bluuebunny/crossref_metadata_2025_split huggingface dataset:
Oxidative Stress Responses Accompanying Photoinactivation of Catalase in NaCI‐treated Rye Leaves
Authors: Streb P. , Feierabend J. 
Published: February 2014

Abstract:When segments of rye leaves (Secale cereale L.) grown at 90 μmol m−2 s−1 PAR were incubated at a higher photon flux of 400–500 μ mol m−2 s−1 PAR in the presence of 0.2‐0.6 M NaCl, a preferential loss of catalase activity was induced. The extent of this decline increased with the concentration of NaCl. In addition, the accumulation of alternative antioxidative components, such as ascorbate, glutathione, glutathione reductase, or peroxidase, was inhibited. The total content of H2O2 was, however, lower in catalase‐depleted than in untreated control leaves. The occurrence of strong oxidative stress in NaCl‐treated leaves was indicated by marked declines in the ratios of reduced to oxidized ascorbate and glutathione and by the degradation of chlorophyll in light. The specific elimination of catalase activity by the inhibitor aminotriazole was also accompanied by a rapid decline in the ratio of reduced to oxidized glutathione but other symptoms of oxidative stress were much less severe than in the presence of NaCl. However, all symptoms of photooxidative damage seen in NaCl‐treated leaves were closely mimicked by treatment with the translation inhibitor, cycloheximlde, in light. The results suggest that NaCl‐induced oxidative damage in light was predominantly mediated by the inhibition of protein synthesis. By this inhibition the resynthesis of catalase, which has a high turnover in light, was blocked and the leaves were thus depleted of catalase activity and, in addition, the intensification of alternative antioxidative systems was also prevented.
Phylogenetic Relationships between some Members of the Subfamily Lamioideae (Family Labiatae) Inferred from Nucleotide Sequences of the rbcL Gene*
Authors: Wink M. , Kaufmann Martina 
Published: February 2014

Abstract:Total DNA was extracted from 25 species (8 genera) of the subfamily Lamioideae sensu Erdtman (family Labiatae). Using rbcL‐specific primers, the rbcL gene was amplified by polymerase chain reaction (PCR) and 1420 bp were sequenced directly, or after cloning. RbcL sequences were evaluated with character‐state (maximum parsimony; PAUP) and distance methods (neighbour‐joining; MEGA). In agreement with classical systematics all taxa studied cluster outside the Nepetoideae. The following clades are apparent: I ‐ Westringia/Prostanthera, II ‐ Ajuga/Teucrium and III ‐ Scutellaria, Stachys, Lamium and Marrubium. Lamium album, L. amplexicaule and L. garganicum appear as a sister clade to Marrubium. Both share a common ancestor with a second Lamium clade (including L. purpureum, L. maculatum and L. galeobdolon). The phylogenetic relationships are discussed with regard to the systematic classification of the subfamilies Lamioideae and Nepetoideae (sensu Erdtman).
Ecology and Morphology of Blossfeldia liliputana (Cactaceae): a Poikilohydric and almost Astomate Succulent*
Authors: Barthlott W. , Porembski St. 
Published: February 2014

Abstract:Plants of the monotypic Blossfeldia liliputana have the smallest bodies of all Cactaceae. The button‐like plants with a diameter of usually some 10 mm occur in rock crevices in arid regions between S Bolivia and N Argentina. Based on observations and experiments in the field and in cultivation, morphology, anatomy, reproductive biology, certain aspects of ecophysiology, and behaviour under water stress are described. The very small flowers are autogamous; the arillate hairy seeds are unique within the family and represent a particular adaptation to ant dispersal. These CAM‐plants virtually lack stomata: 0.6 stomata/mm2 represents the lowest number in terrestrial autotrophic vascular plants. However, all other xeromorphic features characteristic for globular cacti are absent (e.g. no thickened cuticle, no thickended outer cell walls, no thickened hypodermal layers). These features allow a high degree of desiccation: under water stress the plants lose up to 80% of their weight within one year and can withstand an additional drought of at least another year. Thus Blossfeldia is poikilohydric like many lichens and mosses and represents the unique life form of a succulent resurrection plant.
Functional Morphology of Aztekium ritteri (Cactaceae)
Authors: Porembski St. 
Published: February 2014

