bluuebunny/crossref_metadata_2025_split huggingface dataset:
Purification and Characterization of Oxopantoyl Lactone Reductase from Higher Plants: Role in Pantothenate Synthesis
Authors: Julliard J. H. 
Published: February 2014

AbstractOxopantoyl lactone reductase has been purified to homogeneity from a crude extract of spinach leaves (Spinacia oleracea L.) using affinity chromatography on Red‐Agarose and several subsequent ion exchange steps. The enzyme is monomeric with a relative molecular mass between 33,000 to 36,000. Affinity‐purified antibodies directed against the homogenous enzyme have been used to determine the amount of oxopantoyl lactone reductase in the crude leaf extract as well as the chloroplast stroma. The overall purification factor has been determined to be 22,000. The subcellular location of the enzyme is chloroplastic. The final specific activity (strictly NADPH‐dependent) is 4.5 μmole . min−1 . mg−1. The enzyme is also able to reduce isatin, bornanedione and acenaphthenequinone. The enzyme activity is strongly and uncompetitively inhibited by 2‐keto‐4‐hydroxybutyrolactone and substituted 4,5‐dioxopyrrolidines. An oxopantoate reductase associated with acetohydroxy acid isomeroreductase could be detected in the plant extract. Using a specific inhibitor of this latter enzyme or oxopyrrolidines, complementation studies with branched chain amino‐acids and pantothenate have shown that oxopantoyl lactone reductase is likely to be involved in pantothenate biosynthesis. Furthermore, pantoyl lactone, the putative product of the reaction, together with β‐alanine and ATP, has been shown to be the substrate of pantothenate synthase using a novel assay for pantothenate.
The Use of DNA Fingerprinting in Ecological Studies of Phragmites australis (Cav.) Trin. ex Steudel
Authors: Zeidler A. , Schneider S. , Jung C. , Melchinger A. E. , Dittrich P. 
Published: February 2014

SummaryA number of reed populations (Phragmites australis) from natural locations on the shore of Lake Ammersee in the south of Bavaria as well as artificially grown reed plants were analyzed for restriction fragment length polymorphisms (RFLPs) in order to evaluate for further ecological studies the dynamics of the restriction pattern within the genome of plants which propagate themselves asexually. The artificially grown reed plants were raised in four ponds supplemented with different phosphate concentrations (8 μg, 16 μg, 50 μg, and 200 μg/l) from rhizomes taken from a neighbouring fish pond. The genomic DNA of 25 of these plants and the DNA from 37 plants out of 18 stands from the lakeshore was isolated and restricted with the enzyme EcoRI, EcoRV, XbaI and HindIII and hybridized to three probes from a shot‐gun cloned reed plasmid library. The probes gave between 15 and 26 bands (DNA fingerprints) of high polymorphic frequency (68% − 100%) after hybridization with repetitive sequences of restricted DNA. A cluster analysis based on the banding pattern as a measure of genetic similarity (GS) was performed with the two sets of reed plants. The plants from the lakeshore exhibited a clear formation of clusters with GS up to 100%; the 20 plants grown from rhizomes, in contrast, did not show any clear correlation among themselves, neither to the phosphate concentration they grew in, nor to the five plants tested from the pond their rhizomes came from. The value of genetical investigations of the plant genome in context with environmental impact on plants is being discussed.
Structural Aspects of the Lichen‐Rock Interface Using Back‐scattered Electron Imaging
Authors: Ascaso C. , Wierzchos J. 
Published: February 2014

AbstractThe profound knowledge of the structural and chemical characteristics of the interface between lichen thallus and rock, seems to be indispensable for the process of understanding the lichen symbiosis as well as the significance of the weathering action of lichens. One of the most promising techniques to be used in this investigation is the Scanning Electron Microscopy (SEM) in the back‐scattered electron (BSE) emission mode. In the present work thalli of Parmelia conspersa, Aspicilia intermutans and Lecidea auriculata growing in granitic rock were examined by SEM in BSE mode with (Energy Dispersive Spectroscopy) EDS. In the case of the foliose thalli the observation of the interface permits detection of the rhizine/hyphae adherence and determination of the origin of the minerals which adhere to the rhizine/hyphae. In the case of the crustose thalli BSE permits investigation within the ultrastructure of the crustose thallus and crustose lichen‐rock contact zone and also allows observations of the penetration and filling of the fissures and cracks of the underlying rock by components of the thallus and other living organisms. The BSE images could contribute to a better knowledge of the cytological state of the rock‐inhabiting organisms and also to the understanding of the action of the chemical treatments used in the removal of lichen from building materials.
“Pollen Buds” in Ophiorrhiza (Rubiaceae) and their Role in Pollenkitt Release
Authors: Weber Martina , Igersheim A. 
Published: February 2014

