bluuebunny/crossref_metadata_2025 huggingface dataset:
Phenology and Pollination Ecology of Three Brazilian Fig Species (Moraceae)
Authors: De Figueiredo R. A. , Sazima Marlies
Published: February 2014

The phenology and pollination ecology of three native fig species were studied in southeastern Brazil. Populations displayed continual syconia production, with one species showing intra‐tree flowering asynchrony. Pollination of the fig flowers was necessary for the development of the syconia; lack of pollination induced abortion of syconia. All three species follow the general pattern of pollination known for figs, but the behavior of the pollinator wasps, Pegoscapus spp., differed in some aspects from those of other neotropical and paleotropical fig wasps, mainly with respect to pollen loading and unloading during pollination. The longevity of Pegoscapus wasps outside the syconium was about two days.
Nuclear DNA Amounts in Palms (Arecaceae)
Authors: Röser M. , Johnson M. A. T. , Hanson L.
Published: February 2014

Nuclear DNA amounts are reported for 83 species and 53 genera of palms, covering all of the six subfamilies. 4C DNA contents range between 3.89 and 55.62 pg in diploids, showing an approximate 14.3‐fold variation in genome size. Polyploids have DNA contents of up to 156.40 pg/4c which demonstrates a 40.2‐fold variation. Diploids with high DNA contents occur in three subfamilies of palms (Coryphoideae, Calamoideae, Arecoideae), and seem to be further restricted to particular tribes or subtribes (Thrinacinae, Borasseae, Lepidocaryeae, Caryoteae, some subtribes of Areceae). Palms from the subfamilies Nypoideae and Phytelephantoideae have the lowest DNA amounts, followed by the Phoeniceae and the Corypheae: Livistoninae from the subfamily Coryphoideae. Although DNA amounts in some genera and subtribes are usually constant, e.g., in Phoenix, Phytelephas, the Livistoninae, Dypsidinae, diploid Butiinae), considerable variation occurs at the diploid level in some large and apparently actively evolving genera such as Chamaedorea, Pinanga, Cenoma and possibly Bactris. Formaldehyde fixation is recommended for palms, as conventional ethanol‐acetic acid fixation has proved to be unsuitable for DNA estimation of Feulgen‐stained nuclei by microdensitometry, since it can lead to errors up to 2.5‐fold in extent. Chromosome counts are reported for 72 of the species studied, of which 42 are new.
Root Anatomy and Mycotrophy (AM) of the Achlorophyllous Voyria truncata (Standley) Standley & Steyermark (Gentianaceae)
Authors: Imhof S. , Weber H. Chr
Published: February 2014

Roots of Voyria truncata retain the primary root structure even though they can grow as thick as 2 mm in diameter. These root diameters are due to a retained capability for cell division in the cortex parenchyma. This is explained as a vital adaptation to its life form. Based on the extraradical mycelium, the mode of penetration, the structurally incompatible intraradical phase, the presence of intercellular vesicles in the root cortex, and the occurrence of immediate hyphal bridges from arbuscular mycorrhizal roots of neighbouring plants, the mycorrhiza of V. truncata is described as an arbuscular mycorrhiza (AM), although the characteristic arbuscles are missing. Special features of the AM in V. truncata are interpreted as an improved efficiency in taking advantage of the mycorrhiza. Root connections with roots of neighbouring plants are common and preferred locations for fungal infections. An evolutionary tendency towards parasitism of higher plants is discussed.
Terrestrial Biomass‐Reconstruction for the Pleniglacial and the Holocene Climatic Optimum Around 7000 cal yr BP in Europe
Authors: Gliemeroth Anne Kathrin
Published: February 2014

The aim of this research was to estimate the former below‐ and aboveground biomass during the Last Pleniglacial (22,000 cal yr BP) and during the Holocene climatic optimum, the Atlantic Period (7,000 cal yr BP). Vegetation distributions and soil conditions during these periods were reconstructed according to published literature. Using the present‐day bio‐masses of similar (but not identical) vegetation and soil types as analogues, estimates of the terrestrial biomass were made for 22,000 and 7,000 cal yr BP. Biomass was low during the Pleniglacial, representing only 5.0 to 12.5 Gt. This reflects weak soil development under cold climatic conditions, combined with soil erosion due to severe frost and strong wind. The results are compared with other biomass reconstructions for the Pleniglacial. The values for terrestrial biomass of the Pleniglacial presented in this paper are much lower than the results of the various studies for this time slice. These differences are likely to be related to the method applied. Biomass was high during the Holocene climatic optimum around 7,000 cal yr BP, representing 261 to 325 Gt compared to 232 to 273 Gt in the present potential situation and 165 to 197 Gt in the present‐day real situation. This reflects intensive soil development under warm and moist conditions during the climatic optimum of the Holocene. These results demonstrate the fluctuation of C‐content in terrestrial ecosystems since the Last Glacial Maximum on the European continent.
Essential Oils with 1,2‐Epoxy‐p‐menthane Derivatives from Mentha spicata Plants Growing Across the Island of Crete
Authors: Kokkini Stella , Karousou Regina , Lanaras T.
Published: February 2014

