bluuebunny/crossref_metadata_2025_split huggingface dataset:
Fusicoccin Binding to its Plasma Membrane Receptor and the Activation of the Plasma Membrane H+‐ATPase. II. Stimulation of the H+‐ATPase in a Plasma Membrane Fraction Purified by Phase‐partitioning
Authors: De Michelis Maria Ida , Rasi‐Caldogno Franca , Pugliarello Maria Chiara , Olivari C. 
Published: February 2014

AbstractThe effect of fusicoccin (FC) on the activity of the PM H+‐ATPase was investigated in a plasma membrane (PM) fraction from radish seedlings purified by the phase‐partitioning procedure.FC stimulated the PM H+‐ATPase activity by up to 100 %; the effect was essentially on Vmax with only a slight decrease of the apparent KM of the enzyme for ATP.FC‐induced stimulation of the PM H+‐ATPase was evident within the first minute and maximal within five minutes of membrane treatment with the toxin indicating that transmission of the signal from the activated receptor to the PM H+‐ATPase is very rapid.Both FC‐induced stimulation of the PM H+‐ATPase and FC binding to its receptor decreased dramatically upon incubation of the membranes in ATPase assay medium at 33 °C in the absence of FC, due to the lability of the free FC receptor.FC‐induced stimulation of the PM H+‐ATPase was strongly pH dependent: absolute increase of activity was maximal at pH 7, while percent stimulation increased with the increase of pH up to pH 7.5; FC binding was scarcely influenced by pH in the pH range investigated. Taken as a whole, these results indicate that FC binding is a condition necessary, but not sufficient, for FC‐induced stimulation of the PM H+‐ATPase.
Effects of Relative Humidity on Carbon Isotope Fractionation in Plants
Authors: Madhavan S. , Treichel Isabel , O'Leary Marion H. 
Published: February 2014

AbstractFour C3 plants and a C4 plant were grown from seeds at four levels (30, 45, 60, and 75 %) of relative humidity. All plants were subjected to a 16 h day, at 500 μE/m2.s−1 photon flux density. Mature leaves were analyzed for their carbon isotopic composition. Isotope fractionation decreased by up to 3 ‰ with decreasing relative humidity in all C3 plants, while the opposite trend was observed in the C4 plant. The observed shifts in both C3 and C4 plants are attributed to decreased stomatal conductance at low relative humidity, resulting in a smaller Pi.
Comparative Microscopical Studies on the Patterns of Calcium Oxalate Distribution in the Needles of Various Conifer Species
Authors: Fink S. 
Published: February 2014

AbstractThe distribution of calcium oxalate crystals in various conifer needles is visualized by light and electron microscopy. Such crystals occur (1) in the vascular bundle, either intracellularly in the xylem or phloem parenchyma, or extracellularly within the radial phloem walls; (2) extracellularly on the outside of the walls of mesophyll cells which face the intercellular spaces; (3) and finally as numerous small crystals within the cell walls of the epidermal cells, especially in the cuticular layer. The development and distribution of these apoplastic crystals is described in detail. Some hypotheses are finally presented for interpretations of these unusual patterns of the crystallization of Ca‐oxalate outside the vacuole. Possible evolutionary aspects of this feature among the different conifer families are also discussed.
Receptor‐Independent Sporopollenin
Authors: Rowley J. R. , Claugher D. 
Published: February 2014

AbstractPollen of some species of the genus Quercus shows rod‐shaped substructures in fresh or acetolysed exines, while in other species rod substructure is mostly masked by sporopollenin. Oxidation with potassium permanganate removes exine substance (sporopollenin) from between the rod substructures. We propose that the rods include receptors for sporopollenin. The sporopollenin between rods we refer to as ‘receptor‐independent sporopollenin’.Pollen of Typha, when mature, has tectal surfaces with concave tops and sides, whereas during development the tectal surfaces are smoothly rounded. After acetolysis treatment followed by potassium permanganate the tectum surfaces again appear rounded. When these exines are subsequently eroded by a fast atom source, rod‐shaped substructures are seen to protrude from the tectum. These structures are equivalent in size and shape to the rods of the exine of Quercus.Sporopollenin that accumulates over and masks rod substrucutre is less resistant to our degradative methods than the sporopollenin in rod structures of exines. We suggest that the exine material we call “receptor‐independent sporopollenin” be given a simple positive name, such as masking‐sporopollenin or abbreviated to masking‐spn.
Fascicled Androecia in Dilleniidae and Some Remarks on the Garcinia Androecium
Authors: Leins P. , Erbar Claudia 
Published: February 2014

