bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effects of Calcium Ions and of Calcium Channel Blockers on Galvanotaxis of Chlamydomonas reinhardtii
Authors: Dolle R. , Nultsch W. 
Published: February 2014

AbstractThe effects of calcium ions and of the calcium channel blockers verapamil, diltiazem and nifedipine on galvanotaxis in Chlamydomonas have been investigated using a fully automated and computerized population system. Galvanotaxis is a function of the voltage applied to the cell population. However, the galvanotactic orientation also depends on the external calcium concentration. In a calcium‐deprived nutrient medium which still contains 6 × 10−7M calcium, galvanotactic orientation is about 20% of orientation at optimal calcium concentration of 10−4 M at 9 V. The higher the external calcium concentration is, the lower is the voltage necessary for optimal galvanotactic orientation. The calcium channel blockers diltiazem and nifedipine likewise inhibit galvanotaxis of Chlamydomonas very specifically without impairing motility. Verapamil is effective, but also inhibits motility by causing detachment or shortening of the flagella. Nevertheless, inhibition of galvanotaxis by verapamil is not the only result of decreased motility, because the galvanotactic orientation is impaired to a greater extent than motility. The effectiveness of the three blockers tested in inhibiting galvanotaxis depends on the concentration and on the voltage applied. At 10−5 M, verapamil causes maximal inhibition of galvanotaxis at 9 V. At increasing concentrations up to 10−4 M, diltiazem inhibits galvanotaxis more strongly than the other blockers. If the voltage is varied at a constant blocker concentration of 2 × 10−5 M, nifedipine causes maximal inhibition at 3 V–6 V, diltiazem at 9 V and verapamil above 12 V.
Measurement of Light‐Dependent Changes of the Stromal pH in Wheat Leaf Protoplasts
Authors: Heineke D. , Heldt H. W. 
Published: February 2014

AbstractThe stromal pH of chloroplasts contained in wheat leaf protoplasts was determined by incubating the protoplast suspension with radioactively labelled DMO, followed by rapid subcellular fractionation and measurement of the radioactivity in the separated chloroplast fraction. The stromal pH was found to be about 8.0 upon illumination and 7.6 in darkness. These results demonstrate that light‐dependent stromal pH changes, which have been found earlier in isolated chloroplasts, also occur in a plant cell.
Evidence for Ideal and Non‐Ideal Equilibrium Freezing of Leaf Water in Frosthardy Ivy (Hedera helix) and Winter Barley (Hordeum vulgare)
Authors: Hansen J. , Beck E. 
Published: February 2014

AbstractTemperature dependences of leaf water potentials (ψleaf) of frozen leaves of frosthardy ivy and winter barley were determined psychrometrically and found to coincide with the respective water potentials of ice which were obtained using the same technique. The water potentials of ice showed good agreement with theoretically established data. Analysis of the components of ψ of frozen leaves of Hedera helix revealed ideal equilibrium freezing, i.e. the governing of the relative content of liquid (or frozen) water solely by the osmotic potential. In winter barley, by contrast, a negative pressure potential was demonstrated to contribute to ψleaf. even under conditions of moderate frost. This reduced the degree of protoplast dehydration and the extent to which the concentrations of the cellular solutes rose. Such a freezing behavior is termed non‐ideal equilibrium freezing. Depending on the original content of leaf water, the volume increments of liquid water due to the negative pressure potential amounted up to 10% at −6 °C and even more at a lower temperature. In addition to the experimental data, a theoretical treatment of psychrometry at subzero temperatures is presented.
Euopsis and Harpidium, Genera of the Lichinaceae (Lichenes) with Rostrate Asci*
Authors: Henssen A. , Büdel B. , Titze A. 
Published: February 2014