The essential oil content and composition of Mentha splcata plants, collected from 11 localities, scattered across the island of Crete (S. Greece), have been studied. The qualitative and quantitative essential oil analyses by means of CC and GC‐MS, have shown that these are characterized by a high quantity of trans‐piperitone oxide and/or piperitenone oxide. The pattern of essential oil quantitative variation follows a NW→SE direction on Crete. Along this direction, the total essential oil content of the plants increased whereas, the essential oil components formed via the pathway leading to the formation of cis‐piperitone oxide are gradually substituted by those leading to the formation of trans‐piperitone oxide.
Plant Polyamines in Reproductive Activity and Response to Abiotic Stress*
Authors: Galston A. W. , Kaur‐Sawhney R. , Altabella T. , Tiburcio A. F.
Published: February 2014

In this review we will focus on two areas in which the accumulated evidence for a critical physiological role of polyamines is becoming compelling, i.e. reproductive activity and response to abiotic stress. Regarding reproductive behavior, it seems clear that polyamines are members of the array of internal compounds required for flower initiation, normal floral organ morphogenesis, fruit growth and fruit ripening in particular plant species. Abiotic stresses such as osmotic stress can “turn on” arginine decarboxylase (ADC) genes, resulting in a rapid increase in their mRNA levels. Localization of ADC enzyme in the chloroplast suggests a role of PAs in the maintenance of photosynthetic activity during senescence responses induced by osmotic stress. We envisage that the use of transgenic plants and improved molecular probes will resolve in the near future the physiological significance of stress‐induced changes in PA metabolism as well as the role of these compounds in reproductive activity.
Solving a Puzzle Piece by Piece: Sexual Development in the Basidiomycetous Fungus Schizophyllum commune
Authors: Kothe Erika
Published: February 2014

In the homobasidiomycete fungus Schizophyllum commune recognition of mates is based on four multiallelic genetic loci. While Aα and Aβ independently but redundantly regulate formation of clamp cells, nuclear migration is under control of the B loci Bα and/or Bβ. In the A loci two homoeodomain transcription factors, Y and Z in Aa and one yet, V in Aβ, are encoded which form acitve heterodimers only if different specificities are combined (like Y3 Z4), e.g. via mating of strains differing in Aα loci. In both Bα and Bβ, pheromone receptors and several pheromone genes habe been found. While the homoeodomain transcription factors are thougth to directly activate downstream genes, a signal transduction cascade culminating in activation of target genes is postulated for B‐regulated development. Only if both A and B pathways are turned on, fruit body formation and spore production are observed.
Some Aspects of the Importance of Genetic Diversity in Phragmites australis (Cav.) Trin. ex Steudel for the Development of Reed Stands
Authors: Koppitz H. , Kühl H. , Hesse K. , Kohl J.‐G.
Published: February 2014

Various sites of Phragmites australis in Germany (Uckermark and Mark Brandenburg) and sites in Hungary and Denmark were investigated by PCR fingerprinting in order to determine their genetic diversity. Genetic similarities were calculated and, based on this, a cluster analysis was performed. The genetic similarity of reed clones around one lake ranged from between 70 to 100%, that of clones from different lakes was clearly lower. The further apart the clones were situated from each other, the less similar they were. At a wetland site near the shore a sudden colonisation by several new Phragmites clones was observed. This site was located in front of a well established genetically almost homogenous stand within the eulittoral. All the results are discussed in connection with a proposed model of establishment and development of water reed stands: colonization, selection of best adapted clones by competition and the stability of stands.
Seed of Cercis siliquastrum L (Leguminosae, Caesalpinioideae): Reserves and their Utilization after Germination
Authors: Rascio Nicoletta , Mariani Paola , Perin Vilma , Vecchia Francesca Dalla , Castaldo Paola
Published: February 2014

An ultrastructural study on the reserves stored in cotyledons and endosperm and on their utilization after germination has been carried out in Cercis siliquastrum seeds. The observations have shown that all the cotyledonal reserves of proteins and lipids are used during seedling growth. However, inside the endosperm cells only the protein reserves are depleted, and large quantities of lipids remain undigested. In both cell walls and intercellular spaces of the endosperm cells huge masses of polysaccharide reserves are stored. However, only the polysaccharides inserted in the cell walls are dismantled, while those located in the intercellular spaces are not attacked by the lytic enzymes. Some hypotheses regarding the possible roles of those endospermic non‐nutritional materials in the strategies of seed germination and seedling growth are suggested.
Reproduction and Hybridisation in the Genus Rosa, Section Caninae (Ser.) Rehd.
Authors: Wissemann V. , Hellwig F. H.
Published: February 2014

Crossing experiments were carried out in order to investigate the importance of apogamy in relation to autogamy, geitonogamy and xenogamy in the reproductive biology of pentaploid members of the genus Rosa, section Caninae (Ser.) Rehd. About 10,000 seeds from 900 crossing experiments were examined, 4500 of them for both filling of the grain and viability of the embryo. The results were compared with experimental reports and literature dating from 1753 to 1995. Apomictic reproduction was shown to be possible in all species of the section tested, but viable seed yields were only about 5% of those produced by xenogamy. This contradicts the hypothesis of Fagerlind (1940,1944,1945,1950) and Custafsson and Hakansson (1942), but supports the results of Matsson (1912) and Schwertschlager (1915). The number of viable seeds increased in the order apogamy, autogamy, geitonogamy to xenogamy. Reciprocal crossings showed significant differences in the number of seeds produced in the hip. This contradicts the hypothesis on the genomic constitution of the pentaploid Caninae with unbalanced heterogamy, as advocated by Hurst (1927) and Custafsson and Hakansson (1942).
Phosphate and Sulfate Activate the Phosphoenolpyruvate Carboxylase from the C4 Plant Cynodon dactylon L.
Authors: Salahas G. , Hatzidimitrakis K. , Georgiou C. D. , Angelopoulos K. , Gavalas N. A.
Published: February 2014

