bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Colacosomes: New Structures at the Host‐parasite Interface of a Mycoparasitic Basidiomycete*
Authors: Bauer R. , Oberwinkler F. 
Published: February 2014

AbstractThe ultrastructure of mycoparasitic interactions in heterobasidiomycetes is diverse. A previously unknown cell structure, involved in a specific parasitic interaction, is described and illustrated. Cells of the parasite Platygloea peniophorae (Auriculariales s.l., Basidiomycetes) which attach to host cells of Hyphoderma praetermissum (Aphyllophorales, Basidiomycetes) form distinct marginal vesicular bodies with electron‐opaque cores and electron transparent sheaths. Finally, the vesicular content projects through the cell wall of the parasite and then interacts with the cell wall of the host. Ontogenetic stages are described and illustrated in detail.
Rapid Phosphorylation of H3 Histone in Isolated Nuclei of Barley (Hordeum vulgare L.)
Authors: Grimm R. , Eckerskorn Chr , Lottspeich F. , Schäfer E. 
Published: February 2014

AbstractWe studied the in vitro phosphorylation pattern of the proteins from in vivo irradiated isolated nuclei in relation to the investigations on rapid phytochrome effects on in vitro transcription of specific genes in isolated nuclei from barley (Mösinger et al., 1985, 1987). Although phosphorylation with carrier‐free [γ‐32P]ATP raises a variety of labeled proteins, the overall pattern does not show any difference due to the light pretreatment of the nuclei. Time‐course analysis revealed a 17 and a 45 kDa protein as the most rapidly phosphorylated proteins. To obtain more information about the identity of both proteins we tried to determine the amino‐terminal sequences of both proteins. Whereas the 45 kDa protein has a blocked amino‐terminus, we identified the 17 kDa protein as H3 histone due to its sequence homology to other H3 histones from different sources.
Properties of Oligomeric Forms of Phosphofructokinase from Chlorella kessleri Grown under Different Light Conditions
Authors: Grotjohann N. , Kowallik W. , Ruyters G. 
Published: February 2014

AbstractFast protein liquid chromatography on Superose 6 of crude extracts from Chlorella kessleri, Fott et Novákóva, grown autotrophically in blue or in red light yields three different oligomeric forms of phosphofructokinase (PFK, EC 2.7.1.11). Their substrate affinities and responses to homotropic and heterotropic effectors are different. In vitro, the degree of oligomerization of the enzyme can be influenced by specific intermediates or cofactors. Its substrate, MgATP (10 mM/5 mM), and the negative effector, phosphoenolpyruvate (5 mM), both lead to some dissociation, while the second substrate, fructose‐6‐phosphate (5 mM), and the positive effector, inorganic phosphate (50 mM), have no effect. It is discussed whether formation or dissociation of oligomeric PFK forms in vivo result from alterations in the levels or in the intracellular distribution of effector molecules and whether such processes are involved in the different regulation of cell metabolism in blue or in red light.
The Preparation of Plasmodesmata from Plant Tissue Homogenates: Access to the Biochemical Characterization of Plasmodesmata‐Related Polypeptides
Authors: Monzer J. , Kloth Sabine 
Published: February 2014

AbstractA technique for the preparation of plasmodesmata within a cell wall fraction of Solanum nigrum tissue homogenates has been developed, featuring good ultrastructural preservation of plasmodesmatal structure. SDS‐PAGE of protein extracts of this plasmodesmata‐containing cell wall fraction revealed the distinct enrichment of two bands, with molecular weights of 28 and 43 kD.
Localization of Tubulin and a Centrin‐Homologue in Vegetative Cells and Developing Gametangia of Ectocarpus siliculosus (Dillw.) Lyngb. (Phaeophyceae, Ectocarpales)
Authors: Katsaros Chr , Kreimer G. , Melkonian M. 
Published: February 2014

