bluuebunny/crossref_metadata_2025_split huggingface dataset:
MALATE OXIDATION BY ARUM SPADIX MITOCHONDRIA: PARTICIPATION AND CHARACTERISTICS OF NAD MALIC ENZYME *
Authors: WEDDING R. T. , WHATLEY F. R. 
Published: May 2006

SummaryWhen oxygen uptake by mitochondria from Arum spadix was determined at pH 6.5 and 7.7, striking differences were found in the response of malate oxidation to the addition of ADP, KCN, salicylhydroxamic acid (SHAM) and NAD. These responses are consistent with the hypothesis that at pH 6.5 malate was oxidized primarily through the NAD malic enzyme while at pH 7.7 the primary enzyme oxidizing malate was malate dehydrogenase.Oxygen uptake rate plotted as a function of malate concentration up to a concentration of 120 mM produced curves which are best fitted by a model which assumes the presence of two enzymes with different affinities for malate. The change in the relative activities of the two enzymes at pH 6.5 and 7.7 is in agreement with the suggestion that malic enzyme was more active at the lower pH and malate dehydrogenase at the higher.The NAD malic enzyme was purified from Arum spadix mitochondria and was found to utilize either Mg2+ or Mn2+ as the required divalent cation. Although the enzyme was capable of using NADP, it did so at a rate only 10% of that with NAD. The enzyme displayed hysteretic behaviour, with bursts of activity under some conditions and lags under others, perhaps indicating a shifting state of aggregation such as has been found with other plant malic enzymes. The Michaelis constants for the components of the reaction were similar to those found with other plant NAD malic enzymes.Sulphate, fumarate, coenzyme A, AMP, ADP and ATP were activators of the enzyme, with activation constants similar to those found with malic enzyme from other plant sources. The relative effectiveness of ADP and ATP was strongly in favour of ADP, so that the enzyme may be under energy charge control in the cell.The exceptionally high concentration of NAD malic enzyme found supports the suggestion that this enzyme may be important in the metabolism of Arum spadix during floral development.
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 solution culture for a prolonged period at either 1 or 40 mg P dm−3. Large numbers of unrooted tillers were taken from these plants and grown for 8 weeks in similar solutions (low P‐ and high P‐pretreatrnents). Over the subsequent 10‐week period, the acid phosphatase (NPPase) activity of intact roots was measured in the presence of various concentrations of cationic Al.Activity of NPPase was not dependent on membrane permeability, as measured by K+‐leakage into the assay medium, suggesting an extracellular enzyme location. The low P‐pretreatrnent resulted in, depending upon population, between four and six‐fold increases in root‐NPPase activity, with the highest activities being found in populations from the most acidic soils. The NPPase activity of the roots was not a linear function of plant P‐status and there was evidence that there was a genetic component in the regulation of enzyme activity in low P‐pretreated plants.Increasing Al concentration had little effect on the NPPase activity of high P‐pretreated plants, but that of low P‐pretreated plants was inhibited to some extent (up to 30%) by the higher concentrations of Al (8 and 16 mg Al dm−3). Populations did not differ in the extent of this inhibition.The low P‐pretreatment resulted in an increase in the K+‐leakage from intact roots, and populations differed in the degree of this increase. Populations from colliery spoils had a lower K+‐leakage than would be expected on the basis of the low concentrations of P in their shoots. There was some reduction in K+‐leakage with increasing concentration of Al in high P‐, but not in low P‐, pretreated plants.
RAY FLORET MORPHOLOGY AND THE ORIGIN OF VARIABILITY IN SENECIO CAMBRENSIS ROSSER, A RECENTLY ESTABLISHED ALLOPOLYPLOID SPECIES
Authors: INGRAM RUTH , NOLTIE H. J. 
Published: May 2006

SummaryThe genetic basis of polymorphism in the capitula of Senecio cambrensis has been shown to be the result of interaction between genes at two loci for ray floret length. This polymorphism is likely to be augmented by infrequent inter‐genomic pairing, despite the predominance of preferential homologous pairing. It is suggested that homoeologous pairing may be an important source of variability in the species.
THE COMPARATIVE ECOLOGY OF TWO SAND DUNE BIENNIALS: LACTUCA VIROSA L. AND CYNOGLOSSUM OFFICINALE L.
Authors: BOORMAN L. A. , FULLER R. M. 
Published: May 2006

