bluuebunny/crossref_metadata_2025 huggingface dataset:
Sub‐Cellular Element Analysis of a Cyanobacterium (Nostoc sp.) in Symbiosis with Gunnera manicata by ESI and EELS
Authors: Jäger Karin M. , Johansson Christina , Kunz Ulrike , Lehmann H.
Published: February 2014

Element analysis using electron spectroscopic imaging (ESI) and electron energy loss spectroscopy (EELS) was performed in a symbiotic Nostoc sp. strain found in the upper stem tissue of Gunnera manicata, and in Nostoc PCC 9229, a free‐living heterocyst‐forming cyanobacterium able to enter into symbiosis with the angiosperm Gunnera in reconstitution experiments. ESI and EELS unequivocally identified the four elements nitrogen (N), sulphur (S), phosphorus (P) and oxygen (O) in different inclusion bodies of these biological specimens. High amounts of nitrogen were solely detected in huge cyanophycin granules in vegetative cells of the symbiotic Nostoc strain, whereas large polyphosphate bodies, containing high amounts of phosphorus, sulphur and oxygen, could be seen in the free‐living Nostoc PCC 9229. The latter were usually not present or, when found, very small in vegetative cells of the cyanobiont.
Modifications of Cortical Cell Walls in Roots of Seedless Vascular Plants
Authors: Damus M. , Peterson R. L. , Enstone Daryl E. , Peterson Carol A.
Published: February 2014

Forty‐three species of seedless vascular plants were assessed for modifications to root cortical cell walls. All species except Lycopodium had an endodermis with distinct Casparian bands. Experiments with the apoplastic tracer berberine hemisulfate showed that walls of all root cortical cells in the two Lycopodium species tested were permeable to this tracer. Although most species examined lacked a hypodermis several Equisetum species had a hypodermis with modified walls. Three Selaginella species had distinct Casparian bands in this cortical cell layer. This layer, therefore, is an exodermis in Selaginella and its presence limited the inward diffusion of the apoplastic tracer berberine hemisulfate.
Immunochemical Studies on the Clp‐protease in Chloroplasts: Evidence for the Formation of a CIpC/P Complex*
Authors: Desimone M. , Weiß‐Wichert C. , Wagner E. , Altenfeld Ursula , Johanningmeier U.
Published: February 2014

Chloroplasts contain a proteolytic system whose activity is ATP‐dependent. The presence of genes encoding homologues of the ATP‐dependent E. coli CIpA/P protease on the plastome and nuclear genome suggests that a similar protease is located in chloroplasts. Antibodies raised against a recombinant chloroplast‐encoded proteolytic ClpP subunit detect this polypeptide in chloroplasts prepared from barley leaves or the eukaryotic algae Chlamydomonas reinhardtii and Euglena gracilis. Co‐immunoprecipitation experiments using the anti‐ClpP antibody and an antibody against the nuclear encoded regulatory CIpC component (a ClpA homologue) provide direct evidence for the existence of a CIpC/P complex in the chloroplast stroma. These results suggest that at least a part of the ATP‐dependent proteolytic reactions in the chloroplast is catalyzed by an enzyme complex similar to the E. coli CIpA/P protease.
Seasonal Pattern of Isoprene Synthase Activity in Quercus robur Leaves and its Significance for Modeling Isoprene Emission Rates
Authors: Schnitzler J.‐P. , Lehning Andrea , Steinbrecher R.
Published: February 2014

Biogenic emission of hydrocarbons plays an important role in the interactions between plants, especially trees, and the atmosphere. Among these volatile organic compounds isoprene (2‐methyl‐1,3‐butadiene) is the predominant component emitted by many photosynthesizing leaves. Its rapid atmospheric breakdown substantially affects the oxidation potential of the atmosphere. An enzyme, isoprene synthase, extracted from leaves of European oak (Quercus robur L.) was previously found to catalyse the Mg 2+–dependent elimination of diphosphate from dimethylallyldiphosphate to form isoprene. The present paper describes the seasonal variation of this enzyme acitivity in Quercus robur (L.) leaves in 1995. The enzymatic data obtained were used to create an additional term for the isoprene emission algorithm (ISOC93). The addition of this correction term for the seasonality of isoprene synthase to the emission model improved considerably the simulation of seasonal isoprene emission rates in oaks, avoiding over‐ and underestimations in the current modeling approach.
Sexual and Asexual Reproduction in Natural Stands of Populus nigra
Authors: Legionnet Agnès , Faivre‐Rampant Patricia , Villar M. , Lefèvre F.
Published: February 2014

The balance between sexual and asexual propagation in the establishment of natural stands of Populus nigra was assessed from the genotypes of trees sampled in different natural stands. One site was completely sampled and genotyping proceeded using STS and RAPD markers. Among 118 trees, only four were vegetative copies of other trees of the site. Isozymes were used in four stands, and a method to detect the presence of vegetative copies in a sample is proposed for these markers. No vegetative copies were found in two cases, and a low number of copies was detected in the other two. Observations are reported for seedlings as well as for different modes of vegetative propagation in natural stands. We conclude that sexual and asexual propagation play complementary roles in the dynamics of this species, and that in most cases the adults originate from seedlings.
Importance of Cycling and Recycling of Mineral Nutrients within Plants for Growth and Development
Authors: Marschnert H. , Kirkby E. A. , Engels C.
Published: February 2014