AbstractBased on corresponding ascocarp ontogeny and thallus structure, the genera Euopsis and Harpidium are included in the family Lichinaceae. In the two species of Euopsis, E. granatina and E. pulvinata, the apothecia develop from ascogonia in generative tissue, while in H. rutilans they are pycnoascocarps. In thallus anatomy, the species of Euopsis resemble Pyrenopsis haematopsis and allied species, while H. rutilans corresponds in structure and development of the thallus and apothecia to Pyrenopsis haemaleella (syn. P. sphinctotricha).H. rutilans is the first member of Lichinaceae known to have only a green algal symbiont. In E. granatina, two phycobionts are always present, a species of Gloeocapsa and a chlorococcalean alga.In Euopsis and Harpidium, the ascus wall is composed of an outer, non‐expansible and an inner, expansible layer; the latter surrounds the protoplast as an amyloid collar, which expands during spore release into a long, tapering rostrum. In Euopsis, the outer wall layer is strongly amyloid and the upper part separated from the expanded amyloid rostrum by a non‐amyloid zone, appearing like a slit in LM studies. The ultrastructure and function of the ascus in E. granatina has been studied in TEM and is interpreted as functionally unitunicate‐rostrate. Unitunicate asci with short rostrum are described for P. haemaleella and P. haematopsis.
In vitro Approach to Bacterial Chemotaxis
Authors: Eisenbach M. , Matsumura P. 
Published: February 2014

AbstractAn in vitro approach to study bacterial motility and chemotaxis is described. The approach is based on a preparation of flagellated cell envelopes. The envelopes are prepared from bacteria by a penicillin treatment and subsequent osmotic lysis. When the envelopes are energized, their flagella rotate. The direction of rotation in wild type envelopes is counterclockwise. Inclusion of the CheY protein within the envelopes may restore clockwise rotation. The advantages and disadvantages of this approach are pointed out.
Control of Ion Fluxes in Stomatal Guard Cells
Authors: MacRobbie E. A. C. 
Published: February 2014

AbstractOpening and closing of the stomatal pore is associated with very large changes in K‐salt accumulation in stomatal guard cells. This review discusses the ionic relations of guard cells in relation to the general pattern of transport processes in plant cells, in plasmalemma and tonoplast, involving primary active transport of protons, proton‐linked secondary active transport, and a number of gated ion channels. The evidence available suggests that the initiation of stomatal opening is regulated through the uptake mechanisms, whereas initiation of stomatal closing is regulated by control of ion efflux at the plasmalemma, and of fluxes to and from the vacuole. In response to a closing signal there are large transient increases in efflux of both Cl− (or Br−) and Rb+ (K+) at the plasmalemma, with also a probable increase in anion flux from vacuole to cytoplasm and decrease in anion flux from cytoplasm to vacuole. A speculative hypothetical sequence of events is discussed, by which the primary response to a closing signal is an increase in Ca2+ influx at the plasmalemma, producing depolarisation and increase in cytoplasmic Ca2+. The consequent opening of Ca2+‐sensitive Cl− channels, and voltage‐sensitive K+ channels (also Ca2+‐sensitive?) in the plasmalemma, and of a Ca2+‐sensitive nonspecific channel in the tonoplast, could produce the flux effects identified by the tracer work; this speculation is also consistent with the Ca2+‐sensitivity of the response to closing signals and with evidence from patch clamping that such channels exist in at least some plant cells, though not yet all shown in guard cells.
Developmental Physiology Apparent Dark Decay of Phytochrome Pfr in Fern Spores
Authors: Haupt W. , Filler E. 
Published: February 2014

AbstractGermination of spores of Dryopteris fllix‐mas has been induced by two pulses of saturating red light, separated by a dark period of about 8 to 24 h. By chosing different wavelengths, different Pfr/Ptot levels could be established. Thus, by a “null method” the second pulse could be used as a “test pulse”, determining the actual Pfr level remaining from the “start pulse”, and thus providing information about an apparent Pfr decay. It cannot be decided yet whether this apparent Pfr decay results from dark destruction or dark reversion.The apparent Pfr decay depends, as expected, on the temperature, being accelerated with increasing temperatures. Moreover, the later after sowing that the decay is tested, the faster it proceeds; a tentative interpretion is that newly synthesized Pr undergoes faster decay after phototransformation than that phytochrome pool present in the resting spores. A third factor that influences the apparent Pfr decay is the Pfr/Ptot level established by the first pulse (start pulse). The lower this level, the slower the decay kinetics. This could be due to phytochrome biosynthesis partly compensating for Pfr destruction, and the relative contribution of this biosynthesis to the total effect increases with lower Pfr levels. Spores of D. paleacea yield virtually the same results.Whatever the real basis of the observed Pfr decay, i.e. destruction, reversion, or a combination of these reactions with biosynthesis, it can be concluded that modification of this Pfr decay by various factors is the basis of the effect of those factors on light‐induced germination.
Characterization of the Vacuolar Proton Pumps of the Cortex, Stele and Tip of Maize Roots: Effects of Salinity
Authors: Walker K. E. , Taiz L. 
Published: February 2014