SummaryThis paper compares two contrasting biennial plant species of the sand dunes of Holkham, North Norfolk. A survey of distribution, in relation to various habitat factors, showed that Lactuca virosa L. is characteristic of the tall, Ammophila‐dominated grassland on the younger dunes. It is favoured by gaps in the vegetation cover such as those produced by local wind erosion, but it is very sensitive to rabbit grazing. Cynoglossum officinale L. is a plant of older dune grassland and is not normally grazed by rabbits. It can exploit the bare ground around rabbit warrens, benefiting from the higher nitrogen levels resulting from rabbit excreta.Studies on seed production and germination showed that Lactuca can produce large numbers (> 60000 per plant) of very small (c. 0–8 mg) wind‐dispersed seeds that germinate readily in the autumn. Cynoglossum, on the other hand, produces fewer (< 2500) seeds per plant that are larger (c. 30 mg) and animal‐dispersed. Cynoglossum seeds are inherently dormant; most germination is in the late winter and early spring, after a period of cold. Lactuca compensates for small seed size by having a higher growth rate than Cynoglossum as well as by its earlier germination. Despite all these differences, the two species survive at comparable densities.
THE INFLUENCE OF TEMPERATURE AND MOISTURE STATUS ON THE PHOTOINHIBITION OF SEED GERMINATION IN BROMUS STERILIS L. BY THE FAR‐RED ABSORBING FORM OF PHYTOCHROME
Authors: HILTON JANET R. 
Published: May 2006

SummaryGermination of Bromus sterilis L. seeds is unusual in that it is inhibited when the photoreceptor phytochrome exists as Pfr, the degree of inhibition being dependent on the proportion of Pfr established. However, inhibition of germination is transitory and at 15 °C is evident only at l.5 d from sowing. Although germination is reduced at temperatures lower than 15 °C, Pfr is nevertheless inhibitory to germination; inhibition persisting far longer than at 15 °C C. Temperatures higher than 15°C C are also inhibitory to germination but at these temperatures there is no additional inhibitory effect mediated by Pfr. Under conditions of low moisture status the inhibitory effect of Pfr is also markedly increased. The results are discussed in relation to the role of light in the germination behaviour of B. sterilis seeds in the natural environment.
COMPARATIVE DEVELOPMENT OF INFECTION BY THREE VESICULAR‐ARBUSCULAR MYCORRHIZAL FUNGI
Authors: WILSON J. M. 
Published: May 2006

SummaryThe effect of inoculum density on the development of infection by Gigaspora decipiens Hall and Abbott, Glomus fasciculatum (Thaxter sensu Gerdemann) Gerdemann and Trappe and Glomus tenue Greenall (Hall) was investigated. From individual propagules, infection increased logarithmically for each fungus but, at higher inoculum levels, the infectivities differed. Of the three fungi, Gi. decipiens was the least, and Gl. fasciculatum the most infective. The fungi showed different strategies for infection spread. Glomus fasciculatum produced larger infection segments, and spread within the root more extensively than the other fungi. Gigaspora decipiens and GL tenue were more dependent on external spread by the formation of secondary entry points. The intensity of infections was affected by inoculum density, but not by the age of the infection.
THE EFFECT OF PHOSPHORUS ON THE FORMATION OF HYPHAE IN SOIL BY THEVESICULAR‐ARBUSCULAR MYCORRHIZAL FUNGUS, GLOMUS FASCICULATUM
Authors: ABBOTT L. K. , ROBSON A. D. , DE BOER G. 
Published: May 2006

SummaryHyphae formed in soil by the vesicular‐arbuscular (VA) mycorrhizal fungus, Glomusfasciculatum (Thaxter sensu Gerd.) Gerd. and Trappe were extracted using the membrane filter techniqe and their length was estimated by the grid intersection method. The effect of phosphorus on the formation of this external mycelium was assessed after sampling procedures had been investigated. Phosphorus supply was varied from amounts severely deficient to those adequate for the growth of subterranean clover. After 6 weeks, the alleviation of severe phosphorus deficiency increased both the length of infected root and the length of external hyphae per centimetre of infected root. Further additions of phosphorus decreased both of these measurements. However, the level of added phosphorus at which the most external hyphae was formed per centimetre of infected root was higher than the level of phosphorus which gave the greatest length of infected root. The increase in phosphorus supply which gave the greatest increase in the length of external hyphae per centimetre of infected root also decreased the formation of vesicles within infected roots. At phosphate levels adequate for growth of mycorrhizal plants, there was little development of either external hyphae in soil or vesicles within the mycorrhizal roots.
A COMPARISON OF THE ABILITY OF LEAF SURFACES OF THREE SPECIES TO NEUTRALIZE ACIDIC RAIN DROPS
Authors: ADAMS C. M. , HUTCHINSON T. C. 
Published: May 2006