AbstractPollen buds are apertural protrusions formed by the ectintine. In their wall unesterified and methyl‐esterified pectins are detected by immunogold labeling. During pollenkitt formation pollen buds become adpressed and connected to the tapetum wall. The following expansion of the endothecium causes the mechanical rupture of the tapetum at the binding sites of the pollen buds. These events are accompanied by the release of the pollenkitt.
Pre‐adaptation of Arctic Plants to Climate Change*
Authors: Crawford R. M. M. , Abbott R. J. 
Published: February 2014

AbstractRe‐appraisal of high latitude ice cover during the Weichselian and the recent discovery of pre‐Holocene plant communities in Novaya Zemlya and Northern Norway suggests that the contemporary Arctic flora may have had a longer time span in its occupation of high latitude sites than has hitherto been recognised. The present‐day Arctic flora in some regions may therefore have derived at least some of its genetic inheritance from populations that survived in ice‐free refugia in the high Arctic polar deserts during the latter stages of the Weichselian glaciation. Increasing evidence for sudden changes in climate at high latitudes in the past, suggests that Arctic vegetation would have been subjected to rapid climatic warming if it had maintained a presence in these regions during the late Weichselian. A review of what is known about plant survival in the high Arctic since pre‐Holocene times, coupled with an examination of some of the physiological properties of modern populations in these regions is presented in an attempt to ascertain if high Arctic plants possess mechanisms which facilitate their capacity to respond either phenotypically or physiologically to climatic change.
Field Measurements of Water Relations and CO2Exchange of the Tropical, Cyanobacterial BasidiolichenDictyonema glabratumin a Panamanian Rainforest*
Authors: Lange O. L. , Büdel B. , Zellner H. , Zotz G. , Meyer A. 
Published: February 2014

AbstractDiel time courses of microclimate, hydration, and CO2exchange of the basidiolichenDictyonema glabratumand its responses to experimentally changed conditions were measured for 14 days in a clearing of a premontane, tropical rainforest (Panama).Net photosynthesis (NP) was adapted to high temperatures and there was no depression of CO2uptake at the highest thallus hydration. The presence of a CO2concentrating mechanism was demonstrated. Decreased NP occurred after desiccation, and apparent photon yield of CO2fixation was also sensitive to water loss.Natural NP was controlled by the interplay of thallus hydration and radiation. Regular, daily desiccation and dense cloud cover suppressed production. On average, 72 % of the diurnal photosynthetic gain was lost during the night, and there were days with negative carbon balance. Nevertheless, total carbon gain of the lichen was extremely high. A tentative estimation suggests that annual carbon gain amounts to 228 % of initial thallus carbon content.Because of their strong effect on net production, increased nocturnal temperatures as given at lower elevation, would lead to a negative carbon balance. This might explain the lack of abundance of this and other macrolichens in warmer, lowland rainforests.
Quantification of the Daily Cytokinin Transport from the Root to the Shoot of Urtica dioica L.*
Authors: Beck E. , Wagner B. M. 
Published: February 2014

