bluuebunny/crossref_metadata_2025 huggingface dataset:
Detection of a Phytochrome‐like Protein in Macroalgae
Authors: López‐Figueroa F. , Lindemann P. , Braslavsky S. E. , Schaffner K. , Schneider‐Poetsch H. A. W. , Rüdiger W.
Published: February 2014

A phytochrome‐like protein was detected in extracts from the red algae Corallina elongata and Gelidium sp., from the brown algae Cystoseira abiesmarina and Cystoseira tamariscifolia, and from the green algae Ulva rigida, Enteromorpha compressa and Chara hispida. Relative amounts of the photoreversible protein were determined by measurement of Δ (ΔA) values of the crude extract. SDS gel electrophoresis and immunoblotting with monoclonal antibodies directed to phytochrome from etiolated maize and oat seedlings revealed only one phytochrome‐related band with apparent molecular weight of 130 kDa. The absorption difference spectrum after partial purification showed a “normal” absorption band (λmax = 670 nm) for the Pr form but only a very weak band (λmax = 705 nm) for the “Pfr form”.
Fatty Acid Composition of the Peribacteroid Membrane and the ER in Nodules of Glycine max Varies after Infection by Different Strains of the Microsymbiont Bradyrhizobiumjaponicum
Authors: Bassarab S. , Schenk Sigrid U. , Werner D.
Published: February 2014

The fatty acid composition of ER, Golgi and peribacteroid membrane (PBM) from root nodules formed on Glycine max after infection with different strains of Bradyrhizobium japonicum has been analysed by gas chromatography. In each plant‐microsymbiont combination the fatty acid composition (FAC) of the PBM is distinct from ER and Golgi. The similarity between ER and PBM fatty acid composition is significantly stronger than between Golgi and PBM. In addition the fatty acid composition of all membrane systems in nodules is affected by the microsymbiont strain. A comparison of four strains of Bradyrhizobium japonicum grown in agar surface culture and isolated as the symbiotic bacteroids reveals a decrease in oleic acid during bacteroid differentiation.
Investigations on the Starch Content and Ultrastructure of Spruce Needles Relative to the Occurrence of Novel Forest Decline
Authors: Forschner W. , Schmitt V. , Wild A.
Published: February 2014

The starch content and ultrastructure of needles of Norway spruce trees [Picea abies (L.) Karst.] taken from three natural habitats, undamaged or with symptoms of novel forest decline, were investigated during the course of three years.

The starch content was clearly dependent on the seasons, with a maximum in spring and a decline during summer and autumn, leading to a minimum in winter. Needles of damaged trees from one habitat exhibited in all three years from August to October a significantly higher starch content than their undamaged counterparts. Microscopic investigations of these needle samples exhibited severe damage symptoms to the phloem in macroscopically green needles, though more intensely in the needles with yellowing symptoms. The phenomenon of starch accumulation is interpreted as a delay in starch mobilization, caused by a reduction in assimilate transport capacity of the needle phloem.

The lower degree of starch accumulation in needles of damaged trees from a second natural habitat corresponded well to the lesser extent of phloem damage. The difference in damage patterns are discussed in terms of the differing air pollution situations acting on both habitats.
Two Proton Pumps Operate in Parallel Across the Tonoplast of Vacuoles Isolated from Suspension Cells ofChenopodium rubrumL.*
Authors: Hoffmann Bernd , Bentrup Friedrich‐Wilhelm
Published: February 2014

The kinetics of vacuolar acidification upon addition of ATP and/or pyrophosphate (PPi) has been assayed on single immobilized vacuoles by computer‐aided microfluorimetry of 9‐aminoacridine, and by acridine orange absorption photometry on vacuole suspensions isolated from green suspension cells ofChenopodium rubrumL. Two proton pumps at the tonoplast, an ATPase and a pyrophosphatase (PPase), operate in parallel to acidify the vacuole with different contributions adding up to a transtonoplast Δ pH of 2.6 pH units at external pH 7.2. The saturable components of proton pumping reach half maximal velocity with 0.32 ± 0.06 mM ATP and 23 ± 2.5 μM PPi, respectively. At saturating substrate concentrations, ATPase and PPase hydrolyse ATP and PPi, respectively, at a ratio of 2.3. The same ratio holds for the corresponding proton fluxes maintaining a given steady‐state vacuolar pH. We conclude that both pumps operate at the same stoichiometry.
Lipid Profiles of Leaf Tonoplasts from Plants with Different CO2‐Fixation Mechanisms*
Authors: Haschke H.‐P. , Kaiser G. , Martinoia E. , Hammer U. , Teucher T. , Doene A. J. , Heinz E.
Published: February 2014

Tonoplast preparations were obtained from leaves of Hordeum vulgare (C3), Kalanchoë daigremontiana (obligate CAM) and Mesembryanthemum crystallinum (C3 and inducible CAM). Lipid analyses showed reproducible patterns comprising free sterols, glycolipids of plastidic origin, glucose‐containing lipids (steryl glucoside, acylated steryl glucoside, cerebroside) and phospholipids. Predominant components were sterols, cerebrosides, phosphatidyl choline and phosphatidyl ethanolamine. Very long chain fatty acids were found in phosphatidyl serine and hydroxy fatty acids in cerebrosides. Isolation of tonoplasts via protoplasts and vacuoles may have resulted in reduced levels of free sterols. The data show a similarity between tonoplasts and plasma membranes with respect to lipid profiles. Lipid composition was neither affected by different CO2‐fixation mechanisms nor by salt‐induced changes in Mesembryanthemum crystallinum.
Changes in the Subcellular Distribution of Free Amino Acids in Relation to Light Conditions in Cells of Chara corallina
Authors: Mimura T. , Sakano K. , Tazawa M.
Published: February 2014

Subcellular concentrations of free amino acids in internodal cells of a Characeae, Chara corallina, were measured in the dark and in the light. Using an intracellular perfusion technique, we measured concentrations of amino acids in the vacuole, in the flowing sol endoplasm and in the cortical gel layer. The sol endoplasm was predominantly the cytosol. On the basis of microscopic observations, the gel layer appeared to be occupied predominantly by a layer of chloroplasts, while the sol endoplasm was free from chloroplasts.

