bluuebunny/crossref_metadata_2025 huggingface dataset:
The Effect of Light and Exogenously Supplied Ammonium Ions on Glutamate Dehydrogenase Activity and Isoforms in Young Mustard (Sinapis alba L.) Seedlings
Authors: Lettgen W. , Britsch L. , Kasemir Helga
Published: February 2014

Glutamate dehydrogenase (GDH, E.C. 1.4.1.3) of mustard cotyledons was investigated during the first 4 days of seedling development. The enzyme was found to be composed of seven catalytically active isoforms (each with a molecular mass of 270 kDa) which exhibited a charge heterogeneity when investigated by isoelectric focusing. Antibodies against the purified isoform 7, raised in rabbits, cross‐reacted with each of the isoforms in Western blotting experiments. In addition, each of the isoforms was composed of four immunopositive reacting polypeptides with 19, 21, 23 and 25 kDa. During development of the seedlings, a shift in the isoform pattern towards the more acidic forms was found which was more pronounced when the seedlings were supplied with 15 mM NH4Cl. The time course of changes in total GDH level can be correlated with the time course of disappearance of storage proteins. Both parameters are negatively regulated by light possibly via the photoreceptor, phytochrome. There are some indications that GDH in young mustard cotyledons mainly acts in the deaminating direction.
Light‐Induced Fern‐Spore Germination under Reduced Water Potential
Authors: Psaras G. K. , Haupt W.
Published: February 2014

The phytochrome‐mediated spore germination of the fern Dryopteris filix‐mas was studied under reduced water content. Spores were sown on solutions containing polyethylene glycol (PEG), sorbitol, or mannitol as osmotically active substances, yielding water potential values (ψ) between − 500 and − 3500 kPa for most of the experiments.

Our main results can be summarized as follows:

The germination of the spores is completely blocked by ψ ≤ −1200 kPa (≥ 300 g/l PEG).

Reduced water content of the spores, at least up to 300 g/l PEG, does not impair the phototransformation of phytochrome from its inactive form Pr to its active form Pfr.

The inhibiting effect of the osmoticum is phase‐specific: the reduced water content of the spores impairs the coupling of the phytochrome system to the transduction chain. Under these conditions, Pfr is found to be stable for several days.

In addition, the reduced water potential acts on the terminal response, although differently on different parameters of germination: Whereas formation of the rhizoid is completely blocked by 180 g/1 PEG, chlorophyll formation requires 300 g/1 PEG to become slightly retarded.
Effects of Solar Radiation on Photoorientation, Motility and Pigmentation in a Freshwater Cryptomonas
Authors: Häder D.‐P. , Häder Maria
Published: February 2014

The effects of solar radiation on motility, photoorientation and pigmentation have been studied in a freshwater Cryptomonas species. The diaphototactic orientation performed by the cells is impaired within about 90 min of solar radiation. Likewise, the percentage of motile cells within the population and the average velocity of the swimming cells decreases within about the same exposure time. This effect is not due to a thermal stress but rather seems to be caused by the solar UV‐B component, since decreasing short wavelength UV radiation by means of an artificial ozone filter or UV cut‐off filters increased the tolerated exposure time. Solar radiation also bleached the photosynthetic pigments of the cells as shown by absorption difference spectra.
Co‐Localization of Particle Transport with Microtubules in Cytoplasmic Exudates of the Siphonous Green Alga Bryopsis
Authors: Menzel D. , Elsner‐Menzel Christine
Published: February 2014

Organelles in the cortical cytoplasm of the siphonous green alga Bryopsis display various types of motile activities. One of them, saltatory movement along axially oriented linear tracks is typical for mitochondria and other small particles. A method is described which allows in vitro observation of such movements in thin layers of cytoplasm extruded from the alga and attached to a poly‐l‐lysine coated glass surface. By comparing video recordings of motile activities with the position of cytoskeletal elements visualized by immunofluorescence in the same area of a cytoplasmic exudate, it can be shown that tracks along which particles have moved in vitro are identical with microtubules (MTs). Depolymerization of MTs in the cytoplasmic exudates by MT‐specific inhibitors stops particle movement, whereas depolymerization of actin filaments with cytochalasin D disrupts actin bundles but has little effect on particle motility. These data are consistent with the model of MT guided particle transport.
Life Cycle and Morphology ofBryopsidella ostreobiformisspec. nov. (Bryopsidaceae, Chlorophyta) from the Mediterranean, under Culture Conditions, with Comments on the Phylogeny of theBryopsis/DerbesiaComplex
Authors: Calderón‐Sáenz E. , Schnetter R.
Published: February 2014

Bryopsidella ostreobiformissp. nov. is presented as the second species of the genus. The latter is amended to accomodate this new species. The derbesioid sporophyte is capable of producing three‐ to eight‐rayed stellate propagules. The dioecious gametophyte is a heterotrichous thallus with branched, prostrate filaments and unbranched, erect ones, and does not resembleBryopsis. The life cycle is distinctly diplohaplontic, with a diploid sporophyte and a haploid gametophyte.B. ostreobiformisis postulated as the starting point of a hypothetical evolutionary sequence of life histories in theDerbesia/Bryopsiscomplex.
Phosphate Uptake by Eukaryotic Algae in Cultures and by a Mixed Phytoplankton Population in a Lake: Analysis by a Force‐Flow Relationship*
Authors: Falkner Renate , Falkner Univ.‐Doz. Dr Gemot
Published: February 2014

The phosphate uptake behaviour of monospecific cultures of green algae in the laboratory and of mixed phytoplankton populations in a mesotrophic lake has been analyzed with the aid of a force‐flow relationship. This analysis yields two parameters:

A conductivity coefficient, that characterizes the activity of the phosphate uptake system.