Abstract:The dwarf globular cactus Aztekium ritteri shows a high degree of surface differentiation. The stem consists of 8–15 ribs, these in turn being sculptured by transverse furrows: compared with a sphere of equal size, the surface/volume ratio is increased by more than 10‐fold. At the same time, only 20% of the stem surface is exposed to direct sunlight, 80% lying in the shade of its own body, in a system of furrows and crypts. The exposed areas have few stomata and the epidermal cell walls are notably thickened and cutinised. In addition, these form an exoskeleton by means of a hypodermis containing calcium oxalate crystals while the unexposed cell surface regions, hidden in the furrows, lack xeromorphic characters and calcium oxalate crystals. By far the greatest number of stomata are found in the furrows mostly in deep crypts. When dehydration occurs as a consequence of longer periods of drought, the furrows and crypts close together, thereby reducing transpiration losses. The complicated interlocking nature of the surface architecture of Aztekium is discussed in terms of the functional aspects as an adaptation to an extreme habitat (vertical shale cliffs in Nuevo León, Mexico).
Field Studies on Growth and Regenerative Capacity in the Foliose Macrolichen Xanthoria parietina (Teloschistales, Ascomycotina)
Authors: Honegger Rosmarie , Conconiy S. , Kutasi Verena 
Published: February 2014

Abstract:Growth and development of the foliose macrolichen Xanthoria parietina and adjacent lichen and bryophyte spp. was photographically monitored over a period of five years. This association developed on a plane quadrangle on the top surface of a sandstone block in the botanical garden of the University of Zürich. Line tracings of the thalline outlines were used for a quantitative estimation of laminal growth by means of gravimetric morphometry. Average radial growth of approximately 6 mm yr−1 was recorded, with maxima around 7 mm yr−1. The oldest, apothecia‐covered central parts of the thalli lost contact with the substratum and broke off along stress cracks but the blank substratum was rapidly re‐colonized by new thallus lobes which regenerated along the wound margins, to our present knowledge a peculiarity of X. parietina and few related species among the Teloschistales. Approximately 50% of the surface area of the experimental plot was covered by X. parietina at the beginning and again at the end of this five years period, with significant fluctuations in the time between. New growth in the range of 87% of the total surface area almost compensated the losses of approximately 90% per surface area in five years. New growth and losses within these five years accounted for more than 170% of the initial coverage. X. parietina gains a significant ecological advantage from its very remarkable regenerative capacity.
Pigment Accumulation and Photosynthesis in Developing Rye Coleoptiles
Authors: Bette A. , Kutschera U. 
Published: February 2014

Abstract:Rye seedlings (Secale cereale L.) were grown in darkness or irradiated with white light (WL) of medium intensity (100 μmol quanta . m−2 . s−1). In the coleoptile and primary leaf of irradiated plants synthesis of chlorophylls a and b with average ratios of 2.4 and 2.7, respectively, were measured. The chlorophyll content of the fully green primary leaf was about 10‐fold larger than that of the pale green coleoptile. In darkness a large increase in carotenoid content occurred in the primary leaf, but in the coleoptile the level of carotenoids remained very low. In both organs a WL‐induced increase in carotenoid synthesis was observed. The level of anthocyanin was likewise enhanced by WL. In the coleoptile and primary leaf of irradiated seedlings light‐dependent oxygen evolution was measured. The specific activity of the enzyme ribulose‐1,5‐bisphosphate carboxylase/oxygenase was enhanced after WL treatment. The results indicate that the mature rye coleoptile is a photosynthetically active plant organ.
Inhibition of Photosystem II by UV‐B Radiation and the Conditions for Recovery in the Liverwort Conocephalum conicum Dum.
Authors: Ihle Carolin , Laasch H. 
Published: February 2014