Both in the light and in darkness, the major amino acids in the internodal cells were isoasparagine, glutamic acid, aspartic acid, serine, glycine and alanine, as reported by Sakano and Tazawa (1984). The same major amino acids are found in each of the three compartments. The pattern of distribution of amino acids in the vacuole was similar to that in the sol endoplasm, but quite different from that in the gel layer. The total level of amino acids in the light was lower than that in darkness. The amino acid composition did not change very much, but the subcellular distribution of amino acids differed significantly between cells subjected to illumination and those kept in the dark. Concentrations of amino acids in both the vacuole and the gel layer decreased, whereas those in the sol endoplasm were almost constant.
Regulation of the Synthesis of Isocitrate Lyase and the Corresponding mRNA in the Green Alga Chlorogonium
Authors: Schmidt A. , Zetsche K.
Published: February 2014

In the unicellular green alga Chlorogonium elongatum the level of isocitrate lyase (ICL), the rate of its synthesis and the level of ICL‐mRNA measured by in vitro translation are considerably increased after addition of acetate to the culture medium of autotrophically precultured cells.

Almost identical increases are obtained independently of whether the cells are cultured after the addition of acetate in the dark (heterotrophically) or in the light (mixotrophically). Transfer of heterotrophic cells to autotrophic conditions results in a fast decrease of ICL‐mRNA and ICL protein, while a transfer to mixotrophic conditions causes no alterations in both molecular species. Therefore the concentration of ICL and its translatable mRNA is controlled only by acetate and is unaffected by light.
Photoinhibition of Photosynthetic Oxygen Production and its Recovery in the Subtidal Red Alga Polyneura hilliae
Authors: Nultsch W. , Pfau J. , Huppertz K.
Published: February 2014

In the marine red alga Polyneura hilliae photoinhibition of photosynthesis was investigated by measuring the photosynthetic oxygen production. The extent of photoinhibition in this alga depends on the fluence rate as well as on the time of exposure. Strongly photoinhibited algae recover slowly. Full recovery is reached only in weak light after 3 days. Two phases of recovery can be distinguished: a first relatively fast phase of recovery that is independent of light, and a second slow phase which begins after about 6 hours and requires weak light. Consequently, even in complete darkness partial recovery is observed.

An action spectrum of photoinhibition and its comparison with the in vivo absorption spectrum of Polyneura demonstrates that photoinhibition is mainly caused by light which is absorbed by phycobiliproteins, chlorophyll a and carotenoids. This fact and the ineffectiveness of light above 686 nm clearly indicate that the main photoinhibition site in this alga is PS II.

No photosynthetic oxygen production is detectable after 3 h irradiation at 402 nm, 150 μmol quanta m−2s−1. As photosynthetic activity recovers slowly and to a limited extent, the suppression of oxygen production is apparently only in part the result of photoinhibition sensu strictu and in part due to permanent photodamage.
Hummingbird Pollination in Two Species of Vellozia (Liliiflorae: Velloziaceae) in Southeastern Brazil*
Authors: Sazima M. , Sazima I.
Published: February 2014

Pollination by hummingbirds was observed in two species of Vellozia (Velloziaceae) in southeastern Brazil. Both species have purplish‐pink to dark purple tepals, tube‐like arrangement of stamens, large and protected nectar chamber, and no odour. Tepals are reflexed in V. leptopetala and narrow in V. declinans, further enhancing the tube‐like effect given by the long yellow anthers. Nectar is very dilute (ca. 10%). Three species of hummingbirds were observed pollinating these Vellozia species: Colibri serrirostris, Augastes scutatus, and Chlorostilbon aureoventris. The first species established feeding territories in the vicinity of V. leptopetala flowers. A bee‐pollinated Vellozia flower‐type may give rise to a hummingbird‐flower by relatively simple adjustments, consisting mainly of the reflexion of tepals, increase in stamen length, enhancement of reddish pigments, enlargement of nectar chamber and dilution of nectar. Vellozia declinans may be likened to one of the hypothetical stages of this trend towards ornithophily, whereas V. leptopetala is possibly one of the extremes within the genus.
Blue Light‐Dependent Chloroplast Differentiation in Cultured Plant Cells: Evidence for Transcriptional Control of Plastid Genes*
Authors: Richter G. , Ottersbach N.
Published: February 2014