An external threshold phosphate concentration, below which uptake of phosphate is excluded on energetic grounds.

When the phosphate concentration lies below the threshold value, the algae show an activation of the uptake system, reflected in an increase in the conductivity coefficient. Correspondingly, excess phosphate above the threshold value leads to a diminuation of the conductivity.

Using this simple analysis, phosphate discharge into lake water may be readily monitored.
Potassium Channels in Eremosphaera viridis: Modulation of Channel Opening, Conductance and Inhibition*
Authors: Köhler K. , Förster B. , Kolbowski J.
Published: February 2014

I/V relationships were performed by the voltage clamp technique in the sphaerical green alga Eremosphaera viridis de Bary. We focused on the course of the transient potential (TP) found in light‐off experiments when specific potassium channels open. I/V measurements done during this period show a N‐shaped curve. The shape depended on external potassium. TPs could be released by light‐off and by addition of barium, strontium, or α‐naphthyl phosphate. We calculated the number of specific potassium channels to be between 1750 and 34 825 channels per cell.

Barium (1 mol × m−3) and tetraethylammonium (10 mol × m−3) inhibited TPs. I/V relationships demonstrated, when N‐shaped, that potassium channels start to close at voltages more negative than −195 mV (0.1 mol × m−3 K+), −160 mV (1 mol × m−3 K+) and −148 mV (10 mol × m−3 K+). In the region of −300 mV conditions similar to those at rest are reached. External sodium suppressed the development of N‐shaped I/V relationships and reduced the membrane conductance during a TP between 8 % and 29 %. This indicates an influence of external sodium on potassium channels.
Chlorophyll Fluorescence of Lichens Containing Green and Blue‐Green Algae During Hydration by Water Vapor Uptake and by Addition of Liquid Water*
Authors: Lange O. L. , Bilger W. , Rimke S. , Schreiber U.
Published: February 2014

The fluorescence yield at room temperature of the lichens Ramalina maciformis and Peltigera rufescens, containing either green or blue‐green algae (Cyanobacteria) as phycobionts, has been investigated during rehydration of the dry lichens by water vapor uptake or by wetting with liquid water. In the dry state the fluorescence yield with all reaction centers open, Fo, was low and no variable fluorescence could be induced with both species. Whereas R. maciformis, containing green algae, regained normal fluorescence behavior during water vapor uptake, the photosynthetic apparatus of the blue‐green algae‐containing P. rufescens stayed inhibited and could be reactivated only by addition of liquid water. During stepwise rehydration at increasing air humidities, a pattern was established for the recovery of the different fluorescence parameters in R. maciformis. At a dry‐weight related water content between 30 and 40%, Fo rose sharply. Maximal variable fluorescence yield expressed as (Fv)m/Fo, strongly increased in the same range of water content and remained constant above a water content of 50%. Non‐photochemical fluorescence quenching, qNP, determined at the end of a period of actinic illumination, decreased with increasing water vapor uptake. While spraying the lichen with liquid water did not induce a further decrease of qNP, slow dehydration at lowered air humidity led to a minimal value of qNP at a water content of 65 % indicating optimal photosynthetic rate under these conditions. These results extend the conclusions drawn from earlier gas exchange experiments that blue‐green algae‐containing lichens are unable to reactivate photosynthesis by water vapor uptake. During a re‐ and de‐hydration cycle, no hysteresis in the hydration dependence of the fluorescence parameters was found. From this and the presence of a stable and low Fo value at prolonged incubation in nearly water vapor saturated air, we conclude that the reactivation of photosynthesis in blue‐green algae‐containing lichens is not prevented through high diffusion resistances for water.
Turnover of O‐Glucosides of Dihydrozeatin and Dihydrozeatin‐9‐riboside During the Cell Growth Cycle of Photoautotrophic Cell Suspension Cultures of Chenopodium rubrum
Authors: Fußeder A. , Ziegler P. , Peters W. , Beck E.
Published: February 2014