AbstractTonoplast and Golgi ATP‐driven proton pumping was measured in membrane vesicles isolated from the cortex, stele and tip of maize roots. Two nitrate‐sensitive peaks of tonoplast proton pumping were detected on sucrose gradients, a light peak at 16% sucrose, believed to represent small vacuoles, and a denser peak at 25% sucrose, possibly derived from large vacuoles. The nitrate‐insensitive Golgi peak occurred at 31 % sucrose. Membrane preparations of the stele and tip were active in H+‐transport activity and were rich in mitochondria. In contrast, the membranes of the cortex had low levels of both ATP‐driven proton pumping and mitochondrial activities. Salinity caused a doubling of the tonoplast H+‐transport activity of the tip and cortex, particularly in the 25 % sucrose peak. The enhancement of the 25 % peak by salinity was correlated with an increase in vacuolation of the tip. The stelar proton pumps were only slightly stimulated by salinity. The results indicate that the cortex of maize roots is deficient in the metabolic machinery needed for vacuolar solute accumulation, but that it shows some ability to adapt to saline conditions. The physiological implications of these findings are discussed.
Quantum Requirements of Photosynthetic Oxygen Evolution and 77 K Fluorescence Emission Spectra in Unicellular Green Algae Grown Under Low‐ and High‐CO2‐Conditions
Authors: Burger J. , Miyachi S. , Galland P. , Senger H. 
Published: February 2014

AbstractQuantum requirements of photosynthetic oxygen evolution at 682 nm and fluorescence spectra at liquid nitrogen temperature (77 K), were investigated in Dunaliella tertiolecta, Chlamydomonas reinhardtii C‐9, Chlorella vulgaris 11g, Chlorella vulgaris C3, and Chlorella pyrenoidosa 8b grown under low‐ and high‐CO2 conditions. Dunaliella, Chlamydomonas and C. vulgaris 11g show higher quantum requirements and a higher ratio of F710–740/F680–695 fluorescence when grown under low‐CO2 conditions, indicating a change in excitation energy distribution towards PS I. In C. pyrenoidosa the quantum requirement for low‐CO2 grown cells is higher than in high‐CO2 grown cells, but there was practically no change in the fluorescence ratio. In C. vulgaris C3, the quantum requirements of low‐ and high‐CO2 grown cells are the same, but the fluorescence ratio is higher in high‐CO2 grown cells than in low‐CO2 grown cells. These results indicate that most of the low‐CO2 grown cells require more PS I light than high‐CO2 grown cells. It is possible that this energy is used for cyclic electron flow. In C. vulgaris C 3, a mechanism may exist for excitation energy distribution which leads to the same quantum requirements under low‐ and high‐CO2 conditions.
Protoplast Culture in Agarose Media with Particular Emphasis to Streaky Culture Lenses*
Authors: Binding H. , Görschen E. , Jörgensen J. , Krumbiegel‐Schroeren G. , Ling H. Q. , Rudnick J. , Sauer A. , Zuba M. , Mordhorst G. 
Published: February 2014

SummaryIsolated protoplasts of 60 species of the Magnoliatae and 19 species of the Liliatae were embedded in droplets of agarose‐containing media in such a way that streaks of locally high cell densities were obtained. For comparison, agarose cultures with dispersed protoplasts and liquid cultures were prepared. Fast and reliable regeneration was obtained in several taxa. After transfer to low osmolar media, shoots were formed in 18 species belonging to the genera Arabidopsis, Asparagus, Biscutella, Brassica, Cichorium, Clianthus, Hypericum, Nicotiana, Petunia, Reseda, Senecio, and Solanum. Only protoplast‐derived callus which did not organize shoots was grown in species of Agrimonia, Daucus, Cucumis, Duchesnea, Helianthus, Potentilla, Prunus, Reseda, Solanum, Sorbus, Spinacia, and Vicia.
Cells with Crystals of Calcium Oxalate in the Leaves of Phaseolus vulgaris — a Comparison with those in Canavalia ensiformis
Authors: Zindler‐Frank E. , Wichmann E. , Korneli M. 
Published: February 2014