AbstractThe distribution of tubulin and centrin in vegetative cells and during gametogenesis of Ectocarpus siliculosus was studied by immunofluorescence. In interphase cells bundles of microtubules are focused on the centriolar region near the nuclear surface. Some of the bundles ensheath the nucleus while others traverse the cytoplasm in various directions, sometimes reaching the cell cortex. Evaluation of serial optical sections by confocal laser scanning microscopy (CLSM) revealed that the perinuclear and “cytoplasmic” microtubule bundles presumably constitute a single complex. In interphase cells centrin is localized as a single bright spot in the centriolar region. In dividing cells duplication and separation of the microtubular complex and the centrin spot takes place. In post‐mitotic cells with two nuclei, the centrioles are located at opposite cell poles, short microtubule bundles emanate from them and partially encompass the nucleus. During gametogenesis a gradual transformation of the vegetative cytoskeleton to the gametic flagellar apparatus occurs.
High Humidity and Heat Stress Causes Dissociation of Endoplasmic Reticulum in Tobacco Pollen
Authors: Ciampolini F. , Shivanna K. R. , Cresti M. 
Published: February 2014

AbstractHigh humidity (95 % RH) and temperature (38/45 °C) stress for 4h applied to pollen grains of Nicotiana tabacum did not affect pollen viability, assessed on the basis of the fluorochromatic reaction test, but affected in vitro germination; pollen grains treated at 38 °C showed marked delay in germination, while those treated at 45 °C failed to germinate in vitro.The major ultrastructural effect of the stress was on RER. Stacks of RER, characteristically present in fresh pollen, were largely dissociated in the stressed pollen. The extent of dissociation of RER was greater in pollen samples stressed at 45 °C than at 38 °C. The generative cell did not show any obvious change in the stressed pollen. RER was restored in pollen grains which showed germination following culture; but not in those which failed to germinate. Apart from affecting other RER‐related functions the dissociation of RER is likely to result in the destruction of long‐lived mRNA and thus affect the ability of pollen grains to initiate protein synthesis needed for germination.
Acid‐Base Regulation byAzollaspp. with N2as Sole N Source and with Supplementation by NH+4or NO−3
Authors: Raven J. A. , Rothemund C. , Wollenweber B. 
Published: February 2014

AbstractDiazotrophic cultures of three species ofAzolla (Az. caroliniana, Az. microphylla, Az. pinnata)symbiotic withAnabaena azollaeaccumulated some 0.10–0.24 mol organic anion per mol N assimilated (0.010–0.018 mol organic anion per mol C assimilated), with a corresponding efflux of 0.05–0.11 mol H+per mol N assimilated (0.006–0.009 mol H+per mol C assimilated). These values are lower than those found for terrestrial diazotrophic vascular plants; this may be related to the decreased possibility of increasing Fe and P availability by rhizosphere acidification in a free‐floating plant. Modification of the organic anion content, and of the quantity (and direction) of H+exchange with the medium, with 5 mol m−3NH+4or NO−3added to diazotrophic cultures, are consistent with substantial N acquisition from combined N as well as N2assimilation. This conclusion is consistent with previously published work with15N.
Differential Regulation of Nuclear Genes during Blue Light‐dependent Chloroplast Differentiation in Cultured Plant Cells
Authors: Bockholt S. , Kaldenhoff R. , Richter G. 
Published: February 2014

AbstractNuclei capable of RNA synthesis were isolated from both dark‐grown and blue light‐irradiated cell cultures of Chenopodium rubrum. Analysis of the heterodisperse RNA sequences synthesized showed that the SSU and LHCP gene as well as early light‐induced genes were specifically transcribed. The relative transcription rate of their mRNAs increased with the onset of blue light irradiation reaching a maximum at about 12 h, then dropped to the dark level. A comparison with the steady‐state concentration of the same mRNAs in vivo revealed a substantial difference between the two groups of genes: For the three early light‐induced genes the in vitro transcription rate is in good accordance with the observed steady‐state level of their transcripts supporting the notion that the blue light‐dependent rapid and transient accumulation in vivo is caused by a temporary increase in the transcription rate of the corresponding genes. In contrast, for the SSU and LHCP gene, the changes in transcription rate do not follow those in steady‐state concentration; thus the observed steady increase of the latter in blue light cannot be explained as an enhancement in the transcription rates of both genes, but is a likely consequence of post‐transcriptional events.
Energy Metabolism in Rhizomes of Acorus calamus (L.) and in Tubers of Solanum tuberosum (L.) With Regard to their Anoxia Tolerance
Authors: Sieber Mirjam , Brändle R. 
Published: February 2014