AbstractIn Dilleniidae, stamen fascicles are interpreted either as phylogenetically secondary structures (derived from a single stamen primordium by dédoublement), or as the most archaic type of androecial organs in angiosperms. In context with an assumed high plasticity in the flowers at the beginning of angiosperm evolution (Endress, 1987 a, b), fascicled androecia can also be regarded as having coexisted with “magnolioid” spiral androecia since early in the evolution. On the basis of this assumption, it is easy to link the Dilleniidae, via their basal group, the Paeoniaceae, to the Magnoliidae. In Paeonia, the stamen clusters continue the spiral arrangement of the perianth members, with “limiting divergence” (Hiepko, 1964). Our investigations of Paeonia officinalis show that the fascicle primordia follow the spiral not only in their position, but also in their temporal sequence. In some Theaceae (Stewartia) and Clusiaceae (species of Garcinia) the divergence angle changes to 2/5, resulting in an epipetalous position of the stamen fascicles. The transition from fascicled (complex) androecia to simple ones (one‐ or two‐whorled) has occurred repeatedly within the Dilleniidae. A great diversity of androecial structures, based on a fascicled androecium, can be found in the palaeotropical genus Garcinia (Clusiaceae), which comprises about 200 species. Some of these forms, including exceptional ones, are presented in this article. The diversity in the androecium in Garcinia can be interpreted phylogenetically as a secondarily increased plasticity, resulting in morphological curiosities.
Temperature Effects on Crassulacean Acid Metabolism: EPR Spectroscopic Studies on the Thermotropic Phase Behaviour of the Tonoplast Membranes ofKalanchoë daigremontiana
Authors: Kluge M. , Kliemchen A. , Galla H.‐J. 
Published: February 2014

AbstractThe thermotropic phase behaviour of tonoplast material isolated from leaf mesophyll protoplasts of the obligatory CAM plantKalanchoë daigremontianawas investigated by electron power magnetic resonance (EPR) spectroscopy using a spin label technique. The data clearly show that at temperatures below 9 °C the tonoplast membrane is in a rigid state. Above 9 °C, an increasing fluidization of the tonoplast occurs. Two distinct temperature ranges were observed: a cooperative melting process between 9 and 14 °C being followed by a second broad melting process starting at 18 °C, with continuously increasing membrane fluidity up to 51 °C, which was the highest temperature tested. These results are important for a better understanding of the mechanism of the temperature modulation of CAM. The data support the hypothesis that temperature affects CAM via the permeability of the tonoplast membrane, which determines the rates of the passive malic acid efflux from the vacuole and thus the capability of the plant to accumulate malic acid in the vacuoles overnight at a given temperature.
Immunocytochemical Localization of Phosphoribulokinase in Microalgae
Authors: McKay R. M. L. , Gibbs S. P. 
Published: February 2014

AbstractEmploying immunogold electron microscopy, the subcellular location of the Calvin cycle enzyme phosphoribulokinase (PRK) was determined for two diverse species of microalgae. In both the red alga Porphyridium cruentum and the green alga Chlamydomonas reinhardtii, PRK was distributed throughout the thylakoid‐containing chloroplast stroma. In contrast, the next enzyme in the pathway, ribulose 1,5‐bisphosphate carboxylase/oxygenase, was predominantly pyrenoid‐localized in both species. In Porphyridium, the chloroplast stroma abuts the pyrenoid but in Chlamydomonas and other green algae, the pyrenoid appears encased in a starch sheath. Unique inclusions found in the pyrenoid of Chlamydomonas were immunolabelled by anti‐PRK and thus identified as regions of chloroplast stroma. It is postulated that such PRK‐containing stromal inclusions in the pyrenoids of Chlamydomonas and perhaps other green algae provide a means for exchange of Calvin cycle metabolites between pyrenoid and stroma.
An Impasse in Plant Water Relations?
Authors: Passioura J. B. 
Published: February 2014

