bluuebunny/crossref_metadata_2025_split huggingface dataset:
DECOMPOSITION OF SUPPRESSED OAK TREES IN EVEN‐AGED PLANTATIONS.
Authors: THOMPSON WENDY , BODDY LYNNE 
Published: May 2006

SUMMARYArmillaria (=Armillariella) bulbosa, and several cord‐forming basidiomycetes were found to be the principal colonizers of suppressed oak tree roots on one site studied, whilst A. ostoyae and cord‐forming fungi prevailed on a second site. Interestingly A. mellea was not isolated at all. The rhizornorphic and cord‐forming fungi appeared to colonize peripherally at first but ultimately occupied large volumes of wood. Some cord‐forming fungi were able to replace others in culture whilst in other pairings deadlock was reached. There is some evidence that cord‐forming fungi can replace A. bulbosa and A. ostoyae but cultural experiments were difficult to interpret. A. bulbosa acts mostly saprophytically and probably occupies a similar ecological niche to cord‐forming fungi, e.g. Phanerochaete velutina, Hypholoma fasciculate and Phallus impudicus, which are also saprophytes. Whether A. ostoyae acts pathogenically or purely saprophytically is uncertain. Tricholomopsis platyphylla, another cord‐forming fungus, was prevalent on a third site studied in less detail and is suggested as being a later colonizer than the other cord‐forming and rhizomorphic fungi.Individual mycelia of A. bulbosa, A. ostoyae and P. velutina are shown to colonize roots in large areas of the sites studied and it is suggested that these fungi may be of significance in nutrient translocation in deciduous woodland ecosystems.
CHRONOLOGY AND DYNAMICS OF VEGETATION CHANGE IN THE PRAIRIE‐WOODLAND REGION OF SOUTHERN MINNESOTA, U.S.A. *
Authors: GRIMM ERIC C. 
Published: May 2006

SUMMARYThe pollen and sediment stratigraphy of Wolsfeld Lake and French Lake in the Big Woods of southern Minnesota was investigated. Wolsfeld Lake is in the northeastern Big Woods, and French Lake is in the western Big Woods about 1.5 km from the prairie‐woodland border. During the mid‐postglacial, most of the present Big Woods was prairie. Oak woodland began invading prairie about 5000 years ago in the eastern Big Woods, then expanded westward, becoming established near French Lake 2400 years ago. Topography and water bodies, which control fire frequency, strongly influenced where and when woodland invaded prairie. Oak woodland persisted until 300 years ago, when Ulmus, Ostrya virginiana, Tilia americana and Acer saccharum rapidly expanded and became dominant. The changes from prairie to oak woodland and from oak woodland to ‘bigwoods’ must have required reductions in fire frequency, which were probably caused by increased precipitation and possibly decreased temperatures. About 100 years before the expansion of bigwoods, sediment influx increased at the coring site in Wolsfeld Lake, probably because of an increase in runoff and, therefore, precipitation. A conceptual model is presented in which climatic changes trigger vegetation changes, but interactions among the existing vegetational pattern, fire, and topography cause climatic thresholds for vegetation change to vary in space and time.
VESICULAR‐ARBUSCULAR MYCORRHIZA IN FIELD‐GROWN CROPS
Authors: JAKOBSEN TVER , ERIK NIELSEN NIELS 
Published: May 2006

SUMMARYDevelopment of infection by vesicular‐arbuscular mycorrhiza (VAM) was studied in some field‐grown crops. An infection plateau was reached within the first month after seedling emergence of spring barley, oats and peas. During the rest of the growth period the proportion of root length infected by VAM remained at about 50% in the cereals and 75% in the peas. In the spring, infection levels were low in winter wheat, winter rye and winter barley, and development of infection was slower in them than in the spring‐sown crops.VAM infection was also studied in relation to soil depth and root density. The proportion of root length infected decreased markedly below 40 cm soil depth. Root density varied greatly between crops, whereas the absolute length of infected roots was similar in all crops. This indicates that susceptibility to infection was independent of host species.The results are discussed in relation to final phosphorus uptake and dry‐matter production, and it is proposed that a relatively low soil‐phosphorus availability was counterbalanced, to some extent, by a well‐developed VAM infection.
NITROGEN ASSIMILATION IN MYCORRHIZAS. I. PURIFICATION AND PROPERTIES OF THE NICOTINAMIDE ADENINE DINUCLEOTIDE PHOSPHATE‐SPECIFIC GLUTAMATE DEHYDROGENASE OF THE ECTOMYCORRHIZAL FUNGUS CENOCOCCUM GRANIFORME
Authors: MARTIN FRANCIS , MSATEF YAMINA , BOTTON BERNARD 
Published: May 2006

