bluuebunny/crossref_metadata_2025_split huggingface dataset:
Anatomical Studies of Haustorium Ontogeny and the Remarkable Mode of Penetration of the Haustorium in Nuytsiafloribunda (Labill.) R. Br.
Authors: Beyer Christine , Forstreuter W. , Weber H. Chr 
Published: February 2014

AbstractThe development and structure of secondary haustoria of Nuytsia floribunda are described and compared with other Santalalean haustoria.After establishing contact with the host root, cortical folds of the haustorium grow around the root in separate directions and fuse forming a ring around it. At an early stage of development, meristematic tissue differentiates in the interior proximal part of the haustorium. Zones of collapsed layers are present in the outer cortical region. Subsequently, in the proximal part, two vascular cores, two lysigenous cavities and extensive masses of sclerenchyma develop prior to penetration of the host root. The sclerenchymatous cells form a characteristic structure, described as the sclerenchyma prong.During penetration the intrusive part of the haustorium reaches not only the host xylem but continues growing downwards until it entirely splits the host root. Comparable to a guillotine, the sclerenchyma prong is directly involved in this remarkable process. The sclerenchyma prong finally lies in the distal part of the haustorium.Following this mechanical slicing of the host root, tube‐like cells of the intrusive part actively penetrate the host xylem in an axial direction.
On an Inhibitor of Ferredoxin Catalyzed Cyclic Photophosphorylation in Thylakoid Membranes*
Authors: Trebst Achim , Wietoska Helga 
Published: February 2014

AbstractDibromo‐ and diiodo‐naphthoquinones are shown to be inhibitors of the cytochrome b6/f complex in isolated thylakoid membranes from spinach chloroplasts. Dibromo‐naphthoquinone inhibits ferredoxin catalyzed cyclic photophosphorylation at 0.1 μM concentrations, but non cyclic e‐flow only at 10 μM. It does not inhibit cyclic systems with artifical cofactors, nor non‐cyclic electron flow from duroquinol through photosystem I via the cytochrome b6/f complex. Dibromo‐naphthoquinone does however, lower the stoichiometry for ATP formation in the duroquinol donor system. This inhibitory pattern is quite different from that of DBMIB, but very similar to that of antimycin. This antimycin‐like behaviour of these inhibitors is interpreted to indicate a) the existence of a Qc site in the cytochrome b6/f complex and its obligate function in ferredoxin catalyzed cyclic electron flow and b) a non‐essential role of the Qc site in non‐cyclic electron flow, but which — when operative — pumps an extra proton across the thylakoid membrane increasing the ATP yield.
Photosynthetic Characteristics and the Ratios of Chlorophyll, β‐Carotene, and the Components of the Xanthophyll Cycle Upon a Sudden Increase in Growth Light Regime in Several Plant Species*
Authors: Demmig‐Adams B. , Winter K. , Winkelmann E. , Krüger A. , Czygan F.‐C. 
Published: February 2014

AbstractAmong three species, Gossypium hirsutum, Rhizophora mangle, and Monstera deliciosa, which were transferred from low to high growth PFD, only small decreases in the efficiency of photochemical energy conversion were observed in those plants which exhibited an increase in photosynthetic capacity. Leaves of plants which showed no increase in photosynthetic capacity experienced a continuous decrease in photochemical efficiency, accompanied by a more pronounced loss of chlorophyll than that observed in the former group. In all species marked increases in the xanthophyll/β‐carotene ratio resulted from small increases in lutein, and several‐fold increases in the sum of the three components of the xanthophyll cycle, zeaxanthin, antheraxanthin, and violaxanthin. A strong increase in the level of zeaxanthin was only partially matched by a decrease of violaxanthin to zero, and was further paralleled by a decrease in β‐carotene. Antiparallel changes in the sum of zeaxanthin + antheraxanthin + violaxanthin and β‐carotene between morning and evening were observed in all species. These diel changes were overlaid on a net increase in β‐carotene as well as total carotenoid content in those plants in which photosynthetic capacity increased. In those, however, which exhibited no photosynthetic acclimation upon transfer to high light, a decrease in both β‐carotene and total carotenoid content was observed. Rhizophora mangle grown at 100 % seawater exhibited a particularly high capacity for increasing the level of zeaxanthin in response to high light.
Photoacoustic Spectroscopy and its Application in Plant Science
Authors: Buschmann C. 
Published: February 2014