A DNA‐protein complex capable of RNA synthesis (transcriptionally active chromosome, TAC) was isolated from plastids of dark‐grown and blue light irradiated cell cultures of Chenopodium rubrum. The transcriptional activity of TAC increased rapidly upon irradiation of dark‐grown cells with blue light. Analysis of the RNA synthesized showed that plastid rRNA genes as well as genes coding for membrane and stroma proteins were specifically transcribed; their quantities depended on the developmental stage of the plastids produced by blue light exposure. The in vitro transcription rate seems to reflect fairly well the in vivo situation insofar as its enhancement in blue light irradiated cells is in good accordance with the observed steady‐state level of plastid mRNAs. The results obtained support the notion that the blue light‐dependent accumulation of plastid mRNAs in vivo is caused by an increase in the transcription rate of the corresponding genes. Thus an alternative exists to the light‐induced transformation of etioplasts to chloroplasts in seedlings where primarily posttranscriptional and translational controls are effective.
Comparison of Properties of the Proteolytic Degradation of Unassembled Nuclear‐encoded Subunits of Ribulose‐1,5‐bisphosphate Carboxylase and of the Coupling Factor of Photophosphorylation CF1*
Authors: Feierabend J. , Bergmann C. , Otto S.
Published: February 2014

The proteolytic degradation of unassembled small subunit polypeptides of ribulose‐1,5‐bisphosphate carboxylase and of the δ‐subunit of the coupling factor of photophosphorylation CF1 were analyzed and compared in vitro in the presence of stroma or membrane preparations from ribosome‐deficient plastids isolated from 32°C‐grown rye leaves (Secale cereale L.). Extracts obtained from 70S ribosome‐deficient rye leaves after radioactive labeling were used as substrate source for the unassembled polypeptides. Soluble stroma as well as membrane preparations from isolated plastids contained proteolytic activities catalyzing the degradation of both the small subunits of ribulose‐1,5‐bisphosphate carboxylase and CF1‐δ in vitro. Maximal in vitro degradation was observed at pH 2–3 for the unassembled small subunits, but at pH 6–7 for the purified holoprotein of ribulose‐1,5‐bisphosphate carboxylase, and at pH 6.0 for unassembled CF1‐δ. Degradation of unassembled small subunits of ribulose‐1,5‐bisphosphate carboxylase at pH 3.0 was stimulated by Cu2+ but not by Ca2+, Mg2+ or ATP. At pH 3.0 the degradation of unassembled small subunits of ribulose‐1,5‐bisphosphate carboxylase was not inhibited by various protease inhibitors but was even stimulated. At pH 7.0 its degradation was inhibited by HgCl2 and diazoacetyl nor‐leucine methyl ester + Cu‐acetate. The degradation of CF1‐δ was markedly inhibited by phenylmethylsulphonyl fluoride (PMSF) and to a lesser extent by 1,10‐phenanthroline. According to present results different proteolytic systems appear to be involved in the degradation of unassembled small subunits of ribulose‐1,5‐bisphosphate carboxylase and of unassembled CF1‐δ.
Diurnal Nitrogenase Modification in the Cyanobacterium Anabaena variabilis*
Authors: Ernst Anneliese , Liu Yong‐Ding , Reich Sabine , Böger P.
Published: February 2014

The nitrogen‐fixing cyanobacterium Anabaena variabilis (ATCC 29413) was cultivated as continuous culture under a 12 h: 12 h light‐dark cycle. In the light, photosynthetic activity resulted in a continuous increase in cellular glycogen content, followed by an almost complete dissimilation of the polysaccharide during the dark period. Nitrogenase activity, assayed by the acetylene reduction technique, was low at the end of the dark period and increased quickly upon illumination to reach a maximum after 4 to 6 h of light. The activity rapidly declined after darkening the culture. Increase and decrease of activity were accompanied by a change in the electrophoretic mobility of the Fe‐protein of nitrogenase (dinitrogenase reductase) indicative of enzyme modification being involved in the diurnal control of nitrogenase activity. Modification and demodification of the Fe‐protein were not coupled to the cell cycle since they followed darkening and illumination when the light or dark periods were changed. Addition of fructose increased nitrogenase activity even in darkness and caused demodification of the Fe‐protein. Ammonium chloride supplied at the onset of illumination slowed down the increase of nitrogenase activity. A delayed inhibition of the enzyme was accompanied by partial Feprotein modification only. The reaction was completed after transfer to darkness. The function of enzyme modification in maintaining a constant C: N ratio is discussed and a dominating role of carbohydrate supply in this regulation is indicated by the reported findings.
Peroxisomes in the Alga Vaucheria are Neither of the Leaf Peroxisomal Nor of the Glyoxysomal Type*,1
Authors: Backeshoff K. , Stabenau H.
Published: February 2014

Microbodies were isolated from the freshwater alga Vaucheria sessilis as well as from a marine Vaucheria. The organelles equilibrated on sucrose gradients at densities 1.23 g . cm−3 and 1.24g . cm−3, respectively. On electron micrographs they showed an ovoid or spheroid shape with a diameter of 0.5 to 0.8 μm.

Besides catalase, the peroxisomes of both algae possess glycolate oxidase and glutamate‐glyoxylate aminotransferase, but no other leaf‐peroxisomal enzymes. Instead, the enzymes malate synthase and isocitrate lyase, which are markers of glyoxysomes in higher plants, are constituents of the peroxisomes in the marine as well as in the freshwater alga.