SummaryIn order to compare the ability of leaf surfaces of different species to neutralize acidic rain, acidic droplets of identical size were placed on leaves of Artemisia tilesii, Spinacea oleracea and Phaseolus vulgaris. The pH values over time were measured using a micro‐pH electrode. The pH of rain droplets initially of pH 3.0, 3.5 and 5.6 increased after contact with leaves of these species. However, for droplets of pH 2.5 the pH of droplets actually decreased with time on leaves as the drops evaporated, despite the very large quantity of hydrogen ions neutralized by the leaf surface. Neutralization of acidic droplets was greatest in A. tilesii plants, which also showed the lowest sensitivity to foliar injury from simulated acid rain, Spinacea oleracea leaves were the least able to neutralize acid droplets and also were most sensitive to foliar damage. In each species the more acidic the rain, the greater the quantity of hydrogen ions neutralized by the leaf surface. This ability to neutralize acidic droplets on the leaf surface may be an effective means of reducing damage by acid rain, especially since rain events with a pH < 3.0 are very rare. Neutralization of acidic droplets may be brought about when cations are leached from exchangeable pools or by dissolution of salts deposited on the leaf surface through guttation. Large increases in Ca especially, but also in Mg and K in droplets collected from leaves of A. tilesii, suggest that these cations may play an important role in increasing the pH of acidic droplets.
VARIATION DUE TO ENVIRONMENT AND HEREDITY IN BIRCH TRANSPLANTED BETWEEN HEATH AND BOG
Authors: DAVY A. J. , GILL J. A. 
Published: May 2006

SummaryVariation in growth and morphology within the Betula penduia/B. pubescens complex has been investigated by means of a reciprocal transplant experiment. Phenotypic responses to adjacent bog and heath environments have been contrasted and the heritability of morphometric characters has been investigated. The extent to which selection by the two environments had occurred was also examined.Four tetraploid parent trees were selected: two from the bog resembled B. pubescens and two from the heath resembled B. pendula. Progeny were raised from seed and transplanted into the bog and heath field sites as established year‐old seedlings. Survival, growth, leaf and twig morphology, and the responses to fire and deer browsing were monitored for up to three years after planting.Few of the transplanted individuals died, even after burning. Growth was determined largely by environment. Transplants grew much faster on the heath than on the bog; analysis of the annual radial growth increments in the boles of the parents and their neighbours revealed the same effect had occurred in the longer term. The slower growth of both parents and progeny on the bog was presumed to be due to the effects of soil anaerobiosis. After a fire on the heath, several main sterns regenerated from each burned stump, but the progeny of B. pendula‐like parents produced taller, more competitive growths than those of B. pnbescens parents. Deer were highly selective; they browsed only the progeny of B. pubescens‐like trees and only on the heath. Browsed trees became bushier and more branched.Principal Components Analysis of eight continuously varying leaf variables showed consistent displacements between bog and heath plantings and between parent and progeny for all four half‐sib families. Regressions of progeny on parental values for the individual leaf variables suggested high heritabilities for all except base angle, even allowing for juvenile characters. Despite similar regression coefficients in the transplants to bog and heath, the relationships were displaced relative to one another between bog and heath by large differences of intercept for measurements of size; this reflected dwarfing of the leaves of bog transplants relative to heath transplants. Such displacements were much smaller for measurements of leaf shape, although apex angle was consistently more acute (i.e. more B. pendula‐like) in the transplants into the heath than in the transplants into the bog.The significance of soil conditions, heath fires and deer browsing in interacting with heredity to mould the observed phenotypes of birch is discussed.
AGE‐SPECIFIC SEX RATIO IN A MONOECIOUS SPECIES CROTON BONPLANDIANUM BAILL
Authors: UMA SHAANKER R. , GANESHAIAH K. N. 
Published: May 2006