Cycling of mineral nutrients, i.e. retranslocation in the phloem from the shoot to the roots, and recycling, i.e. translocation of cycled nutrients back in the xylem to the shoot can contribute substantially to the fluxes of phloem‐mobile nutrients between roots and shoot. Cycling and recycling of nutrients serves several well defined functions. These include supplying the root with nutrients assimilated in the shoot (nitrate and sulphate reduction), maintenance of cation‐anion balance, providing additional driving force for solute flow in the xylem and phloem, and acting as a shoot signal to convey nutrient demand to the roots. Cycling of mineral nutrients like K is also required to cover the demand for growth of apical root zones and to smooth out fluctuations that occur spatially and with time in the external nutient supply of soil‐grown plants. Cycling and recycling of mineral nutrients is also closely related to the process of phloem loading and export of photosynthates from source leaves. This is particularly true for potassium, magnesium and phosphorus. Nutrient deficiency‐induced shifts in dry matter partitioning between shoot and roots are therefore closely related to the solute flow in the phloem not only of photosynthates but also mineral nutrients from source leaves to roots. More research is needed, however, to elucidate in greater detail the contribution of cycling and recycling of mineral nutrients in the integration of growth processes at the whole plant level.
Phototropic Stimulation can Shift the Gradient of Crown Root Emergence in Maize
Authors: Nick P.
Published: February 2014

The crown roots in the coleoptilar node of maize emerge asymmetrically: emergence at the dorsal flank of the node (opposite to the caryopsis) precedes emergence at the ventral flank (facing the caryopsis). This asymmetry can be altered by phototropic stimulation: emergence of crown roots is delayed in the lighted flank and promoted in the shaded flank causing an inversion of the endogenous asymmetry. The curvature induced by the phototropic stimulation is transient, the effect on crown root emergence, in contrast, persists. This stable effect is not a consequence of curvature per se and becomes irreversibly fixed between one and two hours after stimulation. The emergence of crown roots depends on directional signalling from the coleoptile to the node. The data are discussed in terms of a stable blue light induced transverse polarity of the coleoptile that can imprint a stable asymmetry upon the coleoptilar node guiding the emergence of crown roots.
Root Anatomy and Mycotrophy of the Achlorophyllous Voyria tenella Hook. (Gentianaceae)
Authors: Imhof S.
Published: February 2014

The central cylinder of the root of Voynet tenella consists of up to ten central, non‐lignified, tracheidal xylem elements surrounded by some parenchymatic tissue and 5–7 groups of phloem. A pericycle could not be discerned. Even though the endodermis carries a faint suberin lamella it cannot be discerned anatomically without special staining. The cells of the 1–3 cortex layers next to the endodermis are elongated longitudinally, the subsequent cortex parenchyma is multi‐layered and consists of isodiametric cells. The cells of the 2–3 layered outer dermal tissue are smaller than those of the adjacent cortex, their walls carry a suberin lamella and the outermost of them constantly scale off. The dermal tissue is interpreted as a multilayered exodermis. The fungal colonization in roots of Voyria tenella remarkably differs from any known mycorrhizal pattern. After having penetrated the dermal tissue, the always intracellularly‐growing hyphae head straight towards the inner cortex layers, where they spread along the central cylinder. Ramifications from these inner‐spreading hyphae then colonize the cortex parenchyma from the inside and they develop dense hyphal coils. Eventually, the coiled hyphae swell and collapse, resulting in amorphous clumps of fungal material. This mycorrhizal pattern is referred to as an intraradical fungus garden. Arguments are given to call the mycorrhiza in Voyria tenella a specialized arbuscular mycorrhiza. Phylogenetic and ecological implications of the observations and the results are discussed.
Photosynthetic Capacity Increases with Plant Size
Authors: Zotz G.
Published: February 2014

The photosynthetic capacity of mature leaves of the epiphytic orchid, Dimerandra emarginata, was studied in plants of different size. There was a linear increase of both area‐based and dry weight‐based rates of O2‐evolution with size by more than 100% from the smallest (1 cm tall) to the largest (50 cm tall) individual. Similar size‐related changes were observed in the leaf nitrogen content but not in the chlorophyll content. The results are discussed in the context of the optimal partitioning theory.
Distribution of Phenylalanine Ammonia Lyase and Chalcone Synthase within Trunks of Robinia pseudoacacia L.
Authors: Magel Elisabeth , Hübner Barbara
Published: February 2014

During heartwood formation, a kind of apoptosis in the inner parts of woody axes, phenolic substances are accumulated by in situ biosynthesis. In Robinia pseudoacacia L, these compounds are mainly flavonoids. In the present work, we performed a study to show if there is a correlation between measurable activities and detectable protein levels of phenylalanine ammonia lyase (PAL; EC 4.3.1.5) and chalcone synthase (CHS; EC 2.3.1.74), key enzymes of general phenylpropanoid metabolism and flavonoid biosynthesis, respectively. After separation of total protein extracts by one‐dimensional micro‐gel electrophoresis, newly emerging polypeptides were detectable within the sapwood‐heartwood transition zone, pointing toward a transient activation of metabolism shortly before cell death occurs. Most prominent was a polypeptide around 46 kDa. By immunoblotting, this band was identified as a CHS subunit. Thus, the exclusive presence of both enzyme protein and extractable enzyme activity of CHS in the heartwood bordering tissue was shown. In contrast, levels of PAL protein were similar in all xylem tissues which contain living cells. PAL activity, however, was measurable only in the differentiating xylem and the sapwood‐heartwood transition zone. From these results we conclude that during heartwood formation, CHS and PAL differ in their mode of regulation. It seems likely that CHS activity is regulated at the level of enzyme protein while PAL regulation is most probably post‐translational.
Eye Attached Hemipollinaria in the Hawkmoth and Settling Moth Pollination of Habenaria (Orchidaceae): A Study on Functional Morphology in 5 Species from Subtropical South America
Authors: Singer R. , Cocucci A. A.
Published: February 2014