Citrate synthase, aconitase, malate dehydrogenase and enzymes of the fatty acid β‐oxidation pathway are located exclusively in the mitochondria. Therefore, the peroxisomes from Vaucheria do not belong to either the type of leaf peroxisomes or to the type of glyoxysomes.
Oligomeric Forms of Glycolytic Enzymes in Chlorella Grown in Different Light Qualities*
Authors: Kowallik W. , Grotjohann N. , Ruyters G.
Published: February 2014

Fast protein liquid chromatography on Superose 6 of crude extracts from the green alga Chlorella kessleri cultivated autotrophically in white light reveals several peaks with phosphofructokinase (PFK, EC 2.7.1.11) or pyruvate kinase (PK, EC 2.7.1.40) activity with molecular weights larger than the usually reported ones of 320–380 and 240 kDa, respectively. All other glycolytic enzymes are eluted as one peak each with a molecular weight corresponding to data from the literature. Indirect evidence indicates that the various forms of PFK and presumably PK are oligomers. The occurrence of different PFK species depends markedly on growth conditions such as wavelength of light: Red light leads to only one rather large PFK (1,580 kDa), blue light to two smaller species (760 and 360 kDa). All species are probably present in white light‐grown cells (1,500, 1,050, 930, 700 and 440 kDa). The various light qualities do not significantly affect all other glycolytic enzymes. PK constantly exhibits four forms with molecular weights of 830, 680, 480, 305 kDa. Experiments with the chlorophyll‐free mutant no. 20 of Chlorella kessleri support the assumption that oligomerization of enzymes is characteristic of regulatory enzymes, thereby providing the cell with an additional regulatory means.
The Supramolecular Organization of Photosynthetic Membranes of the Thallus Stage of Porphyra leucosticta Thuret. (Bangiales, Rhodophyta) Visualized by Freeze‐Fracture
Authors: Tsekos I. , Reiss H.‐D.
Published: February 2014

The supramolecular organization of the thylakoid membranes of the thallus stage in the red alga Porphyra leucosticta is studied in replicas of rapidly frozen and fractured cells. Freeze‐fractured thylakoid membranes exhibit only two types of fracture faces (EF and PF), because the lamellae in red algal chloroplasts are not stacked. The PF reveals numerous, tightly packed, but randomly distributed particles (density range from 2970 to 3550 particles/μm2). In contrast, the EF particles appear organized into parallel rows, the spacing of which is about 60–70 nm (about 8–9 particles occur along 100 nm of the line that is formed). Significant numbers of single EF particles are randomly distributed between the EF particle rows. The particles on both fracture faces (PF and EF) fall into two size classes: 10 to 11 nm (major size class) and 14 to 15 nm (minor size class).
Sequence Characteristics and Transcripts of rbcS Genes from Brassica napus: Temporal and Spatial Expression During Crucifer Seedling Morphogenesis*
Authors: Fiebig C. , Kretzschmar F. , Sprenger I. , Link G.
Published: February 2014

The small subunit of ribulose‐1,5‐bisphosphate carboxylase/oxygenase is encoded by a nuclear multigene family (rbcS genes). We have cloned and characterized three rbcS cDNA sequences from Brassica napus. These cDNA clones all appear to encode the same protein, but they differ in their nucleotide sequence, which has been exploited in the construction of clone‐specific oligonucleotides as selective hybridization probes. By using a nonselective RNA probe, the temporal expression of the entire rbcS gene family was analyzed during seedling development of Brassica napus and of Sinapis alba. In both crucifer species, rbcS transcripts show transient peak levels and then decrease, although to a different degree. Only a moderate (twofold) difference in transcript pool sizes is observed in light‐grown versus dark‐grown seedlings at the time of peak levels, while a much higher light/dark ratio is found in late‐stage seedlings. The oligonucleotide probes reveal three subsets of transcripts which differ in their accumulation kinetics and light/dark ratio. Assessment of the spatial distribution by using in situ hybridization indicates that rbcS transcripts are uniformly localized in cross‐sections of cotyledons from either light‐grown or dark‐grown seedlings, whereas they are undetectable in root sections.
Phosphate Activates the Phosphoenolpyruvate Carboxylase from the C4 Plant Amaranthus viridis L.
Authors: Podestá F. E. , Andreo C. S. , Iglesias A. A.
Published: February 2014

Phosphoenolpyruvate carboxylase from Amaranthus viridis leaves was activated by inorganic orthophosphate in a concentration‐ and pH‐dependent manner. Maximal activation at pH 7.0 was achieved at phosphate concentrations above 20 mM, and a positive cooperativity was observed for the binding of the anion at this pH. At pH 8.0 the maximum of activity was achieved at 10 mM phosphate; higher concentrations reduced the activation. KM for phosphoenolpyruvate‐Mg at pH 7.0 was lowered by phosphate in all concentrations tested up to 30 mM. While at pH 8.0 the KM values were lower than that of the control up to 10 mM phosphate; higher anion concentrations raised the minimum value of KM at this pH. VMAX increased at pH 7.0, and remained unchanged at pH 8.0. A KA value of 0.41 mM was calculated for phosphate at the alkaline pH. The phosphate analogue arsenate also behaved as an activating agent, while other anions (e.g. nitrate, nitrite, sulfate, tetraborate) were ineffective. The phosphate‐activated enzyme was shown to be insensitive to glucose‐6‐phosphate, but was inhibited by l‐malate to the same extent as the control.
Distribution and δ 13C Values of Portulacaceae Species of the High Andes in Northern Chile
Authors: Arroyo Mary Kalin , Medina E. , Ziegler H.
Published: February 2014

