bluuebunny/crossref_metadata_2025_split huggingface dataset:
ENZYMES OF AMMONIA ASSIMILATION IN THE CYTOSOL OF DEVELOPING SOYBEAN ROOT NODULES
Authors: SEN DIPANKAR , SCHULMAN HERBERT M. 
Published: May 2006

SUMMARYGlutamine synthetase, glutamate synthase and glutamate dehydrogenase activities were measured in the cytosol extracted from developing effective soybean root nodules and compared to the activities found in cytosol extracted from ineffective soybean root nodules and soybean root tissue. In the cytosol of effective soybean root nodules glutamine synthetase activity was found to increase up to floral initiation while glutamate dehydrogenase activity decreased. Glutamate synthase activity was detected but it did not increase as much as glutamine synthetase. In ineffective nodule cytosol and root tissue much lower levels of glutamine synthetase and similar levels of glutamate dehydrogenase, as compared to effective nodule cytosol, were found but no glutamate synthase was detectable. The results indicated that glutamine synthetase/glutamate synthase cycle is operative for ammonia assimilation in effective soybean root nodules and glutamate dehydrogenase probably has no synthetic role.
ULTRASTRUCTURAL ASPECTS OF HOST‐ENDOPHYTE RELATIONSHIPS IN ARBUTUS UNEDO L. MYCORRHIZAS
Authors: FUSCONI ANNA , BONFANTE‐FASOLO PAOLA 
Published: May 2006

SummaryA morphological examination of white‐amber mycorrhizal roots of Arbutus unedo L. has been carried out using light and electron microscopy and naturally infected tissue. This type of mycorrhiza is slightly different from the typical arbutoid type; it is characterized by a few hyphae which extend along the surface of the root without forming a true mantle. They penetrate between the epidermal cells, giving rise to the Hartig net, and invade the epidermal cells. All the hyphae have simple septa and associated Woronin bodies characteristic of ascomycetous fungi. Intracellular hyphae are surrounded by invaginated host plasmalemma and by an inter‐facial material of varying thickness. No evidence of lysis or digestion of the intracellular hyphae by the plant cells has been observed, the fungal hyphae generally outliving the host epidermal cells.
PHOTOSYNTHETIC CAPACITY CHANGES IN PELTIGERA I. THE SYNTHESIS OF ADDITIONAL PHOTOSYNTHETIC UNITS IN P. PRAETEXTATA
Authors: KERSHAW K. A. , WEBBER M. R. 
Published: May 2006

SummaryChanges in the photosynthetic capacity of Peltigera preaetextata (Somm.) Vain, over the course of a year have been examined using photosynthetic‐illumination curves. The results have been interpreted using the photosynthetic response models originally proposed by Prézelin. The low net photosynthetic rates obtained following prolonged winter snow cover are interpreted as resulting from the interruption of energy transduction in some photosynthetic units. In spring, full energy transduction is rapidly re‐established by the storage of experimental replicates at a warm temperature and results in a marked increase in net photosynthetic rates. As expansion of the tree canopy takes place both apparent quantum efficiency and photosynthetic capacity increase markedly, whilst respiration decreases significantly, providing high rates of net photosynthesis even under light levels as low as 75 μmol m−2 s−1. This change in summer capacity is interpreted as being due to the synthesis of additional photosynthetic units in response to the low light conditions on the woodland floor. The data are discussed both in relation to comparable events in other lichen species and to the potential significance of seasonal changes in photosynthetic capacity in the ecology of P. praetextata.
IRRADIANCE AND ADVENTITIOUS ROOT FORMATION IN STEM CUTTINGS OF PHASEOLUS AUREUS ROXB.
Authors: JARVIS B. C. , ALI A. H. N. 
Published: May 2006

SummaryRooting of cuttings of mung bean (Phaseolus aureus Roxb.) is enhanced when the stock plants, from which cuttings are taken, are grown under high irradiance. When rooting is induced by treatment with indolebutyric acid (IBA), high irradiance during the rooting period increases the number of roots developing on each cutting. However, when it occurs in the absence of supplied auxin, rooting is increased when cuttings are held under low irradiance. Irrespective of whether roots are induced by supplied IBA or by endogenous factors their growth, as evidenced by mean length, is greatest when stock plants are raised under high irradiance but cuttings are maintained under low irradiance.
THALLUS SIZE AS A COMPLICATING FACTOR IN THE PHYSIOLOGICAL ECOLOGY OF LICHENS
Authors: LARSON D. W. 
Published: May 2006