SummaryLeaflets of Phaseolus vulgaris contain crystals of calcium oxalate in the adaxial bundle sheath extensions. Most of the crystals accompany the lateral veins of third order. The average oxalate content of the leaves is 0.8% of dry weight. Some features of leaflet anatomy of Phaseolus and Canavalia are shown and the possible relation of anatomy to localization and development of crystals in each of the species is discussed. The majority of crystals in Phaseolus originate with the young leaflets newly unfolded. Calcium deficiency reduces number and size of crystals.
Cadmium‐Induced Structural and Ultrastructural Changes in the Vascular System of Bush Bean Stems
Authors: Barceló J. , Vázquez M. D. , Poschenrieder Ch. 
Published: February 2014

AbstractThe effects of a phytotoxic cadmium concentration (4.45 . 10−5 M) on the structure and ultrastructure of bean plant stems were analysed by light (LM), transmission electron (TEM) and scanning electron microscopy (SEM). Cadmium significantly reduced both the number and the size of tracheary elements. Cadmium‐induced electron dense depositions, which seemed to obstruct partially some xylem vessels, were found only in the later maturing tracheary elements (helical, scalariform or reticulate structure), but not in the annular structured early differentiated ones. Plants exposed to Cd showed less fiber development than the control plants. In the plants treated with Cd abnormally high amounts of calcium oxalate crystals were found in the paratracheary parenchyma cells of the bottom of the stems. The levels of soluble Ca2+ in the expressed stem sap of Cd‐treated plants was significantly decreased, while substantial amounts of soluble Cd were detected. The probable mechanisms of the structural alterations observed are discussed.
Biophysical Examinations of the Bending Stability of Various Stele Types and the Upright Axes of Early “Vascular” Land Plants
Authors: Speck Dipl. ‐Biol. T. , Vogellehner D. 
Published: February 2014

AbstractBiophysical methods allow quantitative deductions as to the “bending effectivity” of various stele types and the contribution of different tissues to the stability of upright plant axes. Considering the first occurrence of the different stele types in geological history, a strong tendency towards a higher “bending effectivity” can be observed. It can be shown that Rhynia gwynne‐vaughanii, Aglaophyton major (Rhynia major) and Asteroxylon mackiei as well as probably the vast majority of early “vascular” land plants were turgor systems, i.e. that the parenchyma (when fully turgescent) is by far the most important contributory factor towards the bending stability of the upright axes.
Nuclear Degeneration during Ballistospore Formation of Cronartium asclepiadeum (Uredinales)*
Authors: Bauer R. , Oberwinkler F. 
Published: February 2014

AbstractWhen basidia of Cronartium asclepiadeum (Uredinales) develop basidiospores, nuclei migrate from the basidial cells into the basidiospores. A mitotic nuclear division yields two nuclei in the basidiospore. One of these nuclei degenerates if the basidiospore develops a secondary ballistospore. Several stages in the degeneration of the nuclei can be recognized: (1) Condensation of chromatin, (2) separation of the nucleus into a portion containing the chromatin and a portion containing the nucleoplasm by an invagination of the nuclear envelope, (3) reduction of nuclear volume, (4) enveloping and (5) twisting of nuclear membranes around the degenerating nucleus, (6) homogenization of the chromatin with reduction of the nuclear envelope, and reduction of the enclosing membrane complex from a multilamellar structure to a single membrane layer, and (7) invagination or splitting off of the spiralled membranes. The nuclear behavior during early developmental stages of secondary spore formation is similar to that of budding basidiomycetous yeasts. Basidiomycetes producing ballistospores may possibly have arisen from those whose reproducing phase is yeast‐like.
Cytokinin, Light, and “Developmental Control” of Protein Synthesis in Cucurbita Cotyledons
Authors: Le Silva , Le W. , Wollgiehn R. , Parthier B. 
Published: February 2014