SummaryThe ratio of male to female flowers (sex ratio) in the monoecious Croton bonplandianum Baill decreased as plants aged in three habitats. Two major forces, male and female gametic success and intra‐sexual selection, have been invoked to explain the decrease in sex ratio. While increasing female gametic success at successive stages of growth might be responsible for the enhanced allocation of resource to the females and hence for the absolute increase in number of female flowers at a later age, increasing male gametic success does not change the absolute number of male flowers but merely causes an increase in the number of pollen grains deposited on the stigma. Differences in the sex ratio between habitats was influenced by the differential fitness gained by the two sexes in the various habitats.
VARIATION IN SIZE AND DEVELOPMENT OF SPIKELETS WITHIN THE EAR OF BARLEY
Authors: COTTRELL JOAN E. , DALE J. E. 
Published: May 2006

SummaryCarpel size at anthesis is known to vary with position along the ear in barley (Hordeum vulgare L.) and the aim of this work was to determine when differences in the size of spikelets at given developmental stages are established. The width of spikelet primordia at the double ridge stage was progressively less from the base to the tip of the developing ear and the difference in spikelet or floret size was maintained until the stage of stamen initiation. With the exception of the two lowest fertile spikelets measured, there was a good correlation between width of the spikelet at the double ridge stage and the final weight of the grain produced. The possible reasons for the differences in spikelet size are discussed.
OBSERVATIONS ON ZOOSPORIC FUNGI OF CERATIUM SPP. IN LAKES OF THE ENGLISH LAKE DISTRICT; IMPORTANCE FOR PHYTOPLANKTON POPULATION DYNAMICS
Authors: CANTER HILDA M. , HEANEY S. I. 
Published: May 2006

SummaryThree fungi and a monad‐like protozoan have been found living in the vegetative cells of Ceratium hirundinella (O. F. Müll.) Bergh. and C. furcoides (Levander) Langhans in Windermere, Esthwaite Water and Blelham Tarn, lakes in the English Lake District. The life‐histories of two, hitherto unknown, biflagellate fungi are described and one is named as a new species, Aphanomycopsis cryptica. Based on the long‐term examination of phytoplankton samples, the occurrence of these fungi as well as Amphicypellus elegans Ingold is presented for 26 years. The effects of some fungal epidemics on populations of Ceratium are discussed.
STUDIES ON BUD INDUCTION IN THE MOSS TREMA TODON BREVICALYX DIXON
Authors: CHOPRA R. N. , DHINGRA‐BABBAR SADHANA 
Published: May 2006

SummaryProtonema of Trematodon brevicalyx remains bud‐free on basal medium (Knop's Major and Nitsch's Minor salts). Indoleacetic acid (IAA), gibberellic acid, abscisic acid, chelates, salicylic acid and altered temperature, pH, agar, sucrose levels, light levels and photoperiod do not induce buds but affect gemma initiation and growth rates of protonema. Buds are induced only by cytokinins, the largest number being produced with kinetin, followed by benzylaminopurine, bryokinin (2iP) and zeatin. When varying concentrations of IAA (10−4 to 10−8M) were added together with the optimum concentration of kinetin (10−5 M), normal shoot buds were formed but their number was considerably reduced.
THE ROLE OF THE EPIDERMAL CELLS IN THE CARBON DIOXIDE RESPONSE OF STOMATA OF VICIA FABA L.
Authors: SPENCE R. D. , SHARPE P. J. H. , POWELL R. D. 
Published: May 2006

SummaryThe role of the epidermal cell has rarely been adequately investigated in studies of stomatal movements. In this study of Vicia faba, the changes in aperture in isolated epidermal strips and in intact leaf sections in response to a variety of CO2 concentrations and temperatures in both light and darkness have been observed for guard cells that were in contact with live epidermal cells. The results indicate that the response of the stomatal system to CO2 is largely dependent upon the degree to which the guard cell is functionally connected to the rest of the leaf. Stomata of guard cells in contact with live epidermal cells from leaf sections showed a significant decrease in aperture with increased CO2. Stomata of guard cells in contact with live epidermal cells on isolated epidermal strips, however, showed an increase in aperture with increased CO2 which also appears to be related to temperature. Results can be interpreted as supporting the chemiosmotic hypothesis of stomatal movements. The data also indicate that there are two opposing responses in the stomatal system to CO2: an opening response located in the epidermis and an overriding closing response controlled by the mesophyll.
ALTERATION OF 13C‐ASSIMILATE PARTITIONING IN PLANTS OF PHASEOLUS VULGARIS EXPOSED TO OZONE
Authors: OKANO K. , ITO O. , TAKEBA G. , SHIMIZU A. , TOTSUKA T. 
Published: May 2006