SummaryThe relationship between size of lichen thallus and net photosynthetic rate, respiration rate, rate of water uptake, rate of water loss and maximum thallus water content has been examined in five species of Umbilicaria. While two species show large effects of thallus size, three others show small, or no effects. The lack of a consistent pattern complicates the studies of physiological ecology in these and other lichen species because the vast majority of the published literature contains no mention of the dimensions of thallus or clones used. A major research effort should be made to determine other physiological functions that are age‐ or size‐dependent. In addition, future work should include, where possible, information regarding dimensions of the thallus used and the range of dimensions normally found in the field. Only in this way can conclusions be tested by other workers.
THE POISONING OF ROOTS OF ZEA MA YS BY NICKEL IONS, AND THE PROTECTION AFFORDED BY MAGNESIUM AND CALCIUM
Authors: ROBERTSON A. I. 
Published: May 2006

SummaryThe growth of seedlings oiZea mays L. has been studied in water cultures containing Ni2+, Mg2+ and Caa+ singly and in certain combinations. Root growth was reduced to half that of the controls (RG50) by as little as 01 mg I−1 Ni2+. This poisoning was prevented by 4 mg I”1 Mg2+ and by 32 mg T1 Ca2+. RG50 for Mg2+ alone was 64 mg T1 and for Ca2+ more than 1000 mg I−1. Root growth could be stopped within 8 h of exposure to 1 mg I−1 Ni2+. In the absence of Ni2+, Ca2+ protected against Mg2+ toxicity but Mg2+ did not reduce the effects when CaCl2 created osmotic loss at very high concentration. In combination, a ratio of 6:1 excess of Mg: Ca was necessary for Mg2+ to begin to reduce growth. At higher concentrations Mg2+ exerted its own toxicity despite the presence of Ca2+. When Ni2+ would otherwise have poisoned growth, Ca2+ added only to the relief of poisoning by Mg2+ if the Ca2+ was in excess by more than 4:1 over Mg2+. Thus Mg2+ appeared to be more fitted to prevent Ni2+ poisoning, yet at higher concentrations it was toxic itself, while Ca2+ could at still higher concentrations protect against both Ni2+ and Mg2+. Ni2+ poisoned growth by stiffening the expansion zone tissues and by destroying the integrity of root meristems. This latter was the first and most important toxic effect, and was achieved by arresting mitosis.
PHOTOCONTROL OF TURION FORMATION BY POTAMOGETON CRISPUS L. IN THE LABORATORY AND NATURAL WATER
Authors: CHAMBERS P. A. , SPENCE D. H. N. , WEEKS D. C. 
Published: May 2006

SummaryThe freshwater angiosperm Potamogeton crispus produces specialized vegetative buds, known as turions, in early summer, in contrast to their autumn production by other temperate climate species. Laboratory experiments showed that turion production by P. crispus is triggered by long days (16 h or longer) and high temperatures (16 °C and above) together. Long days represent a photoperiodic signal apparently perceived by phytochrome. A midnight exposure to dim R light is necessary to induce turion formation in plants kept under short days, irrespective of total daily light dose. A single long day suffices to initiate turion formation.Under inductive long warm days few turions form at low photon fluence rates (whatever the total daily light dose) or at low R: FR ratios near 1 during the photoperiod. Rate and magnitude of turion production are greatly increased by increased photon fluence rates and R: F ratios above 1. Sucrose feeding hastens turion development, but turion initiation is not significantly altered.As predicted from experimental findings and natural lakewater photoperiods and temperatures, turions were observed on plants in lakes studied from June until August. Also, turions were confined as predicted to approximately the upper 15 m depth range in lakes where R: FR ratios and photon fluence rates were inductively high. Below these depths the R: FR ratio remains high but photon fluence rate is inadequate. Thus laboratory and field findings concur. In north temperate waters, turions of P. crispus appear to act as summer propagules which settle and germinate by autumn, rather than as overwintering hibernaculae.
ION AND WATER TRANSPORT IN SEEDLINGS OF MUSTARD (SINAPIS ALBA L.)
Authors: COLLINS J. C. , ABBAS M. A. 
Published: May 2006

SummaryIon and water transport were measured in young mustard seedlings which had been grown in the dark on a simple culture medium. The growth of seedlings was exponential during the period 2 to 5 d from germination, though there was a decline in the rate of respiration with age. A comparison of the fluxes from excised roots with those in the roots of intact plants showed that the fluxes of potassium and chloride were much greater in intact plants, and it is argued that transport to the shoot might be regulated by some factors from the intact shoot. The flux of water was similar in both systems.
GERMINATION RESPONSES TO LIGHT AND ALTERNATING TEMPERATURES IN EUROPEAN POPULATIONS OF DACTYLIS GLOMERATA L.
Authors: PROBERT R. J. , SMITH R. D. , BIRCH P. 
Published: May 2006