AbstractCytokinins are predominantly root‐born phytohormones which are distributed in the shoot via the xylem stream. In the hormone message concept they are considered as root signals mediating the transport of the photosynthates to the various sinks of a plant. In this paper the cytokinin relations of Urtica dioica L., the stinging nettle, are described, based on the daily flux from the roots to the shoot. Trans‐zeatin‐type cytokinins predominate in the various tissues of Urtica (Wagner and Beck, 1993), and accordingly trans‐zeatin riboside and trans‐zeatin are the forms transported by the xylem sap. The daily time‐course of cytokinin concentration in root pressure exudates and in xylem sap collected from a petiole after pressurizing the root bed showed high concentrations in the morning, followed by a substantial drop to a level of 15–30% of the initial concentration which was then maintained during the afternoon. This time‐course is interpreted as resulting from continuous synthesis and exudation of cytokinins into the xylem fluid of the roots whose cytokinin concentration is then modified by the dynamics of the transpiration stream. Loading of cytokinins into the xylem sap could be enhanced several times by increasing the flux rate of the xylem stream to the maximal transpiration rate when a maximum export rate was reached. The total daily cytokinin gain by the shoot depended on the nitrogen status of the plant. Roots of Urtica plants grown on a sufficient nitrogen supply had a significantly higher cytokinin content and exuded more cytokinins into the shoot than those of plants raised under nitrogen shortage. A positive correlation was found between the steady rates of cytokinin export measured during the afternoon and the shoot to root‐ratios of biomass which, in turn, corresponded to the nitrogen status of the plants.
Micromorphological and Phytochemical Research on Teucrium scorodonia and Teucrium siculum from the Italian Flora
Authors: Servettaz O. , Pinetti A. , Bellesia F. , Maleci L. Bini 
Published: February 2014

AbstractMicromorphology and distribution of trichomes in different plant parts of Teucrium scorodonia and Teucrium siculum from five populations in Italy are described. The composition of volatile compounds in the same plants has also been studied. The micro‐morphological characters of the two taxa differ only in the calyces. T. siculum from the Euganean hills shows a great shape variability in the bracts. As far as the volatile compounds are concerned, this taxon reveals a somewhat special position, particularly for the presence of monoterpenes, which are lacking in T. siculum from Central and Southern Italy.
Physical Interactions of two Rhizomorph‐forming Lichens with their Rock Substrate
Authors: Sanders W. B. , Ascaso Carmen , Wierzchos J. 
Published: February 2014

AbstractSamples of a calcareous conglomerate rock colonized by Squamarina cartilaginea and a siliceous schist colonized by Acarospora scotica were cut and examined with SEM‐backscattered electron imaging. Both species produce extensive rhizomorphs (sensu lato), whose component hyphae interpenetrated, separated, and incorporated substrate particles in the course of development. Rhizomorph expansion and contraction associated with hydration cycles could also detach adherent fragments within the substrate. In S. cartilaginea, rhizomorphs and associated hyphae also directly penetrated the calcareous substrate matrix, probably by chemical dissolution. Those of A. scotica appeared to penetrate the schist mainly by forcing their way between the fine, angular, somewhat flattened particles which comprises the substrate. The orientation of these particles influenced the form of developing rhizomorphs and the subsequent pattern of substrate exfoliation. Lichen compounds of potential biode‐teriorative significance occurred within the squamules of both species but were not detectable in their rhizomorphs. Lichenized photobionts were abundant within the substrate; their developmental relationship to epilithic squamules could be demonstrated in the case of A. scotica.
New Insights into the Protein Import Machinery of the Chloroplast's Outer Envelope
Authors: Soll J. 
Published: February 2014

AbstractA large number of plastid localized proteins are post‐translationally imported as precursor proteins from the cytosol into the organelle. Recognition and translocation is accomplished by a subset of chloroplast envelope proteins, which were identified by different but complementary methods. The outer envelope proteins OEP 86, OEP 75, OEP 70 (a heat shock cognate 70 homologue) and OEP 34 are clearly involved in the import event and can be isolated as one functionally active translocation unit. For three of these proteins cDNA clones have been very recently obtained, namely OEP 86, OEP 75 and OEP 34. OEP 86 seems to be a precursor protein receptor which could be regulated by GTP binding and ATP‐dependent phosphorylation‐dephosphorylation. OEP 75 is part of the translocation pore traversing the membrane in multiple β‐sheets. OEP 34 is tightly associated with OEP 75. It represents a new type of GTP‐binding protein which possesses endogenous GTPase activity. Multiple GTP binding and hydrolysis cycles as well as protein phosphorylation‐dephosphorylation events might, therefore, regulate the interaction of a precursor protein with the translocation machinery of the outer envelope, making it very distinct from the mitochondrial outer membrane system. Further proteins of the inner envelope membrane, namely IEP 97 and IEP 36, have been implied to function in the translocation event. These recent data allow not only identification of the players in the game but also speculation about mechanisms and regulation of translocation.
Reproductive Biology of the Distylous Manettia luteo‐rubra (Rubiaceae)
Authors: Passos Luciana , Sazima Marlies 
Published: February 2014

