bluuebunny/crossref_metadata_2025_split huggingface dataset:
Oil‐Gathering Bees Visit Flowers of Eglandular Morphs of the Oil‐Producing Malpighiaceae1
Authors: Sazima M. Sazima and I. 
Published: February 2014

AbstractThe visiting behaviour of oil‐gathering, anthophorid bees on eglandular morphs of two Malpighiaceae species was observed in southeastern Brazil. The bees landed on eglandular flowers apparently by mistake, as suggested by their making one to a few scraping movements on landing, and behaving in the same way as they scrape oil glands on glandular flowers. After perceiving their mistake the bees either left the flower, making one to a few additional visits to other eglandular flowers before leaving the plant, or switched to pollen collecting. Large and medium‐sized species ofCentris, and someEpicharis, left the flowers after mistake visits, thus wasting time and energy, whereas smallCentrisand largerEpicharisswitched to pollen harvesting, thus turning a mistake into a rewarding visit. Eglandular flowers of bothBanisteriopsis muricataandHeteropterys aceroidesattracted oil‐gathering bees by deceit and probably acted as mimics of glandular flowers of their own species (automimicry). The pollination of eglandular morphs of these two Malpighiaceae species seems dependent mainly on the opportunistic, mixed oil‐pollen gathering behaviour of deceived bees such asEpicharis schrottkyi. We suggest that some showy, eglandular species such asBanisteriopsis luteamay act as general mimics of other, oil‐rewarding Malpighiaceae species.
Induction of Actin‐Based Cytoplasmic Contraction in the Siphonous Green Alga Acetabularia (Chlorophyceae) by Locally Restricted Calcium Influx
Authors: Menzel D. , Elsner‐Menzel C. 
Published: February 2014

AbstractPerfused cell segments dissected from the stalk or from detached cap ray chambers of Acetabularia were used as an experimental system to study the induction of cytoplasmic contractions and concurrent cytoskeletal changes in plant cells. Immunofluorescence microscopy revealed that the actin cytoskeleton quickly rearranges upon induction of contraction by forming bundles oriented circumferentially around the affected area, whereas microtubules were not detected. Contraction is blocked by cytochalasin D or N‐ethylmaleimide but is unaffected by microtubule specific inhibitors. Contraction requires external Ca2+ at concentrations of 1 μM or more, but fails to occur below 0.1 μM. Higher concentrations of Ca2+ up to 10 mM have no adverse effect. Contraction is prevented in the presence of micromolar Ca2+ by either 1 mM of the calcium channel blocker LaCl3 or 10 μM of the calmodulin inhibitor fluphenazine. Calcium ionophore A 23187 (1 μM) does not perturb wound contraction per se but causes the entire cytoplasm of wounded or unwounded cells to contract slowly. These data suggest that a localized influx of calcium ions at the wound edge causes major rearrangements in the distribution of cytoskeletal actin prior to contraction in Acetabularia. An involvement of calmodulin in calcium signaling is proposed.
Determination of the Apparent Km of Nitrate Reductase from Spinach Leaves for NADH by a Coupled Assay
Authors: Sanchez J. , Heldt H. W. 
Published: February 2014

AbstractUsing a novel coupled enzyme activity assay, with a partially purified preparation of spinach leaf nitrate reductase, the apparent Km for NADH was determined as 1.4 μM. These measurements were carried out in the presence of 0.5 mM NAD, which is within the physiological range found in the cytosol of a leaf cell. The results show that an NADH/NAD ratio of 3 × 10−3 is sufficient for a half maximal rate of nitrate reductase.
Geographical and Ecological Differentiation of Roadside Vegetation in Temperate Europe*
Authors: Ullmann I. , Heindl B. 
Published: February 2014

AbstractA first attempt is made towards a synopsis of the general features and differentiation of roadside phytocoenoses in temperate Europe. The evident similarity between synchorological variation of roadside vegetation and the general chorology of Europe is demonstrated with plant communities dominated by species of Poaceae, Apiaceae, and Asteraceae. A more detailed differentiation along the geographical‐ecological cline between the North Sea and the Mediterranean Sea is represented in modifications of the sequence of coenoses within the roadside profile.
Nematode‐Capturing Hyphomycetes from Soils over Xerophytic Calcareous Rock in Upper Bavaria*
Authors: Fritsch Anne‐Ruth , Lysek G. 
Published: February 2014