AbstractRhizomes of the marsh plant Acorus calamus (L.) and tubers of the flooding‐intolerant Solanum tuberosum (L.) var. Bintje, both kept under strict anoxia, differ markedly in their fermentation properties. The fermentation capacities as measured by ADH and LDH activities and their respective product concentrations were estimated.While rhizomes of Acorus calamus, having high ADH and low LDH activities, accumulate mainly ethanol, tubers of Solanum tuberosum tend towards lactic acid fermentation.The total amount of adenine nucleotides is quite stable in Acorus calamus, whereas they show a sharp decline in S. tuberosum during the first 6h of anoxia. The adenylate energy charge of A. calamus recovers after a short initial drop (AEC > 0.8). AEC values of S. tuberosum decrease rapidly and remain at very low values (AEC ∼ 0.3). Tuber tissues became soft and lost viability after about 48–72 h of anoxia at 25 °C. This might be due to tissue acidification and impaired energy metabolism, but not to the lack of energy reserves. Energy metabolism of A. calamus is well adapted to anoxia.
Photorespiration is More Effective than the Mehler Reaction in Protecting the Photosynthetic Apparatus against Photoinhibition
Authors: Wu J. , Neimanis S. , Heber U. 
Published: February 2014

AbstractI. Isolated intact chloroplasts: Photosystem II, but not photosystem I, of the electron transport chain is rapidly photoinactivated even by very low intensities of red light when no large proton gradient can be formed and the electron transport chain becomes over‐reduced in the absence of oxygen and other reducable substrates. Electron acceptors including oxygen provide protection against photoinactivation. Nevertheless, photosystem II is rapidly, and photosystem I more slowly, photoinactivated by high intensities of red light when oxygen is the only electron acceptor available. Increased damage is observed at increased oxygen concentrations although catalase is added to destroy H2O2 formed during oxygen reduction in the Mehler reaction. Photoinactivation can be decreased, but not prevented by ascorbate which reduces hydrogen peroxide inside the chloroplasts and increases coupled electron flow.II. Leaves: Simple measurements of chlorophyll fluorescence permit assessment of damage to photosystem II after exposure of leaves to high intensity illumination. In contrast to isolated chloroplasts, chloroplasts suffer more damage in situ at reduced than at elevated oxygen concentrations. The difference in the responses is due to photorespiration which is active in leaves, but not in isolated chloroplasts. After photosynthesis and photorespiration are inhibited by feeding glyceraldehyde to leaves, photoinactivation is markedly increased, although oxygen reduction in the Mehler reaction is not affected by glyceraldehyde. In the presence of reduced CO2 levels, photorespiratory reactions, but not the Mehler reaction, can prevent the overreduction of the electron transport chain. Over‐reduction indicates ineffective control of photosystem II activity. Effective control is needed for protection of the electron transport chain against photoinactivation. It is suggested to be made possible by coupled cyclic electron flow around photosystem I which is facilitated by the redox poising resulting from the interplay between photorespiratory carbohydrate oxidation and the refixation of evolved CO2.
The Occurrence of Vascular Cavities and Specialized Parenchyma Cells in the Roots of Cool‐season Legumes
Authors: Rost T. L. , Lu P. , Gladish D. 
Published: February 2014

AbstractThe seeds of 20 legume species were grown in the greenhouse or in growth chambers at different temperatures. Under warm temperature conditions (above 15 °C), six species, pea (Pisum sativum), broadbean (Vicia faba), chickpea (Cicer arietinum), lentil (Lens culinaris), wild lupine (Lupinus latifolius), and soybean (Glycine max), formed cavities in the vascular cylinder of their primary roots, which in turn became filled by the ingrowth of specialized parenchyma cells (SP cells). When these species were grown at low temperature (below 15 °C), however, a “normal” vascular cylinder formed in the primary roots with late‐maturing metaxylem vessel members differentiating in the center. These species were all cool‐season legumes except soybean, a warm‐season legume, which sometimes also formed cavities and SP cell ingrowths. The occurrence of cavities and SP cells therefore was restricted to the cool‐season legumes (except soybean) when they were grown under warm temperature conditions. The position and size of cavities varied among these species. Pea and broadbean usually formed large, axially elongated cavities in the central vascular cylinder, or in the xylem poles. Others formed smaller cavities of various lengths.
Studies of the Mature Pollen of Spinacia oleracea after Freeze Substitution and Observed with Confocal Laser Scanning Fluorescence Microscopy
Authors: Theunis C. H. , Cresti M. , Milanesi C. 
Published: February 2014