Morphological adaptations to sphingophily and pollination by moths was studied in 5 South American Habenaria species. For H. gourlieana and H. hieronymi direct evidence of hawkmoth (Agrius cingulatus and Manduca sexta) and settling moth (Rachiplusia nu) pollination, respectively, by hemipollinaria attachment on the eyes, is presented. In two other species (H. paucofilia, H. rupicola) pollination by settling moths and eye attachment of the hemipollinaria can be inferred by indirect evidence (placement of scales and massulae on the flowers) and by flower structure. For the fifth species (H. montevidensis) pollination by small moths or mosquitoes with hemipollinaria attachment on the proboscis is postulated. A comparative study in floral features revealed clear morphological divergence between sphingophilous and phalaenophilous species. In addition to deeper spurs the former have slender, exerted, and upturned petal lobes (acting as mechanical guide to the hovering visitors), a much developed median rostellar lobe (acting as deflecting surface of the hawkmoths towards the viscidia), flexible and sinuous hemipollinarium caudicles (appropriate for frontal strikes against the stigma when hemipollinaria are brought by the hawkmoths dangling against the flower). Male efficiency was compared between 4 species with overlapping flowering time in the same area. Male efficiency factors were unexpectedly low in all species. Only in one species (H. hieronymi) each pollen donation accounted for more than one pollination. H. gourlieana is part of a more or less rich sphingophilous flora interacting with the same two long‐tongued hawkmoth species. Interspecific competition for pollen placement on the pollinator's body surface is probably low on account of different pollination mechanisms.
Pollination of Pteroglossaspis ruwenzoriensis (Rendle) Rolfe (Orchidaceae) by Beetles in Argentina
Authors: Singer R. B. , Cocucci A. A.
Published: February 2014

Beetle pollination by Euphoria lurida (Scarabaeidae: Cetoninae) is documented for Pteroglossaspis ruwenzoriensis (Orchidaceae: Epidendroideae: Cymbideae: Eulophiinae) in its natural habitat in Central Argentina (South America). Flower features with special emphasis on those related to beetle pollination are given. These include: long rigid and well exposed inflorescences, sturdy inconspicuous and deep flowers with small entrance, emission of a yeast‐like fragrance, jelly‐like nectar, short column, and a head‐attaching pollinarium with a broad saddle‐like viscidium. Pollinator behaviour and pattern of flower opening favour cross pollination and probably long distance pollen dispersal. Flowering, which lasts about 3 weeks, peaks in summer past mid‐January. In natural conditions about 68 flowers are pollinated for every 100 pollinaria removals.
Ammonium and Methylammonium Transport in Egeria densa Leaves in Conditions of Different H+ Pump Activity
Authors: Venegoni A. , Moroni A. , Gazzarrini S. , Marrè Maria Teresa
Published: February 2014

Previous data in Egeria densa leaves demonstrated a strong inhibitory effect of Cs+ on passive K+ influx and on K+‐induced, ATP‐dependent electrogenic proton extrusion. In this paper we analyzed, using the same material, the effects of Cs+ on ammonium (NH4+) and methylammonium (CH3NH3+) transport in order to elucidate whether a common transport system for K+ and NH4+ could be demonstrated. The effects of Cs+ on NH4+‐ and CH3NH3+‐induced titratable H+ extrusion (–ΔH+) and on transmembrane electrical potential difference (Em) in E. densa leaves were analyzed in parallel. All experiments were run either in the absence or presence of fusicoccin, corresponding to low or high H+‐ATPase activity and membrane hyperpolarization and leading, in this material, to respectively active or passive transport of K+. The results suggest the presence in E. densa leaves of two distinct pathways for NH4+ uptake: one in common with NH4+ and (with lower affinity) CH3NH3+, insensitive to Cs+, and a second system, operating at higher H+‐ATPase activity and Em hyperpolarization, strongly inhibited by Cs+ and impermeable to CH3NH3+. In agreement with this hypothesis, Xenopus laevis oocytes injected with the KAT1 RNA of Arabidopsis thaliana were permeable to K+ and NH4+, but not to CH3NH3+.
Cyanobacteria and Cyanobacterial Lichens from Inselbergs of the Ivory Coast, Africa
Authors: Büdel B. , Becker U. , Porembski S. , Barthlott W.
Published: February 2014

This study focuses on the saxicolous lichens and cyanobacteria of the open, exposed rock surface of inselbergs. Twenty‐three species of cyanobacteria and 17 cyanobacterial lichen species (“cyanolichens”) from several inselbergs and other rocky outcrops of three major climatic regions, savanna, transition zone and rain forest, are reported from the Ivory Coast. Inselbergs are isolated and frequently mountains consisting of Precambrian granites or gneisses that abruptly rise from the surrounding plains. Cyanobacteria were found to be the dominating organisms on all rock surfaces. The lichens found mainly belong to the family Peltulaceae and a few were present from the family Lichinaceae. Nine species of the cyanolichens and most of the cyanobacteria are new for the Ivory Coast. A gradient in total species number (cyanolichens and cyanobacteria) occurs from the savanna to the rain forest, with a decrease in species number towards the rain forest. Saxicolous cyanobacterial lichens reached a higher species number in the savanna type ecosystem (11) than on inselbergs in the rain forest (7). The cyanolichens and cyanobacteria found are characteristic for larger, light‐exposed rock surfaces and species like P. congregate, P. lingulata, P. tortuosa and P. umbilicata preferentially occur on the granite or sandstone of inselbergs.
UV Effects on Pigments and Assimilation of 15N‐Ammonium and 15N‐Nitrate by Natural Marine Phytoplankton of the North Sea
Authors: Döhler G. , Hagmeier E.
Published: February 2014