AbstractBalling and Zimmermann [Planta 182 (1990), 325–338] used a pressure probe to measure directly negative pressures in the xylem of transpiring plants. They obtained data that challenge the standard framework that plant physiologists use when thinking about plant water relations, and, most notably, found a substantial discrepancy between their measurements of xylem pressure and of leaf water potential measured with a Scholander pressure bomb. Their data are critically examined and it is shown that most of them can be accommodated within the established principles of plant water relations. In particular, there are several reasons, consistent with the established principles, why leaf water potential and xylem pressure may differ.
Medium Acidification by Maize Root Tips and its Inhibition by Heavy Water
Authors: Kotyk A. , Fischer‐Schliebs E. , Lüttge U. 
Published: February 2014

AbstractAcidification of external solution by maize root tips can apparently proceed by two mechanisms. The first, significant only above pH 6, does not require the presence of salts in the medium and appears to be due to respiratory CO2 release with subsequent hydration and dissociation into H+ + HCO−3. The second, much more efficient process, requires permeant ions and proceeds to well below pH 4 under mediation by the plasma membrane H+‐ATPase.While the first process is affected by acetazolamide (an inhibitor of carbonate dehydratase), the second is blocked by vanadate, erythrosin B, diethylstilbestrol and miconazole, and is strikingly stimulated by fusicoccin. Both mechanisms are markedly inhibited by heavy water, the first by up to 80% with an ID50 of 18–25% D2O, the second up to 91%, with an ID50 of 20–30% D2O. The inhibition of the acidification by ATPase can be relieved by replacing D2O with H2O, indicating that the effect of D2O is kinetic rather than on covalently‐bound hydrogen atoms. Apparently the H+‐ATPase uses H+ (or possibly H3O+) as substrate which binds to a rather specific site where it cannot be functionally replaced by D+ or D3O+.
The Irreversible C3 to CAM Shift in Well‐watered and Salt‐stressed Plants of Mesembryanthemum crystallinum is under Strict Ontogenetic Control
Authors: Herppich W. , Herppich Margaretha , VON Willert D. J. 
Published: February 2014

AbstractThe shift from C3 to CAM was investigated as a function of both leaf and plant age in well‐watered and salt‐stressed (300 mM NaCl solution) plants of Mesembryanthemum crystallinum. Initiation of a night‐time accumulation of malic acid, the decisive criterion of CAM, was followed in plants that were continuously stressed at different points in their life cycle. The deinducibility of CAM was examined after the release from stress by extensively rinsing the potting soil with de‐mineralized water.Our results show that in M. crystallinum CAM is under strict developmental control, since CAM appeared only when a certain stage of development of the whole plant was reached. CAM was not present in any plant before this threshold, which was the same in salt‐stressed as well as in well‐watered plants. The metabolic shift coincided with the change from the seedling to the juvenile growth phase, and not with that from vegetative to reproductive growth, represented by the start of branching. The latter is timed to the end of extension growth.In well‐watered plants, after this decisive point in development, a weak nighttime accumulation of malic acid could be measured (≅ 0.05 mol kgDW−1) in the oldest, mature leaves but not in young, developing ones. This “CAM capacity” gradually increased up to 0.2 mol kgDE−1 with further plant ageing. Leaf senescence, characterized by wilting and yellowing, diminished the CAM activity. In mature leaves salt stress drastically enhanced the magnitude of diurnal fluctuation in malic acid content.Removal of salt stress did not deinduce CAM activity, but diminished the amplitude of malic acid oscillations to some extent in those plants which had been stressed from early in their life cycle. In these plants, salt stress delayed plant development and growth thus retarding the life cycle. Well‐watered plants, for example, branched about three weeks earlier than those that had been stressed continuously from one week after germination. After removal of stress a quasi‐preserved earlier developmental stage in relation to the control plants determined the weaker CAM expression.
Isolation and Characterization of the Putative Photoreceptor for Phototaxis in Amoebae of the Cellular Slime Mold, Dictyostelium discoideum
Authors: Vornlocher H.‐P. , Häder D.‐P. 
Published: February 2014

