bluuebunny/crossref_metadata_2025 huggingface dataset:
Receptor‐Independent Sporopollenin
Authors: Rowley J. R. , Claugher D.
Published: February 2014

Pollen 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

In 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

The 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

Employing 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

Balling 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

Acidification 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

The 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

Amoebae 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

The 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

Nitrogenase 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

This 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

Mesophyll 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

The 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).
Hydroxycinnamic Acid Transferases in the Biosynthesis of Acylated Betacyanins: Purification and Characterization from Cell Cultures of Chenopodium rubrum and Occurrence in Some Other Members of the Caryophyllales*
Authors: Bokern Maria , Heuer Susanne , Strack D.
Published: February 2014

An acyltransferase from cell cultures of Chenopodium rubrum was purified 515‐fold with a 2.5 % recovery. This enzyme catalyzes the transfer of hydroxycinnamic acids from 1–0‐hydroxycinnamoyl‐/β‐glucose to the C‐2 hydroxy group of glucuronic acid of amaranthin (betanidin 5‐O‐glucuronosylglucose). The invivo products formed are celosianin I (4‐coumaroylama‐ranthin) and celosianin II (feruloylamaranthin). The enzyme can be classified as l‐0‐hydroxycinnamoyl‐β‐glucose: amaranthin O‐hydroxycinnamoyl‐transferase (EC 2.3.1.‐). Its molecular weight was determined by gel filtration column chromatography to be ca. 69.5 kDa. Maximal rate of product formation was found to be at pH 5.6. The isoelectric point of the enzyme was at pH 4.7. The reaction temperature maximum was at 37 °C and the apparent energy of activation was calculated to be 44.5kJ mor−1. The enzyme showed a Vmax of 910pkat (mg protein)−1 with amaranthin as acceptor and feruloylglucose as acyl donor. The ratios of Vmax/Km values for sinapoyl‐, feruloyl, caffeoyl‐ and 4‐coumaroylglucoses were found to be 100:56:56:40. Donor competition experiments support the conclusion that one single enzyme is responsible for the ester formation with the different hydroxycinnamic acids. From the possible acceptors tested, only amaranthin (15S configuration) and isoamaranthin (15R) were esterified with Km values of 280 and 800 μM, respectively. Catalytic effectivity (Vmix/Km) was found at a relative ratio 15S:15R of 100:42. Betanin (betanidin 5‐O‐glucoside) and gomphrenin I (betanidin 6‐O‐glucoside) were not accepted. Some other acylated betacyanin‐containing members of four families of the Caryophyllales were investigated and showed the same type of hydroxycinnamoyltransferase activity with 1‐O‐hydroxycinnamoylglucose as acyl donor, but with different acceptor molecule specificities.
γ‐Glutamylcysteinylserine — A New Homologue of Glutathione in Plants of the Family Poaceae*
Authors: Klapheck S. , Chrost B. , Starke J. , Zimmermann H.
Published: February 2014

In addition to glutathione (γ‐GluCysGly), many species of the family Poaceae have another tripeptide which has the amino acid sequence γ‐GluCysSer. This thiol was isolated from etiolated leaves of wheat (Triticum aestivum L. cv. Star). Its structure was elucidated by quantitative amino acid analysis after total hydrolysis and by partial hydrolysis with carboxypeptidase A and γ‐glutamyltranspeptidase. The content of γ‐GluCysSer in the leaves of T. aestivum is increased by incubation with sulfate and is severely diminished by incubation with buthionine sulfoximine, a specific inhibitor of γ‐glutamylcysteine synthetase. Oxidized γ‐GluCysSer is reduced by yeast glutathione reductase with a rate somewhat lower than for glutathione, but the new tripeptide is not a substrate of glutathione‐S‐transferase from equine liver.