The distribution of species of Portulacaceae in the northern Andes of Chile was recorded during the late growing season along altitudinal transects from 1500 m up to the vegetation limit. The transects were located towards the east of the towns of Arica (18 °S) and Vallenar (28 °S). Whole plants were analysed for δ 13C values to examine the occurrence of different photosynthetic pathways. Three species of Calandrinia (C. thyrsoidea, C. spicata and C. grandiflora) and two species of Philippiamra (P. amaranthoides and P. celosioides) were found to have δ 13C values indicative of CAM. Portulaca philippi was the only C4 plant in the sample. The CAM species tend to occupy the lower altitudinal levels, which are also relatively drier. All the C3 species occur in the Andean belt, with more favourable water supply. Their δ 13C values averaged −25.1 ‰, a value significantly lower than the average of lowland C3 Calandrinia species reported elsewhere or the general average for lowland C3 plants of −28.8 ‰. CAM species are also limited to the western slope of the Andean range, while C3 species occur at both sides, but often have discontinuous distributions north or south of the driest section of the Andes (21–24 °S) indicating that their migration along the western side has probably been prevented by extreme aridity. The C3 species occurring on both sides of the aridity barrier are also annual in habit.
Effect of Lateral Root Formation on the Vascular Pattern of Barley Roots
Authors: Luxová M.
Published: February 2014

The vascular pattern in the root of barley (Hordeum vulgare L.), characterized by discontinuous xylem, is markedly affected by its branching. The roots become divided into unbranched segments alternating with branched segments with a more complex vascular pattern, formed by two systems differing in origin and age: the primary vascular system derived from the procambium and ontogenetically younger connective vascular system derived from stelar parenchyma.

Adjacent to the sites of the lateral root initiation, reprogramming of parent stelar parenchyma for connective vascular elements occurs. The connecting phloem is represented by small sieve elements and companion cells, the connecting xylem is composed of small vessel elements with reticulate or scalariform‐reticulate wall thickenings and simple perforations. Development of the connective vascular system secures continuous lateral and axial vascular connection between lateral root and parent root. The extent of the vascular connection in the parent root increases in an acropetal direction.

Hydraulic effects of connective vascular tissue formation and parent root segmentation are discussed.
The Localization of Lead in the Lichen Ramalina duriaei (De Not.) Bagl.
Authors: Garty J. , Theiss Heide‐Birgitt
Published: February 2014

In an attempt to ascertain whether the lichen Ramalina duriaei could be employed to biomonitor atmospheric lead pollution, specimens of this lichen were exposed to Pb (NO3)2 solutions and a buffered solution (tartaric acid/sodium bitartrate, pH 2.8) of sodium rhodizonate (C6O6Na2) was used to locate lead in their thalli. The procedure entailed exposure of the lichen to 0, 5, 50 and 100 ppm Pb for 5 min and 1 h and the subsequent determination of the lead contents from photographs of the thalli. Distribution of lead in different parts of the thallus was assessed after exposure of the lichens to 2 ppm Pb (9 h or three d), 50 ppm (45 min) or 200 ppm (4d). Cross sections of vegetative parts of the thallus and of the apothecia revealed that lead penetrated into the cortical cells of the thallus but not into the algal cells of the phycobiont nor the ascospores or medullary cells. The observed massive penetration of lead into cortical cells supports the notion that Ramalina duriaei is sensitive to atmospheric lead pollution.
Flowers and Beetles in the South American Tropics
Authors: Gottsberger G.
Published: February 2014

Examples of beetle pollination in the South American tropics are given. The case histories refer to representatives of the families Cyclanthaceae, Annonaceae, and Araceae. In most cases the cantharophilous syndrome does not seem to be the result of coevolution but of a one‐sided adaptation of flowers to the behavior, necessities, and sense‐capacities of beetle species. It is emphasized that cantharophily may not necessarily be an indication of ancientness of a flower/insect relationship. Besides primitive angiosperms, there are derived and modern groups which, in their pollination, are specialized for beetles.

Carludovica palmata (Cyclanthaceae) is pollinated by small curculionids which are attracted by odors in the early morning hours. Annona coriacea (Annonaceae) and Philodendron selloum (Araceae) are pollinated by large dynastid scarab beetles in the evening hours. In all three species thermogenesis occurs. Although belonging to widely separate systematic groups, Annona flowers and Philodendron inflorescences have a similar pollination biology, which indicates that their adaptations to beetles are the result of convergent evolutionary developments.
Bird‐Flowers: Hovering Versus Perching Exploitation
Authors: Westerkamp Chr
Published: February 2014

Usually, bird‐flowers are classified into New World flowers (used by hovering hummingbirds) and Old World species (adapted to perching birds). Since there are many observations which violate this classification the proposal is made to distinguish between blossoms adapted to hovering birds and those providing a well‐defined perch. Characters and examples are given for both groups including the different ways a perch is provided by the plant and the distinct methods of hover‐flight in birds. The diverse adaptive solutions for bird pollination within some taxa are exemplified. To understand bird‐flowers the actual functioning of flowers must be in focus, and not the geographic distribution nor the systematic affiliation of their visitors.
Exchange of Metabolites in Cyanophora paradoxa and its Cyanelles*
Authors: Schlichting R. , Zimmer W. , Bothe H.
Published: February 2014