The effect of phosphate, sulfate and other inorganic ions on the activity of phosphoenolpyruvate carboxylase (PEPC) from the C4 plant Cynodon dactylon were investigated for the first time, as well as their interaction with Clc‐6‐P, AMP and ma‐late. Activation of PEPC by phosphate and sulfate ions was demonstrated and it was not dependent on the accompanying cations, something that was not clarified for PEPCs from other plant sources. No activation of this enzyme was observed by nitrate. PEPC activation was found to be competitive with glucoses‐phosphate (Clc‐6‐P) and AMP stimulation and less sensitive to malate inhibition. This work showed that PEPC from C4plants could exhibit similar activation properties with the enzyme from CAM plants and different activation properties in plants of the same type, rendering the study of this enzyme from different plant sources necessary.
The Pollinators of the Malagasy Star OrchidsAngraecum sesquipedale, A. sororiumandA. compactumand the Evolution of Extremely Long Spurs by Pollinator Shift
Authors: Wasserthal L. T.
Published: February 2014

The pollination process of the extremely long‐spurred orchidsAngraecum sesquipedaleandA. sororiumis described and documented here for the first time. The pollinaria and viscidia load was examined in moths captured in central and south Madagascar. Visits to orchids by hawkmoths were rarely observed in the field and were therefore systematically recorded in large flight tents using a night‐vision video technique and flashlight photography.Angraecum sesquipedalein Fort Dauphin is pollinated byXanthopan morgani praedictaandA. sororiumon Mt. Angavokely byCoelonia solani. By combining a deep nectar spur of extraordinary length with a protruding labellum functioning as a landing platform, these orchids overcome the moth's stereotypic swing‐hovering flight thus enabling full insertion of the long tongue.Angraecum compactumin Forêt d'Ambohitantely is pollinated by both the shorter and longer‐tongued forms ofPanogena lingenswhich never swing‐hover but is also exploited byX. morganiandC. solaniwith wastage of pollinaria. The duration of tongue insertion, nectar exploitation and tongue withdrawal were analyzed: legitimate and illegitimate visitors differ in their time budget and approach to the flower. Nectar volume, nectar level and sugar concentration ofA. sesquipedaleandA. sororiumwere compared with the nectar requirements of the pollinating hawkmoths. The evolution of very long spurs in these orchids is likely to have involved a series of pollinator shifts. The orchids adapted to different hawkmoth species with increasingly long tongues which primarily evolved to avoid predator attacks during visits to less specialized flowers. This “pollinator shift” model modifies the classical “coevolutionary race” model. The relevance of the taxonAngraecum bosseriSenghas is questioned.
A Spectroscopic View of Some Recent Advances in the Study of Blue Light Photoreception*
Authors: Horwitz B. A. , Gloria M. , Berrocal T.
Published: February 2014

The blue to UV‐A region of the spectrum, spanning the region of about 320–520 nm, strongly influences the growth and development of plants and fungi. Photomorphogenesis in plants is, to a great extent, controlled by phytochrome, but there are unique contributions of the blue region, which cannot be duplicated by any amount of red light. Phototropism is, with few exceptions, a purely blue light response. In fungi, the blue region dominates the photocontrol of growth and development, though some red light effects have been reported. Many blue light action spectra fit the definition of cryptochrome, a pigment class defined by its UV‐A and blue peaks. The action spectrum, if measured to sufficient resolution, displays several minor maxima or shoulders in the blue region which call to mind the vibrational levels of carotenoids and flavins. Recent molecular genetic studies, as well as photobiological work, have shown that some cryptochromes are related to the DNA repair enzyme photolyase, while others appear genetically and spectroscopically distinct. In this review, we have applied established criteria from photobiology, in particular, comparison of action spectra with absorption spectra, to these recent results. It is apparent that photolyase homologs such as CRY1 can explain the blue light portion of the action spectrum for hypocotyl elongation, assuming participation of the oxidized flavin. In fungi, the photoreceptor question remains open. Identification of the nph1 gene in Arabidopsis may soon lead to a photoreceptor for higher plant phototropism. Also, we present a possible solution to the most recent version of the long‐standing flavin‐carotenoid controversy, the zeaxanthin hypothesis for higher plant phototropism. In conclusion, there appear to be at least three classes of cryptochromes.
SIMS Investigation of the Distribution of K+, Na+, Mg2+ and Ca2+ Cations in Birch Pollen
Authors: Lhuissier F. , Verdus M. C. , Labulle B. , Lefebvre F. , Bocquel C. , Ripoll C.
Published: February 2014