SUMMARYThe nicotinamide adenine dinucleotide phosphate‐specific glutamate dehydrogenase (L‐gluta‐mate: NADP+ oxido‐reductase, ECI .4.1 .4) of the ectomycorrhizal Ascomycete Cenococcum graniforme was purified twofold to electrophoretic homogeneity. The native enzyme was shown to have a molecular weight of 320000 and to be composed of six identical subunits with a molecular weight of 48 000. The pH optimum for the animating reaction was 7.6 NADP‐GDH showed a negative co‐operativity with respect to ammonia (Km1:2mM, Km2:8 mM). The Km values for α‐ketoglutarate and NADPH were 2 mM and 0.03 mM, respectively. The physical and kinetics properties of this enzyme are similar with those reported for NADP‐GDH of other fungi.Cross‐reactivity of a rabbit monospecific antiserum raised against the NADP‐GDH from Sphaerostilbe repens, a saprophytic Ascomycete, was tested against the enzyme of C. graniforme. The immunochemical homology of both enzymes are low suggesting that a substitution occurs in amino acid residue of the protein.
WATER DEFICIT AND THE GROWTH AND ANATOMY OF THE RADISH FLESHY AXIS
Authors: JOYCE D. C. , ASPINALL D. , EDWARDS G. R. 
Published: May 2006

SUMMARYRadish (cv. Mars) plants were subjected to different water deficits during the expansion of the fleshy axis, and cell division and expansion in the various tissues of the axis were measured both during stress and in recovery. Water deficit inhibited both cell division and cell expansion in all axis tissues, but there was no evidence that the relationship between the various tissues was disturbed. The walls of parenchyma cells significantly thickened during a period of water deficit and staining with toluidine blue suggests that this was due to lignification. When water stress was relieved, cell expansion in the pericycle cells out‐stripped the recovery of cell division.
EFFECTS OF PRETREATMENT WITH PHOSPHATE IN NATURAL POPULATIONS OF AGROSTIS CAPILLARIS L.
Authors: McCain S. , Davies M. S. 
Published: May 2006

SUMMARYClones of six populations of Agrostis capillaris L., collected from contrasting soils, were grown in sand culture for 6 months supplied with either 1 or 40 mg P dm−3 with weekly applied solutions (low and high P‐pretreatments. Plants from the low P‐pretreatment were extremely P‐deficient. Individual unrooted tillers of the pretreated plants were subseqently grown in sand culture for 10 weeks with main treatments of 1 and 40 mg P dm−3. High P‐pretreated plants produced higher yields than low P‐pretreated plants in the 1 mg P dm−3 treatment, demonstrating a distinct P ‘carry‐over’ effect.Plants of populations from nutrient‐deficient sites were not slower growing or less responsive to P than those from more fertile sites, and plants of the very acidic soil populations were particularly vigorous. However the populations from colliery spoil appeared to be more efficient at utilizing P when P supply was low.There were no differences between P‐pretreatments in yield at 40 mg P dm−3 but, depending on population, low P‐pretreated plants accumulated between 5 and 55% more P in expanded leaf material than plants of the high P‐pretreatment. This indicates that the increases in rates of P uptake and translocation induced by P‐deficiency, frequently reported in short‐term investigations, may persist for several weeks. The relationship between initial and final P‐status of shoots was examined using genetic variability within populations as the basis of correlations. No simple linear relationship between these variables existed and possible reasons for this are discussed.The greatest increase in P concentration in shoots at 40 mg P dm−3 as a consequence of low P‐pretreatment occurred in a population from colliery spoil and it is suggested that this, together with a high efficiency of utilization of P, may be part of an adaptive physiological strategy.
INDOLE‐3‐ACETIC ACID PRODUCTION BY MYCORRHIZAL FUNGI DETERMINED BY GAS CHROMATOGRAPHY‐MASS SPECTROMETRY
Authors: EK M. , LJUNGQUIST P. O. , STENSTRÖM ELNA 
Published: May 2006