AbstractNematode‐capturing hyphomycetes were isolated from soil and plant debris on the south slope of a hill in the Jurassic of Upper Bavaria. The following species were found: Arthrobotrys arthrobotryoides, A. dactyloides, A. oligospora, A. superba, Dactylella astenopaga, Monacrosporium cionopagum, M. psychrophilum. Endozoic fungal parasites of nematodes were not isolated. With one fungal propagule of nematode‐destroying fungi in 1.7 g soil, the density is only slightly lower than values given for agricultural soils.
Permeability and Ultrastructure of Bundle Sheath Cells Isolated from C4 Plants: Structure‐Function Studies and the Role of Plasmodesmata
Authors: Valle E. M. , Craig S. , Hatch M. D. , Heldt H. W. 
Published: February 2014

AbstractBundle sheath cells from leaves of C4 plants can be isolated as strands surrounding vascular tissue. In this form these cells are highly permeable to metabolites and, as a consequence, they have a variety of experimental uses. The present paper reports on anatomical and ultrastructural features of isolated bundle sheath cell strands in relation to their integrity and permeability. This analysis shows that the cells retain a high degree of structural integrity during isolation. The plasmodesmata that originally connected the bundle sheath cytosol with mesophyll cells are apparently also retained in their entirety. However, at the external surface (mesophyll side) a membranous sac was commonly observed protruding from the end of plasmodesmata. The functional integrity of cells and the molecular weight exclusion limit for entry of compounds was assessed by following plasmolysis and cytorrhysis induced by polyethylene glycol solutions of varying molecular weights. Other evidence for the retention of cell compartment semipermeability is also provided.
Dithionite‐Induced Fluorescence Quenching does not Reflect Reductive Activation in Spinach Chloroplasts*
Authors: Neubauer Christian , Schreiber Ulrich 
Published: February 2014

AbstractDithionite is found to cause substantial quenching of chlorophyll fluorescence in intact spinach chloroplasts. In a light‐on induction curve, the I‐P fluorescence rise is selectively suppressed, with a half‐maximal effect at 1.7 × 10−5 M dithionite. Quenching analysis by the saturation pulse method reveals that the dithionite‐induced quenching is photochemical, in analogy to the effect of a Hill reagent. The quenching is suppressed by catalase, KCN and by O2 removal before dithionite addition. These observations, in combination with recent findings on H2O2‐induced photochemical quenching (Neubauer and Schreiber, 1989), lead to the conclusion that H2O2 is formed from reduction products of O2 by dithionite and that it is this H2O2 which, via the action of the ascorbate peroxidase, sustains Hill activity. The results are discussed with reference to the concept of reductive activation of the ferredoxin: NADP oxidoreductase put forward by Satoh (Satoh, 1982). It is concluded that such activation is unlikely to play an essential role in spinach chloroplasts. This conclusion is supported by the observation of suppression of the I‐P fluorescence rise by oxidized NADP in dark‐adapted spinach chloroplasts.
Abscisic Acid Content of Algae under Stress*
Authors: Hirsch R. , Hartung W. , Gimmler H. 
Published: February 2014

AbstractThe distribution of the phytohormone, abscisic acid (ABA), within the phylum of Phycophyta was investigated by an enzyme‐linked immunoassay (ELISA). Of 64 algal species tested (originating from 9 divisions, 20 classes and 36 orders, including procaryotes) all species contained ABA, whereas no ABA could be detected in the bacteria Escherichia coli, Rhodospirillum rubrum, and Halobacterium halobium. It is concluded that ABA is universally distributed within the algal kingdom and is not restricted to cormophytes. The ability to synthesize ABA must have been developed even within the procaryotes. The physiological role of ABA in some selected algae was studied by investigating 1. the distribution of ABA between the cells and the culture medium, 2. the responses of endogenous ABA to stress, 3. the synthesis of 14C‐ABA from externally applied 14C‐mevalonic acid, 4. the metabolism of ABA, 5. the effect of externally applied ABA on various physiological reactions of the algae, and the effect of norflurazon on ABA content. 14C‐mevalonic acid served as precursor of 14C‐ABA synthesis in Dunaliella cells and ABA was metabolised to the same products which have been observed in higher plants. In D. parva the internal ABA level increased upon hyperosmotic salt shocks, and in D. acidophila upon alkalization of the medium. Norflurazon caused an increase of ABA content in Dunaliella. Externally applied ABA did not affect photosynthesis, respiration and K+ content of the cells. The permeability of the plasma membrane of D. acidophila to water was slightly decreased by ABA. The possible physiological function of ABA in algae is discussed.
On the Mechanisms of Secondary Pollen Presentation in the Campanulales‐Asterales‐Complex1
Authors: Leins P. , Erbar Claudia 
Published: February 2014