Besides homoglutathione (γ‐GluCysßAla), a tripeptide found in plants of the order Fabales, the tripeptide γ‐GluCysSer is the second homologue of glutathione detected in plants.
Enzymatic Characteristics of UDP‐sulfoquinovose: Diacylglycerol Sulfoquinovosyltransferase from Chloroplast Envelopes*
Authors: Seifert U. , Heinz E.
Published: February 2014

Envelope membranes from chloroplasts contain UDP‐sulfoquinovose: diacylglycerol sulfoquinovosyltransferase which catalyses the final step in sulfolipid assembly. In situ produced diacylglycerol served as radioactive acceptor to measure enzymatic activity. With this assay, several enzymatic parameters were investigated. The enzyme, which has maximal activity at pH 7.5, was stimulated by magnesium ions due to a decrease of the Km for uridine 5′‐diphospho‐sulfoquinovose from 80 pM (no magnesium) to 10 μM (5 mM magnesium). This stimulation had a Km of 0.7 mM magnesium and may be relevant in light/dark modulation of the enzymatic activity. The lower efficiency of guanosine 5′‐diphospho‐sulfoquinovose observed before can be ascribed to a higher Km of this sugar nucleotide (400 μM). Under optimized and linearized conditions the sulfoquinovosyltransferase displayed about 10% of the activity of the UDP‐galactose: diacylglycerol galactosyltransferase which competes in the same membrane system for diacylglycerols. Addition of acidic lipids, such as sulfolipid and phosphatidylglycerol, to envelope membranes resulted in an inhibition of the sulfoquinovosyltransferase, whereas the galactosyltransferase was not affected. In vivo this may contribute to an adjustment of the sulfolipid proportion in plastid membranes. In contrast to the galactosyltransferase the sulfoquinovosyltransferase did not discriminate against the dipalmitoyl molecular species of diacylglycerol when offered together with the oleoyl‐palmitoyl species. Under conditions when oleoyl‐palmitoyl‐and dipalmitoyl‐diacylglycerols were synthesized with concurrent conversion to monogalactosyl and sulfoquinovosyl diacylglycerol, the sulfolipid was highly enriched in the fully saturated species. This may explain the occurrence of dipalmitoyl species in sulfolipids, as found in many plants.
Enzymatic Pathways for the Consumption of Carbonyl Sulphide (COS) by Higher Plants*
Authors: Protoschill‐Krebs G. , Kesselmeier J.
Published: February 2014

Carbonyl sulphide (COS) is an important trace gas of the atmosphere. Considerable uncertainties remain concerning the global sinks of COS. Vegetation is believed to be an unqualified sink in the global cycle of COS. We investigated whether there is an enzymological background for the consumption of COS by higher plants in analogy to CO2. Photometric measurements demonstrated that all enzymes involved in C02 assimilation by higher plants can also metabolise COS. The key enzyme for COS metabolism in higher plants is carbonic anhydrase, an enzyme which probably directly splits COS into C02 and H2S. Such a pathway would explain the observed deposition of COS to vegetation.
Transport Processes in Vacuoles of Higher Plants
Authors: Martinoia E.
Published: February 2014

The vacuole is the largest compartment of a mature plant cell and serves as an internal reservoir of metabolites and nutrients. In the last years transport of solutes across the tonoplast has been intensively investigated. It was shown that two different proton pumps reside in the tonoplast. These pumps generate an electrochemical gradient which can be used as an energy‐source to accumulate solutes. Cation uptake is driven by an H+ antiport mechanism. Anions are accumulated in response to the inside positive membrane potential. In addition, the existence of ion channels was shown using the patch clamp technique. The aim of this review is to compare and to discuss the present state of our knowledge of solute transport across the tonoplast.
K+ and Cl− Conductance of Arabidopsis thaliana Plasma Membrane at Depolarized Voltages
Authors: Cerana Raffaella , Colombo Roberta
Published: February 2014