SummaryGermination responses to light and alternating temperatures were investigated in a range of populations of Dactylis glomerata L. of contrasting origin. Despite quantitative variation, similar responses to both factors were recorded in 12 British populations. In 11 European populations, levels of response were dependant on original dormancy status and apparently related to climatic origin. Whereas northern European populations required both light and alternating temperatures for maximum germination, Mediterranean populations germinated to high levels in complete darkness at a constant temperature. In Mediterranean populations, germination capacity declined sharply with increasing daily photoperiod in light from warm white fluorescent tubes. It is postulated that different patterns of response in European populations were related to differences in a basic mechanism of germination control involving phytochrome.
GERMINATION RESPONSES TO LIGHT AND ALTERNATING TEMPERATURES IN EUROPEAN POPULATIONS OF DACTYL1S GLOMERATA L.
Authors: PROBERT R. J. , SMITH R. D. , BIRCH P. 
Published: May 2006

SummaryBasic patterns of germination response to light and alternating temperatures were relatively stable in three European populations of Dactylis glomerata L. during four years of cultivation in field plots. Small inconsistent quantitative differences were probably due to differences in the reproductive output of individual genotypes and seasonal variation in climatic factors. Germination responses were directly related to temperature conditions (over the range 6 to 26 °C) which prevailed during seed development and maturation. The relative effects of light and alternating temperatures were independent of maturation temperature suggesting a physiological link in the requirement for these factors.
CHLOROPHYLL A FLUORESCENCE AS A QUANTITATIVE PROBE OF PHOTOSYNTHESIS: EFFECTS OF CO2 CONCENTRATION DURING GAS TRANSIENTS ON CHLOROPHYLL FLUORESCENCE IN SPINACH LEAVES
Authors: FURBANK ROBERT T. , WALKER DAVID A. 
Published: May 2006

SUMMARYThe relationship between changes in chlorophyll a fluorescence and changes in CO2 concentration in spinach leaves is analyzed. The height of the fluorescence excursion, when plotted against the CO2 concentration during the transient, results in a hyperbola. When these data are replotted on an inverse‐reciprocal plot, an apparent Km (CO2) for the fluorescence transient can be obtained which closely approximates the Km (CO2) for carbon assimilation under similar conditions. Transitions in CO2 concentration at 2 % O2 result in deviation from this hyperbolic relationship, reducing the apparent Km (CO2) for this process. The relationship between carbon assimilation and chlorophyll fluorescence is discussed with reference to the two components of fluorescence quenching. This technique raises the possibility that chlorophyll fluorescence could be used as a quantitative as well as a qualitative tool in plant screening.
EFFECTS OF NITROGEN DEPRIVATION ON RATES OF UPTAKE OF NITROGENOUS COMPOUNDS BY THE DIATOM, PHAEODACTYLUM TRICORNUTUM BOHLIN
Authors: SYRETT P. J. , FLYNN K. J. , MOLLOY C. J. , DIXON G. K. , PEPLINSKA A. M. , CRESSWELL R. C. 
Published: May 2006

SummaryA culture of Phaeodactylum tricornutum was suspended in nitrogen‐free growth medium under conditions which favoured photosynthesis. Nitrogen deprivation was continued for 60 h and, over this period, samples were removed for measurement of rates of uptake of arginine, guanine, nitrate, nitrite, lysine, methylammonium and urea. In another experiment, the effect of nitrogen deprivation on the ability to take up methylammonium and ammonium was compared. Cells developed, or increased, their abilities to take up all of these nitrogen compounds during nitrogen deprivation but ability to take up the two amino acids increased only slowly whereas the ability to take up the other compounds increased markedly during the first few hours of deprivation. The maximum rates of uptake developed were some 50–100 × higher for methylammonium and ammonium than they were for the other compounds. The rates of uptake are compared with those necessary to sustain growth.
REGULATION BY AZIDE OF HETEROCYST AND NITROGENASE IN AZIDE‐RESISTANT MUTANTS OF THE CYANOBACTERIUM, NOSTOC MUSCORUM
Authors: BAGCHI S. N. , SINGH D. T. , SINGH H. N. 
Published: May 2006