The cellular levels of O‐glucosides of 3H‐(diH)Z and 3H‐(diH)[9R]Z, the major short‐term metabolites of 3H‐(diH)Z having been exogenously supplied to photoautotrophically growing suspension cell cultures of Chenopodium rubrum, decreased significantly during further culture, irrespective of whether the cells were maintained in the stationary phase or were transferred to conditions restoring cell divison. Metabolism of both compounds was more pronounced during the active growth phase than during the stationary phase. The O‐glucosides were converted preferentially to polar compounds of as yet unknown nature, which were partly excreted into the medium. The cellular pools of both glycosides remained compartmented within the vacuole. In contrast to the O‐glycosides, the small cellular pools of the aglycones 3H‐(diH)Z and 3H‐(diH)[9R]Z maintained their level during the experimental period of 30 days. Small amounts of the glucosides, as well as of the aglycones, were recovered from the medium and could have resulted from the lysis of a few cells. The results demonstrate, for the first time, that O‐glucosides of cytokinins are not irreversibly deposited within the vacuole of plant cells but may serve to maintain a small, but more or less constant pool of extra‐vacuolar, presumably cytosolic, aglycones. (DiH)Z and its derivatives could be demonstrated to be endogenous cytokinins of Chenopodium rubrum suspension cultured cells occurring along with those of the isopentenyladenine and zeatin types.
Membrane Particles, Proteins and ATPase Activity of Tonoplast Vesicles of Mesembryanthemum crystallinum in the C‐3 and CAM State*
Authors: Klink R. , Haschke H.‐P. , Kramer D. , Lüttge U.
Published: February 2014

Dimensions and area densities of membrane particles were studied by electron microscopy of replicas of freeze‐fractured suspensions of tonoplast vesicles of Mesembryanthemum crystallinum L. in the C‐3 state and after induction of crassulacean acid metabolism (CAM) by salinity. The results are compared with the relative contribution of tonoplast‐ATPase protein to total membrane protein obtained from integration of elution profiles in size‐exclusion chromatography. Coverage of tonoplast area by globular membrane particles was 20% and 36 % and ATPase in relation to total membrane protein was 33 % and 35 % in C‐3 and CAM M. crystallinum, respectively. Thus, by order of magnitude, it is most likely that the particles represent the ATPase. In Kalanchoë daigremontiana Hamet et Perrier de la Bâthie the ATPase also constituted 36% of total tonoplast protein. Induction of CAM in M. crystallinum was associated with an increase in specific ATPase activity of the tonoplast and an increase of the size and area coverage of tonoplast particles, whereas the relative contribution of ATPase protein to total tonoplast protein and the molecular mass of the ATPase holoenzyme, as seen in size‐exclusion chromatography, remained almost unchanged.
The Effect of Phosphinothricin (Glufosinate) on Glutathione Synthesis in Plants
Authors: Herold A. , Wendler C. , Wild A.
Published: February 2014

The inhibitory effect of DL‐phosphinothricin (glufosinate) on glutathione synthesis was studied in vivo and in vitro. The influence of phosphinothricin on γ‐glutamylcysteine synthetase was compared with the already known effects of l‐buthionine sulfoximine and l‐methionine sulfoximine. The results showed that phosphinothricin and buthionine sulfoximine are inhibitors of γ‐glutamylcysteine synthetase of plants. With both substances the enzyme was inhibited by 50 % at a concentration of 7 . 10−4M (pI50 = 3.15). Methionine sulfoximine reduced the enzyme activity by 50% at 5 . 10−2 M (pI50 = 1.30). It is discussed that the target enzyme of phosphinothricin is the glutamine synthetase whereas the γ‐glutamylcysteine synthetase is only an accessory target.
A Virus Infection in the Marine Brown Alga Ectocarpus siliculosus (Phaeophyceae)
Authors: Müller D. G. , Kawai H. , Stache B. , Lanka S.
Published: February 2014

Laboratory cultures of Ectocarpus siliculosus originating from New Zealand showed a defect in gametangium formation. Nuclear divisions in gametangium initials are not followed by cell wall formation. In the resulting multinucleate cells nuclear DNA increases dramatically, and nuclear membranes disintegrate. Eventually, the entire structure is filled with hexagonal particles of approximately 130 nm diameter. These were isolated and shown by EM to consist of a dense core surrounded by a 3‐layered shell. They are released into the culture medium when the host cells burst. Ectocarpus gametes from healthy cultures could be infected by these particles. The resulting partheno‐sporophytes developed pathological symptoms, suggesting that the particles are viruses.

The expression of the defect is temperature dependent. At 10°C all gametangia are abnormal, while between 15 and 20 °C defective and normal gametangia and gametes are formed on the same plant. Partheno‐sporophytes developing from such gametes carry the viral particles expressed in deformed unilocular and plurilocular sporangia.
Is Cell Elongation Regulated by Extracellular Auxin?
Authors: Knauth Beate , Klämbt D.
Published: February 2014

Experiments with isolated epidermal strips of maize coleoptiles, pretreated with auxin and further incubated on sucrose agar containing different concentrations of auxin (indole‐3‐acetic acid, IAA or naphthalene‐1‐acetic acid, NAA) and/or naphthylphthalamic acid (NPA), are described. Preincubation for 2h with 2 . 10−4M IAA or 10−5M NAA in buffer, followed by 30 min wash in buffer results in measurable cell elongation during a subsequent incubation for 6 h on sucrose agar. Addition of 10−4M NPA inhibited the response to auxin and this inhibition could be reversed by providing IAA in addition to NPA. Inner tissue fragments (without outer epidermis) did not respond to external IAA. These results lead to the conclusion that auxin secretion at the outer epidermis may be an essential step in auxin‐regulated coleoptile growth.
Contributions to the Biomechanics of Plants. I. Stabilities of Plant Stems with Strengthening Elements of Different Cross‐Sections Against Weight and Wind Forces*
Authors: Speck Th. , Spatz H. — Chr , Vogellehner D.
Published: February 2014