The flagellate Cyanophora paradoxa contains blue‐greenish, organelle‐like inclusions termed cyanelles which perform photosynthetic CO2‐fixation in place of chloroplasts. By the use of the HPLC‐technique, Cyanophora was shown to form glucose, sucrose, maltose, mannitol, ribose, glycerol and trehalose. Extracts from the whole organism and from the eucaryotic host, but not from the cyanelles, convert 14C‐labelled UDP‐glucose to polyglucan. Synthesis of sucrose from UDP‐glucose and fructose‐6‐P or fructose could not be demonstrated in any extract from Cyanophora. The transfer of metabolites into cyanelles was monitored by the silicone oil filtering technique. The solute spaces for 14C‐labelled sorbitol and 3H2O were the same indicating that sorbitol freely penetrated the plasma membrane of cyanelles in contrast to the situation found in chloroplasts. The measurements of the solute spaces for the different compounds showed that maltose and sucrose were not accumulated by isolated cyanelles. Other compounds like fructose, fucose, glutamine or glycine had intermediate sizes of their solute spaces. Cyanelles apparently possess a rapidly transporting glucose carrier and not a malate/oxaloacetate shuttle and also not an ATP/ADP translocator. The carrier composition at the plasma membrane of cyanelles and at the inner envelope membrane of chloroplasts seems to be totally different.
Malate Uptake into Isolated Vacuoles from Catharanthus roseus Cells: Role of the Membrane Potential
Authors: Marigo G. , Bouyssou Huguette
Published: February 2014

The mechanisms involved in the transport of malate into isolated vacuoles of Catharanthus roseus (L.) cells were investigated with special reference to the effects of induced changes in membrane potential and surface charges of the tonoplast. For this purpose, thiocyanate (SCN−), a highly permeant anion often used as a membrane potential probe, was extensively exploited. In the absence of Mg‐ATP, the low accumulation ratio of 14C SCN− could be related to the presence of negative charges at the outer surface of the tonoplast exerting a screening effect on the displacement of lipophilic anionic species. Nevertheless, malate was taken up continuously by vacuoles supporting the concept of a transport component which facilitates its transfer through the tonoplast. From experiments showing the pH dependence of malata uptake, it is suggested that the protonated form of the transporter is implicated in this process. Moreover, when the vacuoles are energized by Mg‐ATP, the study of the equilibrium distribution of 14C SCN− indicated an inside positive membrane potential difference. Advantage was taken of these results to modulate the membrane potential with high levels of thiocyanate. The data obtained demonstrate that malate uptake results from electrophoretic movement in response to the positive potential difference.
X‐Ray Microprobe Analyses of Vacuoles of Spruce Needle Mesophyll, Endodermis and Transfusion Parenchyma Cells at Different Seasons of the Year*
Authors: Stelzer R. , Lehmann H. , Kramer D. , Lüttge U.
Published: February 2014

The needles of an outdoor‐grown healthy Picea abies (L.) Karst. tree were routinely investigated from bud break up to 16 months thereafter. Transmission electron microscopical (TEM) and cryoscanning electron microscopical (CSEM) techniques were used for structural observations. Energy dispersive microanalyses (EDX) on bulk‐frozen hydrated specimens served for direct determination of element levels in the vacuoles of the mesophyll, endodermis and transfusion parenchyma cells.

Both, CSEM and TEM micrographs show comparable seasonal variations e.g. in chloroplast structure and in vacuolar inclusions. EDX‐analyses clearly point out that high Mg concentrations are characteristic of mature endodermis cells. Conversely, K concentrations incline to become lower in the maturing endodermis than in the surrounding tissues. The elements P and S represent the major part of the potentially inorganic counterions for Mg and K. It is concluded that the endodermis cells serve as a storage buffer for maintaining homeostasis of Mg and S levels in the adjacent cells throughout the year.
Import of 14C‐Photosynthate by Developing Leaves of Sugarcane
Authors: Robinson‐Beers Kay , Sharkey Th. D. , Evert R. F.
Published: February 2014

Sink‐to‐source transition was studied in developing sugarcane (Saccharum interspecific variety L62–96) leaves. Fully‐expanded, mature sugarcane leaves were fed 14CO2 for 20 minutes, incorporating about 617 Bq. After five hours the leaves of each plant were cut into 1‐cm‐length segments that were weighed and then placed in scintillation cocktail for counting. All leaves younger than the leaf fed 14CO2 imported labeled photoassimilate. Three to four leaves had both importing and non‐importing regions within the blade and a distinct transition region between them. A transition region was observed in leaves which had expanded to between 30 and 90 % of final blade length. Radioactivity per gram fresh weight was calculated as a measure of sink strength. Sink strength was greatest in the youngest leaf and declined with leaf age. The results of this study indicate that 1) import of photosynthate by developing sugarcane leaves occurs over a longer span of developmental ages than in dicotyledonous leaves and 2) the actual tissue region undergoing transition within such a leaf can be resolved as narrow zone between the importing and non‐importing regions.
Salt Tolerance of Ectocarpus siliculosus (Dillw.) Lyngb.: Comparison of Gametophytes, Sporophytes and Isolates of Different Geographic Origin
Authors: Thomas D. N. , Kirst G. O.
Published: February 2014

Forty Ectocarpus siliculosus isolates from a wide geographical range, including gametophyte and sporophyte plants, have all been acclimated to the same salinity for several years. Their salinity tolerances in respect of cell viability, photosynthesis and dark respiration were evaluated over the salinity range: 8 to 96 ‰. Significant differences in the physiological tolerances to salt stress compared with viability measurements were evident. Genotypic differences in salt tolerances between groupings of the isolates, and also differences in responses of gametophyte and sporophyte generations were found. However, diploid and haploid sporophyte material had similar tolerances. Triploid and tetraploid sporophytes did not have improved tolerances over those of diploid plants. Culture plants originating from low salinities in the Baltic Sea had broader tolerances than field material collected from Baltic waters of similar salinity.
Carbon and Hydrogen Isotope Ratios in Bromeliads Growing under Different Light Environments in Natural Conditions
Authors: Medina E. , Lüttge U. , Leal F. , Ziegler H.
Published: February 2014