The ion currents, activated by depolarizations, across the plasma membrane of Arabidopsis thaliana cultured cells were studied by means of the patch‐clamp technique in the whole‐cell configuration. The electrical conductance of the membrane could be shifted from a cation to an anion conducting state by changes in the [K+]: [Cl−] ratio in the external medium. For ratios between 1:1 and 1:5 the currents were due to K+ efflux and for a ratio of 1:10 to Cl− influx. In the cation conducting state the permeability ratio of K+ over NH+4 and the alkali metal ions was: K+ ≅ NH>Na+ ≅ Li+ >Cs+. In the anion conducting state the permeability of NO−3 was the same as that of Cl−. These channels were activated by depolarizations in the range of physiological potentials (‐70/‐80mV) and, either by mediating the efflux of cations or the influx of anions, they could function to re‐hyperpolarize the membrane potential after depolarizations due to the influx of cations or of solutes cotransported with protons and/or to the inhibition of electrogenic pumps.
Nectar Secretion Pattern and Removal Effects in Six Argentinean Pitcairnioideae (Bromeliaceae)
Authors: Galetto L. , Bernardello L.
Published: February 2014

Nectar secretion pattern and effects of nectar removal were analyzed in six hummingbird‐pollinated Argentinean Pitcairnioideae: Abromeitiella brevifolia. A. lorentziana, Deuterocohnia longipetala. Dyckia floribunda, D. ragonesei and Puya spathacea. Flower lifetime was determined in each case. Nectar volume, concentration and sugar production were measured from bud opening till fading of flowers at different time intervals according to the species' flower life‐span. Nectar volume varies while nectar concentration and cumulative sugar production increase as a function of flower age in all the studied species. In general, total nectar volume and concentration values can be affected by periodic removal, but total sugar production is unaffected. Only in Puya spathacea did periodic nectar harvesting reduce the total amount of sugar produced.
Lipophilic Phenolics from the Leaves of Empetrum nigrum — Chemical Structures and Exudate Localization
Authors: Wollenweber E. , Dörr M. , Stelzer R. , Arriaga‐Giner F. J.
Published: February 2014

In the course of continuing studies on the occurrence and chemical composition of lipophilic exudates on plant surfaces, the leaves of Empetrum nigrum have been studied. They were found to produce a considerable amount of lipophilic material which mostly consists of phenolic compounds. We here report the identification of two dioxygenated chalcones, three dioxygenated dihydrochalcones, and two dihydrophenanthrene derivatives. Exept for one chalcone, all these compounds were found for the first time as natural products.

The upper and lower epidermis of the rolled hypostomatous leaves bear glandular trichomes. By flavonoid specific staining it can be shown that these natural products are accumulated within the capitate glandular cells.
Effects of Exogenously Supplied Ammonium on Root Development of Scots Pine (Pinus sylvestris L.) Seedlings
Authors: Vollbrecht P. , Kasemir Helga I.
Published: February 2014

The effect of potentially toxic concentrations of ammonium on root development of Scots pine seedlings raised on Perlite was investigated during growth periods of 3 or 10 weeks after sowing. It was shown that imbalanced ammonium nutrition led to conspicuous changes of root morphology provided the pH value in the medium was allowed to decrease to 3.9 due to the NH+4‐dependent proton excretion into the rhizosphere. Ammonium toxicity could not be observed with seedlings treated either with ammonium nitrate or with ammonium chloride at pH 5.3 − 6.8. While the supply of NH+4 considerably inhibited root development the biomass production of the shoot was increased. Determination of the endogenous level of ammonium in roots and the leaf whorl exclude a simple causal correlation between ammonium toxicity and accumulated ammonium as has been postulated for herbaceous plants.
Selection of Microspore Derived Embryogenic Structures in Maize Related to Transformation Potential by Microinjection
Authors: Gaillard A. , Matthys‐Rochon E. , Dumas C.
Published: February 2014

Microspores are attractive targets for transformation of maize through DNA microinjection since they may allow, through the development of embryogenic structures, the regeneration of transgenic plants without chimerism. Unfortunately, microinjection into unicellular microspores is technically difficult because of the presence of the exine. However, in later stages of development, this difficulty may be overcome. In this regard, our objective was to determine the most suitable stages of early androgenic development for microinjection using lucifer yellow as a marker dye. Experiments have shown that the fluorescent dye is able to spread inside the whole embryogenic structure (about 4–10 days old), only in those cases where internal cell walls are still absent or incompletely formed, as assessed by cytological observations. At later stages, when the septation is completed and the embryo is cellularized, diffusion of the dye is no longer possible. These results demonstrate that multinuclear structures with the broken exine and a cytoplasm not yet partitioned, may be conveniently used for direct transformation via microinjection.
Towards a Revision of the Systematics of the Genus Chlamydomonas (Chlorophyta)
Authors: Ettl H. , Schlösser U. G.
Published: February 2014