AbstractThe reproductive biology of Manettia luteo‐rubra was studied in the coastal montane Atlantic rain forest of southeastern Brazil. This Rubiaceae is a perennial vine that flowers all the year round, but has a flowering peak during the dry season. It presents reciprocal herkogamy, thus the plants are morphologically distylous. The morphs occur in a 1:1 ratio, and pollen diameter and corolla length vary between short and long‐styled flowers. Manettia luteo‐rubra displays typical heterostylous self‐incompatibility and sets almost no fruits from self‐ or intramorph pollinations. The flowers are tubular, red with yellow lobes, and odourless. Anthesis is asynchronous, and the flowers last about four days. Concentration of sugars in nectar is similar in both morphs, ca. 24%, this concentration being typical for hummingbird flowers. Three species of hummingbirds are the major pollinators of the flowers of M. luteo‐rubra at the study site: the hermits Phaethornis eurynome and P. squalidus, and the trochiline Thalurania glaucopis. Three species of Heliconius butterflies act as minor pollinators. Both morphs of M. luteo‐rubra exhibit natural fruit‐set of about 80%, this reproductive output being maintained throughout the year by the pollinators' constancy to the flowers.
Seasonal Changes of the Antioxidative Systems in Foliar Buds and Leaves of Field‐grown Beech Trees (Fagus sylvatica, L.) in a Stressful Climate
Authors: Polle Andrea , Morawe Birgit 
Published: February 2014

AbstractThe activities of superoxide dismutase, ascorbate peroxidase, monodehydroascorbate radical reductase, and dehydroascorbate reductase and the contents of ascorbate, chlorophyll and soluble protein were determined in beech (Fagus sylvatica, L.) foliage over two or three seasons. Four important stages of leaf development were distinguished: resting buds, emerging, mature and senescent leaves. Foliar buds in spring, prior to the emergence of new leaves, contained a lower chlorophyll content but a higher protein content and higher activities of ascorbate peroxidase and monodehydroascorbate radical reductase than mature leaves in summer. By contrast, superoxide dismutase and glutathione reductase activities and ascorbate contents were higher in mature leaves than in swollen foliar buds. Dehydroascorbate reductase activity was low in all developmental stages. Resting buds in winter contained activities of superoxide dismutase, ascorbate peroxidase and monodehydroascorbate radical reductase that were similar to those found in mature leaves in summer, whereas the contents of total and reduced ascorbate were 6‐ and 20‐times lower, respectively, in buds than in mature leaves. The low foliar concentration of reduced ascorbate in resting buds, despite high monodehydroascorbate radical reductase activity, suggests that the regeneration of ascorbate might be limited by the availability of reductant. High antioxidative capacity was conferred by mature beech leaves and may be an important protection measure for coping with the large fluctuations in temperature and exposure to elevated ozone concentrations in summer.
Low Molecular Weight Carbohydrate Patterns in Geographically Different Isolates of the Eulittoral Red Alga Bostrychia tenuissima from Australia
Authors: Karsten U. , Bock Chr , West J. A. 
Published: February 2014

AbstractSixteen isolates of the red alga, Bostrychia tenuissima King et Puttock, from New South Wales, Victoria and South Australia were cultured in the laboratory and analysed for low molecular weight carbohydrates using 13C‐NMR and HPLC techniques. All populations south of 34 °S contain D‐sorbitol in combination with the heteroside digeneaside. The isolates north of 34° S lack digeneaside, but contain D‐sorbitol and, in addition, an isomeric form D‐dulcitol. Moreover, the 13C‐NMR spectra showed an unknown metabolite which was only measured in combination with digeneaside. While in the strains south of 34 °S digeneaside and the unknown compound occur in small quantities and remained unchanged with increasing salinities (5–60 ppt), the relatively high D‐sorbitol contents strongly increased under hypersaline conditions. In the populations north of 34 °S both the concentrations of D‐sorbitol and D‐dulcitol increased with increasing salinity. These data demonstrate the important role of polyols in the osmotic acclimation of B. tenuissima. The ecological and/or biological factors controlling this geographical pattern of metabolite content are not known. However, the different carbohydrate patterns within B. tenuissima are considered as indicators of the development of physiological ecotypes.
Transient Expression Activity of RbcS Promoter Regions from Brassica napus in Mesophyll Protoplasts from Nicotiana tabacum*
Authors: Beck I. , Wittig C. , Link G. 
Published: February 2014