AbstractThe principles of photoacoustic spectroscopy are outlined. This new and still developing technique enables one to detect non‐radiative de‐excitation processes. It is possible to distinguish between signals emenating from different depths of the sample. In plant science photoacoustic spectroscopy has mainly been applied in photosynthesis research. Here it allows the detection of gross oxygen evolution and gives information about the energy balance of the primary photosynthetic reaction.
Implications of Control Theory for Homeostasis and Phosphorylation of Transport Molecules*
Authors: Hansen U.‐P. 
Published: February 2014

AbstractHomeostasis of a cytosolic substrate (e.g. H+) can be achieved by transmembrane transport. Control theory implies that the involved activation and deactivation of a transport molecule (as observed in patch clamp experiments) requires input of energy. This energy can be provided by a so‐called non‐consuming binding site or by other sources and is necessary in order to achieve asymmetric rate‐constants required for an efficient integral controller. Another important prediction of control theory is the involvement of two different binding sites for the substrate and its antagonist in order to define a non‐zero set‐point.The kinetic behavior of a homeostatic feed‐back loop is calculated. The system can generate weakly damped oscillations or exponential responses. Numerical calculations using data from the pH‐controller of Nitella show that a buffer is necessary in order to explain the observed long periods of 1 hour/cycle. Theoretically, the damping factor can originate from shunting transporters or from special terms of the biochemical reaction schemes. The effect of shunting transport systems is demonstrated in the case of data from the light‐effect on H+‐fluxes in Nitella.
The Plasma Membrane Ca2+‐Pump of Plant Cells: A Radiation Inactivation Study
Authors: Rasi‐Caldogno Franca , Pugliarello Maria Chiara , Olivari C. , De Michelis Maria Ida , Gambarini Grazia , Colombo Paola , Tosi G. 
Published: February 2014

AbstractThe functional molecular weight of the plasma membrane Ca2+‐ATPase of radish (Raphanus sativus L.) seeds was determined by measuring the Ca2+‐dependent ATPase activity and the MgATP‐dependent Ca2+ transport activity of membrane samples irradiated, in the lyophilized state, with γ rays from [60Co] source. The results gave a target size of about 270,000 dalton for both the measured activities, thus confirming (i) that both activities are catalyzed by the same enzyme and (ii) the similarity between the plasma membrane Ca2+‐ATPase of higher plants and that of the erythrocytes.
Growth of Anacystis in the Presence of Thiosulphate and its Consequences for the Architecture of the Photosynthetic Apparatus
Authors: Koenig F. 
Published: February 2014

AbstractWith the aim of obtaining information on the degree of flexibility maintained in cyanobacteria in context with their phylogenetic position, Anacystis was grown in the presence of thiosulphate, oxidized in a photosystem I (PSI) dependent reaction (KM 7.4 × 10−3 M thiosulfate). Besides DBMIB, only o‐phenanthroline and p‐hydroxymercuribenzoate blocked thiosulphate‐dependent PSI activity to some extent; iodonitrothymol, DCMU and cyanide had no influence. Growth of Anacystis in the presence of thiosulphate induced a reorganization of the photosynthetic apparatus characterized by a shift in the PSII/PSI ratio in favor of PSI, comparable to low light conditions. Capability for oxygenic photosynthesis never completely disappeared; structural elements of PSII were retained in the membrane to a certain degree. The antenna pigment system signalled high light under conditions of thiosulphate oxidation as judged from the ratio of phycocyanin to chlorophyll. Besides a shift in the ratio of PSII to PSI components, the polypeptide pattern of thylakoids from thiosulphate grown cells shows several additional components compared to the controls and, moreover, higher concentrations of some polypeptides present in the controls, particularly a Mr 41000 polypeptide. The process of thiosulphate oxidation appears bound to the thylakoid membrane.
Auriculora byssomorpha, a Tropical Lichen with a Remarkable Developmental Morphology*
Authors: Henssen A. , Titze A. 
Published: February 2014

AbstractThe thallus, pycnidia, and the structure and ontogeny of the ascocarp in Auriculora byssomorpha are described and illustrated. The ontogeny of the apothecia is characterized by the repeated formation of new hymenia within the subhymenial layer. The development of the first hymenium is gymnocarpous but the de novo differentiation of new hymenia, each beneath the next older disintegrating one, gives rise to a peculiar type of secondary hemiangiocarpy. Portions of the decaying hymenia and adjacent subhymenial tissue frequently remain fastened to the apothecial margin and disc in the shape of ear‐like appendages or as superimposed layers. In aged apothecia such decaying tissue may form a sheath around the apothecial margin and on the disc. The systematic position of the genus is briefly discussed.
Regulation of LHCa‐Polypeptide‐Biosynthesis in the Phototrophic Green Alga Chlamydobotrys stellata*
Authors: Wiessner W. , Kohnke B. , Kloppstech K. , Mende D. , Radunz A. , Winter J. 
Published: February 2014