SummaryA novel class of azide‐resistant mutants of N, muscorum is described in which azide caused inhibition of heterocyst differentiation and nitrogen fixation without causing inhibition of growth. The results indicate the utilization of azide, as a fixed nitrogen source, by the mutant strain. An increase in the ability to take up azide and in the phycocyanin/chlorophyll ratio following growth of the mutant in azide‐containing medium are additional findings which support the conclusion that the mutant utilizes azide as a source of nitrogen. In the parental strain, Ca2+‐dependent and Mg2+‐dependent ATPases, and cellular nitrate reductase were inhibited by azide. The corresponding ATPases from the mutant strain were not inhibited by azide. There was evidence, in cell‐free extracts, for an enzyme system which utilized azide as an electron acceptor and NADPH‐ferredoxin as electron donor. The activity of this system was significantly higher (on a protein basis) in cells of the mutant grown on azide than in cells of either the parent or the mutant when grown on nitrate.It is suggested that the azide resistance of this class of mutant is due to a mutation which leads to azide resistant Ca2+‐ and Mg2+‐ ATPases. Such a mutation may allow an azide utilizing system, inherently present in both parent and mutant strains, to be expressed.
COMPARATIVE STUDIES ON THE SUB‐UNIT COMPOSITION OF THE ALBUMINS, VICILINS AND LEGUMINS OF ISOLATED PROTEIN BODIES FROM COTYLEDONS OF DRY SEEDS OF TWO MEMBERS OF THE LEGUMINOSAE: CYTISUS SCOPARIUS (L.) LINK AND C. SCOPARIUS SSP. MARITIMUS (ROUY) HEYWOOD
Authors: CITHAREL J. , CITHAREL L. 
Published: May 2006

SummaryThe isolated protein bodies of Cytisus scoparius (L.) Link and Cytisus scoparius ssp. maritimus (Rouy) Heywood were observed by scanning electron microscopy; they showed comparable shapes and sizes. The protein content and the sub‐unit composition of the fractionated albumins, vicilins and legumins, however, showed significant electrophoretic differences between the two plants, both at the qualitative and quantitative levels.
ASSIMILATION OF 15NH4+BY BEECH (FAGUS SYLVATICA L.) ECTOMYCORRHIZAS
Authors: MARTIN F. , STEWART G. R. , GENETET I. , LE TACON F. 
Published: May 2006

SummaryAmmonia assimilation has been followed in ectomycorrhizal roots of Fagus sylvatica. The absorption of ammonium ions was associated with a rapid synthesis of free amino acids in mycorrhizal tissues, glutamine being the most prominent. In the presence of [15N]ammonium, glutamate, glutamine and alanine became the most strongly labelled metabolites of ectomycor‐rhizas. Nitrogen‐15 nuclear magnetic resonance spectroscopy demonstrated that the glutamine amide‐N was the most highly enriched component of the extracts. Methionine sulphoximine and albizine, inhibitors of glutamine synthetase and glutamate synthase, almost completely blocked the incorporation of 15N label into amino acids and induced an accumulation of NH4+. These observations suggest that in the ammonia‐fed beech ectomycorrhizas, ammonia assimilation occurs mainly via the glutamine synthetase/glutamate synthase pathway, and that glutamate dehydrogenase plays little, if any, part in this process. Alternative models for the nitrogen assimilation pathways in fungal and host tissues are presented.
GERMINATION RESPONSES TO LIGHT AND ALTERNATING TEMPERATURES IN EUROPEAN POPULATIONS OF DACTYLIS GLOMERATA L.
Authors: PROBERT R. J. , SMITH R. D. , BIRCH P. 
Published: May 2006

SummaryDetailed germination responses to temperature and light in two populations of Dactylis glomerata L. originating from S.E. Denmark and W. France were defined using thermogradient bars. Despite quantitative differences patterns of response were broadly similar. In both cases seeds were sensitive to the relative periods spent at the warm and cool phases of alternating temperature cycles with germination markedly reduced in diurnal cycles involving a 16 h warm phase and an 8 h cool phase. Whereas the proportion of seeds capable of germination increased sharply as the amplitude of temperature alternation increased the optimum amplitude was dependent on both the period spent at each phase and the presence or absence of light. Even under optimum temperature conditions there was an overriding requirement for light in a high proportion of individuals. When five 21/11 °C cycles of reduced duration were applied at 24 h intervals, 1 h/2 h alternations were as effective in stimulating germination as diurnal cycles. Germination response was directly related to the logarithm of the number of diurnal 21/11 °C cycles applied in three different seed samples. Sensitivity was not related to inherent dormancy status (between populations) or to a degree of after‐ripening.
IDENTIFICATION OF VESICULAR‐ARBUSCULAR MYCORRHIZAL FUNGI IN ROOTS OF LEEK (ALLIUM PORRUM L.) AND MAIZE (ZEA MAYS L.) ON THE BASIS OF ENZYME MOBILITY DURING POLYACRYLAMIDE GEL ELECTROPHORESIS
Authors: HEPPER CHRISTINE M. , SEN R. , MASKALL C. S. 
Published: May 2006