Two microanalytical techniques were used to investigate the inorganic cation content and distributions in birch (Betula verrucosa Ehrh.) pollen. With intact pollen grains. X‐ray microanalysis (EDX) could only give a mean ionic composition. Secondary Ion Microscopy and Spectrometry (SIMS) appeared to be a more suitable technique to image ion distributions in the different pollen structures. This was carried out with samples prepared using a new vapour phase technique designed to improve ion retention. Transmission electron microscopy (TEM)showed good structural preservation of the samples. Monovalent ion (K+, Na+) distribution showed features different from those of the divalent cations (Ca2+, Mg2+). In the vegetative cell, the alkaline cations were mainly distributed in the most internal part of the cytoplasm and they were probably associated with starch grains or concentrated in dry vacuoles. Calcium distribution correlated well with the areas in the cytoplasm of the vegetative cell containing a dense network of mitochondria and endoplasmic reticulum. Within the pollen grain, the sperm cell appeared to contain the most calcium. Calcium was also abundant in the sporoderm. These results reveal the potential of SIMS for pollen studies that include germination, the monitoring of air pollutants and the allergens‐ion interactions.
Transient Stimulation of Oxygen Uptake Induced by Sulfhydryl Reagents in Egeria densa and Potamogeton crispus Leaves
Authors: Bellando M. , Sacco S. , Albergoni F. , Rocco P. , Marrè Maria Teresa
Published: February 2014

A vigorous and transient increase of O2 uptake associated with a simultaneous release of CO2 was elicited in Egeria densa and in Potamogeton crispus leaves by treatment with N‐ethylmaleimide (NEM) and by other ‐SH group reagents (iodoacetate, p‐(chloromercuri)benzenesulfonate (p‐CMBS), Ag+, Hg2+, Cu2+). The NEM‐induced respiratory burst was apparent even in the absence of photosynthesis (darkness, or presence of DCMU) as well as in the presence of the respiration inhibitors cyanide and propyl gallate or SHAM, separate or in combination. In contrast, a complete suppression of the respiratory burst was induced by diphenylene iodonium and by quinacrine, inhibitors of the plasma membrane NADPH oxidase activated in the pathogen‐elicited oxidative burst in granulocytes and in plants. The respiratory burst induced by NEM and by the uncoupler CCCP were additive. The intensity of the respiratory burst was markedly decreased by increasing the pH of the medium from 5 to 8, and partially decreased by the presence of K+ in the medium. Azide inhibited the burst (as well as basal respiration) at pH 6.5 but not at pH 5. The stimulation of QO2 by SH reagents was associated with an early, pronounced membrane depolarization together with a rapid increase of the release into the medium of K+ and other electrolytes, and with a rapid decrease of the intracellular ATP, ADP and G6 P contents. The possible relationships between this SH reagent‐induced respiratory burst and the associated effects on Em and electrolyte leakage are discussed.
Mechanism of Protein Targeting to the Chlorarachniophyte Plastids and the Evolution of Complex Plastids with Four Membranes — A Hypothesis
Authors: Bodyl A.
Published: February 2014

Chlorarachniophyta are phototrophic amoeboflagellates, with plastids surrounded by four membranes. Contrary to other plastids of this type which occur in chromists, their outermost membrane bears no ribosomes. It is argued that the nuclear‐encoded chlorarachniophyte plastid proteins are first transported into the ER, then to the Colgi apparatus, and finally to the plastids. The same import mechanism could be originally present in the chromist ancestor, prior to the fusion of their plastids with the RER membranes. According to the most recent concept, the complex plastids of Chromista and Chlorarachniophyta have evolved through replacement of the cyanobacterial plastids. The assumption that these plastids had an envelope composed not of two, but of three membranes makes it possible to avoid the erlier discerned difficulties with conversion of a eukaryotic alga into a complex plastid. My scenario provides an additional support to the hypothesis on polyphy‐letic origin of four‐membraned plastids.
Biochemical Characterization of Plasma Membrane Vesicles of Cyanophora paradoxa*
Authors: Heimann Kirsten , Becker B. , Harnisch Helga , Mukherjee K. D. , Melkonian M.
Published: February 2014

Plasma membrane vesicles (PMVs) were isolated from Cyanophora paradoxa Korshikov (Claucocystophyta) and purified by differential and sucrose density gradient centrifugation. PMVs were identified ultrastructurally and biochemically using marker enzymes. Analysis of monosaccharides revealed a sugar content of 37.3% of dry weight of delipidated PMVs with high amounts of fucose (28 mol% of total carbohydrate), galactose (23%), mannose (21%) and the minor constituents xylose, rhamnose, glucose and N‐acetylglucosamine. Proteins were analyzed by SDS‐PACE. More than 20 polypeptides were resolved and several were identified as glycopeptides, as shown by PAS staining and lectin blots. Fucose linked α‐1→6 to N‐acetylglucosamine (AAA‐binding), mannose linked α‐1→2,3,6 to mannose (CNA‐binding) and terminally bound galactose (RCA‐binding) were identified on several polypeptides. Sterols (β‐sitosterol and an additional unknown sterol, 40% of total lipids) and diacylglycerol (43%) are the major lipid components in the PMVs of C. paradoxa. Minor components are PE, PC, PC and an unknown glycolipid. Fatty acid analysis revealed 12 different fatty acids, predominantly 16:0,18:0 and the polyunsaturated acids 20:4 and 20:5 (together 69% of total fatty acids), α‐Linolenic acid, common in higher plant PMs, could only be detected as a minor constituent (< 1 %) of PMVs of C. paradoxa.
The G4 Gene of Arabidopsis thaliana Encodes a Chlorophyll Synthase of Etiolated Plants
Authors: Oster U. , Rüdiger W.
Published: February 2014