AbstractThe three‐dimensional configuration of the nuclei of the trinucleate pollen grain of Spinacia oleracea L. has been examined by means of confocal laser scanning fluorescence microscopy (CLSM). It shows the presence of a male germ unit (MGU) in which all three nuclei are usually positioned in the periphery of the pollen grain. After freeze fixation and freeze substitution, the ultrastructure is better preserved than with standard chemical fixation. It shows the presence inside the pollen grain of mitochondria, dictyosomes, large starch‐containing plastids, endoplasmic reticulum (ER), vacuoles and the MGU. In the sperm cells mitochondria, vesicles, dictyosomes and ER are also found. No microtubules were found in the grain and only very few inside the sperm cells. This is in contrast with earlier published results where fluorescent‐labeled antibodies were used.
Gametophyte Regeneration and Apospory from Archegoniate Protoplasts Under Conditions Devised for Higher Plants*
Authors: Binding H. , Mordhorst G. 
Published: February 2014

AbstractDevelopmental pathways from isolated protoplasts were investigated with the moss Funaria hygrometrica, the liverwort Anthoceros crispulus, and the fern Anogramma leptophylla. Gametophytic protoplasts regenerated gametophytes. Apospory was obtained with sporophytic protoplasts of the moss and the fern. The archegoniates also grew in interdivisional co‐cultures with solanaceous species.
p‐CMBS Modifies Extrafacial Sulfhydryl Groups at the Chara Plasma Membrane: Activation of Ca2+ Influx and Inhibition of Two Different K+ Currents
Authors: Thiel G. 
Published: February 2014

AbstractThe effect of the membrane impermeant sulfhydryl group (SH) reagent, p‐chloromercuribenzenesulfonic acid (p‐CMBS), on electrical membrane transport properties of the giant alga, Chara corallina, was determined. In an external medium with a high K+ concentration (5 mM) cells typically exhibited stable membrane potentials close to the K+equilibrium potential. The steady‐state current‐voltage (I‐V) relation could be dissected into two distinct components: an almost linear ohmic leak current and a voltage‐dependent K+ current. Adding 0.5 mM p‐CMBS to the external medium resulted in an immediate, short depolarization transient (resembling the time course of an action potential) and was associated with a slow down of the cytoplasmic streaming velocity. The depolarization, as well as the streaming inhibition, could be abolished by pretreating cells with the Ca2+ channel inhibitor, LaCl3. This suggests that the depolarization transient reflected a p‐CMBS induced Ca2+ influx, a scenario known to trigger membrane excitation and slow down of cytoplasmic streaming. From the I‐V analysis it appeared that p‐CMBS also caused a reversible inhibition of two additional transmembrane currents: (1) a reduction of a leak current and (2) a modification of the deactivation kinetics of the voltage‐dependent K+ channels. From the I‐V difference analysis, the inhibited leak current was identified as a K+ current, because the reversal potential was close to the estimated K+ equilibrium potential. Control experiments have furthermore shown that the mercapto reagent, dithiothreitol, partly reversed the effect of p‐CMBS. This strengthens the view that the action of the mercurial is related to a specific and direct modification of SH groups. The p‐CMBS‐evoked inhibition of K+ currents was not abolished by the LaCl3 pretreatment, which suggests that the effect of the SH reagent is not induced indirectly by p‐CMBS‐triggered Ca2+ influx. Therefore, it is suggested that the mercurial interacts direcly with the K+ transport protein.
Flexibility in CO2 — Fixation Pathway of a Highland Kalanchoë, Kalanchoë petitiana A. Rich.
Authors: Fetene M. , Lüttge U. , Ziegler H. 
Published: February 2014

AbstractPhotosynthetic flexibility and water use efficiency of Kalanchoë petitiana A. Rich., a facultative CAM plant endemic to the highlands of Ethiopia, were investigated to determine the physiological determinants for the ecological success of the plant. Both field measurements of δ13C and greenhouse gas exchange studies showed a shift from C3 photosynthesis to CAM as leaves aged or at the onset of water stress. Recycling of CO2 was observed in developing leaves without concomitant net CO2 uptake. Accumulation of malate was positively correlated with increased cell sap osmolality and improved daily water use efficiency. The importance of flexibility in carbon uptake pathway and of recycling CO2 for the ecological success of the plant is discussed.
Composition of Orchid Scents Attracting Euglossine Bees
Authors: Gerlach G. , Schill R. 
Published: February 2014