SUMMARYA method for determining indole‐3‐acetic acid (IAA) production in mycorrhiza‐forming fungi was developed. Culture medium and the fungal mycelium were, extracted with ethyl ether together with deuterated IAA as an internal standard, and the extracts thereafter evaporated to dryness. The dry extracts were then silylated in pyridine with BSTFA and analysed by gas chromatography‐mass spectroscopy. Compared to other methods the procedure required a minimum of preparatory work, gave good reproducibility and a standard deviation of acceptable level for studies involving biological material.The method was used to study IAA production in 16 mycorrhiza‐forming fungi. Results indicated large differences in the ability of the fungal strains to produce IAA. Pisolithus tinctorius 185, a strain previously shown by other workers to give a strong root infection in field experiments, produced the largest amount of IAA. Several other fungi showing high IAA values also infected plant roots with relative ease in laboratory experiments.
THE PATTERN OF PRODUCTION WITHIN INDIVIDUAL UMBILICARIA LICHEN THALLI
Authors: LARSON D. W. 
Published: May 2006

SUMMARYPredictive simulation models of lichen growth and distribution should be sensitive to the pattern of production and growth within thalli, and yet little work has dealt directly with the problem of intrathallus variability in production and thus growth.It has been assumed for many years that lichens show marginal or apical growth as a result of the allocation of local supplies of photosynthate to the proliferating tissues. Only recently have intrathallus gradients in photosynthetic activity been demonstrated in foliose and fruticose species which mirror the observed pattern of growth. This present study aimed to determine whether there was intrathallus variation in production in the form of production gradients in Umbilicaria lichens.Discs of tissue were removed from large thalli of four species of Umbilicaria and sampled for net CO2 exchange under constant conditions. The results were plotted as maps of physiological activity both on a weight and area basis, but showed an absence of clear intrathallus gradients in activity. This suggests that production is diffuse over the entire surface of the thallus and thus the growth pattern is diffuse.These results are interpreted to mean that not all lichens grow apically and that greater research effort should be directed towards discovering the extent of variation in growth pattern amongst various families of lichens.
VARIATION AND POLYPLOIDY WITHIN LOWLAND POPULATIONS OF THE BETULA PENDULA/B. PUBESCENS COMPLEX
Authors: GILL J. A. , DAVY A. J. 
Published: May 2006

SUMMARYVariation and cytotype distribution have been studied in secondary birch woodland where intermediates between Betula pendula and B. pubescens appear to predominate. Trees at three sites in lowland eastern England, with contrasting soil conditions, were examined.Thirty‐eight of the trees studied proved to be tetraploid (2n= 56) and the remaining 12 were diploid (2n= 28); no triploids or aneuploids were detected.Principal Components Analysis of up to 20 biometric characters of leaves, catkins, fruits and achenes revealed an essentially continuous pattern of variation. The diploid trees displayed rather limited variation and corresponded fairly well with B. pendula. In contrast, the tetraploids showed very great variation which included that normally associated with both species and most of the possible kinds of intermediate. The same pattern of variation was evident in several discontinuous variables and also in measurements of pollen diameter and guard‐cell length made on 20 trees at one site (Holme Fen).Variation was in part site‐dependent, suggesting that the different environments were influencing phenotype. Twenty trees at one site (Dersingham) were located on a topographic gradient from bog to heath; here there was a strong correlation between the loadings of individual trees on the principal axes of variation and the elevation of those trees on the gradient. This indicates a morphological cline which might be determined by site‐wetness. The cline was not associated with polyploidy, as it was mostly attributable to variation within the tetraploids.
THE RELATIONSHIP BETWEEN NITRATE REDUCTASE AND PLANT PRODUCTIVITY IN AGROSTIS SPECIES
Authors: HARRIS P. , WHITTINGTON W. J. 
Published: May 2006

SummaryAlthough many ecological and agricultural experiments have sought to prove that nitrate reductase activity (NRA) could be directly related to productivity, this has proved to be difficult. The experiments indicate that Agrostis tenuis and A. stolonifera may differ in both productivity and NRA but the results are much affected by environmental factors such as temperature, plant density and probably by variety. The environment can apparently determine whether the products of NRA are directed into storage protein or directly into growth. Thus, while NRA should always be correlated with total plant nitrogen, experiments may show a negative, positive or no relationship at all between growth and NRA depending on the environments imposed during the period of observation because alternatives exist for the utilization of reduced nitrate.
UPTAKE OF METHYLAMINE BY SYMBIONTS OF THE LICHEN, CLADONIA CONVOLUTA (ALGAL SYMBIONT: TREBOUXIA)
Authors: TAPPER R. C. 
Published: May 2006

SummaryThe uptake of methylamine by Trebouxia and its associated fungal partner in the lichen, Cladonia convoluta, has been examined directly using quantitative autoradiography. Uptake of methylamine by Trebouxia is about five times that by the fungal symbiont. The membrane permeability of methylamine measured for both symbionts is higher than can be accounted for by the permeation of the uncharged molecule and provides evidence for the presence of a membrane transport system for protonated methylamine.
ELICITATION OF ACCUMULATION OF TERPENOID ALDEHYDE PHYTOALEXINS IN VERTICILLIUM DAHLIAE‐NFECTED COTTON
Authors: MACE M. E. 
Published: May 2006