The gene coding for a putative chlorophyll synthase gene (C4) from Arabidopsis thaliana was amplified by the polymerase chain reaction and cloned into the expression vector pQE‐ 31. Lysates of bacteria (E.coli) that had been transformed with this construct were used for in vitro enzymatic assays. The chlorophyll synthase catalyzed esterification of chlorophyllides a and b at the same rate but preferred geranylgeranyl‐PP over phytyl‐PP. This corresponds to the enzyme specificity previously described for etiolated plants and differed from that of green plants.
In Situ Localization of Phenylpropanoid Biosynthetic mRNAs and Proteins in Parsley (Petroselinum crispum)
Authors: Reinold Susanne , Hahlbrock K.
Published: February 2014

Using in situ RNA/RNA hybridization, enzyme immunolocalization, and histochemical techniques, several phenylpropanoid biosynthetic activities and products were localized in tissue sections from various aerial parts of parsley (Petroselinum crispum) plants at different developmental stages. The enzymes and corresponding mRNAs analyzed included two representatives of general phenylpropanoid metabolism: phenylalanine ammonia‐lyase (PAL) and 4‐coumarate: CoA ligase (4CL), and one representative each from two distinct branch pathways: chalcone synthase (CHS; flavonoids) and S‐adenosyl‐L‐methionine: bergaptol O‐methyltransferase (BMT; furanocoumarins). In almost all cases, the relative timing of accumulation differed greatly for mRNA and protein and indicated short expression periods and short half‐lives for all mRNAs as compared to the proteins. PAL and 4CL occurred almost ubiquitously in cell type‐specific patterns, and their mRNAs and proteins were always coordinately expressed, whereas the cell type‐specific localization of flavonoid and furanocoumarin biosynthetic activities was to a large extent mutually exclusive. However, the distribution patterns of CHS and BMT, when superimposed, closely matched those of PAL and 4CL in nearly all tissues analysed, suggesting that the flavonoid and furanocoumarin pathways together consituted a large majority of the total phenylpropanoid biosynthetic activity. Differential sites of synthesis and accumulation indicating intercellular translocation were observed both for flavonoids and for furanocoumarins in oil ducts and the surrounding tissue. The widespread occurrence of both classes of compounds, as well as selected, pathway‐specific mRNAs and enzymes, in many cell types of all parsley organs including various flower parts suggests additional functions beyond the previously established roles of flavonoids in UV protection and furanocoumarins in pathogen defence.
Variations of the Surface Sculpture and Cell Wall Ultrastructure of the Zygospores in Chlamydomonas geitleri (Chlorophyta)
Authors: Sulek J.
Published: February 2014

The superficial cell wall ornamentation in the zygospores of the alga Chlamydomonas geitleri Ettl (Chlorophyta) is formed by thickenings of the cell wall which are shaped into a network of anastomosing ribs, sometimes with local wart‐like protuberances. Clearly different sculpture patterns (given by presence, arrangement and/or morphological modification of sculpture elements) were accompanied by many transient forms. Sculpture variations occurred even in clonal cultures. In the zygospore cell wall of C. geitleri, the inner, outer and middle layer can be distinguished from the morphological point of view. The relatively thin outer (sporopollenin) layer covers the whole surface of the zygospore wall. The thicker inner layer adhering to the zygospore protoplast forms, either solely or together with the middle layer (possessing a fine meshwork substructure), variously shaped thickening of the zygospore cell wall. Discussed are the ultrastructural morphology of the cell wall in Chlamydomonas zygospores, the striking similarity of the cell wall ultrastructure of zygospores in C. geitleri to the ultrastructure of the cell wall of vegetative cells in some green algae (subfamily Scotiellocystoideae), as well as the extensive morphological variability of the zygospore wall sculpture in C geitleri and its species specificity.
Stem Anatomy of Uebelmannia (Cactaceae) — with Special Reference to Uebelmannia gummifera
Authors: Nyffeler R.
Published: February 2014

The three species of Uebelmannia (Cactaceae: Cactoideae; endemic to Minas Cerais, Brazil) are noteworthy for their tough, bumpy stem surface and the presence of conspicuous mucilage cavities restricted to the outer part of the stems. The anatomy of the mature structures and their ontogeny was investigated from microtome sections. The uncommon surface relief is caused by groups of unequally elongated hypodermis cells. The mucilage cavities consist of solitary and considerably enlarged mucilage cells (U.buiningii and U. pectinifera). In U.gummifera groups of mucilage cells disintegrate and form large cavities which are finally united into longitudinal ducts. A comparison of these stem features with species of the superficially similar genera Islaya and Wigginsia (representing tribe Notocacteae), does not indicate a close phylogenetic relationship between Uebelmannia and members of tribe Notocacteae. Finally, some short comments touch on the adaptational aspect of the characteristic stem features of Uebelmannia.
Pollination and Breeding System of two Co‐Occurring Hirtella Species (Chrysobalanaceae) in Central Brazil
Authors: Arista M. , Oliveira P. E. , Gibbs P. E. , Talavera S.
Published: February 2014