Strains of Chlamydomonas with cross‐reacting sporangium wall autolysins also correspond in morphology, reproduction, development, and physiological properties. We therefore undertook a revision of the systematics of the genus based on this correlation. Isolates of Chlamydomonas available in culture collections were re‐examined microscopically, preferably with respect to their reproduction and development. In particular all authentic clones, on which earlier species diagnoses had been founded, were included. Their detectable autolysins were tested crosswise in bioassays. We intend to complete and extend species diagnoses in order to separate species more precisely. ‐ At first 7 strains with a common sporangium autolysin have been examined, four of which are the authentic cultures of the species C. aggregate Deason et Bold, C. akinetos Deason et Bold, C. applanata Pringsheim, and C. humicola Lucksch. They have been brought together under the name of the species first described, C. applanata Pringsheim, due to their apparent similarities in morphology and development. An amended species diagnosis is presented. The significance of authentic cultures as important sources of further information is discussed.
Leaf Surface Microflora May Significantly Affect Studies on Foliar Uptake of Chemicals
Authors: Schreiber L. , Schönherr J.
Published: February 2014

Uptake and desorption kinetics of methylglucose and pentachlorophenol (PCP) by needles of Picea abies (L.) Karst. were studied. Uptake of methylglucose was very rapid, equilibrium was obtained within 2 h and the amounts of methylglucose associated with the needles could be completely desorbed within 8 h. In contrast, PCP uptake was steady for several hours and the amounts of PCP taken up could only partially be desorbed again. Needles treated with NaN3 prior to uptake measurements, showed no methylglucose uptake at all, whereas PCP uptake was not affected. Thus it is concluded that the hydrophilic methylglucose was taken up solely by epiphytic microorganisms, whereas the lipophilic PCP was taken up into the needle interior in significant amounts. Consequences of these results on studies of foliar uptake of chemicals are pointed out.
Bafilomycin Inhibits Vacuolar pH Regulation in a Fresh Water Charophyte, Chora corallina
Authors: Okazaki Y. , Tazawa M. , Moriyama Y. , Iwasaki N.
Published: February 2014

Bafilomycin A1, known as an inhibitor of vacuolar type H+‐ATPase, was used to study involvement of the vacuolar ATP‐dependent H+‐pump in the vacuolar pH regulation in a fresh water charophyte, Chara corallina. When bafilomycin A1 (100 nM) was externally given to intact cells, the vacuolar pH (about 5) was not affected. Internodal cells were then pretreated with 100 nM bafilomycin for 1 − 2 h and the vacuolar sap was replaced with a weakly buffered solution of pH 7.4. The readjustment of the modified vacuolar pH in bafilomycin‐treated cells was significantly retarded compared with that in untreated cells.

Next, bafilomycin A1 was directly introduced into the vacuole by vacuolar perfusion with the artificial cell sap of pH 7.4. At 100 nM bafilomycin A1, the decrease in the vacuolar pH was significantly inhibited. When cell sap was replaced with the artificial cell sap containing no buffer (pH 5.2 − 5.5), the vacuolar pH increased in the presence of vacuolar bafilomycin, suggesting that the PP1‐ dependent H+ pumping alone was not sufficient for the pH regulation of Chara vacuoles.