Biophysical considerations allow estimates of the mechanical stresses on self‐bearing vertical stems of plants. Even at moderate wind velocities the stresses induced by aerodynamic forces dominate over those induced by the own weight. Using polar coordinates, analytical expressions of cross‐sectional area and axial second moment of area for centrisymmetric structures with symmetries threefold or higher are derived. Calculating the relative section modulus for various (centrisymmetric) arrangements of stabilizing structures leads to an estimate of the “mechanical effectivity” of these structures. If for plant stems, seen as composite materials, the second moments of area and the elastic moduli are known, the contribution of the different tissues to mechanical stability can be determined quantitatively. The mechanical design of early “vascular” land plants and of stems of (fossil) trees and lianas in different ontogenetic stages can be assessed.
Contributions to the Biomechanics of Plants.; II. Stability Against Local Buckling in Hollow Plant Stems*
Authors: Spatz H. — Chr , Speck Th. , Vogellehner D.
Published: February 2014

Hollow plant stems are, compared to solid ones, endangered by a particular kind of mechanical damage: local buckling. In upright stems centric forces due to the weight of the plant itself are not critical. Bending, however, as caused by wind forces causes transverse stresses that lead to local buckling, long before the critical tension or compression stresses are reached.

A new numerical method is proposed to treat local buckling of hollow plant stems caused by bending forces. The results emphasize the importance of transverse reinforcements in the nodes and/or the nodal thickenings for the stability of hollow structures.
Activities of Photosystems I and II in Chlamydomonas segnis Adapted and Adapting to Air and Air‐enriched with Carbon Dioxide*
Authors: Badour S. S. , Irvine B. R.
Published: February 2014

Activities of photosystems I and II were compared at a saturating irradiance in air‐ and 5% CO2‐adapted and adapting Chlamydomonas segnis at the active phase of photosynthesis during the cell cycle. PSII activity was 200% greater in air‐ than in 5% CO2‐adapted cells, while PSI activity was similar in both types of cells and matched the level of PSII activity in air‐adapted cells. As a result, air‐ and 5% CO2‐adapted cells were characterized by low and high PSI/PSII ratios, respectively. In air‐adapted cells, the greater PSII activity (rate of O2 evolved) exceeded that of photosynthetic (Ps) O2 evolution, resulting in a Ps/PSII ratio below unity. This was associated with higher levels of catalase activity, lower l‐ascorbate content, and higher dehydro‐l‐ascorbate content than in 5% CO2‐adapted cells. During adaptation to air or 5% CO2 for 6 h in light, PSI rather than PSII was sensitive to changes in the concentration of CO2, and the adapting cells acquired the characteristics of air‐ and 5% CO2‐adapted cells as indicated by PSI/PSII, Ps/PSII, catalase activity, l‐ascorbate and dehydro‐l‐ascorbate contents. The results are discussed in the light of changes in the molecular organization of the thylakoid membranes and enhanced non‐cyclic electron transport coupled with O2‐uptake (Mehler reaction) for the generation of the ATP required for CO2/HCO−3‐transport in air‐adapted and adapting cells.
Analysis of the Molecular Organization of Photosystem I During Light‐Dependent Chloroplast Differentiation in Mutant C‐6D of Scenedesmus obliquus*
Authors: Römer S. , Humbeck K. , Senger H.
Published: February 2014

Cells of pigment mutant C‐6D of the green alga Scenedesmus obliquus synthesize only Chl a and precursors of carotenoids during heterotrophic growth in the dark. These cells exhibit high PSI‐activity per Chl and a low Chl/P700‐ratio. After transfer to light, Chl a, Chl b and carotenoids are formed with different kinetics.

Analysis of chlorophyll fluorescence emission and excitation spectra revealed a sevenfold increase in the amount of the long wavelength antenna of PSI (720 nm) resulting in an increase in the absorption cross section of PSI during illumination. The underlying changes in molecular organization of PSI were investigated by sucrose density centrifugation of solubilized thylakoids after digitonin treatment and subsequent identification of the components by gel electrophoresis, HPLC and fluorescence. In dark grown cells one blue‐green band (0‐II) could be resolved. This band contained only Chl a and the reaction center complex of PSI, CPI.

After 24 hours of illumination three pigmented zones and a small amount of free pigment were observed. One of the zones (24‐I) was identified as a light‐harvesting fraction containing the pigment‐protein complexes LHCP1 and LHCP3. In the second fraction (24‐II) the reaction center complexes of PSI and PSII were found. The highest molecular weight fraction (24‐III) was enriched in PSI‐complexes of higher molecular weight and contained a high amount of long wavelength fluorescence antenna (720 nm) attributed to PSI. In contrast to band 24‐II which contained a high percentage of β‐carotene and a high Chl a/b‐ratio, the Chl a/b‐ratio of fraction 24‐III was lower and the xanthophyll content increased.