Wild Ananas species in northern South America occur in shady environments and appear to be relatively intolerant to droughts associated with growth under full sun exposure. This behaviour contrasts with the higher productivity of commercial varieties of Ananas comosus when grown under full sun exposure. Such differentiation within the genus offers an opportunity to study the process of adaptation of apparently high light avoiding species into true sun plants. As a first approximation, the analysis of nitrogen content and carbon and hydrogen isotope ratios of bromeliads growing under natural conditions was undertaken to test the following hypotheses: 1. Leaf nitrogen content of plants grown under partial shade is higher than that of the same species in the same habitat growing under full sun exposure, due to the higher availability to nitrogen in the under‐canopy, but also to the lower proportion of structural carbohydrates in shade leaves; 2. δ13C values are usually more negative in CAM bromeliads growing under partial shade because of the lower contribution of CAM to total carbon gain, and the probable fixation of CO2 originating from soil respiration; 3. δD values of CAM bromeliads are less negative than those of C3 bromeliads, but CAM bromeliads grown in shady habitats tend to have more negative δD values because of the lower relative accumulation of deuterium in leaf tissue water, and also because of their relatively lower CAM activity. The results show a clear differentiation between CAM and C3 bromeliads based on δ13C values, and in general δD values are less negative in CAM bromeliads. However, in several species overlapping δD values between C3 and CAM bromeliads were observed. The analysis of paired samples of the same species grown under contrasting light intensity usually conformed with the expectations. A number of deviations from the hypotheses were observed which appeared to be related to particular environmental conditions. The interpretation of δD values obtained from total organic matter is made difficult by the local variation of hydrogen/deuterium ratios in water available to the plant.
The Colacosomes: New Structures at the Host‐parasite Interface of a Mycoparasitic Basidiomycete*
Authors: Bauer R. , Oberwinkler F.
Published: February 2014

The ultrastructure of mycoparasitic interactions in heterobasidiomycetes is diverse. A previously unknown cell structure, involved in a specific parasitic interaction, is described and illustrated. Cells of the parasite Platygloea peniophorae (Auriculariales s.l., Basidiomycetes) which attach to host cells of Hyphoderma praetermissum (Aphyllophorales, Basidiomycetes) form distinct marginal vesicular bodies with electron‐opaque cores and electron transparent sheaths. Finally, the vesicular content projects through the cell wall of the parasite and then interacts with the cell wall of the host. Ontogenetic stages are described and illustrated in detail.
Rapid Phosphorylation of H3 Histone in Isolated Nuclei of Barley (Hordeum vulgare L.)
Authors: Grimm R. , Eckerskorn Chr , Lottspeich F. , Schäfer E.
Published: February 2014

We studied the in vitro phosphorylation pattern of the proteins from in vivo irradiated isolated nuclei in relation to the investigations on rapid phytochrome effects on in vitro transcription of specific genes in isolated nuclei from barley (Mösinger et al., 1985, 1987). Although phosphorylation with carrier‐free [γ‐32P]ATP raises a variety of labeled proteins, the overall pattern does not show any difference due to the light pretreatment of the nuclei. Time‐course analysis revealed a 17 and a 45 kDa protein as the most rapidly phosphorylated proteins. To obtain more information about the identity of both proteins we tried to determine the amino‐terminal sequences of both proteins. Whereas the 45 kDa protein has a blocked amino‐terminus, we identified the 17 kDa protein as H3 histone due to its sequence homology to other H3 histones from different sources.
Properties of Oligomeric Forms of Phosphofructokinase from Chlorella kessleri Grown under Different Light Conditions
Authors: Grotjohann N. , Kowallik W. , Ruyters G.
Published: February 2014

Fast protein liquid chromatography on Superose 6 of crude extracts from Chlorella kessleri, Fott et Novákóva, grown autotrophically in blue or in red light yields three different oligomeric forms of phosphofructokinase (PFK, EC 2.7.1.11). Their substrate affinities and responses to homotropic and heterotropic effectors are different. In vitro, the degree of oligomerization of the enzyme can be influenced by specific intermediates or cofactors. Its substrate, MgATP (10 mM/5 mM), and the negative effector, phosphoenolpyruvate (5 mM), both lead to some dissociation, while the second substrate, fructose‐6‐phosphate (5 mM), and the positive effector, inorganic phosphate (50 mM), have no effect. It is discussed whether formation or dissociation of oligomeric PFK forms in vivo result from alterations in the levels or in the intracellular distribution of effector molecules and whether such processes are involved in the different regulation of cell metabolism in blue or in red light.
The Preparation of Plasmodesmata from Plant Tissue Homogenates: Access to the Biochemical Characterization of Plasmodesmata‐Related Polypeptides
Authors: Monzer J. , Kloth Sabine
Published: February 2014

A technique for the preparation of plasmodesmata within a cell wall fraction of Solanum nigrum tissue homogenates has been developed, featuring good ultrastructural preservation of plasmodesmatal structure. SDS‐PAGE of protein extracts of this plasmodesmata‐containing cell wall fraction revealed the distinct enrichment of two bands, with molecular weights of 28 and 43 kD.
Localization of Tubulin and a Centrin‐Homologue in Vegetative Cells and Developing Gametangia of Ectocarpus siliculosus (Dillw.) Lyngb. (Phaeophyceae, Ectocarpales)
Authors: Katsaros Chr , Kreimer G. , Melkonian M.
Published: February 2014