Effects of ambient solar UV radiation in the field and of artifical UV irradiation under controlled laboratory conditions were studied with natural phytoplankton populations from Helgoland, German Bight, North Sea. The pattern of pigments varied after UV‐A or UV‐B plus a low dose of UV‐A radiation: UV‐A usually induced a stimulation of pigment biosynthesis; whereas UV‐B plus UV‐A led to a reduction of the contents of chlorophyll a, diadinoxanthin, fucoxanthin, peridinin and an unknown carotenoid; content of diatoxanthin was significantly enhanced. The damaging effect on nitrogen assimilation by UV was more pronounced after artificial UV‐B plus UV‐A irradiance compared to the influence of ambient solar UV under field conditions. The uptake of inorganic nitrogen was dependent on the dose and exposure time of UV radiation as well as on the species composition. The uptake of 15N‐nitrate by natural phytoplankton collected in spring was more sensitive to UV irradiation than the assimilation of 15N‐ammonium. UV‐A radiation with a small part of shorter wavelengths at 315 nm (Philips‐lamps in conjunction with the cut‐off filter WG 320) caused a reduction of up to 12% whereas a stimulation of the 15NH4+ uptake was observed after exposure to UV‐A without any UV‐B (Philips lamps TL 60W/09N). Pattern of 15N‐incorporation into free amino acids and pool sizes varied in dependence on the applied nitrogen compound and on the irradiation conditions. The impact of UV radiation on the pattern of 15N‐Iabelled free amino acids and the pool sizes was different. 15N enrichment into all the tested amino acids was reduced after 5 h UV‐B plus UV‐A exposure and after application of 15NH4+. A depression of the glutamate and glutamine pools was observed after addition of 15N‐nitrate alone. Pools of all main amino acids from phytoplankton in summer 1993/94 were inhibited by UV irradiance. Results are discussed with reference to the UV target (e.g. enzymes, pigments) and the adaptation to the environmental conditions.
Development, Genetics and Molecular Biology of Mosses
Authors: Reski R.
Published: February 2014

The first descriptions of sex chromosomes in plants, of the continuity of chromosomes during the mitotic cycle and of non‐Mendelian inheritance as well as the introduction of UV‐mutagenesis to genetic research are landmarks in biological sciences first achieved by scientists working on bryophytes. Haploidy of the tissue facilitates mutant isolation and many developmental moss mutants have been isolated. Early moss development is triggered by auxin, by cytokinin and by light, mainly acting via phytochrome and a blue‐light receptor. Due to the simplicity of the plants, development can be pinpointed to the differentiation of a single cell and be analysed in living tissue, making mosses ideal candidates for the analysis of development in an integrated approach of cell and molecular biology. Molecular genetic techniques have been applied mainly to Physcomitrella patens (Hedw.) B.S.G., where efficient protocols for transformation of nuclear DNA have been established and several nuclear, chloroplast and mitochondrial genes have been analysed. These studies reveal that Physcomitrella may be an appropriate model to study plant development in molecular terms. Recently, it has been shown that, in this species, nuclear genes can be targeted very efficiently by homologous recombination, now opening the door to reverse genetics for plant biologists.
Responses of Photosynthesis, Carbohydrates and Antioxidants in Needles of Norway Spruce to Slow and Rapid Changes in Ozone
Authors: Wieser G. , Havranek W. M. , Loidoldt‐Nagele M. , KronfuG G. , Polle A.
Published: February 2014

The goal of the present study was to examine the effects of slow and rapid changes of ozone (O3) concentrations on the physiological behaviour of current‐year needles of Norway spruce (Picea abies(L.) Karst.). For this purpose five‐year‐old spruce seedlings were exposed in growth chambers for 49 days to either charcoal‐filtered air, slowly increasing O3concentrations from zero up to 100 nl I−1in weekly steps of 25 nl I−1, or immediately to 100 nl I−1of O3. During the investigation period gas exchange, carbohydrate and antioxidant contents of the current flush were measured. In needles which experienced slowly increasing O3concentrations, cumulative O3uptake was approximately 30 % lower than in needles continuously fumigated with 100 nl I−1of O3. The higher 03uptake in the permanent 100 nl I−1O3treatment caused a pronounced decline in net photosynthesis, in the efficiency of CO2uptake and in the starch content of the seedlings. Initially the ascorbate pool increased, but after 5 weeks of exposure ascorbate concentrations declined and were comparable to values obtained in charcoal‐filtered controls, while the thiol contents were enhanced during fumigation with permanent 100 nl I‐−1O3. On the contrary, slowly increasing O3caused a significant increase in total needle ascorbate throughout the fumigation period, which probably prevented an O3‐induced decline in the photosynthetic machinery as photosynthesis was not affected although the thiol contents were not enhanced. Furthermore, starch content was slightly higher than in O3‐free controls. These results suggest that seedlings of Norway spruce have the possibility to acclimate to O3stress, as slowly increasing O3concentrations seemed to increase resistance and the seedlings were able to compensate.
Responses of Glutathione and Glutathione S‐Transferase to Cadmium and Mercury Exposure in Pedunculate Oak (Quercus robur) Leaf Discs
Authors: Gullner G. , Uotila M. , Kömives T.
Published: February 2014