The phenology, major floral characteristics, breeding systems and fruiting success of two co‐occurring species of Hirtella: H. glandulosa and H.gracilipes (Chrysobalanaceae) were studied in Central Brazil. The two species occur as trees in mesophyllous forests but H. glandulosa is frequent also in dense savanna areas. Both species flower at the end of the dry season (September) and have flowers with one‐day longevity. In both species flowers produce nectar and are pollinated exclusively by butterflies. The number of visits recorded and pollination rate in each species were significantly different and indicate that pollinators prefer H. glandulosa flowers. Natural and controlled fruit sets were low in both species. The index of self‐incompatibility (ISI) was 0.17 in H. glandulosa and 0.86 in H. gracilipes. Although ISI in H. glandulosa could denote an incompatibility system, the presence of fruits with aborted embryos at different degrees of development point to an inbreeding depression situation. Low pollen viability and fruit set in H. gracilipes suggested reproductive problems which may be linked to hybridization events.
Hydrodynamics and Biomechanics of the Submerged Water Moss Fontinalis antipyretica ‐ a Comparison of Specimens from Habitats with Different Flow Velocities
Authors: Biehle C. , Speck T. , Spatz H.‐Ch.
Published: February 2014

Flow velocity has an influence on the hydrodynamic and biomechanical properties, as well as on the morphology and the anatomy of the submerged water moss Fontinalis antipyretica Hedw. Cross‐sections of the plant stems show two main types of tissues. The strengthening tissue in the outer part is characterized by thick‐walled cells with a small lumen, the parenchyma in the centre by thin‐walled cells with a large lumen. The specimens from habitats of different flow velocities differ in the proportions of the strengthening tissue and the branching angle of the leaves.

A flow tank with a special sensitive two‐component balance inserted into the bottom of the flume was used to measure the hydrodynamic drag, which acts on the plant stems at different flow velocities. The drag forces increase with the length of the plant.

Mechanical properties such as elasticity and ultimate strength of the plant stems were tested in tension. Relating the data to the relative proportions of the strengthening tissue results in different estimates of Young's moduli for the strengthening tissue of plants from the different sites. The critical strains to which the stems can be extended are remarkably high. Loading and unloading cycles reveal viscoelastic behaviour of the stem tissues. In the first cycle plastic deformation is also observed, but only to a lesser degree in subsequent cycles.
Influence of the Parasite Pilostyles ingae (Rafflesiaceae) on some Physiological Parameters of the Host Plant, Mimosa naguirei (Mimosaceae)*
Authors: Fernandes G. W. , De Mattos E. A. , Franco A. C. , Lüttge U. , Ziegler H.
Published: February 2014

plants found at this site were densely covered by flowers of the parasite on their stems indicating heavy development of cellular The holoparasite/host interaction of Pilostyles ingae (Karst.) Hook. f. (Rafflesiaceae) and Mimosa naguirei Barneby (Mimosaceae) was studied in the open campo rupestre vegetation of Serra do Cipó (State of Minas Gerais, Brazil). Infected M. naguirei threads of the parasite in the bark of the hosts. Cellular threads of the parasite are likely to be richer in lipids and hence depleted in 13C. This may explain the significantly more negative carbon isotope ratios (δ13C values) of the bark of infected host plants observed as compared to other tissues of infected and non‐infected host plants. Photosynthetic parameters such as potential quantum yield of photosystem II (Fv/Fm), apparent photosynthetic electron transport rates (ETR) and effective quantum yield of photosystem II (A F/F'm) in light dependence curves, as well as δ13C values of leaves as a relative measure of average intercellular CO2 partial pressure during photosynthesis over the lifetime of the leaves, which is also related to average stomatal conductance via water use efficiency, were remarkably similar. This suggests a well balanced relation between the Mimosa host and the Pilostyles parasite, in contrast to other hemiparasitic angiosperm parasite/host interactions where the parasite (e.g. Striga) is known to have strong detrimental effects on host photosynthesis.
Mitochondrial DNA Variation Follows a Geographic Pattern in Japanese Beech Species
Authors: Koike T. , Kato S. , Shimamoto Y. , Kitamura K. , Kawano S. , Ueda K. , Mikami T.
Published: February 2014

The amount and distribution of mitochondrial (mt) DNA restriction fragment length polymorphism was determined among individual tree samples of two Japanese beech species, Fagus crenata and F.japonica. Individual plants were collected from 16 F. crenata populations throughout the range of the species, and from three F. japonica populations. We detected enough variation to characterize eleven and three chondriome types in F. crenata and F.japonica, respectively. The grouping of beech chondriome types based upon the cladistic analysis of mtDNA polymorphism allowed us to recognize the apparent geographical patterns of mtDIMA diversity: the resulting three main groups occupied distinct geographic areas. This geographic differentiation is likely to reflect the history of the Japanese beech forests after the last glacial period of the Pleistocene. In addition, the mtDNA polymorphism encountered within F. crenata encompassed all the variation observed in F.japonica. Our result suggests the need for re‐evaluation of their phylogenetic relationships.
Moss (Physcomitrella patens) Expressed Sequence Tags Include Several Sequences which are Novel for Plants*
Authors: Reski R. , Reynolds Susan , Wehe M. , Kleber‐Janke Tamara , Kruse S.
Published: February 2014

The moss Physcomitrella patens (Hedw.) B.S.G. is the first land plant in which gene disruption by homologous recombination Is directly accessible. In order to obtain cloned sequences which may be used in such an approach, complementary DNAs (cDNAs) have been isolated by subtractlve hybridisation of representative cDNA libraries from cytoklnin‐treated tissue. Sequencing of these clones from both ends yielded over 35 kb of non‐redundant sequence Information, of which 20 kb results from clones which appear to be novel to plants. Database comparisons have revealed that 39 of the expressed sequence tags (ESTs) generated show significant homology to identified sequences. Analysis of these ESTs shows a high degree of conservation between Physcomitrella and seed plant sequences, and codon usage is found to be very similar to that In dicotyledonous species. Furthermore, 43 sequences showing no significant homology to sequences in the databases represent previously unidentified expressed genes.
Phenology, Seed Development, and Reproductive Success of an Alpine Population of Centianella germanica in Climatically Varying Years
Authors: Wagner J. , Mitterhofer E.
Published: February 2014