Our data demonstrate an increase in the PSI‐unit size during chloroplast development in mutant C‐6D of Scenedesmus obliquus. Dark‐grown cultures have small functional PSI‐units composed of the chlorophylls involved in charge separation and the core antenna. This unit contains only Chl a and no carotenoids. After transfer to light Chl b and carotenoids are formed. Simultaneously with the appearance of carotenoids and Chl b, PSI‐complexes of higher molecular weight are synthesized indicating the addition of a LHC to the reaction center complex of PSI.
PPiase‐Activated ATP‐Dependent H+ Transport at the Tonoplast of Mesophyll Cells of the CAM Plant Kalanchoë daigremontiana*
Authors: Marquardt‐Jarczyk Gisela , Lüttge U.
Published: February 2014

The co‐ordinated action of the two proton‐transporting enzymes at the tonoplast of the CAM plants. daigremontiana, viz. the ATPase and the PPiase, was studied by measuring fluorescent dye quenching. The initial rates of ATP and PPi‐dependent H+ transport into tonoplast vesicles were additive, i.e. the sum of the rates obtained with each substrate alone was in the range obtained with both substrates added together at the same time. Conversely, the activities of the two H+ pumps were non‐additive in establishing the steady‐state level, indicating that the final steady state was under thermodynamic control of a maximal attainable proton gradient. The initial rates of ATP‐dependent H+ transport were stimulated enormously if ATP was added a few minutes after pre‐energization of the vesicles with PPi. This stimulation was observed only when the PPiase was active. A similar effect was not found for PPi‐dependent H+ transport after pre‐energization with ATP. Hence, a PPiase‐activated ATP‐dependent H+ transport can be distinguished from the basic ATP‐ and the basic PPi‐dependent H+ transport. In parallel a PPi‐dependent stimulation of ATP hydrolysis in the absence of ionophores was measured, which can only be attributed to the activity of the PPiase. PPiase‐activated ATP‐dependent H+ transport depends on the presence of permeant anions. It shows properties of both H+ transport activities, i.e. the chloride and malate stimulation and the DCCD inhibition of the ATP‐dependent H+ transport activity, the nitrate stimulation and the KF inhibition of the PPi‐dependent H+ transport activity. Only MgPPi and MgATP were effective as the respective substrates. The PPiase‐activated ATP‐dependent H+ transport had a half life of about 5–9 minutes. It is concluded that the PPiase may play an important role in kinetic regulation of the ATPase, and implications for CAM metabolism are discussed.
Potential Consequences of Virus Infection for Shade‐Sun Acclimation in Leaves
Authors: Osmond C. B. , Berry J. A. , Balachandran S. , Büchen‐Osmond C. , Daley P. F. , Hodgson R. A. J.
Published: February 2014

Attention is drawn to literature evidence that leaf virus infection may interfere with synthesis of ribulose‐1,5‐bisphosphate carboxylase oxygenase, and with the activity of photosystem II, two main requirements for shade‐sun acclimation. Preliminary experiments which show that virus infections resulting in these interactions can lead to photosynthetic physiology diagnostic of nitrogen limited plants and/or shade ecotypes are presented. Other observations on the diversity of virus infections in sun populations of wild species commonly found in the shade are presented. Together, this evidence leads to the hypothesis that virus infection may well confine individuals of some species to shaded habitats because infection prevents acclimation to bright light, and predisposes them to photoinhibition.
The Compatibility of d‐Pinitol and 1d‐1‐O‐Methyl‐Muco‐Inositol with Malate Dehydrogenase Activity
Authors: Sommer Christiane , Thonke Barbara , Popp Marianne
Published: February 2014

Pinitol (1d‐3‐O‐methyl‐chiro‐inositol) and 1d‐1‐O‐methyl‐muco‐inositol, two cyclitols wide‐spread in the plant kingdom, were isolated from plant sources in order to test their compatibility with malate dehydrogenase activity. Both compounds had no inhibitory effect on malate dehydrogenase from Rhizophora mangle in a range of 100 to 1000 mol . m−3.

Their influence on malate dehydrogenase activity from different plant sources (Rh. mangle L., Mesembryanthemum crystallinum L., Cicer arietinum L. and Spinacia oleracea L.) was also small and similar to that observed for a number of well established compatible solutes (e.g. proline, glycine betaine). A possible role of cyclitols as cryoprotectants or radical scavengers is discussed.
Isoenzyme Variation in Asian Beans
Authors: Jaaska Velio , Jaaska Vilve
Published: February 2014

Electrophoretic variation of isoenzyme characters encoded by 20 gene loci has been studied in 9 species of Asian beans, comprising subgenus Ceratotropis of the genus Vigna. Four species of hypogeal germination type, V. angularis, V. umbellata, V. dalzelliana and V. minima, are shown to form a distinct monophyletic group in the subgenus, sharing common electromorphs of two major isoenzymes of aspartate aminotransferase. V. glabrescens is confirmed to be an allotetraploid derivate of two diploids closely related to V. radiata and V. umbellata, but divergent from their contemporary accessions analyzed. V. trilobata is the most variable species of the subgenus in isoenzyme characters. It reveals intraspecific differentiation at several isoenzyme loci correlated with the seed morphology and geographical localization.
Primary Phloem Development in the Shoot Apex of Rhizophora mangle L. (Rhizophoraceae)
Authors: Behnke H.‐D. , Richter K.
Published: February 2014

The primary phloem in the shoot apex of the mangrove Rhizophora mangle L. is largely confined to the comparatively condensed area between the first three leaf pairs. The main extension zone, surrounded by the stipular sheath of the third leaf pair, contains vascular bundles arranged in a procambial ring and characterized by a well‐developed primary phloem and a less advanced xylem. The phloem consists of a great number of sieve elements, an equal number of associated companion cells, and a few phloem‐parenchyma cells.

