bluuebunny/crossref_metadata_2025_split huggingface dataset:
Regulation of Glutathione Synthesis in Suspension Cultures of Parsley and Tobacco*
Authors: Schneider St. , Bergmann L. 
Published: February 2014

AbstractExperiments in vitro have shown that γ‐EC synthesis, the first step in GSH formation, is subject to feedback inhibition by physiological GSH concentrations. In order to evaluate the role of this feedback inhibition on γ‐EC synthetase in vivo GSH synthesis was modulated in suspension cultures of P. crispum and N. tabacum by administration of cadmium. The alterations in the thiol contents were measured and in addition the effect of Cd exposure on γ‐EC synthetase (E.C. 6.3.2.2) and GSH synthetase (E.C. 6.3.2.3) was studied. Decreasing cellular GSH concentrations by cadmium induced PC synthesis caused 7–10 fold increase in the rate of glutathione synthesis as measured by the accumulation of (γ‐EC)nG. This increase was not linked to an increase in extractable activities of γ‐EC‐ or GSH synthetase in parsley. In tobacco the activities of γ‐EC‐ and GSH synthetase increased by a factor of 1.6 and 1.8, respectively, after 3 d of Cd exposure. In both species the exposure to Cd resulted in an increased cellular γ‐EC content that reached a plateau within 24 h, and in a doubling of the cysteine content. In vitro experiments showed that GSH synthetase activity is inhibited by cadmium concentrations that have no effect on γ‐EC synthetase activity. This may explain the accumulation of γ‐EC in Cd exposed cells. Incubation with 0.25 mM cysteine did not effect the γ‐EC‐ and GSH content in tobacco cells. In parsley the cellular GSH content increased threefold and the y‐EC content twofold and stayed constant thereafter at the elevated levels. Taken together the results show that GSH synthesis in vivo is controlled by feedback inhibition as well as by the supply with cysteine. In the latter case the feedback inhibition may act as a kind of safety valve and prevent the accumulation of unphysiological GSH concentrations if the supply of cysteine is too large.
Symplasmic Sieve Element Continuity between Orobanche and its Host*
Authors: Dörr Inge , Kollmann R. 
Published: February 2014

AbstractElectron microscopical investigations of primary haustoria of Orobanche crenata parasitizing the roots of the highly compatible host, Vicia narbonensis, reveal an uninterrupted phloem system connecting both partners. Individual sieve elements belonging to the host and parasite could be identified by the cell markers: plastids, mitochondria and P‐protein, which in the present system turned out to have species‐specific fine structure.Sieve pores of normal structure interconnect the sieve elements of host and parasite. They originate from interspecific plasmodesmata.
Concanamycin 4‐B: A Potent Inhibitor of Vacuolar pH Regulation in Chara Cells
Authors: Tazawa M. , Okazaki Y. , Moriyama Y. , Iwasaki N. 
Published: February 2014

AbstractConcanamycin 4‐B, a macrolide antibiotic with an 18‐membered lactone ring, is known as a specific inhibitor of the vacuolar type of H+‐ATPase, as is bafilomycin A1. The drug was tested for its effect on regulation of the vacuolar pH (pHv) of internodal cells of a fresh water characean alga, Chara corallina, under normal conditions and under salt stress. The pHv was measured either on isolated vacuolar sap with a conventional pH electrode or directly by inserting a pH‐sensitive glass microelectrode into the vacuole. Proton‐pumping into tonoplast vesicles was almost completely inhibited by concanamycin 4‐B at 1 nM.Concanamycin 4‐B at 1 μM significantly increased pHv while bafilomycin A1 was ineffective when applied at 1 μM. Concanamycin 4‐B did not affect pHv when applied at 0.1 μM and increasing the concentration to 10 μM did not amplify the degree of alkalization.Concanamycin 4‐B also inhibited pHv regulation under NaCl stress. When Chara cells were treated with 100 mM NaCl, pHv promptly increased and then recovered to the original level. The reacidification was completely inhibited by concanamycin 4‐B (1 μM), suggesting that the reacidification was achieved by the H+‐ATPase of the tonoplast.
Characterization of the Carotenoidless Strain of Scenedesmus obliquus, Mutant C‐6E, a Living Photosystem I Model*
Authors: Römer Susanne , Senger H. , Bishop N. I. 
Published: February 2014