Intracellular bafilomycin A1 had no effect on the plasma membrane potential of tonoplast‐free cells, which is evidence that it does not affect the electrogenic H+‐pump in the plasma membrane. Bafilomycin A1 inhibited the ATP‐dependent H+ transport of tonoplast vesicles but not the PP1‐dependent H+ transport. The ATPase activity of tonoplast vesicles was also inhibited by bafilomycin A1.
Apoplastic Transport through the Fungal Sheath of Pinus sylvestris/Suillus bovinus Ectomycorrhizae
Authors: Behrmann P. , Heyser W.
Published: February 2014

Roots of Pinus sylvestris L. were inoculated in vitro with the basidiomycete Suillus bovinus (Fr.) O. Kuntze. To investigate apoplastic transport in mycorrhizal and sterile roots of Pinus sylvestris, roots of intact plants were submerged for 20 h in 0.1% solutions of the fluorescent dye sulphorhodamine G (SR‐G) or for 6 h in 1.5% solutions of lanthanum nitrate. Samples treated with the dye were cryofixed, freeze‐dried or freeze‐substituted and embedded into Spurr's medium, maintaining strictly anhydrous conditions to prevent movement of the water‐soluble dye after cryofixation. Lanthanum‐treated roots were fixed in glutaraldehyde, post‐fixed in OsO4, dehydrated in a graded acetone series and embedded in Spurr's resin. The apoplastic distribution of the two tracers were examined either using fluorescence optics (sulphorhodamine) or with the electron microscope (La3+).

The yellow‐green fluorescence of sulphorhodamine could be detected within the apoplast of the fungal sheath, the Hartig net and the host cortex, up to the endodermis. Electron‐dense lanthanum deposits were located in the fungal sheath, the Hartig net and in the root cortex. Greater deposition was detected within the matrix material, in which the hyphae of the mantle are embedded. The apoplastic distribution of the two tracers within the plant root did not indicate any significant qualitative differences between sterile and mycorrhizal rootlets. In contrast to reports by other authors, we conclude that the fungal sheath does provide an apoplastic pathway for water and ions at least in Pinus sylvestris/Suillus bovinus mycorrhizae. However, the mobility of charged molecules, particularly cations, may be limited by the fungal matrix.
Investigations of the Blue‐green Fluorescence Emission of Plant Leaves
Authors: Lang M. , Siffel P. , Braunová Zuzana , Lichtenthaler H. K.
Published: February 2014

The UV light (337 nm) induced blue‐green fluorescence emission of green leaves is characterized at room temperature (298 K) by a maximum near 450 nm (blue region) and a shoulder near 525 nm (green region) and was here also studied at 77 K. At liquid nitrogen temperature (77 K) the blue (F450) and green fluorescence (F525) are much enhanced as is the red chlorophyll fluorescence near 735 nm. During development of green tobacco leaves the blue fluorescence F450 (77 K) is shifted towards longer wavelengths from about 410 nm to 450 nm. The isolated leaf epidermis of tobacco showed only slight fluorescence emission with a maximum near 410 nm. The green fluorescence F525 was found to mainly originate from the mesophyll of the leaf, its intensity increased when the epidermis was removed. The red chlorophyll fluorescence emission was also enhanced when the epidermis was stripped off; this considerably changed the blue/red fluorescence ratios F450/F690 and F450/F735. The epidermis, with its cell wall and UV‐light‐absorbing substances in its vacuole, plays the role of a barrier for the exciting UV‐light. In contrast to intact and homogenized leaves, isolated intact chloroplasts and thylakoid membranes did not exhibit a blue‐green fluorescence emission.
Altered Pterin Patterns in Photoreceptor Mutants of Phycomyces blakesleeanus with Defective madl Gene
Authors: Hohl N. , Galland P. , Senger H. , Eslava A. P.
Published: February 2014