AbstractFamilies of the Campanulales‐Asterales‐complex are characterized by special mechanisms for secondary pollen presentation: pump mechanism, brushing mechanism, deposition mechanism, cup mechanism and combination of cup mechanism with brushing mechanism. These different mechanisms are based on three successive events: elongation of the filaments, opening of the anthers, elongation of the style. The diversity of the mechanisms arises through different auxiliary structures such as an indusium, hairs or an anther tube, and the relative rate and time of filament and style growth. An advantage of secondary pollen presentation lies in the prolongation of the male phase of anthesis through portioned pollen release. A probable phylogeny of the different mechanisms of secondary pollen presentation is proposed (Fig. 7).
C3‐ and C4‐Plants of the Xerophilic Vegetation in the Loess Hills of the Yellow River, Gansu‐Province, NW‐China*
Authors: Wang X.‐C. , Lüttge U. , Ziegler H. 
Published: February 2014

AbstractThe climate of the loess‐hill area near Lanzhou, on the Yellow River, Gansu‐Province, NW‐China is arid throughout the year. The vegetation is xerophilic and mainly dominated by species of Zygophyllaceae, Chenopodiaceae, Plumbaginaceae, Tamaricaceae, Asclepiadaceae and Asteraceae. Among 11 species sampled of these families, δ13C‐analyses only indicated C4‐photosynthesis for 2 species. This relatively low frequency of C4‐plants may be due to elevation (1978 m a.s.l.) and the relatively cold temperatures (annual mean 5.9°C).
Flagellar Development During the Cell Cycle in Chlamydomonas reinhardtii
Authors: Madey P. , Melkonian M. 
Published: February 2014

AbstractFlagellar development during the asexual synchronous cell cycle of Chlamydomonas reinhardtii (11.32 aM) was studied by light microscopy. Cell walls of sporangia of different developmental status were dissolved using gamete lysin (g‐lysin) enabling direct observation of flagellar development. Flagellar growth in progeny cells exhibits a linear kinetic with a growth rate of 28 nm/min at 30°C leading to a flagellar length of 7–7.5 μm in 4–4.5 h. After this time the flagellar growth rate drops to 2.8 nm/min (as in interphase). Both flagella of a single cell and all flagella within a sporangium grow out at the same time and with the same rate. Cycloheximide (10 μg/ml) completely blocks flagellar development. If cycloheximide is removed flagellar growth resumes at the normal rate with no lag‐phase.Flagellar development during the cell cycle in C. reinhardtii differs considerably from the well‐studied model system of flagellar regeneration following amputation in the same species.
Die Ontogenese der Salzdrüsen von Limonium (Plumbaginaceae); The Ontogenesis of the Salt Glands of Limonium (Plumbaginaceae)
Authors: Wiehe W. , Breckle S.‐W. 
Published: February 2014

ZusammenfassungDie Salzdrüsen der Gattung Limonium leiten sich ontogenetisch von einer einzelnen epidermalen Zelle ab, die sich in fünf Teilungsschritten zu einem 20‐zelligen Drüsenkomplex differenziert. Die Cutinisierung des Drüsenkomplexes erfolgt bereits nach dem vierten Teilungsschritt bei der Bildung der vier Sammel‐ und der vier Bechermutterzellen. Diese werden durch den fünften Teilungsschritt in innere und äußere Becherzellen geteilt.AbstractThe Limonium‐salt gland develops from only one epidermal cell in five steps of cell‐division to a gland complex of 20 cells. Cutinisation on the gland complex starts after the fourth step of cell‐division, when four collecting cells and four mother cells of the cup cells are formed. In the last step the mother cup cells divide into four inner cup cells and four outer cup cells.
Biochemical Taxonomy of Symbiotic Chlorella Strains from Paramecium and Acanthocystis*
Authors: Kessler E. , Huss V. A. R. 
Published: February 2014

AbstractBiochemical and physiological characters of 5 symbiotic Chlorella strains, 4 of them from Paramecium (Ciliata) and one from Acanthocystis (Rhizopoda, Heliozoa), were studied. Four strains (3 from Paramecium and one from Acanthocystis) belong to the same species. This is characterized by the presence of hydrogenase, no formation of secondary carotenoids, no growth on mannitol, requirements for thiamine and vitamin B12, and a G + C content of the DNA of 66.4–68.4 mol%; the limits of growth are at pH 5.5, at up to 1% NaCl, and at 26–30°C. The strains are somewhat heterogeneous in their utilization of inorganic nitrogen sources: only two of them are able to use nitrate, whereas all can grow with nitrite and ammonium. Thus, in two strains the nitrate‐reducing system — in contrast to nitrite reductase — seems to be defective. Another strain, which has been claimed to be from Paramecium, belongs to C. protothecoides.
Hypersensitive Reaction of Nodule Cells in the Glycine sp./Bradyrhizobium japonicum‐Symbiosis Occurs at the Genotype‐Specific Level*
Authors: Parniske M. , Zimmermann Christa , Cregan P. B. , Werner D. 
Published: February 2014