During the growing seasons of 1994–1996, the reproductive fitness of an autumn flowering population of G. germanica was assessed at 1980 m in the Austrian Alps. The warmest year of the last two centuries in Austria was 1994, 1995 was a normal year, and the summer of 1996 was exceptionally cold. The Investigations were carried out on large, early‐flowering individuals (L‐plants) and on small, mainly late‐flowering individuals (S‐plants). In both size classes, the sequence of phenophases varied in response to the contrasting climatic conditions of these years. In 1994, peak flowering In L‐plants occurred about one month earlier than in S‐plants; in 1995 and 1996, the periods of full bloom overlapped partially and fully for the two size classes, respectively. Detailed analyses of seed development and thermal time revealed that low temperatures during histogenesis led to remarkable delays in the Initiation of seed and fruit development, whereas seed filling and seed maturation were largely Independent of temperature. Self‐pollination resulted in high seed sets. Irrespective of weather conditions and dates of flowering. In both size classes, the seed: ovule ratio of mature fruits was about 0.9 and 0.75, in apical and basal positions of the stalks, respectively. The fruit: flower ratios, however, depended on temperature; the ratio was around 0.8 in 1994 and below 0.5 in 1996. In the cool year 1996, fruit development was so slow that in many individuals only the fruits in the apical positions of the stalks matured before the onset of winter conditions.
Pyrophosphate as an Energy Donor in the Cytosol of Plant Cells: an Enigmatic Alternative to ATP
Authors: Stitt M.
Published: February 2014

Pyrophosphate serves as an alternative energy donor to ATP for sucrose mobilisation via sucrose synthase, for glycolysis via pyrophosphate: fructose‐6‐phosphate phosphotransferase, and for tonoplast energisation via the tonoplast proton‐pumping pyrophosphatase. This review considers the possible roles of these pyrophosphate‐driven reactions. Correlative evidence based on expression patterns, the distribution of proteins and activities in various tissues, and comparisons of the in vitro properties of the enzymes with thein vivometabolite levels indicates an important role in young growing tissues and in stress conditions including anaerobiosis, but interpretation is complicated by the reversibility of the pyrophosphate‐driven reactions and by their duplication by ATP‐dependent reactions. The review then considers the evidence emerging from experiments using reversed genetics to alter expression of sucrose synthase, the pyrophosphate: fructose‐6‐phosphate phosphotransferase, and the tonoplast proton‐pumping pyrophosphatase. This approach has revealed that sucrose synthase plays an essential role in sucrose breakdown in potato tubers, and that pyrophosphate: fructose‐6‐phosphate phosphotransferase catalyses a near‐equilibrium reaction with a net flux in the direction of glycolysis. However, it does not support a special role of the latter enzymes in stress responses. Interpretation is complicated by compensation, which can include expression of other members of a gene family, use of alternative pathways, and relaxation of the feed back regulation in response to decreased expression of the enzyme. In an alternative approach, ectopic overexpression of soluble pyrophosphatase fromE. colihas been used as a tool to decrease the levels of pyrophosphate in the cytosol. Constitutive overexpression leads to dramatic changes in sucrose and starch synthesis, sink‐source relations and plant growth, phloem‐specific overexpression of soluble pyrophosphatase leads to an inhibition of phloem transport, leaf mesophyll‐specific overexpression leads to a small stimulation of sucrose synthesis, and potato tuber‐specific overexpression leads to an inhibition of starch accumulation.
Use of Genetically Improved Nitrogen‐Fixing Cyanobacteria in Rice Paddy Fields: Prospects as a Source Material for Engineering Herbicide Sensitivity and Resistance in Plants
Authors: Vaishampayan A. , Sinha R. P. , Häder D.‐P.
Published: February 2014

Cyanobacteria are the largest and most widely distributed group of photosynthetic prokaryotes on Earth, forming a prominent component of microbial populations in wetland soils, especially in rice paddy fields, and significantly contributing to fertility as a natural biofertilizer. Modern agricultural fields are generally treated with high doses of synthetic nitrogenous fertilizers and pesticides having adverse effects on the soil microflora of naturally occurring N2‐fixing cyanobacteria. This review deals with some of the advances made during the last few decades in the areas of developing ammonia derepressible pesticide‐resistant cyanobacterial mutants for algalization of the wet agricultural fields as a viable and efficient N‐photobiofertilizer.
Carbon Isotope Discrimination in Cyanobacteria of Rocks of Inselbergs and Soils of Savannas in the Neotropics*
Authors: Ziegler H. , Lüttge U.
Published: February 2014