AbstractAmoebae of the cellular slime mold Dictyostelium discoideum (strain AX2) produce a pigment with an absorption spectrum that closely resembles the action spectrum for phototaxis. The protein‐pigment complex was isolated and purified by sucrose gradient centrifugation, fast protein liquid chromatography (FPLC) and sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS PAGE). It is tightly membrane‐bound and the bulk of it is located in the mitochondrial membrane fraction, while a small part is located in the cytoplasmic membrane fraction, as indicated by marker enzyme tests (succinate dehydrogenase for mitochondria and alkaline phosphatase for the cytoplasmic membrane). It is speculated that the pigment bound to the cytoplasmic membrane acts as photoreceptor and that bound to the mitochondria operates as a shading pigment in the light direction perception mechanism of Dictyostelium amoebae.
Immunolocalization of Cytosolic Phytochrome in the Green Alga Mougeotia*
Authors: Hanstein Christel , Grolig F. , Wagner G. 
Published: February 2014

AbstractThe monoclonal antibody Z‐3Bl (Schneider‐Poetsch et al., Planta 173 [1988] 61–72) was used to localize phytochrome in the Mougeotia cell by indirect immunofluorescence. The antibody detected a protein of about 110 kD in the immunoblot. Immunofluorescence indicated abundant phytochrome throughout the cytoplasm. In Mougeotia, a large cytoplasmic pool of phytochrome is presumably in equilibrium with a probably reactant‐bound Pfr‐pool at the plasmalemma, the latter being responsible for the physiological response.
Immunolocalization and Western Blot Analysis of Nitrogenase in Oscillatoria limosa During a Light‐dark Cycle
Authors: Villbrandt M. , Stal L. J. , Bergman B. , Krumbein W. E. 
Published: February 2014

AbstractNitrogenase of the non‐heterocystous nitrogen‐fixing cyanobacterium Oscillatoria limosa was subjected to western blot analysis and immunogold electron microscopy using antisera raised against dinitrogenase (MoFe‐protein, Component I) and dinitrogenase reductase (Fe‐protein, Component II). O. limosa was grown diazotrophically under an alternating light‐dark cycle (16–8h light‐dark). Although nitrogenase activity (acetylene reduction) was found predominantly during the dark phase, being absent during most of the light period, immunogold electron microscopy revealed label of both subunits of nitrogenase in samples taken throughout the light‐dark cycle. It was also shown that the nitrogenase label was distributed homogeneously in the cell and that it was present in every cell of every trichome whether fixing nitrogen or not. On average, 34 (± 6) gold particles μm−2 thin section were detected. Nitrate‐grown cells did not contain nitrogenase label. Western blot analysis of the Fe‐protein in samples taken during the light phase, revealed a single band with an apparent molecular weight of 37 kDa. At the end of the light period, and during the dark phase when high nitrogenase activities were observed, an additional band of 36 kDa was found. The anti‐MoFe‐protein antiserum revealed a single band of 56 kDa which was present throughout the light‐dark cycle. Nitrate‐grown cells were not recognized by either antiserum. It is concluded that nitrogenase enzyme is present in O. limosa throughout the light‐dark cycle but that the Fe‐protein is modified (inactive form) during the light period when nitrogenase activity is absent.
Ferric Ion and Oxygen Reduction at the Surface of Protoplasts and Cells of Acer pseudoplatanus
Authors: Macrì F. , Braidot E. , Petrussa E. , Zancani M. , Vianello A. 
Published: February 2014