AbstractThe light‐harvesting chlorophyll‐protein system of the phototrophic alga Chlamydobotrys stellata consists of the common photosystem II‐related chlorophyll a/b‐protein complex LHCII and a special photosystem I‐connected chlorophyll protein complex, called LHCa (Brandt et al. 1982, 1983) which is present after cultivation of the algae with acetate as carbon source and in absence of carbon dioxide. LHCII consists of three polypeptides (Mr.103 27, 25.5 and 25), whereas only one polypeptide (Mr.103 24) was obtained after polyacrylamide gel electrophoresis of LHCa. The specific LHCII‐precursor‐polypeptides (Mr.103 38, 32, 26) were among the translation products of poly(A+)mRNA from autotrophic or photoheterotrophic algae. The LHCa‐precursor‐polypeptide (Mr 30 000) was found when the alga had been cultivated in the presence of acetate. The data support the assumption that LHCa‐biosynthesis is controlled by the actual growth conditions at or close to the transcriptional level.
Recent Molecular Approaches to the Physiology of the Plasma Membrane Proton Pump
Authors: Serrano R. 
Published: February 2014

AbstractDuring the last 3 years, genes for plasma membrane H+‐ATPases from fungi, protozoa and plants have been isolated. Sequence similarities indicate that H+‐ATPases constitute a separate group with the family of ATPases with phosphorylated intermediates. Yeast is a convenient model system to approach the physiology of H+‐ATPases by recombinant DNA methodologies. A mutational analysis of yeast H+‐ATPase has demonstrated that the enzyme is essential and rate‐limiting for growth. Intracellular pH homeostasis is one of the crucial functions of H+‐ATPase. In addition, there are indications for the direct energization of some essential transport system. The regulation of ATPase activity is probably mediated by an interaction between the active site and an inhibitory domain at the carboxyl‐terminus.
Thallus Formation of the Cyanobacterial Lichen Peltigera didactyla from Soredia under Laboratory Conditions
Authors: Stocker‐Wörgötter Elfie , Türk R. 
Published: February 2014

AbstractFormation of mature thalli with soredia occurred within an average cultivation time of 5 to 6 months. The size and growth form of the thalli (mussel‐shaped and branched type) were dependent upon the number of the soredia which were involved in the thallus‐forming process. Not only soredia amalgamated forming a soredia‐field, but also whole lobes fused during development.Contamination problems with soredia were partially overcome by using soredia from cultivated thalli.
Isotopic Fractionation of Hydrogen in Plants
Authors: Smith B. N. , Ziegler H. 
Published: February 2014

AbstractThe naturally‐occurring stable isotopes deuterium and hydrogen are fractionated by a number of physical and biological processes. Deuterium has a tendency to precipitate out first from a moist air mass. Thus ground water will become isotopically lighter with an increase in latitude, altitude, or distance inland. Water taken up by the plant from the soil undergoes little change until evapotranspiration results in leaf water becoming isotopically heavier. Thus hydrogen isotopes in plants can reveal something of geography (groundwater) and climate. Hydrogen isotopes undergo little fractionation by passage through the food chain, although plant parasites tend to be enriched in D as compared to their hosts, possibly due to higher rates of transpiration in the parasitic plants. The splitting of water in photosynthesis results in the lighter isotope being incorporated into organic matter. An even larger isotopic fractionation results during lipid synthesis and other processes involving the pyruvate dehydrogenase complex. Differences in metabolic pathway between species can be detected by D/H ratios. Hydrogen isotopic differences can be detected between CAM, C4, and C3 species. Within C4 plants, the NADP‐ME plants are isotopically distinguishable from NAD‐ME and PEP‐CK plants.
Ultrastructural Observations of Papaver rhoeas Mature Pollen Grains
Authors: Cresti M. , Milanesi C. , Salvatici P. , Van Aelst A. C. 
Published: February 2014