AbstractWhen grown heterotrophically in the dark on enriched culture medium, the pigment‐deficient strain of Scenedesmus obliquus, mutant C‐6E, is uniquely characterized by a complete deficiency in carotenoids and chlorophyll b while retaining a low level of chlorophyll a which is exclusively utilized in photosystem I‐type reactions. The strain lacks photosystem II activity but exhibits all PS‐I reactions tested, including P700 redox reactions, photoreduction of CO2 with hydrogen as electron donor, and O2 uptake following methyl viologen reduction. The mutant contains 10 times more P700 per chlorophyll than the wild type and develops the pigment‐protein complex of PS‐I, CP‐I. The action spectrum for methyl viologen reduction compares favorable to the low temperature absorption spectrum of whole cells. Both the chlorophyll fluorescence excitation and emission spectra of pigment‐protein complexes derived from cells of C‐6E show patterns typical of PS‐I. The strain lacks the LHCs and CP‐II as well as their respective apoproteins. The absence of carotenoids appears to prevent the development of the normal variety of pigment‐protein complexes and the accumulation of Chl b. This inability is also expressed by the presence of only single stranded thylakoid membranes in the chloroplast of C‐6E. When heterotrophically grown cells of this mutant are exposed to white light of 8 or 22 W m−2, 50% of its chlorophyll is lost by photooxidation within 4 or 1.5 hours, respectively.
Spectroscopic and Biochemical Analyses of UV Effects on Phycobiliproteins of Anabaena sp. and Nostoc carmium
Authors: Sinha R. P. , Lebert M. , Kumar A. , Kumar H. D. , Häder D.‐P. 
Published: February 2014

AbstractThe effects of UV (280–400 nm) irradiation on phycobiliprotein composition have been studied in two N2‐fixing cyanobacteria, Anabaena sp. and Nostoc carmium, isolated from rice paddy fields in India. Phycobiliproteins were isolated and separated by sucrose density gradient centrifugation. After UV exposure the top fraction mainly contained carotenoids (absorption maximum at 485 nm), which first showed an increase in intensity and absorption and then a gradual decrease with increasing UV exposure in Anabaena sp., whereas, in Nostoc carmium this fraction showed a steady increase over the whole exposure time. The bottom fraction of both organisms mainly contained phycocyanin (absorption peak at 620 nm) which showed a steady decline in intensity, as well as absorption. Fluorescence excitation at 620 nm resulted in an emission at 650 nm which underwent a shift towards shorter wave‐lengths with increasing UV‐exposure time, indicating a disassembly of the phycobilisomal complex and of impaired energy transfer from accessory pigments to the reaction centers. SDS PAGE analysis of the fractions revealed a loss of high molecular mass linker proteins and low molecular mass (αβ monomers indicating that the phycobiliproteins, which function as accessory pigments for the operation of photosystem II, disassemble during UV irradiation.
Hydrodynamic Modelling Study of Angiosperm Leaf Venation Types
Authors: Roth A. , Mosbrugger V. , Belz G. , Neugebauer H. J. 
Published: February 2014

AbstractThe morphology of leaf venation has been studied repeatedly and various systems have been proposed for the classification of the observed leaf venation patterns. Almost nothing is known, however, about the functional properties of the various venation types. Using a computer modelling approach we analysed the water transport properties of typical craspedodromous and brochidodromous venation patterns. The water transport through the leaf and the veins was modelled as a fluid flow through a porous medium and the mathematical model was solved with the Finite Element Method. The simulations illustrate that the leaf margin represents a critical region in terms of water supply. The results provide a plausible functional explanation for three well known phenomena: 1) the correlation between craspedodromous venation and the formation of leaf teeth; 2) the fact that craspedodromous venation is more common in temperate than in tropical regions and 3) the fact that xeromorphic leaves tend to have more closed venation.
Molecular Phylogeny of the Papilionoideae (Family Leguminosae): RbcL Gene Sequences versus Chemical Taxonomy
Authors: Käss E. , Wink M. 
Published: February 2014