The differentiation of the sieve‐element protoplast (with e.g., chromatolytic nuclear degeneration, loss of the vacuole and most organelles) proceeds largely according to a well‐known pattern. Their P‐type plastids, however, form their protein crystals rather late and therefore cannot be used as an early cell marker. Lateral sieve‐element walls are distinct from other wall parts and walls of other cells by their heavy nacreous thickenings, the formation of which is shown to be strictly correlated with the occurrence and orderly arrangement of cortical microtubules.
Antibiotics, Sugars, and Amino Acids in Nectar of Rhododendron and Piptanthus Species from Nepal
Authors: Martini M. , Schmid Angela , Hess D.
Published: February 2014

Nectars were extracted in Helambu and Langtang Nepal Himalayas from Rhododendron arboreum and Rh. barbatum (Ericaceae), and from Piptanthus nepalensis (Fabaceae), and analyzed for sugars, amino acids, and antibiotic activity. Sugar content in Rhododendron nectar varied from 17 to 65%. In most nectars, G and F were present in a 1:1 ratio. In addition, from a Rh. arboreum nectar, S could be detected. Piptanthus nectar showed a very high sugar content (up to 80%), F and G, or F, G, and S, respectively, being the main sugar constituents. In all Rhododendron nectar amino acids could be found. In Piptanthus nectar there were no traceable amino acids. Neither an evolutionary significance of amino acid contents in floral nectar nor their close correlation with bees, the main pollinators of both genera, could be confirmed from our studies. Rhododendron nectar showed antibiotic activity due to the presence of acetylandromedol. The biological significance of acetylandromedol, the main toxic principle from Rhododendron nectar, seems to be its antibiotic activity, which could possibly compensate for lower sugar contents in preventing bacterial growth.
Tetrathiafulvalene Radical Cation — A New Potent Inhibitor of Anion Transport in a Green Alga
Authors: Rybová Renata , Nešpůrková L. , Ryba O. , Janáček K.
Published: February 2014

An inhibitory effect of potassium ferricyanide on the light‐dependent active uptake of chloride anions into the alga Hydrodictyon reticulatum has drawn attention to the possibility that chloride transport proceeds as an exchange for electrons and hence can be impaired by artificial electron acceptors. Tetrathiafulvalene radical cation present in solutions of the highly conductive TTF‐C1 crystals is easily reduced to TTF0 and inhibits the chloride uptake more powerfully than does ferricyanide. A practically complete inhibition of Cl− uptake is brought about by 3 × 10−5 M TTF+. The presence of ferricyanide actually reduces the inhibitory effect of TTF+; the complex equilibria of a mixture of the two electron acceptors were examined by cyclic voltammetry and a competition between the two for the inhibitory function has been suggested as a possible explanation.
Assimilate Partitioning in the Variegated Coleus Leaf
Authors: Plomann Martina , Eschrich W.
Published: February 2014

Mature leaves of a variegated cultivar of Coleus blumei Benth. with a green border and central albino region constitute a source‐sink system suitable for studies on assimilate partitioning. Leaves treated with 14CO2 on a small part of the intact green border export assimilate via the shortest path into the stem. Leaves with all but a small lobe of the green border removed show different partitioning of labeled assimilates when the leaf is exposed to 14CO2 (Fisher and Eschrich, 1985): The whole albino region of the leaf is supplied but no tracer is exported into the stem. When the green border is completely removed, 14CO2‐treatment of the albino region leads to the fixation of CO2, obviously by PEP carboxylase, as indicated by the occurrence of labeled malate. Results show that the albino region of the variegated leaf constitutes a potential sink when deprived of its green border. In addition, CO2‐fixation by PEP carboxylase in albino tissue seems to indicate a common capacity of leaves which is normally masked by photosynthesis. The difference of assimilate partitioning between leaves with intact and leaves with partly removed green borders demonstrates that the unlabeled assimilates control the movement of labeled assimilates.
Nickel‐hyperaccumulating Plants Provide a Niche for Nickel‐resistant Bacteria
Authors: Schlegel H. G. , Cosson J.‐P. , Baker A. J. M.
Published: February 2014