SummaryThe mature pollen grain of Papaver rhoeas is bicellular. The vegetative cell contains numerous mitochondria; endoplasmic reticulum is not very extensive and there are few ribosomes and plastids. Golgi bodies are in a very active state. The generative cell is lobed and spindle‐shaped. The cytoplasm contains many, generally longitudinally arranged, bundles of microtubules. Other organelles are few in number, and include mitochondria, Golgi bodies and short cisternae of endoplasmic reticulum.
Partial Turgor Pressure Regulation in Chara canescens and its Implications for a Generalized Hypothesis of Salinity Response in Charophytes
Authors: Winter U. , Kirst G. O. 
Published: February 2014

AbstractConcentrations of ions and sucrose in the vacuolar sap of Chara canescens growing in an oligohaline lake (1.5 ‰) were estimated over the main growth period of the plants. During fructification vacuolar sap contained a mean of 41 mol m−3 (range 10.2–61.8) sucrose. The mean turgor pressure was 239 mosmol kg−1 (range 219–264).In long‐ and short‐term experiments these plants were subjected to increasing salinities up to 22 ‰. When salinity was increased from 1.5 to 4.4 ‰ turgor pressure was restored to only 80 % of the initial value. This reduced level of turgor pressure was maintained up to a salinity of 22 ‰. The increase in vacuolar osmotic potential was due to the monovalent ions Na+, K+ and Cl−. The relative amounts of Na+ and K+ participating in the regulation process were dependent on external salinity.The regulatory mechanisms observed in the brackish water species Ch. canescens are compared with those reported from freshwater and euryhaline species.
Regeneration of Plantlets from Callus Cultures of Chamaecytisus purpureus and Chamaecytisus austriacus (Leguminosae)*
Authors: Greinwald R. , Czygan F.‐C. 
Published: February 2014

AbstractPlant regeneration via organogenesis and embryogenesis was obtained from callus cultures of Chamaecytisus purpureus and Chamaecytisus austriacus. While 2,4‐D (4 or 0.5 mg/l) proved highly efficient for callus induction, a combination of 0.1 mg/l IBA and 10 mg/1 BAP induced a high frequency of shoots from the calli. It is shown that, beside the growth factors, the composition of the basal medium represents a critical factor for regeneration. With increasing culture age, a strong reduction of the differentiation capacity was observed.
The Polar Organization of the Growing Chara Rhizoid and the Transport of Statoliths are Actin‐Dependent*
Authors: Sievers A. , Kramer‐Fischer Margret , Braun M. , Buchen Brigitte 
Published: February 2014

AbstractHorizontally positioned Chara rhizoids continue growth without gravitropic bending when the statoliths are removed from the apex by basipetal centrifugation. The transport of statoliths in centrifuged rhizoids is bidirectional: 50–60 % of the statoliths are re‐transported on a straight course to the apex at velocities from 1 to 14 μm . min−1 increasing towards the rhizoid tip. The centrifuged statoliths which are located closest to the nucleus are basipetally transported and caught up in the cytoplasmic streaming of the cell. Those statoliths which are located near the apical side of the nucleus are transported either apically or basally. A de‐novo‐formation of statoliths was not observed. After retransport to the apex some statoliths transiently sediment, a process which can induce a local inhibition of cell wall growth. The rhizoid bends again gravitropically only if a few statoliths finally sediment in the apex; the more statoliths that sediment in the apex the shorter the radius of bending becomes. The transport of statoliths is mediated by actin filaments which form a network of thin filaments in the apical and subapical zone of the rhizoid, and thicker parallel bundles in the basal zone where cytoplasmic streaming occurs. Both subpopulations of actin filaments overlap in the nucleus zone.
Ultrastructural Comparison of the Vacuolar and Mitochondrial H+‐ATPases of Daucus carota
Authors: Taiz Saundra Lee , Taiz L. 
Published: February 2014

AbstractEukaryotic vacuolar H+‐ATPases (V‐ATPases) are related to the F0F1‐ATPases of chloroplasts and mitochondria and are believed to be organized into peripheral and integral membrane complexes. Vacuolar membranes isolated from purified carrot (Daucus carota) root vacuoles were observed to be coated with F1‐like particles after negative staining with phosphotungstic acid. The F1‐like particles formed typical “ball and stalk” structures, about 9.4 nm in diameter and 13.6 nm in height. The head portion frequently had a characteristic bifurcation or cleft at the apex and appeared to be composed of subunits. Such “V1” complexes were frequently associated with smaller stalked particles emerging near the base. In contrast, negatively‐stained carrot mitochondrial F1 complexes averaged 8.7 nm in diameter and 11.7 nm in height. The head groups of the mitochondrial F1s were nearly always spherical, and had no other smaller structures associated with them. The V1 complexes of carrot are thus similar in form to the V1 complexes of Neurospora (Bowman et al. J. Biol. Chem. 264 (1989) 15606–15612).
Electron‐Microscopic Demonstration of a “Head and Stalk” Structure of the Leaf Vacuolar ATPase in Mesembryanthemum crystallinum L.
Authors: Klink Rebecca , Lüttge U. 
Published: February 2014