Abstract:Inhibition of photosynthesis by UV‐B was investigated in the thalloid liverwort Conocephalum conicum Dum. UV‐B irradiance was adjusted to a strength producing 50% inhibition of the rate of photosynthesis during 10 min of irradiation. A linear relationship of the fluorescence terms Fv/Fm of photosystem (PS) II and JP was observed following a UV‐B irradiation. This suggested that PS II was a major site of UV‐B‐induced damage of photosynthesis. The apparent inhibition of Fv/Fm was much smaller when electron flow to the secondary PS II acceptor QB was inhibited by DCMU or when Fv/Fm was measured at 77 K. Apparently, the major target of UV‐B effects was electron donation to the PS II reaction center, rather than electron transfer reactions at the PS II acceptor side. The time required for repair of PS II from UV‐B‐induced damage was light‐dependent and minimal at a flux density of 5 μE m−2 s−1. Low temperatures and the presence of streptomycin inhibited the repair processes of PS II, indicating that protein synthesis may be involved in the recovery of PS II. The data indicate that UV‐B irradiation on bright and cool winter days may be most harmful for photosynthesis of C. conicum. A repeated irradiation of the thalli with UV‐B induced tolerance of photosynthesis which was related to an accumulation of pigments with a maximum of absorption around 315 nm.
Mercury Increases Light Susceptibility in the Green Alga Haematococcus lacustris
Authors: Xyländer M. , Hagen Ch. , Braune W. 
Published: February 2014

Abstract:The influence of mercury ions (Hg2+, 10 μM) on photosynthesis was investigated in flagellates and aplanospores of Haematococcus lacustris. Hg2+ stress resulted in a fast decrease of chlorophyll fluorescence yield. This was initially caused by an increase in reversible non‐photochemical quenching of chlorophyll fluorescence. During further exposure to Hg2+, an increasing contribution of pH independent non‐photochemical quenching and a parallel rise in the content of the xanthophyll cycle pigment zeaxanthin was detected. An increase of the initial chlorophyll fluorescence as a final sign of Hg2+ induced adverse effects on photosynthesis supports our hypothesis that mercury ions predispose to non‐reversible, “chronic” photoinhibition.
Scale and Bristle Morphology of Mallomonas tonsurata (Synurophyceae) in Cultures with Varied Nutrient Supply*
Authors: Hahn A. , Gutowski A. , Geißler U. 
Published: February 2014

Abstract:Scale‐bearing taxa of the chrysophytes are important paleoindicators because of their often restricted ecological requirements and their highly preserved extracellular siliceous structures. The diagnostic features can usually only be resolved using electron microscopy and, since these features are often shared between closely related taxa, identification in field studies remain uncertain in most cases. As the respective influences of genetics and environmental factors upon morphological variation cannot be evaluated in field studies, examinations were conducted by growing a clonal culture of Mallomonas tonsurata in different media with varying silicon, nitrogen and phosphorus supply, followed by micromorphological analyses of scales and bristles. Increased silica content resulted in significant elongation of scales with a corresponding tendency to build slender scales. In experiments with varied ratios of nitrogen and phosphorus in the media the most pronounced changes were observed under phosphorus enrichment leading to significantly larger scales and more needle‐like bristle tips. These bristles resemble those of M. areolata. This shows that bristles are more variable than scales and thus must be regarded as of little value for taxonomical description. However, the above‐mentioned changes are not sufficiently pronounced to result in a sharp distinction between two different species. This confirms that siliceous structures of chrysophytes are, in principle, a most valuable tool for taxonomic differentiation although in field studies morphological variability of taxonomically relevant characters should still be considered.
Field Measurements of Photosynthesis of Umbilicarious Lichens in Winter
Authors: Kappen L. , Schroeter B. , Hestmark G. , Winkler J. B. 
Published: February 2014

Abstract:The photosynthetic performance of Lasallia pustulata and Umbilicaria spodochroa was measured both in the field on granitic rock in southern Norway and in the laboratory under controlled conditions of light and temperature. In the field thallus temperatures varied between − 2 and + 5 °C during the daylight period in January 1994. In situ water contents were between 50 and 400% d.wt. in L. pustulata and between 100 and 500% d.wt. in U. spodochroa. The lichens were active during the whole period of investigation. Photosynthetic rates reached 13.03 μmol CO2 g Chl−1 s−1 in L. pustulata and 5.56 μmol CO2 g Chl−1 s−1 in U. spodochroa. Ice formation on the thallus surface did not impede CO2 exchange. Light was mainly the limiting factor, as could be confirmed by the laboratory experiments. In general, habitat conditions never provided optimum photosynthetic rates but photosynthetic carbon balance was positive during 4 of the 5 days investigated. The coldest day was photosynthetically almost as efficient as the warmest day during this period.
Reproduction and Pollination in Central European Populations of Silene and Saponaria Species
Authors: Jürgens A. , Witt Taina , Gottsberger G. 
Published: February 2014