Changes in chlorophyll, non‐protein thiol and glutathione (GSH) levels, and the activity of glutathione S‐transferase (GST) were investigated in cadmium(ll) and mercury(ll) cchloride treated leaf discs of mature pedunculate oak trees (Quercus robur). Both heavy metals caused decreases in chlorophyll content, but mercury was more toxic than cadmium. Cadmium treatments (30–250μiM) resulted in increasing non‐protein thiol levels after 3d, but GSH contents decreased. Mercury (1–20μM) led to a concentration‐dependent decline in both non‐protein thiol and GSH levels. GST activities were not modified significantly by cadmium, but mercury treatments caused a dose‐ and time‐dependent enzyme induction. Both the phytotoxic‐ and GST‐inducing effect of mercury could be prevented by the cysteine precursor L‐2‐oxo‐4‐thiazolidinecarboxylic acid.
Notes on the Evolution of Androecial Organisation in the Magnoliophytina (Angiosperms)
Authors: Decraene L. P. Ronse , Smets E. F.
Published: February 2014

This paper aims to summarize briefly and to update our ideas about androecial architecture formulated in earlier publications. Ontogenetic evidence of stamen development, viz. the initiation, arrangement and relationship of stamens to other floral morphomes, can be translated into a semophyletic scheme reflecting the phylogeny of the androecium. The ancestral androecium is discussed in the light of recent theoriesabout angiosperm phylogeny. Two divergent androecial processes are proposed for the angiosperms starting from a spiral androecium with a moderate number of stamens. However, transitions exist between spiral polyandry, numerous stamens in whorls, and chaotic polyandry. From an androecium with several alternating whorls of paired and single stamens, outer stamen pairs are retained following the successive loss of inner stamen whorls. Single stamens instead of pairs occur at the very end of this line and represent a more advanced condition. This line is mostly present in tri‐ and dimerous flowers. From the same starting point diplostemony (with two alternating whorls of single stamens) originated, again giving rise to various states usually present in pentamerous or tetramerous flowers.
Water Storage in the Lichen Family Umbilicariaceae
Authors: Valladares F. , Sancho L. G. , Ascaso Carmen
Published: February 2014

Quantitative relationships between thallus structure and water storage and retention capacities In 12 species of the lichen family Umbilicariaceae were explored using three recent techniques for plant structure analysis: stereology (3D quantification of microscopic Images), mercury Intrusion porosimetry (determination of pore size distribution of tissues) and low‐temperature scanning electron microscopy (LTSEM). Water storage capacity of the thallus was related neither to thallus density nor surface area of the thallus; It was directly related to the total porosity of the thallus and inversely related to the proportion of thallus volume occupied by cell walls and gelatinous substances. Water retention capacity increased with increasing thallus density and was decreased by slight increases in the surface area of the upper side of the thallus. Water storage and retention capacities exhibited a positive correlation only when the storage capacity was expressed on a surface area basis. LTSEM study of fully hydrated specimens revealed that many intercellular spaces of the upper cortex and upper parts of the algal layer contained liquid water. Intercellular spaces of the lower part of the algal layer and medulla were in general either airfilled or partially occupied by gelatinous substances. Species with rhizinomorphs and substrate‐hygrophytic (water uptake from surface run‐offs) stored more water and retained it longer than aerohygrophytic species (water uptake from the atmosphere) lacking rhizinomorphs. Thallus structure of aerohygrophytic species seems to facilitate rapid gas exchange with the environment, improving water uptake and carbon gain when atmospheric moisture is available but accelerating dehydration when the atmosphere becomes dry.
SNFL3: A Protein Kinase Homologue of Sorghum bicolor with a High Similarity to the Yeast SNF1 Protein Kinase
Authors: Annen Friederike , Stockhaus J.
Published: February 2014

We have identified several protein kinases that are differentially expressed in mesophyll and bundle sheath cells of the C4 plant Sorghum bicolor. Here we describe the characterization of a protein kinase homologue that shows a high amino acid sequence similarity to the SNF1/AMPK family of protein serine/threonine kinases. The mRNA of this gene accumulates to much higher levels in mesophyll cells than in the bundle sheath and can also be detected in root tissue.
Characteristic Trichomes and Indumentum Specialization in African and European Parasitic Scrophulariaceae
Authors: Neumann Ulla , Paré J. , Raynal‐Roques A. , Sallé G. , Weber H. Chr
Published: February 2014

Trichomes and their distribution patterns have been observed in the aerial parts of plants of the genera Striga, Buchnera, Rhamphicarpa, Euphrasia, Melampyrum and Rhinanthus, using both light (LM) and scanning electron microscopy (SEM). All trichomes belong to the multicellular, uniseriate category and can be classified as glandular and nonglandular types. On nearly all organs, the two types can be observed side by side. Apart from a large group of ubiquitous trichomes, some characteristic trichome types are reported; they are restricted either to chlorophyllous organs (foliage leaves, bracts, calyx and stem) or to the corolla. In some nonglandular trichomes mineral deposits have been found. Other morphological and anatomical trichome features are discussed with regard to their possible function.
Effect of Seed Freezing and Storage Conditions on Plasma Membrane Properties of Norway Spruce (Piceo abies Karst.) Seedlings
Authors: Rakowski K. J. , Behzadipour M. , Ratajczak R. , Kluge M.
Published: February 2014