The occurrence and abundance of nickel‐resistant bacteria was studied in various soils originating from serpentine and other ultramafic rocks from both temperate and tropical localities. Samples were taken from soil covered with herbs and shrubs not known to accumulate nickel and from areas inhabited by nickel‐hyperaccumulating shrubs and trees. In samples taken from the humus and mineral soil layers underneath the canopy of nickel‐hyperaccumulating trees, the number of bacteria able to grow at 3, 10 and 20 mM NiCl2, was almost as high as the number of bacteria growing in the absence of nickel ions. In contrast, for soil samples taken outside these areas only moderately nickel‐resistant (3 mM NiCl2) bacteria and low numbers were encountered. It is concluded that, in humid climate zones, the predominance of nickel‐resistant bacteria in the soil is not due to the nickel ions generated by the weathering of nickel‐containing rocks but is due to nickel salts being continuously liberated by the decay of nickel‐rich leaf litter. Nickel‐hyperaccumulating plants can be considered to drive a nickel cycle resulting in the continuous percolation of the top soil by nickel ions.
Agrobacterium‐Mediated Transfer of the GUS Gene into Pollen of Petunia
Authors: Süssmuth Jutta , Dressier K. , Hess D.
Published: February 2014

Transfer of the GUS gene into pollen has been studied in co‐cultures of Agrobacterium and Petunia pollen. The Agrobacterium strain used contains a GUS gene between the two borders of the T‐DNA. Uptake and integration of this GUS gene could be shown using two different restriction systems. First, by appropriate cleavage within the T‐DNA the GUS gene could be isolated intact from Agrobacterium‐treated pollen. Second, using enzymes with cleave the T‐DNA only once, integration of this T‐DNA into individual pollen genomes could be shown. The fragments obtained could not be obtained from Agrobacterium alone. The positive Southern blots were reprobed with vir probes, but all were negative. Also following plating, no Agrobacteria could be detected from our pollen DNA preparations. Therefore, the signals obtained were not due to contaminating bacteria. Due to a high endogenous GUS activity of Petunia pollen the expression of the transferred gene could not be studied. The data demonstrate the uptake and integration of T‐DNA into pollen and are closing a gap in the line of evidence for the functioning of an indirect Agrobacterium — mediated gene transfer. Besides this, it should be stressed that only this indirect pollen system leads to success.
The Symplechosome: a Unique Cell Organelle of some Basidiomycetes*
Authors: Bauer R. , Oberwinkler F.
Published: February 2014

An unusual cell organelle of some basidiomycetes, the symplechosome, is described and illustrated in detail using Saccoblastia farinacea as an example. Symplechosomes are structurally similar, but not identical to “classical” dictyosomes of green plants and animals. As is typical for dictyosomes, each symplechosome consists of a stack of platelike cisternae. The central portions of the symplechosome‐cisternae are flattened, and adjacent cisternae are separated in the mid‐region by an intercisternal space of constant width. In contrast to dictyosomes, the intracisternal spaces are completely obliterated in the central area, and hexagonally arranged bars extend between adjacent cisternae. Identical bars often connect the symplechosomes with mitochondria. Symplechosomes are highly complex‐structured organelles which differ significantly from the simple individual Golgi cisternae or “Golgi bodies” observed in asco‐ and basidiomycetes.
Filament Disruption in Funaria Protonemata: Occlusion of Plasmodesmata
Authors: Schnepf E. , Sawidis Th.
Published: February 2014

Plasmodesmata are occluded when Funaria chloronemata are fragmented by the development of tmema cells (TCs). The TC deposits a new wall layer along the cross wall toward the neighbouring non‐sister cell (NC). This wall layer cuts off the plasmodesmata and its connection with the cross wall is soon lost. The plasmodesmata become isolated when the NC forms a new wall layer along the former cross wall. At the end of TC development, before its disintegration, the sister cell (SC) also deposits a new wall layer along the cross wall toward the TC, cutting off the plasmodesmata. For some time the plasmalemma of the plasmodesmata remains connected to the NC or the TC, whereas the desmotubule soon disappears. Relicts of the plasmalemma remain even after the isolation of the plasmodesmata and the disintegration of the TC. During the decay of the plasmodesmata, a cylinder of electron‐dense material is frequently formed along the border of the plasmodesmatal channel. This may extend over the surface of the cell wall. Eventually, the plasmodesmatal channel is filled with wall material. Callose is only observed around functional plasmodesmata and does not seem to play a role in their occlusion.
Adaptation of the Photosynthetic Apparatus of Chlorella and Ankistrodesmus to Blue and Red Light
Authors: Senge M. , Senger H.
Published: February 2014

The mode of adaptation of the photosynthetic apparatus of three unicellular green algae, Ankistrodesmus braunii, Chlorella fusca and Chlorella saccharophila to red and blue light are documented by the fluence‐rate curves of photosynthetic oxygen evolution. For all three algae tested photosynthetic capacity, respiration and light compensation point were higher for cells grown under red light, while the chlorophyll content increased in blue light‐grown cells. Blue light‐adapted cells have a lower chlorophyll a to chlorophyll b ratio and more chlorophyll in the light‐harvesting system than red light‐adapted cells, as shown in the electrophoretic profile of the pigment‐protein complexes. It is concluded that the action of red light resembles that of high levels of white light, while blue light causes the same effects as low levels of white light. In agreement with previous publications these findings indicate that the mode of adaptation to different light qualities is ubiquitous in unicellular green algae.
Circannual Growth Rhythm in a Brown Alga, Pterygophora californica
Authors: Lüning K.
Published: February 2014