The distribution of tubulin and centrin in vegetative cells and during gametogenesis of Ectocarpus siliculosus was studied by immunofluorescence. In interphase cells bundles of microtubules are focused on the centriolar region near the nuclear surface. Some of the bundles ensheath the nucleus while others traverse the cytoplasm in various directions, sometimes reaching the cell cortex. Evaluation of serial optical sections by confocal laser scanning microscopy (CLSM) revealed that the perinuclear and “cytoplasmic” microtubule bundles presumably constitute a single complex. In interphase cells centrin is localized as a single bright spot in the centriolar region. In dividing cells duplication and separation of the microtubular complex and the centrin spot takes place. In post‐mitotic cells with two nuclei, the centrioles are located at opposite cell poles, short microtubule bundles emanate from them and partially encompass the nucleus. During gametogenesis a gradual transformation of the vegetative cytoskeleton to the gametic flagellar apparatus occurs.
High Humidity and Heat Stress Causes Dissociation of Endoplasmic Reticulum in Tobacco Pollen
Authors: Ciampolini F. , Shivanna K. R. , Cresti M.
Published: February 2014

High humidity (95 % RH) and temperature (38/45 °C) stress for 4h applied to pollen grains of Nicotiana tabacum did not affect pollen viability, assessed on the basis of the fluorochromatic reaction test, but affected in vitro germination; pollen grains treated at 38 °C showed marked delay in germination, while those treated at 45 °C failed to germinate in vitro.

The major ultrastructural effect of the stress was on RER. Stacks of RER, characteristically present in fresh pollen, were largely dissociated in the stressed pollen. The extent of dissociation of RER was greater in pollen samples stressed at 45 °C than at 38 °C. The generative cell did not show any obvious change in the stressed pollen. RER was restored in pollen grains which showed germination following culture; but not in those which failed to germinate. Apart from affecting other RER‐related functions the dissociation of RER is likely to result in the destruction of long‐lived mRNA and thus affect the ability of pollen grains to initiate protein synthesis needed for germination.
Acid‐Base Regulation byAzollaspp. with N2as Sole N Source and with Supplementation by NH+4or NO−3
Authors: Raven J. A. , Rothemund C. , Wollenweber B.
Published: February 2014

Diazotrophic cultures of three species ofAzolla (Az. caroliniana, Az. microphylla, Az. pinnata)symbiotic withAnabaena azollaeaccumulated some 0.10–0.24 mol organic anion per mol N assimilated (0.010–0.018 mol organic anion per mol C assimilated), with a corresponding efflux of 0.05–0.11 mol H+per mol N assimilated (0.006–0.009 mol H+per mol C assimilated). These values are lower than those found for terrestrial diazotrophic vascular plants; this may be related to the decreased possibility of increasing Fe and P availability by rhizosphere acidification in a free‐floating plant. Modification of the organic anion content, and of the quantity (and direction) of H+exchange with the medium, with 5 mol m−3NH+4or NO−3added to diazotrophic cultures, are consistent with substantial N acquisition from combined N as well as N2assimilation. This conclusion is consistent with previously published work with15N.
Differential Regulation of Nuclear Genes during Blue Light‐dependent Chloroplast Differentiation in Cultured Plant Cells
Authors: Bockholt S. , Kaldenhoff R. , Richter G.
Published: February 2014

Nuclei capable of RNA synthesis were isolated from both dark‐grown and blue light‐irradiated cell cultures of Chenopodium rubrum. Analysis of the heterodisperse RNA sequences synthesized showed that the SSU and LHCP gene as well as early light‐induced genes were specifically transcribed. The relative transcription rate of their mRNAs increased with the onset of blue light irradiation reaching a maximum at about 12 h, then dropped to the dark level. A comparison with the steady‐state concentration of the same mRNAs in vivo revealed a substantial difference between the two groups of genes: For the three early light‐induced genes the in vitro transcription rate is in good accordance with the observed steady‐state level of their transcripts supporting the notion that the blue light‐dependent rapid and transient accumulation in vivo is caused by a temporary increase in the transcription rate of the corresponding genes. In contrast, for the SSU and LHCP gene, the changes in transcription rate do not follow those in steady‐state concentration; thus the observed steady increase of the latter in blue light cannot be explained as an enhancement in the transcription rates of both genes, but is a likely consequence of post‐transcriptional events.
Energy Metabolism in Rhizomes of Acorus calamus (L.) and in Tubers of Solanum tuberosum (L.) With Regard to their Anoxia Tolerance
Authors: Sieber Mirjam , Brändle R.
Published: February 2014

Rhizomes of the marsh plant Acorus calamus (L.) and tubers of the flooding‐intolerant Solanum tuberosum (L.) var. Bintje, both kept under strict anoxia, differ markedly in their fermentation properties. The fermentation capacities as measured by ADH and LDH activities and their respective product concentrations were estimated.

While rhizomes of Acorus calamus, having high ADH and low LDH activities, accumulate mainly ethanol, tubers of Solanum tuberosum tend towards lactic acid fermentation.

The total amount of adenine nucleotides is quite stable in Acorus calamus, whereas they show a sharp decline in S. tuberosum during the first 6h of anoxia. The adenylate energy charge of A. calamus recovers after a short initial drop (AEC > 0.8). AEC values of S. tuberosum decrease rapidly and remain at very low values (AEC ∼ 0.3). Tuber tissues became soft and lost viability after about 48–72 h of anoxia at 25 °C. This might be due to tissue acidification and impaired energy metabolism, but not to the lack of energy reserves. Energy metabolism of A. calamus is well adapted to anoxia.