AbstractCotyledons detached from pumpkin seedlings of different stages of development were either illuminated or treated with 4.10−5 M cytokinin (benzyladenine, BA) in darkness. Comparison of the abilities to incorporate 14C‐leucine into proteins in vivo as well as 35S‐methionine in vitro by means of an RNA‐programmed cell‐free wheat germ system demonstrates that the patterns of the two‐dimensionally separated in vivo labelled soluble proteins are very similar in differently developed or treated cotyledons. Although the translatable mRNA patterns were almost identical in qualitative respect, our data do not exclude the appearance of a few minor polypeptides altered by either illumination or BA treatment. The steady‐state levels of the mRNAs in cotyledons from 12 days old seedlings were remarkably similar irrespective of cotyledon treatment (water, BA, light) and resemble those levels obtained with illuminated or BA‐treated cotyledons of earlier seedlings stages. Our results suggest that the amount of abundant (soluble) proteins in pumpkin cotyledons is developmentally regulated mainly at the transcript level. Extrinsic factors such as cytokinins (BA) or light are equally able to accelerate the developmental program of gene expression in early‐detached cotyledons, which are probably deficient in endogenous hormone.
Accumulation of Storage Materials, Precocious Germination and Development of Desiccation Tolerance During Seed Maturation in Mustard (Sinapis alba L.)
Authors: Fisc W. , Bergf R. , Pla C. , Schäfer R. , Schopfer P. 
Published: February 2014

AbstractUnder defined environmental conditions (20°C, continuous light of 15 klx) development of mustard seeds from artificial pollination to maturity takes about 60 d. After surpassing the period of embryo cell division and histodifferentiation (12–14d after pollination = dap), the seed enters into a maturation period. The time courses of various physiological, biochemical, and structural changes of embryo and testa during seed maturation were analyzed in detail (dry and fresh mass changes, osmotic and water potential changes, respiration, DNA amplification by endomitosis, total ribosome and polysome formation, storage protein synthesis and accumulation, storage lipid accumulation). In addition to the final storage products protein and lipid, embryo and testa accumulate transiently large amounts of starch within the chloroplasts during early maturation. Concomitantly with the subsequent total breakdown of the starch, the plastids lose most of their internal structure and chlorophyll and shrink into proplastids, typical for the mature seed. At about 30 dap the seeds shift from a desiccation‐sensitive to a desiccation‐tolerant state and are able then to germinate rapidly upon drying and reimbibition. If isolated from the immature fruit and sown directly on water, the seeds demonstrate precocious germination from about 13 dap onwards. Young seeds (isolated ≦ 38 dap) germinate only after surpassing a lag‐phase of several days (after‐ripening) during which the embryo continues to accumulate storage protein and lipid at the expense of the surrounding seed tissues. We conclude from these results that the maturing seed represents a rather closed developmental system which is able to continue its development up to successful germination without any specific regulatory influence from the mother plant. Immature seeds are able to germinate without a preceding dehydration treatment, which means that partial or full desiccation does not serve as an environmental signal for reprogramming seed development from maturation to germination. Instead, it is argued that the water relations of the seed are a critical element in the control of maturation and germination: during maturation on the mother plant the embryo is subject to a considerable turgor pressure (of the order of 12 bar) accompanied by a low water potential (of the order of −12 bar). This turgor permits maturation growth but is subcritical for germination growth. However, upon imbibition in water, the low water potential provides a driving force for a burst of water uptake overcoming the critical turgor threshold and thereby inducing germination.
Morphogenetic and Histological Events during Somatic Embryogenesis in Intact Carrot Plantlets (Daucus carota L.) in Various Nutrient Media
Authors: Schä F. , Grieb B. , Neumann K.‐H. 
Published: February 2014

AbstractIt is shown that the induction of somatic embryogenesis neither requires the isolation of explants from intact carrot plants nor mechanical or chemical “wounding”.
Breakdown of Galactolipids in Senescent Barly Leaves
Authors: Gut Hans , Matile Philippe 
Published: February 2014

AbstractThe changes of galactolipids (MGDG and DGDG, largely 18:3/18:3), free fatty acids (FFA), and phosphatidylcholine (PC) taking place during senescence of primary barley leaves were analysed employing HPLC and GLC. Upon induction of senescence MGDG and, with some delay, DGDG began to disappear and were largely broken down at the end of the senescence period. A concomitant appearance of a pool of FFA could not be observed. However, PC accumulated during the main period of galactolipid breakdown. This change was due to the marked increase of the 18:3/18:3 molecular species of PC. An inverse correlation between the changes of galactolipids and PC could be established. A hypothesis featuring the conversion of galactolipids via diacylglycerol to PC is presented as the principal route of galactolipid breakdown.