A circannual rhythm was found in the kelp Pterygophora californica which forms a new blade with a free running period of 7 − 8 months under constant conditions. Individual plants exposed to cycles of daylength with T = 12, 6, or 3 months performed 1, 2, or 4 growth cycles, respectively, in one calendar year showing the entrainment of the endogenous circannual rhythm. The annual growth cycle also followed a phase shift of the annual cycle of daylength (T = 12 months) by 3 or 6 months.
Responses of Dictyostelium discoideum to Multiple Environmental Stimuli
Authors: Häder D.‐P. , Hansel A.
Published: February 2014

The movement responses of the cellular slime mold Dictyostelium discoideum to multiple stimuli were investigated. The responses were found to differ depending on the developmental stage of the organism. A novel response, positive gravitaxis, was found in Dictyostelium slugs but not in amoebae. In the presence of a simultaneous light stimulus, gravitaxis is effective only at low fluence rates. Slugs showed positive thermotaxis in a thermal gradient (0.2 °C cm−1) and ignored the simultaneous light stimulus at low fluence rates (< 10−3 W m−2), while at higher fluence rates they moved toward the light source. With a combination of a thermal gradient and gravity Dictyostelium slugs clearly oriented thermotactically ignoring the gravistimulus.
Transient Gene Expression in Sunflower Mesophyll Protoplasts
Authors: Kirches E. , Frey N. , Schnabl Heide
Published: February 2014

Experiments on transient gene expression were performed with mesophyll protoplasts isolated from young leaves of the sunflower (Helianthus annuus L.). Both PEG‐mediated DNA transfer as well as electroporation, were shown to be suitable for the introduction of a foreign gene. The expression of the reporter gene β‐glucuronidase was measured by a fluorimetric GUS assay. Inhibiting RNA synthesis by cordycepine (3‐deoxyadenosine) or translation of mRNA by cycloheximide suggests that biologically active plasmid‐DNA as well as functional mRNA transcripts are available for only short time periods in transfected protoplasts. Electroporation was carried out using rather high pulses in the microsecond range. Results indicate, that DNA uptake is more efficient using PEG, while electroporation causes less damage in DNA treated mesophyll protoplasts.
Non‐light‐dependent Shikimate Pathway in Plastids from Pea Roots
Authors: Leuschner Carola , Schultz G.
Published: February 2014

Non‐green plastids (leucoplasts) isolated from pea roots are shown to be considerably active in forming aromatic amino acids by the shikimate pathway which, in contrast to the chloroplast pathway, is independent of light. Supply of phosphoenolpyruvate and 3‐dehydroquinate, 3‐dehydroshikimate, shikimate and quinate effectively enhances the formation of aromatic amino acids suggesting an intra‐ or/and intercellular intermediate transport.
Hypervariable DNA Fingerprint Loci in Microseris pygmaea (Asteraceae, Lactuceae)
Authors: van Houten W. H. J. , van Heusden A. W. , Voort J. Rouppe v. d. , Raijmann L. , Bachmann K.
Published: February 2014

Oligo‐GATA containing probes reveal DNA fingerprinting patterns in DNA of Microseris pygmaea after restriction enzyme digestion. There are only a few major restriction fragments. These are longer than 2 kb, and they differ completely among plants from different populations, among most members of a single local inbreeding population, and even among some parent and offspring plants. In the F2 of an interpopulation hybrid, major fingerprint bands could be assigned to 2 unlinked loci by 3: 1 and 1: 2: 1 segregations respectively, one further band segregated roughly 1: 1, one band appeared irregularly. The hypervariability of the GATA‐fingerprint loci contrasts with a low variability of other genetic markers in M. pygmaea and with a more complex but less variable GATA‐fingerprint pattern in related species.
Vacuolar Lucifer Yellow Uptake in Plants: Endocytosis or Anion Transport; A Critical Opinion
Authors: Robinson D. G. , Hedrich R.
Published: February 2014

Because of its membrane‐impermeant‐properties Lucifer Yellow‐CH (LY) is regarded by animal cell biologists as an ideal tracer for fluid‐phase endocytosis. When presented to plant cells or protoplasts this fluoroprobe accumulates in the vacuole. On the other hand there are many cases where LY does not enter the vacuole when loaded into the plant cytosol. These, superficially divergent, results have previously been explained in terms of endocytosis whereby access to the vacuole is considered to occur through vesicle transport. This interpretation has now been challenged in three recent papers where the benzoic acid derivative, probenecid, has been shown to prevent vacuolar LY accumulation in plants. Since probenecid is a well‐known inhibitor of organic anion transport in animal cells it has been argued that anion carriers capable of transporting LY might also exist at the plasma membrane and tonoplast of plant cells. Unfortunately probenecid has rarely, if ever, been used in plant transport studies. The fact that it is a weak acid, whose inhibitory effects are observed at concentrations of around 1 mM suggests that caution should prevail when interpreting results obtained with probenecid. The purpose of this article is therefore to highlight the current controversy surrounding LY uptake by plants and to critically evaluate the recent probenecid data.
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

The 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

Four 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

The 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.