An extensive set of data on carbon isotope ratios in samples of terrestrial cyanobacteria from the surface of rocks of inselbergs and soils of savannas in the neotropics is presented. A comparison of the data shows two surprising features. First, all values deviate from the 13C discrimination of carboxylation by ribulose‐bis‐phosphate carboxylase/oxygenase (RuBISCO) which is generally about −27‰. They are less negative than that by between 0.62‰ and 10.46‰. Second, the values show a considerable variation, minima and maxima being −26.38‰ and −16.54‰, respectively. This variation cannot be explained by differences in dominant taxa in the samples. It must be related to microsite characteristics, most probably the extent in time of coverage by liquid water, where diffusion of CO2 constitutes a limiting step with a lower discrimination against 13C than that of carboxylation via RuBISCO.
Intra‐tissue Characteristics of Chloroplasts in the Lamina and Petiole of Mature Winter Leaf of Arum italicum Miller
Authors: Pancaldi Simonetta , Bonora A. , Gualandri Rita , Gerdol R. , Manservigi R. , Fasulo Maria Palmira
Published: February 2014

Abstract: Laminae and petioles from mature winter leaves of Arum italicum were studied in order to obtain information on the sun—shade intra‐tissue properties of chloroplasts. This inference was based on the: (1) micro‐ and submicroscopic characteristics of the chloroplasts, (2) cytochemical localizations of functional PS I and PS II, (3) pigment patterns and compositions, (4) immunolocalization of Rubisco, and (5) net photosynthesis. It was inferred that all the chloroplasts across the lamina had adaptations to intermediate shade conditions, without a sun‐shade dimorphism between the palisade and the spongy tissues. In the petiole, where normally‐structured chloroplasts were surprisingly present in the entire thickness of the organ, a structural and chemical dimorphism was found between the outer chlorenchyma and the inner aerenchyma where intermediate shade‐type and extreme shade‐type chloroplasts were present, respectively. However, some anomalies in the pigment composition were noted chiefly in the inner aerenchyma (low concentrations of β‐carotene and lutein, absence of zeaxanthin, presence of unusual pigments, for instance lutein epoxide, lutein cis‐isomer, and chlorophyllide a). The Rubisco immunolabelling in the outer chlorenchyma of the petiole was similar to that in the lamina, while it was very scant in the inner aerenchyma. Net photosynthesis in the petiole was about 75% of that recorded in the lamina. These data suggest that the petiole of the mature winter leaf of A. italicum closely co‐operates with the lamina for enhancing light capture and utilization.
Is Predetermined Cellular Competence Required for Alternative Embryo or Shoot Induction on Sunflower Zygotic Embryos?
Authors: Jeannin Geneviève , Charrière F. , Bronner R. , Hahne G.
Published: February 2014

Abstract: Somatic embryos and adventitious shoots can be induced simultaneously on immature zygotic embryos of sunflower, their relative distribution on the explant being constant but their relative number depending on the sucrose concentration of the culture medium. We show here that the cells at the origin of both types of structures are competent for either development and express this potential as a function of their position relative to the medium. Two zones, inductive for somatic embryos or adventitious shoots, have been established under the influence of the culture medium. The precision of their localisation is demonstrated by the existence of tissue chimeras which also indicate the presence of diffusible signal(s) responsible for the determination of cellular identity. We have further determined that commitment to the organogenic pathway occurred very rapidly, i.e. within 12 h after the onset of the culture. A synthetic model is presented in which we suggest a possible sequence of key events involved in the morphogenic processes.
Weak Mechanical Stimulation Causes Hyperpolarisation in Root Cells of Lepidium
Authors: Monshausen Gabriele B. , Sievers A.
Published: February 2014

Abstract: In order to study the effect of mechanical stimulation on the membrane potential (Em) of roots of Lepidium sativum L., the roots were subjected to pulses of perfusion medium expelled from a micropipette positioned 1 mm from the root surface at the level of the elongation zone. On the opposite side of the root, a microelectrode was inserted into rhizodermal or cortical cells of the elongation zone to record the membrane potential during such a pulse. A medium pulse elicited a fast transient hyperpolarisation of up to −38 mV, reaching a peak approx. 1 min after the start of a pulse. Both degassing the medium and increasing the buffer strength had no effect on the magnitude of the pulse‐induced hyperpolarisation. Covering the roots with Parafilm, and thereby preventing an exchange of medium in the vicinity of the root during a pulse, while still providing a mechanical stimulus, also did not abolish the response. We conclude that Lepidium roots are capable of perceiving extremely weak mechanical stimuli (less than 1 mN) which induce rapid transient hyperpolarisations of the plasma membrane.
Structure of Crystal Cells and Influences of Leaf Development on Crystal Cell Development and Vice Versa in Phaseolus vulgaris (Leguminosae)
Authors: Kuo‐Huang Ling‐Long , Zindler‐Frank Elisabeth
Published: February 2014

The structure of cells with calcium oxalate crystals and their nelghbouring cells has been studied by light and transmission electron microscopy at different stages of bean leaf development. Plants were grown with varying calcium supply to identify a possible influence of calcium nutrition on cell structure. Crystals are formed inside the vacuole of already highly vacuolated cells of bundle sheath extensions. The membrane around the crystal vacuole is continuous with the plasmalemma. The crystal vacuole contains membraneous structures. In the fully expanded leaf the crystal becomes ensheathed by wall material. Chloroplasts of bundle sheath extension cells, with or without crystals, are smaller, with fewer membranes, and with much narrower stroma regions than those of the palisade parenchyma. There is a stage in the young leaf when only the bundle sheath extension cells without crystals have starch grains in their chloroplasts. As their number is lower in plants grown with high calcium supply this means that, in this case, less cells are competent for photosynthesis.