SummaryStem stele tissues of Verticillium wilt‐resistant (Seabrook Sea Island 12B2) cotton plants were examined for location of the pathogen and localization of terpenoid aldehyde accumulation 5 days after inoculation with Verticiliium dahliae. Mycelia of V. dahliae were confined to the vessel lumina. Terpenoid aldehyde phytoalexins were detected histochemically in fresh sections as red Sb‐chelates after application of the terpenoid aldehyde‐specific SbCl3 reagent. Most terpenoid aldehydes were detected as diffuse deposits in and around colonized xylem vessels; however, some were localized in solitary xylem parenchyma cells appressed to vessel walls or in solitary xylem and pith parenchyma cells removed from any V. dahliae‐colonized vessels. Thus, physical contact with the pathogen is not required for elicitation of terpenoid aldehyde accumulation.
GENETIC COMPONENTS OF MORPHOLOGICAL VARIATION IN SALIX REPENS
Authors: FOWLER NORMA , ZASADA J. , HARPER J. L. 
Published: May 2006

SummaryThe presence of statistically significant levels of genetic variation in a series of quantitative morphological characters in a dune population of Salix repens L. was demonstrated by the comparison of half‐sibs grown in the glasshouse from field‐collected seed. Although the plants showed considerable phenotypic differentiation between ridges and slacks in the natural population, only the amount of branching could be shown to be genetically different between plants grown from cuttings from the two environments. Comparison of plants grown from different collections of cuttings showed that these were genetically different for a variety of other morphological characters, although this variation was not correlated with ridge or slack origin. Analysis of the number of collections of this dioecious species containing male or female flowers, or flowers of both sexes, indicates that even within areas 0–5 m in diameter several different clones frequently occur.
THE FITNESS OF THE COPPER TOLERANCE GENE OF MIMULUS GUTTATUS IN UNCONTAMINATED SOIL
Authors: MACNAIR M. R. , D. WATKINS A. 
Published: May 2006

SummaryTwo experiments looking for differences in fitness between plants of Mimulus guttatus heterozygous for the copper tolerance gene and homozygous for the non‐tolerance gene are described. Experiment 1 used self thinning to look for intraspecific competition; no differences in fitness between the genotypes could be detected. Experiment 2 looked at various fitness‐related characters in spaced plants, and again no difference in fitness was apparent. In both experiments, the trends were for increased fitness of the tolerant genotype. These results may help to explain why metal tolerant plants are often found in non‐tolerant populations at low frequency.
INTERACTIONS OF VESICULAR‐ARBUSCULAR MYCORRHIZAL INFECTION AND HEAVY METALS IN PLANTS
Authors: GILDON A. , TINKER P. B. 
Published: May 2006

SUMMARYThe degree of infection of onions with the vesicular–arbuscular mycorrhizal fungus Glomus mosseae was strongly reduced by additions of zinc, copper, nickel or cadmium to the soil medium, and could be completely eliminated by heavy rates of application. A split pot experiment was used to show that zinc translocated within the plant from other roots was effective in decreasing infection levels. Despite this, clover plants growing on areas which had been heavily contaminated with metal were found to be strongly infected with mycorrhizal fungi. A comparison of G. mosseae isolated from these plants with the isolate used at Rothamsted showed the former to be much more tolerant of zinc and cadmium in the soil. There was some indication that mycorrhizal infection, particularly with the tolerant isolate, could protect plants against the effects of heavy metal additions. These infections might be very important in revegetation of polluted sites.
ESTERASE POLYMORPHISM AND GROWTH FORM DIFFERENTIATION IN POA ANNUA L.
Authors: DARMENCY H. , GASQUEZ J. 
Published: May 2006

SUMMARYLeaf esterase polymorphism in eight populations of Poa annua L., from two habitat types (four opportunist and four semi‐permanent populations), was demonstrated to be controlled by nine loci. Frequencies at five loci were studied. Locus Est 1 proved highly correlated with growth form: homozygotes AA were prostrate, whereas homozygotes BB were erect. All populations were polymorphic both for esterase isozymes and growth form. Mean frequencies of prostrate and erect plants were 12 and 88% respectively in opportunist populations, and 32 and 68% in semi‐permanent populations. The outcrossing rate was strongly dependent upon plant density, but in both types of habitat, prostrate and erect plants appeared to be able to exchange genes.
THE INFLUENCE OF LIGHT ON THE GERMINATION OF A VENA FA TUA L. (WILD OAT) SEED AND ITS ECOLOGICAL SIGNIFICANCE
Authors: HILTON JANET R. , BITTERLI C. J. 
Published: May 2006