AbstractTotal DNA was extracted from 67 species (30 genera) of the subfamily Papilionoideae (family Leguminosae). The rbcL gene was amplified by polymerase chain reaction (PCR) and sequenced directly. RbcL sequences were evaluated with character‐state (maximum parsimony; PAUP) and distance methods (neighbour‐joining; MEGA). Morphology‐based classifications of tribes and subtribes are mostly congruent with rbcL phylogeny. Differences occur for members of the genus Sophora and for intratribal relationships within the Genista/Cytisus complex: Sophora appears in two clades; one clade with S. japonica at the base of the Papilionoideae and a second more advanced group (with S. davidii, S. jaubertii, and S.flavescens) which represents a sister clade of the Thermopsideae. The Cytisus complex includes the genera Cytisus, Chamaecytisus, Calicotome and Spartocytisus but not Cytisophyllum which appears as a distinct member of the Genista complex. Chamaespartium sagittale is very close to Genista supporting the view that it does not represent an independent genus but should be treated as Genista sagittalis. Close to Genista are Teline and Spartium, whereas Argyrolobium, Retama, Cytisophyllum, Ulex, Petteria, Adenocarpus, Chamaespartium tridentatum and Laburnum can be considered as “outliers” of the Genista‐group sensu stricto. RbcL phylogeny is compared with profiles of alkaloids and other natural products. First results indicate that secondary metabolite profiles, if compared with morphology or rbcL sequences, are of limited value as a taxonomic marker.
Fruit and Seed Structures in Menodora (Oleaceae): a Comparison with Jasminum
Authors: Rohwer J. G. 
Published: February 2014

AbstractThe fruit development in Menodora agrees largely with that in Jasminum, except for the final stages. The seed coat resembles that of Jasminum in the presence of ribbon‐shaped wall thickenings in the mesotestal layers, a character not known from any other Oleaceae. In several characters there is more similarity between Menodora and Jasminum sect. Alternifolia, or between Menodora and J. nudiflorum, than there is among the species of Jasminum. This supports the idea that Jasminum might be paraphyletic, if Menodora is retained as a separate genus.
On the Validity of Plasmodesmograms*
Authors: van Bel A. J. E. , Oparka K. J. 
Published: February 2014

AbstractBecause the operation of plasmodesmata is of paramount importance for the integrative action of tissues and organs, it is important to quantify the symplastic continuity. An attempt to visualize the intercellular communication pathways in plant tissues is the plasmodesmogram, a two‐dimensional diagram of plasmodesmatal frequencies. Plasmodesmograms assume that the greater the frequency of plasmodesmata, the greater is the potential for symplasmic communication. In fact, however, the validity of plasmodesmograms hinges on the premise that plasmodesmata are uniform in structure and functioning. In view of recent findings that plasmodesmata are gatable channels with different functional diameters, a correlation between plasmodesmatal frequency and the rate of intercellular communication ‐ including transport ‐ is disputable and the concept of the plasmodesmogram needs to be re‐examined. Its validity appears to vary with the developmental stage and the nature of the plant tissue. Our over‐all conclusion is that plasmodesmograms are an acceptable device for coarse (qualitative) assessment of intercellular transport pathways in mature phloem tissues. Pathways identified by plasmodesmograms often correlate with the physiologically determined modes of photosynthate transport. Whether this applies to differentiated tissues, in general, remains to be elucidated. The value of plasmodesmograms for developmental phyisology seems to be limited, as developmental processes coincide with temporary or permanent closure of plasmodesmata.
Distribution and Function of Proteoid Roots and other Root Clusters
Authors: Dinkelaker Barbara , Hengeler Christine , Marschner H. 
Published: February 2014

AbstractProteoid roots are bottlebrush‐like clusters of rootlets which form along lateral roots. They are characteristic of most species of the Proteaceae, which are mainly distributed in Australia and South Africa. Homologous root clusters are present in species of the Casuarinaceae, Mimosaceae, Fabaceae, Myricaceae and Moraceae. Many similarities exist between these species in relation to morphology and function of root clusters. Many are non‐mycorrhizal and are highly efficient in phosphorus (P) acquisition. In these species, proteoid roots and proteoid‐like root clusters are abundant when grown on infertile soils. Their formation is predominantly affected by the P status of the plants, being induced at low P levels and repressed at high P levels. Proteoid roots and proteoid‐like root clusters play an important role in acquisition of P and other mineral nutrients. Although increase in root surface area may be a contributing factor, in many species these roots excrete large amounts of organic acids and phenolics. The excretion of these compounds in a small soil volume gives rise to extensive nutrient mobilization by acidification, reduction and chelation of sparingly soluble forms of P and micronutrients such as Fe and Mn.
Life History, Reproductive Morphology and Development of the Antarctic Brown Alga Desmarestia menziesii J. Agardh*
Authors: Wiencke C. , Clayton M. N. , Schulz D. 
Published: February 2014