Action spectra of photogravitropic equilibrium were measured for the wild type of the lower fungus Phycomyces blakesleeanus and three photobehavioral mutants with defects in the madl gene. The action spectrum for the wild type NRRL1555 had major peaks at 383 and near 460 nm and subsidiary peaks at 365 and 422 nm. The action spectra of the mutants, L1 49 mad1712, L151 mad1714 and L153 mad1716 differed significantly from that of the wild type. One prominent feature of the three mutants was hat the near‐UV peaks at 365 and 383 nm, which were not well resolved in the wild type, were of approximately equal height in the mutants and were separated by an extremely sharp valley at 378 nm. The steepness of this valley suggests interaction of multiple receptors. The second prominent feature of the mutants was their enhanced 422 nm peak. The gross changes of the photogravitropic action spectra associated with the madl genotype indicate that the respective gene product acts early in the photosensory transduction chain, very likely at the level of a complex photoreceptor system. Flavins and pterins, two pigment classes which were expected to function as chromophores of the near‐UV/blue light photoreceptor system, were analyzed for stage I sporangiophores of the wild‐type and the mutant strains by HPLC with fluorescence detection. In the wild‐type strain NRRL1555, and also in the three madl mutants, flavins were found to be present at the following concentrations: riboflavin (2.9 × 10−6 M), FMN (3.8 × 10−6M) and FAD (1.3 × 10−6 M). No significant effect of the madl mutations on the flavin content could be discerned. Among the pterins found in the wild type and the madl mutants were biopterin, 6,7‐dimethylpterin, neopterin, pterin and xanthopterin. These pterins occurred in all strains in the micromolar range and none of them was significantly reduced in the mutants. However, biopterin, 6,7‐dimethylpterin and xanthopterin occurred in some excess in one of the madl mutants. The most significant feature of the madl mutants was that they had almost completely lost one unidentified pterin with a retention time of 18 − 20 min. Another two unidentified pterins were reduced about twofold in the mutants compared to the wild type. The results suggest an involvement of pterins in the photoreception of near‐UV and blue light in Phycomyces.
Lichenizing Rhizomorphs and Thallus Development in the Squamulose Lichen Aspicilia crespiana Rico ined. (Lecanorales, Ascomycetes)
Authors: Sanders W. B. , Rico V. J.
Published: February 2014

This work describes the rhizomorphs and their relation to thallus development in the squamulose lichen Aspicilia crespiana Rico ined. The rhizomorphs capture algal cells, giving rise to new squamules terminally or laterally. The thallus thus consists of a network of lichenized squamules interlinked by mycobiontic rhizomorphs. A previously proposed comparison of lichen rhizomorphs to the prothallus (hypothallus) of crustose lichens is applied and expanded upon. Other less organized prothallic structures sometimes produced by A. crespiana are also described. The importance of lichenizing rhizomorphs as an essential feature of thallus growth in this species is emphasized and a competitive role in substrate occupation and thallus expansion is suggested.
Austropeltum glareosum gen. et sp. nov., a New Lichen from Mountain Plateaux in Tasmania and New Zealand*
Authors: Henssen A. , Döring H. , Kantvilas G.
Published: February 2014

Austropeltum gen. nov. is described as a monotypic genus of the family Stereocaulaceae. It differs from other genera of the family by a sqamulose habit. The single species, Austropeltum glareosum sp. nov. is characterized by an heteromerous thallus with a thick, heavily gelatinized upper cortex, and stalked, lecideine, glomerate apothecia. The apothecial stalk is a pseudopodetium, which is delimited from the subhymenium by a pigmented boundary tissue. Asci are eight‐spored and possess an amyloid tube‐structure; the simple ascospores are fusiform and colourless. Filiform conidia are produced laterally and terminally in marginal pycnidia. A. glareosum grows over gritty soil on exposed mountain summits and plateaux in New Zealand and Tasmania.
Octadecanoid‐derived Signaling Molecules Involved in Touch Perception in a Higher Plant
Authors: Weiler E. W.
Published: February 2014

Recent evidence suggests that octadecanoid derived metabolites, notably jasmonic acid and/or methyl jasmonate, are involved in the reaction of touch‐sensitive tendrils to mechanical stimulation.
The Ca2+ Pump of the Plasma Membrane of Arabidopsis thaliana: Characteristics and Sensitivity to Fluorescein Derivatives
Authors: De Michelis Maria Ida , Camelli Antonella , Rasi‐Caldogno Franca
Published: February 2014

The transport and hydrolytic activities of the plasma membrane (PM) Ca2+ pump were characterized in a PM fraction purified from seedlings of Arabidopsis thaliana by the aqueous two‐phase partitioning technique.