Norway spruce (Picea abies Karst.) seeds were frozen and stored for 15 months at + 3, − 25, − 75 or − 196°C. After storage, seeds were germinated for 9−14 days to determine viability and plasma membrane protein composition, H+‐ATPase activity and fluidity. The results indicate no significant differences in viability of seed 14 days after germination. Biochemical analyses revealed increased plasma membrane fluidity in 9‐day‐old Norway spruce seedlings raised from seeds pretreated at − 75 °C. and changes in the temperature profile of membrane fluidity in seedlings after pre‐treatment of seeds at − 25 °C. On the other hand, the same treatments did not result in changes in plasma membrane protein content, protein composition or ATPase activity. There was also no difference in plasma membrane H+‐ATPase activity assayed in the presence of different ATP hydrolysis inhibitors. Based on the presented results, and other experimental data, we suggest that during early seedling growth, adaptation of seeds to − 25 and − 75°C freezing and/or storage temperature results in stability of the plasma membrane protein function and composition and increased fluidity or changes in the temperature‐dependent fluidity profile of these membranes.
On Hybrid Formation in the Rock Fern Asplenium x alternifolium (Aspleniaceae, Pteridophyta)
Authors: Vogel J. Chr , Russell S. J. , Rumsey F. J. , Barrett J. A. , Gibby Mary
Published: February 2014

Length polymorphism in a non‐coding spacer (trnLUAA‐trnFGAA) in the chloroplast DNA was used in the investigation of the origin of the most common and conspicuous European fern hybrid, Asplenium x alternifolium (Aspleniaceae, Pteridophyta). The origins of A. x alternifolium, the hybrid between A. trichomanes s.l. and A. septentrionale s.l. was studied at three ploidy levels, diploid, triploid and tetraploid. The cpDNA technique allowed us to investigate the mode of hybrid formation between sexual species for the first time over a wide geographic range and with a large sample size. Morphological variation in this hybrid has previously been attributed to different reciprocal parental combinations, and to the influence of chloroplast genes on morphogenesis. Our results demonstrate that one parent, A. septentrionale s.l., acts predominantly as the female parent in these hybrids, with only one population of A. x alternifolium showing reciprocal hybridity. The discovery of predominantly unidirectional hybrid formation in this hybrid may be explained by the different breeding systems of the parental taxa. The role of gametophyte ecology is also assessed.
Evidence for Maternal Transmission of Chloroplast DNA in the Genus Asplenium (Aspleniaceae, Pteridophyta)
Authors: Vogel J. Chr , Russell S. J. , Rumsey F. J. , Barrett J. A. , Gibby Mary
Published: February 2014

Little is known about the mode of transmission of chloroplasts in ferns, despite the importance of such knowledge for molecular phylogenetic and biosystematic studies. Andersson‐Kötto (1930, 1931) inferred from crossing experiments that chloroplasts are inherited biparentally in Asplenium scolopendrium L. Here we present evidence from artificial hybridisation that demonstrates maternal inheritance of chloroplast DNA in the genus Asplenium (Aspleniaceae, Pteridophyta) using length variation in a non‐coding spacer (trnLUAA‐trnFGAA) in the chloroplast DNA.
Transport of Photoassimilates in Young Trees of Fraxinus and Sorbus: Measurement of Translocation in vivo
Authors: Jahnke S. , Schlesinger Ulrike , Feige G. B. , Knust E. J.
Published: February 2014

Abstract: Translocation of photoassimilates was studied on 2‐year‐old trees of Fraxinus excelsior and Sorbus aucuparia using the short‐lived isotope 11C. Leaflets of different leaves on the same plants were radiolabeled showing that both carbon distribution and speeds of transport may vary with leaf position. Within 2 h after pulse feeding with 11CO2, mainly the lower leaves distributed radiolabel to the roots in Fraxinus, whereas in Sorbus, the upper leaves were also involved. By repeated pulse applications to selected leaves, temporal profiles of 11C transport were followed on individual plants from April to October. Early in the season, within 2 h after pulse labelling, 30–40% of the fixed radiolabel was exported from leaves in Fraxinus and about 20% in Sorbus. Thereafter export started to decline, particularly in Fraxinus, and the distribution of radiolabel between stem and roots could alter depending on the position of the feed leaf. Speeds of translocation obtained along the rachis and stem showed high variability, but they did not necessarily slow down before the end of the season. The speeds monitored at the rachis of Fraxinus leaves (30–75 cm h−1) were generally lower than those found on Sorbus (50–130 cm h−1). As reported in the literature, the two tree species translocate different carbohydrates and show remarkable differences in the ultrastructure of their vascular systems. In that context it is interesting that the temporal profiles of 11C radioactivity obtained from F. excelsior and S. aucuparia could clearly be distinguished by their characteristic shapes. The results are discussed in terms of anatomical characteristics of the conducting tissues and possible differences in phloem loading.
Protein Phosphorylation in Polysomes of Pumpkin Cotyledons after Coumarin Treatment
Authors: Miersch J. , Kullertz C. , Henning Heike
Published: February 2014