AbstractThe life history, reproduction and development of Desmarestia menziesii J. Agardh from Antarctica is described. Unilocular sporangia occur singly or in small groups in the outermost cortical layer of the sporophyte. They are formed by periclinal division of cortex cells into a stalk cell and the sporangium initial. Meiospores germinate into dioecious microscopic filamentous gametophytes. As in other perennial Antarctic species of the Desmarestiales, gametangia are formed in culture under short‐day conditions or in darkness. In nature, juvenile sporophytes should therefore be formed in winter. They develop only attached to the oogonium. At first they are uniseriate and elongate by means of an intercalary meristem located in their middle part. Laterals are formed predominantly in this region, and they subsequently give rise to secondary laterals. The branching pattern is opposite to alternate in both young and adult plants. Cortication of the main axis is initiated by filaments growing out from the lowermost cells of the primary laterals. In sporophytes of this developmental stage the meristem of the main axis is confined to a small region where cortication starts and above. Lateral branches elongate and become corticated in the same way as the main axis. In mature plants, cells of the inner cortex can become meristematic again and form a meristoderm which contributes to axis thickness by periclinal and anticlinal divisions. The observations are discussed in relation to possible evolutionary relationships in the genus Desmarestia and in the order Desmarestiales.
Epilithic and Cryptoendolithic Cyanobacteria of Clarens Sandstone Cliffs in the Golden Gate Highlands National Park, South Africa
Authors: Wessels D. C. J. , Büdel B. 
Published: February 2014

AbstractA cryptoendolithic cyanobacterial community is described from Clarens sandstone in a montane ecosystem of the north‐eastern Orange Free State, South Africa. The community is dominated by a species of the unicellular cyanobacterial genus Chroococcidiopsis. Chlorophylla content of the colonised sandstone ranged between 44.3 and 51.8mg m−2. The establishment and species composition of an artificially created tintenstrich cyanobacterial community is documented. The possible contribution of cryptoendolithic cyanobacterial communities in the biological formation of hollows and caves in Clarens sandstone cliffs is discussed.
Adverse Effects of Epiphytic Crustose Lichens upon Stem Photosynthesis and Chlorophyll of Populus tremula L.
Authors: Solhaug K. A. , Gauslaa Y. , Haugen J. 
Published: February 2014

AbstractDry cork layer (phellem) in stems of Populus tremula transmitted 35–55 percent of incident irradiation, depending upon moisture content. A cover of crustose Lecanora lichens reduced transmission through phellem to 10 percent or less of incident irradiation. The bark contains photosynthetically active cells. Apparent quantum yield for photosynthetic O2‐evolution was 0.017 in bark covered with dry Lecanora compared with 0.070 in naked bark. The capacity for gross photosynthesis in high light (1090 μmol photons m−2 s−1) was reduced by 50 percent in Lecanora‐covered bark. Lecanora did not reduce the ratio between variable and maximal chlorophyll a fluorescence (Fv/Fm). Chlorophyll content per unit area was similar in leaves and naked bark of Populus tremula. The chlorophyll content in the bark decreased with increasing chlorophyll content in Lecanora. Chlorophyll a/b ratio was 2.5 in the bark compared with 4.0 in leaves and in Lecanora, and the ratio decreased down the stems. The a/b ratio was 2.3 in Lecanora covered bark compared with 2.6 in naked bark. The changes in bark photosynthesis below a Lecanora crust were probably due to acclimation of bark photosynthesis to shade, since the lichen acids in the measured lichens neither suppressed photosynthetic O2‐evolution nor changed the Fv/Fm in bark disks.
Differential Effects of Abscisic Acid on Phosphoenolpyruvate Carboxylase and CAM Operation in Kalanchoë blossfeldiana
Authors: Taybi T. , Sotta B. , Gehrig H. , Güçlü S. , Kluge M. , Brulfert J. 
Published: February 2014