AbstractThis work was undertaken to verify whether surface NADH oxidases or peroxidases are involved in the apoplastic reduction of Fe(III). The reduction of Fe(III)‐ADP, linked to NADH‐dependent activity of horseradish peroxidase (HRP), protoplasts and cells of Acer pseudoplatanus, was measured as Fe(II)‐bathophenanthrolinedisulfonate (BPDS) chelate formation. In the presence of BPDS in the incubation medium (method 1), NADH‐dependent HRP activity was associated with a rapid Fe(III)‐ADP reduction that was almost completely inhibited by superoxide dismutase (SOD), while catalase only slowed down the rate of reduction. A. pseudoplatanus protoplasts and cells reduced extracellular Fe(III)‐ADP in the absence of exogenously supplied NADH. The addition of NADH stimulated the reduction. SOD and catalase only inhibited the NADH‐dependent Fe(III)‐ADP reduction. Mn(II), known for its ability to scavenge O−2, inhibited both the independent and NADH‐dependent Fe(III)‐ADP reduction. The reductase activity of protoplasts and cells was also monitored in the absence of BPDS (method 2). The latter was added only at the end of the reaction to evaluate Fe(II) formed. Also, in this case, both preparations reduced Fe(III)‐ADP. However, the addition of NADH did not stimulate Fe(III)‐ADP reduction but, instead, lowered it. This may be related to a re‐oxidation of Fe(II) by H2O2 that could also be produced during NADH‐dependent peroxidase activity. Catalase and SOD made the Fe(III)‐ADP reduction more efficient because, by removing H2O2 (catalase) or preventing H2O2 formation (SOD), they hindered the re‐oxidation of Fe(II) not chelated by BPDS. As with the result obtained by method 1, Mn(II) inhibited Fe(III)‐ADP reduction carried out in the presence or absence of NADH. The different effects of SOD and Mn(II), both scavengers of O−2, may depend on the ability of Mn(II) to permeate the cells more easily than SOD. These results show that A. pseudoplatanus protoplasts and cells reduce extracellular Fe(III)‐ADP. Exogenously supplied NADH induces an additional reduction of Fe(III) by the activity of NADH peroxidases of the plasmalemma or cell wall. However, the latter can also trigger the formation of H2O2 that, reacting with Fe(II) (not chelated by BPDS), generates hydroxyl radicals and converts Fe(II) to Fe(III) (Fenton's reaction).
Immunofluorescent Localization of a Connexin 26‐like Protein at the Surface of Mesophyll Protoplasts from Vicia faba L. and Helianthus annuus L.
Authors: Schulz Margot , Traub O. , Knop Mona , Willecke K. , Schnabl Heide 
Published: February 2014

AbstractMesophyll protoplasts from three week old leaves of Helianthus annuus L. and from four week old leaves of Vicia faba L. were incubated with polyclonal, monospecific antibodies, raised against either cx 32 or cx 26 mouse liver connexin. Crossreactions were visualized by FITC‐labeled anti‐rabbit antibodies. Incubations with the cx 26 antibody resulted in fluorescing spots on protoplast surfaces of both plant species, indicating the presence of a polypeptide, immunologically related to the animal cx 26. A plant protein, exhibiting similarities to cx 26, would present a new member of connexin‐like plant proteins. Controls, performed with preimmune serum or with the FITC‐conjugate alone, were negative. Immunofluorescing spots were not obtained after incubations with the cx 32 antibody. Since the existence of a cx 32‐like plant protein, associated with ultrastructures of plasmodesmata and the plasma membrane, is meanwhile established, several explanations for the failed attempt to demonstrate a cx 32 antibody labeling at protoplast surfaces are discussed.
The Control of Lateral Root Development in Cultured Pea Seedlings. III. Spacing Intervals
Authors: Hinchee Maud A. W. , Rost Th. L. 
Published: February 2014

AbstractThe spacing of lateral root primordia in the primary root of Pisum sativum (cv. Alaska) seedlings is influenced by both predetermined lateral root initiation sites in the embryonic radicle and by factors present during seedling growth. When pea seeds were germinated in the presence of the mitotic inhibitor, colchicine, the triarch radicle produced three ranks of primordiomorphs indicating sites of embryonic lateral root primordia. The number of primordiomorphs was not the same along the three xylem strands in the radicle. Normally germinated seedling roots (5 days old) also showed a different number of lateral root primordia associated with the three strands. In both cases, the strand with the greatest number of primordia (or primordiomorphs) was associated with a cotyledonary trace. This indicated a possible role for the cotyledons in setting the pattern of lateral root distribution during radicle development. The spacing of lateral root primordia could be altered by the application of growth regulators. Seedling root tips (2 mm) were removed (− rt) and replaced with indoleacetic acid (+IAA), and in some instances seedlings were also treated with the auxin transport inhibitor, 3,3a‐dihydro‐2‐(p‐methoxyphenyl)‐8H‐pyrazolo[5, 1‐α]isoindol‐8‐one (+DPX). In the growth regulator treatments, primary root elongation was inhibited, a greater number of lateral root primordia were initiated compared to controls, and the spacing intervals between primordia were greatly reduced. The — rt, +IAA, +DPX‐treatment resulted in the closest possible spacing intervals (av. 0.4 − 0.6 mm), but resulted in fused or fasciated laterals. The — rt, + IAA‐treatment produced the shortest spacing intervals which resulted in “normal” lateral roots (0.8 − 1.1 mm).