SummaryA quantitative tracer experiment was conducted to elucidate the effects of continuous exposure to ozone (O3) at 0.2 μl 1−1 on the translocation and the distribution of 13C‐labelled photosynthetic assimilates from the individual source leaves in 14‐d‐old plants of Phasealus vulgaris.The amount of labelled assimilates exported from the primary leaf, which acted as a main source of photosynthates for growth of the roots, decreased remarkably in the presence of O3 as a result of both a considerable reduction of 13CO2 fixation (62%) and the inhibition of translocation. On the other hand, that from the first trifoliate leaf, which mainly nourished the immature growing leaves, was not decreased in the same way by O3 because a smaller reduction of 13CO2 fixation (24%) was almost compensated by an acceleration of translocation. The pattern of assimilate distribution was altered by O3, so that a greater proportion of assimilates was partitioned to the growing leaves at the expense of the root and the stem. Consequently, the amount of labelled assimilates translocated to the non‐photosynthetic organs (stem and root) decreased by 53 %, while that to the photosynthetic organs (leaves) was reduced by only 28%. These results suggest that the plants might have adapted themselves to an environment containing O3 so that the reduction of growth efficiency caused by O3 could be minimized.
MICROPROCESSOR‐CONTROLLED SYSTEM FOR EXPOSING PLANTS TO FLUCTUATING CONCENTRATIONS OF SULPHUR DIOXIDE
Authors: MUELLER P. W. , GARSED S. G. 
Published: May 2006

SummaryA system is described which uses a combination of solenoid valves under the control of a microprocessor unit and flow‐controllers to provide fumigation chambers with accurately controlled fluctuating concentrations of SO2 for long periods. The system is versatile, both within the specific experimental requirements for which it was built and for other applications.
THE INTERACTION BETWEEN AUXIN AND BORON IN ADVENTITIOUS ROOT DEVELOPMENT
Authors: JARVIS B. C. , YASMIN S. , ALI A. H. N. , HUNT R. 
Published: May 2006

SummaryAn interaction between auxin and boron in the rooting response of stern cuttings of Phaseolus aureus Roxb. is described. The optimum response to one variable is dependent upon the value of the other and vice versa. Whereas the number of roots per cutting which develop is diminished when high concentrations of boron are supplied immediately after treatment of cuttings with auxin, subsequent root growth is enhanced by such treatment. These results are discussed with respect to the possible role of boron in controlling endogenous auxin concentration via an effect on IAA oxidase.
THE ULTRASTRUCTURE OF PLASTIDS IN THE PETALS OF CALTHA PALUSTRIS L.
Authors: WHATLEY JEAN M. 
Published: May 2006

SummaryThe petals of Caltha palustris are unusual in that they contain chromoplasts belonging to two different ultrastructural classes. Other forms of plastid are also present and one of these provides the petal with a reflective starch layer. These different types of plastid and several distinctive features of petal morphology all point to a type of petal which is particularly well‐adapted to encourage pollination of the flower by insects.
THE LEVEL AND DISTRIBUTION OF PHENOLIC PLANT GROWTH INHIBITORS IN YAM TUBERS DURING DORMANCY
Authors: IRELAND C. R. , PASSAM H. C. 
Published: May 2006

SummaryIn this study a possible role for batatasin‐type phenolic growth inhibitors in the control of dormancy and, therefore, the storage life of tubers of Dioscorea alata and D. esculenta, two economically important food yams, was investigated. After extraction, the level of endogenous growth inhibitory phenolics was estimated by a wheat coleoptile growth test and batatasins specifically determined by fluorescence spectroscopy and gas‐liquid chromatography. There was a gradual decrease in growth inhibitory phenolics in tubers of both species during dormancy and in D. alata this closely paralleled a decrease in batatasin content. It was found that batatasin‐type growth inhibitory phenolics accumulated rapidly in developing tubers just prior to the onset of dormancy and were assyrnetrically distributed, being concentrated in the proximal (head) region and in the peripheral zone just beneath the periderm. Gibberellin A3 treatment produced a promotion of the dormant period and a correlative rise in the growth inhibitory phenolic level. Effects of maleic hydrazide and ethylene chlorohydrin are also reported. The results are discussed in terms of the mechanism of dormancy control in these tubers and it is concluded that endogenous batatasin‐type phenolics are involved in this.