AbstractThe 5′ upstream DNA of RbcS genes from Brassica napus contains sequence elements that specifically interact with DNA‐binding proteins of the transcription apparatus in vitro. To clarify if these sequences are functional in vivo, we have studied them in transient expression experiments. Fragments generated by successive deletions of the 5′ upstream regions of two RbcS genes were fused in frame to the β‐glucuronidase (gusA) reporter gene and GUS activity was monitored fluorometrically after polyethylene glycol (PEG)‐mediated DNA uptake in mesophyll protoplasts from Nicotiana tabacum SR1. The results indicate modular organization of cis‐elements that together account for full promoter activity. Whereas the TATA‐box region alone resulted in basal expression levels, enhanced GUS activity was observed in the presence of additional further‐upstream sequences, including the G‐box and the Gs‐box. For maximal activity, the presence of a region containing the I‐box was required. In addition to these putative activating DNA regions, evidence was obtained for regions that negatively affected GUS activity and hence may contain silencer element(s).
Anatomy and Phenylpropanoid Metabolism in the Incompatible Interaction of Lycopersicon esculentum and Cuscuta reflexa
Authors: Sahm Antje , Pfanz H. , Grünsfelder Maria , Czygan F.‐C. , Proksch P. 
Published: February 2014

AbstractA time‐dependent correlation of anatomical and chemical defence reactions was shown during the incompatible reaction of tomato against the phanerogamic parasite Cuscuta reflexa. Microscopical analysis of the infection sites at the tomato stem revealed the elongation of epidermal, hypodermal and collenchymatic cells beneath the parasitic prehaustorium. After 9–11 days of infection the elongated cells had collapsed forming a visible brownish plaque at the tomato stem followed by a scalariform tissue with lignified and suberized cell walls. Concomitantly, an enhanced accumulation of soluble phenolic compounds (chlorogenic acid and an unidentified hydroxycinnamic acid derivative), as well as a stimulation of peroxidases, was observed. In contrast, PAL activity was not increased. Whereas the stimulation of phenylpropanoid metabolism could also be induced by artificial wounding, the described anatomical changes were only observed during attack of Cuscuta.
Auxin‐Binding Protein (ABP1) is not Confined to the Outer Epidermis of Maize (Zea mays L.) Coleoptiles
Authors: Kayser B. , Klämbt D. 
Published: February 2014

AbstractMaize seedlings were studied for their expression patterns of ABP1‐mRNA and ABP1. In situ hybridization did not reveal hot spots of ABP1‐mRNA accumulation. This result was supported by northern hybridization. In coleoptiles the ABP1‐mRNA remains constant during day 1 to day 5 and is of low abundance (1.3 pg/μg total RNA). Northern blots indicated that in primary roots the mRNA level is even 10 times lower. Neither ABP1‐mRNA nor ABP1 was found to be concentrated within the outer epidermis of the coleoptile. Analysis of immunostained western blots did not reveal pronounced differences in ABP1 content on the basis of equal amounts of fresh weight or total protein. We therefore assume ABP1 to be more or less equally distributed among the cells of the shoot tissues of maize seedlings.
Water Potential Modulates Extensibility of Rye Coleoptile Cell Walls
Authors: Edelmann H. G. 
Published: February 2014

AbstractExtensibility of walls of frozen/thawed rye (Secale cereale) coleoptile segments as a function of the water potential of the incubation solution (Ψ0) was analyzed employing the creep test method. Negative Ψ0exerts an inhibiting effect on extension of isolated walls. The lower the Ψ0of polyethylene glycol 6000 (PEG), the less the walls of frozen/thawed segments extended under load. This inhibiting effect of Ψ0on wall creep was reversible and independent of the preincubation temperature of the segments. An increase in Ψ0resulted in increased extension rate within 2–4 min, whereas a decrease in Ψ0resulted in gradually decreasing extension rate after 8–12 min. This finding implies that wall extension changes during growth induced by changes of Ψ0in vivoare not only due to changes of turgor pressure but also due to a direct influence by negative Ψ0on physical wall properties. The results are discussed with respect to the regulation of extension growth during conditions of water stress.