Abstract:Flower morphology, flowering phenology, flower visitors, reproductive systems, and stigmatic receptivity of six species of Silene and Saponaria (Silene alba, S. dioica, S. vulgaris, S. nutans, S. noctiflora. Saponaria officinalis) were studied from April to October 1993 and from April to June 1994 in natural populations around Giessen in Hessen/Central Germany and, additionally, in individuals grown from seeds in the Botanical Garden of the University of Giessen. With the exception of Saponaria officinalis and S. noctiflora, all species were regularly visited and pollinated by crepuscular and nocturnal moths and hawkmoths, but only one species, S. alba, was exclusively pollinated by these night‐active insects. The other species showed mixed pollination syndromes in which nocturnal and diurnal insects both promoted pollen transfer. Geitonogamy or even autogamy occurred in the gynodioecious and hermaphrodite species S. vulgaris, S. nutans, S. noctiflora, and Saponaria officinalis. Silene noctiflora, the only annual species, is pseudocleistogamous; the majority of its flowers did not open, and fruit set occurred after selfing in bud.
Pollen Tubes: a Model System for Plant Cell Growth*
Authors: Derksen J. 
Published: February 2014

Abstract:Recent observations of pollen tubes show that these tubes may grow in a pulsatory fashion (Pierson et al., 1995; Plyushch et al., 1995; Li et al., 1996; Geitmann et al., 1996a, 1996b), in which phases of fast and slow growth alternate regularly. The occurrence of pulsatory growth has been used by Geitmann and coworkers (1996b) to study factors that might control growth. Their results emphasize the role of the cell wall and secretory events in regulating pollen tube growth. Here we will briefly review recent results related to the role of exocytosis, cytoskeleton, calcium and the cell wall in pollen tube growth.
Pigment Evolution in the Caryophyllales: a Systematic Overview*
Authors: Clement J. S. , Mabry T. J. 
Published: February 2014

Abstract:While the apparent mutual exclusiveness of anthocyanins and betalains in the Caryophyllales has given rise to considerable taxonomic debate, historical factors affecting the present distribution of these compounds have rarely been discussed. An understanding of pigment evolution in the order is hindered by a number of unresolved systematic issues and a lack of knowledge of the importance of anthocyanins and betalains beyond their roles in pollination and seed dispersal. The hypothesis that betalains arose in an unpigmented ancestor of the Chenopodiinae in response to selection from pollinators cannot be rejected, but scant evidence exists in favor of it. Questions persist regarding whether the most recent ancestor to the Chenopodiinae presented a pigmented floral display and whether the appropriate pollinators were present at this time to select for floral pigmentation. In view of these ambiguities and the possible non‐monophyly of the Chenopodiinae we consider some alternative scenarios and suggest potentially rewarding avenues for future research. We discuss roles for anthocyanins and betalains beyond their use as optical attractants, possible costs and benefits associated with producing each pigment type, and the possibility that they may have co‐occurred in an ancestor for some period of time.
Inhibition of Intracellular Pectin Transport in Pollen Tubes by Monensin, Brefeldin A and Cytochalasin D*
Authors: Geitmann Anja , Wojciechowicz Kasia , Cresti M. 
Published: February 2014