AbstractThree Glycine genotypes, G. max cv. Williams, G. soja PI 468397, and G. soja PI 342434 in combination with the two rhizobial strains Bradyrhizobium japonicum USDA 123 and Rhizobium fredii USDA 193 were analysed for phytoalexin concentration in the nodules. In the nodules of PI 468397/B. japonicum USDA 123 a very strong glyceollin I accumulation occurred around 30 d.p.i. Ultrastructural analysis of these nodules revealed several symptoms of a severe plant defense response associated with plant cell death (hypersensitive reaction): The cytoplasm of the infected cells was degraded and organelles had vanished. The cell walls of the infected cells showed remarkable thickening. This plant defense response could only be observed in this strain/genotype interaction. The same strain did not elicit a phytoalexin accumulation in the other plant genotypes tested, indicating that this response occurs at the genotype‐specific level. This special character of G. soja PI 468397 is heritable as indicated by glyceollin I analysis of the nodules formed by F1 hybrids of PI 468397xWilliams inoculated with B. japonicum USDA 123. The genotype/strain specific occurrence of the hypersensitive response in root nodules resembles the race/cultivar specific incompatibility of several plant‐pathogen interactions. This specificity, together with the phenomenon of the HR itself, points out the close physiological relationship between the late stages of the root nodule symbiosis and a plant/pathogen interaction.
Neutral Red as a Redox Dye Induces K+ Efflux and Current‐Voltage Changes in Eremosphaera, Lemna, and Guard Cells*
Authors: Ullrich C. I. , Köhler K. , Baier M. , Förster B. , Hartung W. 
Published: February 2014

AbstractMembrane effects of the redox and pH indicator neutral red were studied with the chlorococcal alga Eremosphaera viridis, with Lemna gibba, and with “isolated” guard cells in epidermal peels of Valerianella locusta. Neutral red was extracellularly reduced and caused transmembrane current‐voltage changes, an increase in membrane conductance by about 14 nS, an apparent K+ net efflux of up to 120 μmol g−1 FW in 5 min, and an intracellular acidification by up to 0.7 pH units. Neutral red‐triggered K+ net efflux was most pronounced at low pH, at an Eo more positive than −200 mV, and without extracellular Ca2+. From the experimental data it is concluded that, due to the redox function of the phenazine molecule, extracellular neutral red triggers a trans‐plasmalemma e− transfer, leading to strong membrane depolarization and charge compensating K+ net efflux, in addition to some unspecific ion release. As a consequence the intracellular concentration of strong cations relative to strong anions (SID) decreases, resulting in intracellular acidification.
The Distribution of a Phytochrome‐Like Protein in the Fern Psilotum nudum.; An Immunoblotting Analysis of an Early Ancestor of all Vascular Plants
Authors: Schneider‐Poetsch H. A. W. , John Gabriele , Braun Birgit 
Published: February 2014

AbstractThe distribution of a 125 kg . mol−1 protein recognized by a monoclonal antibody raised against phytochrome of maize was analyzed in the sporophyte of the fern Psilotum nudum. Highest amounts (up to 5 μg per fresh weight) of this protein were found in the tips of expanding shoots. Green sporangia as well as the pale tips of the rhizome contained this 125 kg . mol−1 protein, too. In the brown parts of the rhizome it was more rarely contained. Unlike phytochrome from etiolated higher plants, the Psilotum protein appeared to be scarcely degraded by the illuminated plants. In this respect the protein of Psilotum seems to resemble the small fraction of phytochrome contained in green and illuminated higher plants. Moreover, after illuminating the Psilotum rhizome for 3 d, higher amounts of this protein were detected therein as before.
Temporal Pattern of Gene Expression in Cotyledons of Mustard (Sinapis alba L.) Seedlings
Authors: Wenng A. , Batschauer A. , Ehmann B. , Schäfer E. 
Published: February 2014