Abstract: The natural compound, coumarin, caused a change in protein pattern and influenced the phosphorylation status of some ribosome‐associated proteins of pumpkin seedlings in vivo and in vitro. Low concentrations of coumarin stimulated ribosome‐associated protein phosphorylation only in cotyledons but not in roots and stems. Two phosphoproteins whose phosphorylation state was influenced upon coumarin treatment could be isolated and characterized by their relative molecular weight of about 58 and 65 kDa and pl‐values at 5.2 and 5.7, respectively. These phosphoproteins are not major constituents of small or large subunits of ribosomes. We did not find any influence of coumarin on phosphorylation of ribosomal proteins S6, LAO and LAI–3.
Genome Size in Sphagnum (Peat Moss)
Authors: Temsch Eva M. , Greilhuber J. , Krisai R.
Published: February 2014

Abstract: Genome size was determined in thirty Austrian species of Sphagnum, using Feulgen absorbance photometry conducted on a video‐based image analysis system (CIRES), and for comparison on a scanning cytophotometer (Leitz MPV II) with strongly correlated results. Pisum sativum (1C = 4.42pg DNA) was used for internal standardization. Between species, two levels of ploidy, haploid and diploid, could be unambiguously identified (although this identification remains, strictly speaking, hypothetical, as long as exact parallel chromosome counts are not available). Twenty‐six haploid species yielded values from 0.392 pg to 0.506 pg DNA (1C), and four diploid species (including two varieties of S. palustre) from 0.814 pg to 0.952 pg. The average ratio between levels was 1:2.049. Variation between species within sections was lower than between sections. In some cases significant differences between accessions of one species were found. The genome size of Sphagnum palustre presented here strongly deviates from one estimate of this species in the literature.
Biomechanics and Functional Anatomy of Hollow Stemmed Sphenopsids: III. Equisetum hyemale
Authors: Speck T. , Speck O. , Emanns A. , Spatz H.‐Ch.
Published: February 2014

As in Equisetum giganteum, the hollow stem of Equisetum hyemale owes the mechanical stability of the internodes to an outer ring of strengthening tissue (hypodermal sterome) which provides stiffness and strength in the longitudinal direction. In contrast to hollow‐stemmed grasses, the hypodermal sterome consists of living cells. The compound inner tissue of the overwintering aerial stem of Equisetum hyemale includes a continuous inner and outer endodermis layer of vital thick‐walled cells that have slightly lignified Casparian thickenings. The two endodermis layers provide an inner tension and compression bracing which lend resistance to local buckling. The stress‐strain relation in longitudinal tension is biphasic with remarkably high critical strains especially in the upper parts of the stem. Scraping off part of the epidermis with the built‐in silicate does not change this behaviour, except in the initial steep part of the curve where the Young's modulus is reduced by 20%. No contribution of the endodermis and the parenchyma could be detected in tension tests of longitudinally‐oriented strips. Relaxation experiments reveal viscoelastic behaviour. As with the biphasic stress‐strain relation and the critical strains, the viscoelastic properties have largely to be ascribed to the hypodermal sterome.
Isozymes, Speciation and Evolution in the Polyploid Complex Cochlearia L. (Brassicaceae)
Authors: Koch M. , Huthmann Marion , Hurka H.
Published: February 2014

Within the genus Cochlearia L. sect. Cochlearia three isozyme systems (aspartate aminotransferase, leucine aminopeptidase and phosphoglucomutase) have been analysed at the populational level for eleven species with different ploidy levels. Nine loci complexes were resolved with a total of 33 alleles from 89 populations.

In general, polyploids displayed higher numbers of alleles per species and per population. A notable exception is diploid C. pyrenaica with as many alleles as some polyploids. Data support: (1) the origin of tetraploid C. officinalis from C. pyrenaica s.l., particularly from C. aestuaria; (2) the allopolyploid origin of octoploid C. anglica from C. officinalis; (3) the allopolyploid origin of hexaploid inland taxa C. polonica, C. tatrae and C. bavarica via hybridization between C. pyrenaica and C. officinalis; (4) a putative allopolyploid origin of hexaploid coastal species C. danica by hybridization between C. pyrenaica s.l. and C. officinalis accompanied by a shift in chromosome complement. A scenario summarizing our present understanding of the evolution within Cochlearia sect. Cochlearia is presented.
Spore Liberation and Dispersal in Smut Fungi*
Authors: Piepenbring M. , Hagedorn G. , Oberwinkler F.
Published: February 2014

Teliospores are the most important diaspores of smut fungi, albeit not the only ones. The role of basidla, basidiospores, secondary spores, yeast cells, and infected parts of the host for dispersal has often been neglected. Many smut species have soral structures like galls, peridia, and elaters, which cause teliospores to be liberated over prolonged periods. This increases the chance that at least some spores are released under favourable wet climatic conditions and while host plants are susceptible.

In this review, the diversity of dispersal units as well as vectors of smut fungi are presented. The importance of timing of diaspore liberation, flexibility in dispersal strategies, and the genetic and evolutionary implications of dispersal strategies of smut fungi are discussed.