AbstractFragrance composition of flowers from 101 plant species, especially orchids, were analyzed. Several compounds, including allo‐aromadendrene, β‐bourbonene, α‐copaene, α‐cubebene, 1,2‐dimethoxybenzene, 1,3,5‐trimethoxybenzene, epoxygeranyl acetate, 7,11‐epoxymegastigma‐5(6)‐en‐9‐one, two γ‐lactones, germacradienol, germacrene D, humulene, methoxy‐phenyl‐ethyl acetate, myrcene epoxide, sabinene, styrene, and undecatriene were detected for the first time in orchids. Fragrance composition of flowers pollinated by male euglossine bee species (perfume flowers) of four plant families are compared and contrasted with those of orchid species with other pollination systems.Melittophilous, but highly specialized orchids, produce fragrances rich in different sesquiterpenes and other rare compounds. In the species that are exclusively pollinated by fragrance‐collecting male euglossine bees, the fragrances are primary attractants that serve both as an attractant and as a reward. The unusually intensely smelling flowers mostly produce esters and monoterpenes. The fragrances of euglossophilous flowers of the three plant families investigated are composed of nearly the same sets of chemical compounds, suggesting convergent evolution.Typically, euglossophilous plant species produce large amounts of few fragrant substances while melittophilous species often produce rare compounds in small amounts.
Pollination and Breeding System of Vellozia squamata (Liliales: Velloziaceae): A Species of the Brazilian Cerrados
Authors: Oliveira P. E. , Gibbs P. E. , Bianchi Marta 
Published: February 2014

AbstractThe pollination biology and breeding system of Vellozia squamata (Velloziaceae), a species of cerrado vegetation in Central Brazil, were studied. V. squamata is unusual in being pollinated by a few, generalist bee species despite having very large flowers, and having a distinctive pulsed flowering phenology. The species is self‐incompatible but with a late‐acting, post‐fertilization rejection mechanism.
Direct Measurements of the Pressure and Flow in the Xylem Vessels of Nicotiana tabacum and their Dependence on Flow Resistance and Transpiration Rate
Authors: Benkert R. , Balling A. , Zimmermann U. 
Published: February 2014

AbstractThe relationships between xylem tension, velocity of water ascending and transpiration in tobacco plants were measured by means of the “xylem pressure probe technique” (Balling, A. and Zimmermann, U., Planta 182, 325–338, 1990). The flow velocity was determined by suction or injection of fluorescein (or FITC‐labelled dextrans of various molecular weights) from the microcapillary of the pressure probe into the punctured xylem vessel, followed by serial‐sectioning of the stem after a given propagation time. The distance travelled was defined as the distance from the injection point to the uppermost xylem section in which the dye could be detected. For a transpiration rate of 0.52 ± 0.12 ml . h−1, a linear dependence between the flow velocity and the tension gradients was found as expected from the Hagen‐Poiseuille law. The slope of the straight lines decreased with increasing molecular weight of the fluorescent labelled compound, presumably because of (partial) plugging of the pit membranes. The average value of the flow velocity (2.5 . 10−4 ± 0.9 . 10−4 m . s−1) was one magnitude smaller than the value estimated from the geometric dimensions of the xylem vessels, but agreed well with the literature value of 2.8 . 10−4 m . s−1 for herbs (determined by the heat pulse technique; Huber, B. Ber. deutsch. bot. Ges. 50, 89–109, 1932). The average pressure gradient was determined to be 0.39 ± 0.23 MPa . m−1, in agreement with the literature (Begg, J. E. and Turner, N. C. Plant Physiol. 46, 343–346, 1970).The first response of xylem pressure (or tension) and of flow velocity to a reduction of the transpiration rate (0.14 ± 0.06 ml . h−1) occurred after about 24 h, when an increase of the xylem pressure towards higher values associated with a decrease in flow velocity was observed. In contrast, re‐establishment of the normal transpiration rate brought the pressure (or tension) and the flow velocity back to normal values within half an hour.Similary, introduction of a transverse cross‐sectional cut into the stem did not lead during the first 10 h to a change in xylem tension (or velocity). However, during the following day the pressure fell to relatively low values (about −0.13 MPa). The velocity increased 10‐fold. In the next two days the xylem pressure increased again to normal values (average +0.03 MPa), whereas the flow velocity assumed higher values than normal.The data are discussed in terms of the water status and storage of the adjacent tissue cells.