHCP1 contained a protein of molecular weight 56 ± 24 kilodaltons and LHCP, a 29 kilodaltons protein, however the behaviour of these complexes after denaturation was particularly unusual in that on re‐electrophoresis the denatured monomer appeared to reassociate and proteins of 59, 56 and 28 kilodaltons were resolved. The composition of these pigment/protein complexes suggests that a large proportion of the pigments present inC. fragilechloroplasts function in a light‐harvesting capacity and this may be an adaptation to submarine photosynthesis.
A MODULAR APPROACH TO ANALYSIS OF PLANT GROWTH
Authors: PORTER J. R. 
Published: May 2006

SUMMARYThis paper describes how plants can be studied as developing modular systems, with growth described as a population‐type process defined by the rate of production of modular plant parts.A simple model of dynamics of meristems is developed and is followed by discussion of such features of growth as meristematic flux and the change from vegetative to a flowering state, the positional distribution of meristems and the probabilities of meristems undergoing transitions that result in architectural differences between plants.
PHYSIOLOGICAL‐ENVIRONMENTAL INTERACTIONS IN LICHENS
Authors: MACFARLANE J. D. , KERSHAW K. A. , WEBBER M. R. 
Published: May 2006

SUMMARYDespite the contrasting thermal and light environment of sun and shade ecotypes of Cladonia rangiferina, analysis of the pattern of net photosynthesis throughout the year as well as enzyme polymorphism in each morphotype has found little genotypic difference.The large disparity between photosynthetic capacity in the sun and shade replicates is shown to be due simply to a difference in chlorophyll content. There is a significant decline in photosynthetic capacity in November and this is found to be reversible uncoupling of photosynthetic units (PU's) during the winter period. The control of coupling and uncoupling of PU's is shown to be mediated by both daylength and thallus temperatures, and a double environmental signal in June and July of short days coupled to low temperature will initiate and finalize the event within 12 h. This response pattern is discussed in relation to identical capacity changes in other lichen species. Apart from a single isoenzyme difference in esterase polymorphism, no differences in the zymograms of leucine aminopeptidase, phosphoglucoisomerase, or acid phosphatase were detected and this overall genetic homogeneity was equally evident in a general protein gel.This unexpected degree of homogeneity is discussed in terms of the difficulties in assessing enzyme polymorphisms in different plant populations without maximum refinement of protein preparation methods and electrophoretic techniques. It is concluded that the two quite distinct sun and shade morphotypes only reflect phenotypic differences. In contrast however significant differences are reported in the distribution of specific enzymes between the tops and bases of the podetia.
INFLUENCE OF OZONE ON CARBON PARTITIONING IN TOMATO: POTENTIAL ROLE OF CARBON FLOW IN REGULATION OF THE MYCORRHIZAL SYMBIOSIS UNDER CONDITIONS OF STRESS
Authors: McCOOL P. M. , MENGE J. A. 
Published: May 2006

SUMMARYTomato seedlings inoculated with the vesicular‐arbuscular mycorrhizal fungus, Glomus fasciculatus, were exposed for 3 h to 15 parts 10−8 (294 μg m−3) ozone twice weekly or to 30 parts 10−8 (589 μg m−3) ozone once per week, for 9 weeks. Mycorrhizal infection was reduced by 46 and 63 % in the 15 and 30 parts 10−8 ozone treatments, respectively. The total dry weight of mycorrhizal plants was significantly reduced in the 30 parts 10−8 ozone treatment but dry weights of non‐mycorrhizal plants were not affected by any ozone treatment. In a second experiment, 3–week‐old seedlings of tomato inoculated with G. fasciculatus were twice exposed to 30 parts 1O−8 ozone or filtered air for 3 h with a 7‐day interval. Soluble amino acids in root exudates and root extracts were significantly reduced in mycorrhizal plants exposed to ozone. The amino acid content of non‐mycorrhizal exudates was not reduced by ozone but was significantly increased in root extracts. Levels of reducing sugars also declined in root exudates and in root extracts of mycorrhizal and non‐mycorrhizal plants exposed to ozone. A greater amount of photoassimilated 14CO2 was retained in leaves and less translocated to roots 4 h after fumigation with ozone. Labelled leaves exhibited no leaf injury until 8 h after exposure to ozone and showed only 10 to 20% chlorosis after 24 h.