SUMMARYThe conflicting reports on the influence of light on the germination of A. fatua L. (wild oat) seed may be due to the use of seed of different types and of differing dormancy status. In an attempt to resolve these uncertainties we tested 30 stocks of seed of known type and dormancy status. Light promoted the germination of three types of partially‐dormant seed but had no effect on fully‐dormant and fully non‐dormant seed. The magnitude of the promotory effect was similar in all stocks tested irrespective of the level of dormancy. Following the application of dormancy‐breaking treatments germination of fully dormant seed was also promoted by light. The photoreceptor involved was shown to be phytochrome.
THE RESPONSE OF HAPLOID SECONDARY EMBRYOIDS AND SECONDARY EMBRYOGENIC TISSUES OF WINTER OILSEED RAPE TO TREATMENT WITH COLCHICINE
Authors: LOH C.‐S. , INGRAM D. S. 
Published: May 2006

SUMMARYIt was shown by experiment that the treatment of cultured haploid detached secondary embryoids and secondary embryogenic tissues of Brassica napus ssp. oleifera with colchicine resulted in diploidy, tetraploidy and mixaploidy. The proportions of the different ploidy levels so induced depended on the concentration of colchicine used and the duration of treatment. The highest levels of diploidization were obtained by exposing the tissues to 0.05 % colchicine in 2% dimethylsulphoxide for 72 h. The capacity for secondary embryogenesis was retained in colchicine‐induced diploid, tetraploid and mixaploid tissues, and the majority of the resulting second generation secondary embryoids were of the same ploidy as the parental material. This indicates the stability of the secondary embryogenic potential irrespective of changes in ploidy level. It is suggested that the ability to produce secondary embryoids is a consequence of haploidy and homozygosity. That the phenomenon is not a consequence of growth in culture is indicated by the fact that secondary embryoids are also produced occasionally on mature glasshouse‐grown plants regenerated from secondary embryoids. It is concluded that a system is now available for the continuous production of large numbers of haploid and homozygous diploid plants, and plants of other ploidy types, all derived from the same haploid anther embryoid. Such a system will be of value for oilseed rape breeding and for genetical and biochemical studies of somatic embryogenesis.
PLANT GROWTH RESPONSES TO VESICULAR‐ARBUSCULAR MYCORRHIZA
Authors: BÅÅTH E. , HAYMAN D. S. 
Published: May 2006

SUMMARYThe effect of pre‐inoculation with vesicular‐arbuseular mycorrhiza (VAM) on Verticillium wilt of tomato was assessed in a glasshouse trial. Inoculation with Verticillium albo‐atrum decreased plant growth compared to non‐inoculated controls, irrespective of the mycorrhizal status of the plant. Mycorrhizal plants were slightly smaller than non‐mycorrhizal ones. Addition of extra phosphorus to the soil enhanced plant growth but this enhancement was totally eliminated by Verticillium. It is not expected, therefore, that VAM could affect the severity of disease caused by Verticillium even under conditions where VAM would normally have been beneficial for plant growth. The lowest percentage mycorrhizal infection was found on plants with the most severe disease symptoms.
SEASONAL VARIATION IN FROND MORPHOLOGY AND CHLOROPLAST PHYSIOLOGY OF THE INTERTIDAL ALGA CODIUM FRAGILE (SURINGAR) HARIOT
Authors: BENSON E. E. , RUTTER J. C. , COBB A. H. 
Published: May 2006

SUMMARYThe life cycle of Codium fragile shows strong seasonal trends with respect to frond morphology and chloroplast physiology. The period of maximum carbon fixation, pigment content and chloroplast size occurs during the early winter when competition from other algae is small and the variation in tidal amplitude decreased. At this time of year the alga may be able to accumulate nutrient reserves as evidenced by the seasonal variation in chloroplast alkali: acid‐soluble polyphosphate ratios. In the summer when the physical environment is more extreme (due to prolonged tidal exposure) and competition from other algae greater, photosynthetic rates, pigment concentration and chloroplast size are reduced and the alga enters the reproductive phase. This part of the life cycle is accompanied by the development of frond hairs which may increase nutrient uptake and the mobilization of stored polyphosphates sequestered during the winter vegetative phase. It is proposed that these seasonal trends in frond morphology and chloroplast physiology may constitute an ecologically advantageous growth strategy in C. fragile.