SummaryThe mobilities of three enzymes, esterase (EST), glutamate oxaloacetate transaminase (GOT) and peptidase (PEP), during polyacrylamide gel electrophoresis have been used to identify individual species of vesicular–arbuscular mycorrhizal fungi in roots. The enzyme banding patterns obtained from mycorrhizal root extracts were compared with those of uninfected roots. Chlamydospores, external mycelium and internal mycelium (obtained by enzymic digestion of host root tissue) were used as controls to confirm the position of the fungal specific enzyme bands on the gels. Glomus caledonium (Nicol. and Gerd.) Trappe and Gerd. and Glomus mosseae (Nicol. and Gerd.) Gerd. and Trappe could be detected in leek (Allium porrum L.) roots against the host background by the mobility of bands of EST, GOT and PEP activity and it was possible to detect both G. caledonium and G. mosseae in leek roots which had been grown in the presence of a mixed inoculum, by staining for any of these three enzymes. Glomus mosseae could be identified in maize (Zea mays L.) roots by location of GOT and PEP activity but the major bands of EST, GOT and PEP activity in G. caledonium had the same mobility as those of maize and so this fungus could not be easily identified in this host using these experimental conditions. Glomus fasciculatum (Thaxter sensu Gerd.) Gerd. and Trappe type E3 had a characteristic PEP band which was separable from leek and maize host bands and this fungus could also be identified in maize roots by the position on the gel of fungal GOT activity.
Clinical Experience with Tiered Atrial Therapies and Atrial Arrhythmia Prevention Algorithms in a Dual Chamber Cardioverter Defibrillator
Authors: DAOUD EMILE G. , NADEMANEE KOONLAWEE , FUENZALIDA CHARLES , TOMASSONI GERY F. , SCHUGER CLAUDIO , CHISNER MICHAEL , SIMONES MELISSA , SCHWARTZ MARK , REEVE HELEN 
Published: May 2006

Introduction: The acceptance of atrial arrhythmia features in implantable cardioverter defibrillators (ICDs) will depend on their ability to appropriately discriminate atrial tachyarrhythmias/atrial fibrillation (AT/AF). This study tested the effectiveness of an atrial/ventricular ICD with advanced atrial detection and new algorithms designed to prevent atrial arrhythmias. Methods and Results: Ninety‐five patients were implanted with a dual chamber ICD (Model 1900, Guidant Corporation, MN, USA) at 25 US centers. Ten patients received a coronary sinus (CS) lead allowing a defibrillation vector for AT/AF cardioversion. Follow‐up was 12.2 months. The addition of new atrial features designed for detection, discrimination, and prevention of AT/AF had no adverse effect upon detection of induced ventricular fibrillation (VF) (mean detection time with new features ON was 2.22 seconds vs 2.19 seconds with features OFF). A total of 100% of the induced and spontaneous ventricular and atrial arrhythmias receiving shock therapy were reviewed as appropriate detection. Atrial shock conversion efficacy for spontaneous and induced AT/AF episodes was 83% and 96%, respectively (144 spontaneous, 162 induced episodes). A 3‐month randomized crossover trial of atrial preventative pacing features did not result in adverse effects, but there was no clinical efficacy for prevention of AT/AF. Conclusion: Enhanced atrial detection and discrimination features combined with tiered atrial therapies did not adversely impact the ability of the ICD (Model 1900) to appropriately detect and treat ventricular tachyarrhythmias.
New insights into the molecular biology and targeted therapy of cutaneous T‐cell lymphomas
Authors: Klemke Claus‐Detlev , Goerdt Sergij , Schrama David , Becker Jürgen C. 
Published: May 2006

SummaryCutaneous T‐cell lymphoma is an extra‐nodal non‐Hodgkin lymphoma of mature T cells.These tumor cells home to and persist in the skin,producing a broad spectrum of clinical entities. Recent results of basic research on tumor biology and tumor immunology as well as molecular genetics of cutaneous T‐cell lymphoma have fostered the development of new therapeutic approaches. Several clinical trials testing these targeted therapies have shown encouraging results. This article provides an overview of recent research developments and therapeutic strategies for cutaneous T‐cell lymphoma.