Ca2+ uptake could be energized by ATP and by ITP (at about 70% the rate sustained by ATP). This characteristic was used to measure the hydrolytic activity of the enzyme as Ca2+‐dependent ITPase activity. The PM Ca2+ pump displayed a broad pH optimum around pH 7.2, was drastically inhibited by erythrosin B (EB), and was half‐saturated by 60 μM ITP. It was stimulated by CaM, specially at low, non‐saturating Ca2+ concentrations. All of these characteristics closely resemble those of the PM Ca2+ pump in other plant materials.

Analysis of the effects of EB and other fluorescein derivatives (eosin Y and rose bengal) showed that: i) EB behaved as a competitive inhibitor with respect to ITP; ii) the PM Ca2+ pump was drastically inhibited by concentrations of fluorescein derivatives (submicromolar), much lower than those required to inhibit the PM H+‐ATPase; iii) the different fluorescein derivatives were diversely efficient in inhibiting the activities of the Ca2+ pump and of the H+‐ATPase of the PM (eosin Y was about 10000‐fold, EB 1000‐fold and rose bengal only 50‐fold more active on the Ca2+ pump than on the H+‐ATPase); and iv) the effectiveness of EB in inhibiting the Ca2+ pump was strongly affected by the protein concentration in the assay medium.
Nitrogen Acquisition from Atmospheric NH3 by Lolium perenne
Authors: Wollenweber B. , Raven J. A.
Published: February 2014

Ammonia (NH3) is the third most abundant N species in the atmosphere and, due to various natural and anthropogenic sources, can reach high concentrations in some areas. While some plants show effects of toxicity, others are capable of using this N‐form and grow well without any utilization of soil‐N. Acquisition of atmospheric NH3 will affect the acid‐base balance of the plants as absorption and dissolution causes an alkalinisation (production of OH−) and assimilation of NH3 results in an acidification (generation of H+). As there is only a limited capacity for biochemical disposal of excess H+ in shoots, pH regulation may involve H+/OH− extrusion into the media via roots and transport of (in)organic ions between roots and above‐ground parts of the plant.

Our aim therefore was to assess NH3 acquisition by Lolium perenne and to study the effects of gas phase NH3 on growth, acid‐base balance and mineral composition of the plants. The experiments therefore included application of a range of 14NH3 to the shoots and of 15N as NO3−, NH4+ or NH4NO3 to the roots, from which the amount of gas phase NH3 acquisition could be quantified. Analysis of the mineral composition provided data for calculation of acid‐base balance as well as for water use efficiencies of the plants.

The results indicate that over the range of NH3 supplied, plants from all treatments could utilize gas‐phase NH3 as demonstrated by increases in growth and in N and C use efficiencies. Plants receiving NO3− via their roots had a higher capacity to use gaseous NH3 than those growing with NH4+. NH3 assimilation in shoots reduced both the acid load with NH4+ nutrition and the alkaline load with NO3− supply to the roots. The results of the experiments are discussed in relation to possible acid‐base regulation mechanisms of the whole plant.
The Role of Protons in the Auxin‐induced Root Growth Inhibition ‐ A Critical Reexamination
Authors: Lüthen H. , Böttger M.
Published: February 2014

According to the acid growth theory of auxin action, it has been proposed that auxin decreases root growth by inhibiting the proton pump, thus causing an alkalinization of the apoplast. This paper critically tests this hypothesis with corn (Zea mays L.) roots. It was found that: i) the pH‐growth curve for roots exhibits a broad optimum ranging from pH 4.5 to 9. ii) Any acid‐induced growth is of very short duration, iii) The low sensitivity of root growth to external pH is independent of both the pump activity and the buffer capacity of the bathing solution, iv) Neither incubation in acidic buffer nor stimulation of the proton pump reverts the auxin‐induced root growth inhibition. It is concluded that the auxin‐induced root growth inhibition is not mediated by cell wall alkalinization.