The general considerations are complemented by examples based on original field and laboratory observations: peridia of Farysia corniculata and certain species of Sporisorium expose the spore mass by hygroscopic movement under wet conditions (hygrochasy) favourable for teliospore germination and infection of a host plant. Basidia with firmly attached basidiospores liberated from spore balls of Doassansiopsis deformans, branched basidiospores of Rhamphospora nymphaeae, needle‐shaped basidiospores of species of Entyloma, folded basidiospores of Mycosyrinx cissi, and stellate groups of yeast cells of Trichocintractia utriculicola show enlarged surfaces, which are advantageous for dispersal in water. Galls filled with spore balls of Doassansiopsis limnocharidis and witches' brooms formed by spikelets infected by Cintractia standleyana separate from the host and fall into water where they are dispersed.
Evidence for the Uptake of Large Anions through Stomatal Pores
Authors: Eichert T. , Goldbach H. E. , Burkhardt J.
Published: February 2014

Experiments were conducted with leek (Allium porrum L.) leaves to investigate whether aqueous solutions are able to penetrate stomata. Epidermal strips were used for the determination of transport rates. Stomata were opened by fusicoccin or closed by darkness or abscisic acid. A droplet containing the anionic fluorescent dye, uranine, was placed on the physiologically outer side of the epidermis and allowed to dry. With open stomata 30 times more uranine penetrated through the epidermal strips than with closed stomata (comparison of medians). In another experiment droplets of uranine solution were placed on leaf segments and epidermal strips were removed after drying of the droplets. Penetration of uranine through stomata was detectable under the microscope both with epidermal strips from the transport experiments and with strips obtained after application on leaf segments. As maximum uptake rates occurred during the drying process, it is concluded that penetration took place via water films. These results show that the physical restrictions preventing stomatal penetration of static droplets are not decisive for drying droplets and that stomatal uptake of dissolved ionic substances occurs under natural conditions, i.e. without surfactants or applied pressure.
Modes of Self‐Pollination and Absence of Cryptic Self‐Incompatibility in Drosophyllum lusitanicum (Droseraceae)
Authors: Ortega‐Olivencia A. , Paredes J. A. López , Rodríguez‐Riaño T. , Devesa J. A.
Published: February 2014

We show experimentally that several types of selfing occur simultaneously in Drosophyllum lusitanicum: prior, competitive, insect‐facilitated, delayed and geitonogamous. In addition, we report evidence of cleistogamy in the flower bud. All types of selfing were successful in producing fruits and seeds; however, geitonogamy did not occur uniformly throughout the flowering period in this species. We also report the absence of cryptic self‐incompatibility: the germination rate and pollen tube growth rate of cross pollen were no greater than those of self pollen when both types were placed on stigmas of the same flower (mixed pollination). There was a tendency for self pollen to be more vigorous than cross pollen but it just failed to reach significance.
Climate, Colonisation and Celibacy: Population Structure in Central European Trichomanes speciosum (Pteridophyta)
Authors: Rumsey F. J. , Vogel J. C. , Russell S. J. , Barrett J. A. , Gibby Mary
Published: February 2014

The Killarney fern Trichomanes speciosum Willd. (Hymenophyllaceae) is unique in possessing both extensive sexual (sporophyte and gametophyte generations present) and asexual (gametophyte only) ranges. It was first discovered in central Europe in 1993 and is represented in this area only by its perennial, vegetatively propagating gametophyte generation. Genetic variation has been investigated at 35 sites. Allozyme diversity is partitioned primarily between, not within, sites. Although genetic variation exists at a fine scale (lt 5 m) within some populations, the results suggest that clones were not intimately associated in these cases. The majority of sites support unique multilocus phenotypes. Where phenotypes were present at more than one site they tended to recur at the next closest site. However, similar phenotypes link eastern and western Pfälzerwald sites up to c. 70 km apart. This pattern of diversity suggests that colonisation was not solely of a “stepping stone” or “leading edge” type. We suggest that during a climatically favourable period, probably the Atlantic hypsithermal, there may have been an explosive colonisation by long‐distance dispersal from refugial areas. This was followed by a short period during which sporophyte production, sexual reproduction and local spread were possible. With climatic change, reduction in the available habitat and the loss of the sporophyte generation, different individual genets became fixed within small, favourable, but scattered, sites. The possibility that some central European sites north of the Alps acted as periglacial refugia cannot be discounted, but would appear less likely than (re‐) colonisation from the Atlantic fringe.
The Breeding System of Oxalis squamata, a Tristylous South American Species
Authors: Marco Diana E. , Arroyo Mary T. Kalin
Published: February 2014

Oxalis squamata is a perennial endemic herb of the Chilean‐Argentine Andes previously reported as a distylous species. In this paper, analysis of floral morphology, incompatibility relations and population structure show that O. squamata possesses morphological and functional tristyly. The three floral morphs differ in calyx and corolla length, style and stamen length, pollen grain size and stylar pubescence. Results of hand pollinations showed the presence of a strong incompatibility system. Legitimate pollinations with the L and M morphs as seed parents produced approximately equal numbers of seeds per pollination. The S morph produced less than half the number of seeds per legitimate pollination compared to the other two morphs. Intra‐ and intermorph illegitimate pollinations produce almost no seeds. Morph representation in the population was isoplethic. Fruit and seed production did not differ significantly for the three morphs in the population. Comparison of experimental and natural production of fruits and seeds suggests that seed set in the natural population may be pollen‐limited for the L and M morphs.
SMALL DATA
Authors: Crainer Stuart
Published: February 2014

It really is a numbers business
DOING WELL BY DOING GOOD?
Authors: Coomber Steve
Published: February 2014

A paper by Henri Servaes and Ane Tamayo looks at the real value of CSR
PURCHASING POWER
Authors: Coomber Steve
Published: February 2014

Research by Ahmed Tahoun investigates the reality of political donations
HUAWEI TO THE FUTURE
Authors: De Cremer David , Zhang Jess
Published: February 2014

David De Cremer and Jess Zhang examine the organisational and leadership lessons from the rise of Chinese technology giant Huawei