AbstractThe structure of the vacuolar ATPase from mesophyll tonoplasts of Mesembryanthemum crystallinum has been studied by electron microscopy using negatively stained specimens of membrane‐bound and detergent‐solubilized ATPase molecules. We observed a high density of particles on the surface of tonoplast vesicles and “head and stalk” structures on the edge of the membrane, similar to the F0F1‐ATPases of mitochondrial and chloroplast membranes. The staining conditions, which are often critical for such small objects, were improved by using methylamine tungstate as negative stain for the membrane‐bound ATPase. Compared to other staining solutions generally applied, dissociation of the F1‐like enzyme complex from the membrane was best prevented and structural damage of the vesicles was least observed with methylamine tungstate.In freeze‐fracture electron microscopy of tonoplast vesicles, where dissociation never occurs since no detergent is used, we also observed “head and stalk” structures on the edge of the membranes, beside many particles on the fracture faces.The detergent‐solubilized ATPase forms string‐like structures, caused by the aggregation of the hydrophobic membrane‐embedded F0‐like part of the enzyme. After negative staining the F1‐like enzyme complex is arranged alternately along both sides of the string and connected by a narrow stalk.
Photobiological and Structural Studies of Light‐driven Movements in the Solar‐tracking Leaf of Lupinus palaestinus Bioss. (Fabaceae)
Authors: Werker Ella , Shak T. , Koller D. 
Published: February 2014

AbstractThe compound, palmate lamina of Lupinus palaestinus reorients photonastically, as well as phototropically in response to non‐directional and directional light signals, respectively, by structural deformations of pulvini. When the excitation provided by directional light is maintained constant (fluence rate, angle of incidence and azimuth, with respect to the leaflet laminae), the entire lamina reorients towards it at a constant angular velocity over a considerable time interval and displacement.The laminar pulvinules are considerably longer than the subtending common petiolar pulvinus and therefore contribute most to laminar reorientation. The pulvinar region is characterized by transverse folds around its circumference, and longitudinal rib‐like thickenings on the external walls of its epidermis that facilitate axial and transverse deformations. Specialized “joints”, at the distal and proximal ends of each pulvinule, contribute most to its flexing. Anthocyanin is notable by its absence. Specialized “motor” tissues surrounding the central vascular core participate in pulvinar deformation by undergoing directional and differential volume changes. The bundle sheath is characterized by numerous starch grains. The multi‐layered cortical parenchyma exhibits an abundance of transversely oriented primary pit fields and associated plasmodesmata. When the leaflet lamina rotates around its midrib, the pulvinus twists along its axis, exhibiting epidermal and cortical deformation. The functional significance of these specializations is discussed.
Mechanisms of Reduction of the Stelar Pattern along Barley Roots
Authors: Luxová Mária 
Published: February 2014

AbstractThe stelar pattern along the seminal and nodal roots of barley (Hordeum vulgare L.) is gradually simplified due to a decreasing frequency of longitudinal cell division in the apical meristem. The decrease involves the proportion of stelar parenchyma, the number of vascular strands on the periphery of the stele and, in nodal roots with a more complex structure, the number of central metaxylem files. In spite of the fact that the stelar parenchyma is reduced in distal parts of the roots to approximately one half, the discontinuity of central and peripheral metaxylem is preserved. Reduction of the number of central metaxylem files is due to fusion. In the reduction of peripheral xylem and phloem strands, the development of certain xylem strands is discontinued and they are terminated blindly. Two phloem strands that had alternated radially with them, approach each other, coalesce and a single phloem strand continues to develop. In this way the regular alternation of phloem and xylem is re‐established. The importance of fusions ensuring reduction of the functional continuity in vascular tissue by formation of a network structure must be stressed. This reduction mechanism is involved not only in files of the wide central metaxylem but also in phloem strands which are thus preferred over blindly terminating peripheral xylem strands.