AbstractPhotoperiodism or water stress can shift young leaves of Kalanchoë blossfeldiana from C3‐type photosynthesis to Crassulacean acid metabolism (CAM). CAM induction implies synthesis of phosphoenolpyruvate carboxylase (EC 4.1.1.31, PEPC). Present results show that, in plants as well as in isolated leaves, an increase in endogenous levels of abscisic acid (ABA) preceded PEPC increase, independently of the nature of the CAM inductive parameter.Exogenously applied ABA was taken up and accumulated by isolated leaves to a level similar to the internal ABA concentration in the leaf tissues. Both in entire plants and in isolated leaves, exogenous ABA mimicked the effects of water stress or short days in triggering PEPC capacity. Using a heterologous cDNA probe (derived from Sorghum leaf PEPC gene) it could be shown that an early step of the leaf response to drought or ABA treatment consisted in an increase in the amount of PEPC transcripts. Depending on the duration of ABA application, C3 photosynthesis, typical CAM or CAM‐idling could be triggered in isolated leaves. In each case, similar increases in PEPC capacity (maximum extractable activity) were obtained, suggesting that the type of photosynthesis performed by the leaves is not controlled by the level of the PEPC capacity. The results suggest that the photosynthetic behaviour of the leaves is primarily governed by the progressive drop in availability of external carbon caused by the ABA‐controlled closure of the stomata. Effects of ABA on PEPC synthesis proceed independently of CAM performance.
Mobilization of Starch after Submergence of Air‐Grown Rice Coleoptiles. Implications for Growth and Gravitropism
Authors: Kutschera U. , Hoss R. 
Published: February 2014

AbstractSubmergence of air‐grown rice seedlings (Oryza sativa L. var. Sasanishiki) induces elongation of the coleoptile. We investigated whether rapid underwater extension is associated with a loss of starch. After 1 d of submergence the starch content was reduced by 70%. This loss of reserve carbohydrate was accompanied by a 38% increase in the concentration of glucose in the cell sap of the coleoptiles. The submerged (starch‐depleted) coleoptiles had a slower negative gravitropism than the air‐grown controls, although the rate of elongation in the horizontal position was not impaired. We conclude that the submergence‐induced mobilization of starch provides substrates and osmotica for the rapidly growing cells. In addition, our results indicate that a full complement of starch is necessary for normal gravitropism in the rice coleoptile.
Further Studies of the Phloem Loading Process in Leaves of Barley and Spinach. The Comparison of Metabolite Concentrations in the Apoplastic Compartment with those in the Cytosolic Compartment and in the Sieve Tubes1
Authors: Lohaus Gertrud , Winter Heike , Riens Burgi , Heldt H. W. 
Published: February 2014

AbstractThe concentrations of sucrose, amino acids, nitrate and malate in the apoplastic compartment of illuminated leaves of barley and spinach were determined and compared with the corresponding concentrations in the cytosolic compartment of mesophyll cells and in the phloem sap, as measured previously with plants grown under identical conditions. The concentrations of sucrose and amino acids in the apoplast are found to be much lower than in the cytosol and in the phloem sap, indicating that not only the uptake into the phloem of sucrose, but also of amino acids, requires transport against a concentration gradient. The gradient of sucrose and amino acids between the cytosol and the apoplast was maintained when phloem transport had been blocked by cold girdling. Apparently, the efflux of sucrose and amino acids from the source cells to the apoplast is regulated in such a way that it meets the requirements of phloem transport. The percentages of the single amino acids as part of the total amino acids are quite similar in the cytosol, apoplast and phloem sap. The ratio of sucrose to the total amino acids in the cytosol is similar to that in the apoplast but about five times higher in the phloem sap. It appears from these results that the preferential extraction of sucrose over amino acids from the source cells to the phloem is due to the uptake from the apoplast into the phloem.
Different Patterns of Intercellular Transport of Lucifer Yellow in Young and Mature Antheridia of Chara vulgaris L.
Authors: Maszewski J. , van Bel A. J. E. 
Published: February 2014

Abstract:Intra‐ and intercellular movement of the fluorochrome Lucifer Yellow (LY), microinjected into the shield cells of male sex organs, was examined at different stages of spermatogenesis in Chara vulgaris L. Two distinct stage‐associated types of probe movement were noted: (I) a fast and uniform spreading of fluorescence within the shield cell injected, followed by centripetal transport of LY into the adjoining manubrium and the capitular cells, and subsequent redistribution into the other manubria and shield cells in young antheridia (up to the stage of 4‐cellular filaments), and (II) limited spreading of fluorescence, restricted to the triangle‐shaped area of the impaled shield cell in more mature antheridia with multicellular filaments. These results confirm earlier electron microscopic observations on plasmodesmatal connections indicating an intensive solute movement between all cell types in young antheridia of Chara. Developmental changes appearing at later stages, during differentiation of sperm cells, strongly reduce the capacity for intercellular symplasmic transport.