Abstract:Specific inhibitors of the secretory pathway represent important tools for investigation of cell wall synthesis and tip growth in pollen tubes. Brefeldin A completely inhibits germination of Nicotiana tabacum pollen tubes at 2.2 μM. Ultrastructural investigation of pollen tube cytoplasm showed that brefeldin A caused the appearance of reticular structures and “brefeldin A compartments” containing unesterified pectins. Monensin caused inhibition of pollen tube germination at 80 nM. The drug induced swelling of the Golgi cisternae, many of which contained methyl‐esterified pectins. Cytochalasin D was effective at 1 μg/ml, the inhibition of germination being fully reversible. Application of the drug caused accumulation of secretory vesicles containing methyl‐esterified pectin around the dictyosomes. In contrast to brefeldin A and monensin, cytochalasin D caused a slowdown of cytoplasmic streaming. Monensin, but not the other drugs, caused a considerable decrease in pollen tube diameter. The characterization and quantification of the effects of the drugs on pollen tubes represents a necessary prerequisite for their application in physiological studies.
Distribution of Plasma Membrane H+‐ATPase and Polar Current Patterns in Leaves and Stems of Elodea canadensis*
Authors: Baur Marion , Meyer A.J. , Heumann H.‐G. , Lützelschwab M. , Michalke W. 
Published: February 2014

Abstract:The proton pumping ATPase in the plasma membrane of Elodea canadensis is believed to play a major role in inorganic carbon acquisition. To investigate potentially different carbon uptake strategies within the same plant, plasma membrane H+‐ATPase distribution and polar current patterns were investigated in Elodea leaves and stems. Specific activity of plasma membrane H+‐ATPase in leaf microsomal fractions was tenfold higher than in stem derived microsomes. Probing western blots with a monoclonal antibody specific for plasma membrane H+‐ATPase, yielded strongly visible double bands at 100 kDa in leaf microsome preparations, whereas little antigen was detected in analogous stem microsome preparations. Using the same plasma membrane H+‐ATPase specific antibody on tissue sections, the enzyme was found almost exclusively localized at the border of cells at the lower leaf surface. A positive ion current leaving the lower leaf surface was measured, using a vibrating probe device. Part of this current entered the upper leaf surface and part of it the internodes of the stem. The experimental results support the view, that Elodea leaves have different means of inorganic carbon uptake than stem internodes.
Influence of the Shoot Tip and Leaves on Circumnutation in Green Pea Seedlings
Authors: Tepper H. B. , Yang R. L. 
Published: February 2014

Abstract:Portions of the shoot system from young light‐grown pea (Pisum sativum L.) seedlings were excised and circumnutation studied using time‐lapse cinematography. Removal of the youngest leaf or shoot tip as well as ringing the stem with 20 mM triiodobenzoic acid severely restricted circumnutation. Treating the stump of the excised leaf with lanolin containing 10−4 M indole‐3‐acetic acid or replacing the leaf with an artificial aluminum leaf both partially restored circumnutation. When the leaf was replaced with both auxin and an artificial leaf circumnutation continued at approximately the rate of the intact plant. This graphically shows the involvement of both auxin and gravitropism in circumnutation.
Root Cap Mucilage and Extracellular Calcium as Modulators of Cellular Growth in Postmitotic Growth Zones of the Maize Root Apex*
Authors: Baluška F. , Volkmann D. , Hauskrecht M. , Barlow P. W. 
Published: February 2014

Abstract: The control of maize root growth by root cap mucilage and extracellular calcium (Ca) was examined. Special attention was paid to the influence of these factors on cellular aspects of root growth, such as cell shape and organization of the microtubular (MT) cytoskeleton. Externally supplied Ca impaired the transition of early post‐mitotic cells from a more‐or‐less apolar mode of expansion to a strictly anisotropic mode of elongation accompanied by their more rapid growth. However, this inhibitory effect of Ca was not associated with any re‐arrangement of the cortical MTs, their transverse arrays, with respect to the root axis, being maintained under these conditions. Root mucilage, collected from donor root caps and placed around root tips, exerted a similar effect on cell shapes as did externally supplied Ca. In contrast, roots grown in a medium of low Ca content, or from which the root cap mucilage was continually removed, had more elongated cell shapes in their post‐mitotic growth regions when compared to the control roots. These findings are consistent with a notion that Ca is present in the root cap mucilage in physiologically relevant amounts and can mediate growth responses in both the PIG region and the apical part of the elongation zone.Integrating several known effects of Ca ions on growth at the root apex, a hypothesis is proposed that a Ca‐mediated and MT‐independent control of cell growth in the PIG region might be involved in morphogenetic root movements (e.g. gravitropism), and that root growth responses could be initiated by an asymmetric distribution of extracellular calcium, or root cap slime, around the growing root tip.