AbstractThe time course of appearance of competence to phytochrome (Pfr) was studied in cotyledons of mustard (Sinapis alba L.) with regard to the light‐mediated accumulation of mRNAs encoding for SSU, CAB and the 23 kDa protein of the oxygen evolving complex of photosystem II (OEC). For each gene family a specific starting point of Pfr‐induced mRNA accumulation was observed (SSU: 42 h; CAB: 36 h; OEC: 30 h). An increase of SSU‐mRNA levels can be detected 24 h after sowing in dark‐grown seedlings whereas for OEC the time points for the increase of mRNA are the same whether the seedlings are kept in darkness or induced by light via Pfr. For all gene families a responsiveness to Pfr (coupling point) could be demonstrated before the starting points. The coupling points are also gene specific (SSU: ca. 12 h; CAB and 23 kDa peptide of OEC: ca. 24 h). The responsiveness to light before the starting point indicates that the light‐induced signal must be stored.
The Supramolecular Structure of Photosystem II — Phycobilisome‐Complexes of Porphyridium cruentum
Authors: Lange W. , Wilhelm C. , Wehrmeyer W. , Mörschel E. 
Published: February 2014

AbstractThe structure and arrangement of phycobilisomes of the unicellular red alga Porphyridium cruentum is compared with the organization of the thylakoid freeze‐fracture particles in order to determine the relationship between phycobilisomes and photosystem II. The hemi‐ellipsoidal phycobilisomes, 20 nm thick, are predominantly organized into rows; their centre to centre periodicity is 30–40 nm, so that they are well separated by a gap of 10–20 nm. The phycobilisomes are cleaved by a central faint furrow, parallel to the long axis from top to base.The organization of the exoplasmic particles in rows is similar to the arrangement of the phycobilisomes so that a structural relationship between both systems, previously demonstrated in cyanobacteria, is evident. Within the rows, the 10 nm EF‐particles are grouped in tetrameric complexes separated by distances similar to those observed for phycobilisomes. We propose that the tetrameric EF‐particle complexes correspond to tetrameric photosystem II complexes which bind one hemi‐ellipsoidal phycobilisome on the stroma exposed surface of the thylakoid. A hypothetical model of this photosystem II‐phycobilisome complex is presented.
Characterization of CF1 from the Diatom Odontella sinensis
Authors: Päncic P. G. , Kowallik K. V. , Strotmann H. 
Published: February 2014

AbstractThe CF1 moiety of the chloroplast ATPase of the diatom Odontella sinensis was solubilized from isolated thylakoids by chloroform extraction. Further purification was achieved by HPLC on a Superose‐6 column. The resulting four‐subunit complex was identified as CF1 lacking subunit δ. The larger two subunits, α and β, showed cross‐reactivity with antisera raised against the homologous subunits of spinach‐CF1. Western blot analysis further revealed that — contrary to other ATPases — migration in SDS‐PAGE of α was faster than migration of β, suggesting a deletion of 40 to 50 amino acids in subunit α of Odontella. The assumed deletion does not involve the N‐terminal side of the protein, as was established by protein sequencing. The N‐terminal sequences of subunits α and γ showed highest homologies with the equivalent subunits of blue‐green algae. According to SDS‐PAGE, the apparent molecular weights of the four Odontella subunits were 53.2 (β), 51.2 (α), 39.3 (γ) and 16.2 (ε) kD. ATPase activity of isolated Odontella‐CF1 could be induced by trypsin or octylglucoside, and to a lesser extent by sulfite or by alcohols such as methanol or ethanol.
Light/Dark Modulation: Regulation of Chloroplast Metabolism in a New Light
Authors: Scheibe Renate 
Published: February 2014

AbstractLight‐dark modulation of chloroplast enzymes is achieved by covalent redox‐modification of protein thiols/disulfides mediated by ferredoxin/thioredoxin reductase and thioredoxins. Light‐dependent electron flow leads to reduction of particular chloroplast proteins, while photosynthetically evolved oxygen effects their continuous reoxidation. The oxidized and the reduced forms, respectively, differ greatly in their catalytic properties. The rate of reduction of each target enzyme is specifically fine‐controlled by metabolites. By this combined mode of producing a defined ratio of active to inactive enzyme during steady‐state each of the enzymes is adjusted to the immediate requirements of the chloroplast. Upon changes of the metabolic situation the system can respond in a flexible manner as is known from comparable regulatory mechanisms such as protein phosphorylation/dephosphorylation in animals and bacteria. From sequence comparisons between various light‐dark modulated chloroplast enzymes and their non‐regulated counterparts from other organelles or non‐photosynthetic organisms, the presence of extra‐peptides in the otherwise highly homologous sequences has been estabüshed for the chloroplast enzymes. However, no general pattern in the primary structure of those extra‐sequences can be recognized. By the acquisition of “regulatory peptides” during evolution a new type of metabolic control was created in a compartment uniquely occurring in organisms performing oxygenic photosynthesis.