bluuebunny/crossref_metadata_2025 huggingface dataset:
Biosynthesis of Organic Compounds Emitted by Plants
Authors: Kreuzwieser J. , Schnitzler J.‐P. , Steinbrecher R.
Published: February 2008

Abstract: Trees produce a wide spectrum of volatile organic compounds (VOCs) including isoprene and monoterpenes, as well as oxygenated compounds like aldehydes, alcohols and carboxylic acids. In recent years, much progress has been made regarding the elucidation of metabolic pathways leading to the production of these compounds. This is particularly true for the biosynthesis of the isoprenoid precursors, isopentenyl diphos‐phate (lOP) and dimethyl allyl diphosphate (DMADP). In addition to the classical mevalonate pathway which leads to the biosynthesis of these compounds, recent studies indicate the presence of a non‐mevalonate pathway originating from pyru‐vate and glyceraldehyde‐3‐phosphate (GAP), also leading to isoprenoid precursors. This new 1‐deoxy‐D‐xylulose‐5‐phos‐phate (DOXP) pathway is probably responsible for the formation of all plastid‐derived isoprenoid compounds in plants, including carotenoids, plastochinones, the prenyl side chains of chlorophyll, as well as monoterpenes and diterpenes. Because all plas‐tidic isoprenoids studied so far are formed via this new pathway, it is assumed that isoprene synthesized in the chloroplasts is also produced via this metabolic route. Among the oxygenated hydrocarbons which are emitted by the leaves of trees, C‐1 and C‐2 aldehydes, alcohols and carboxylic acids are of great importance. C‐i compounds are synthesized during many growth and developmental processes such as seed maturation, cell expansion, cell wall degradation, leaf abscission and senescence of plant tissues. The production of C‐2 compounds, however, seems mainly to be associated with changing environmental conditions, particularly during stress. Acetaldehyde, for example, is produced in the leaves of trees if the roots are exposed to anaerobic conditions which in nature may be caused by flooding. As a consequence of anaerobiosis, roots produce ethanol through alcoholic fermentation. Ethanol is loaded into the xy‐lem, transported to the leaves and oxidized there under aerobic conditions, thereby releasing acetaldehyde and acetic acid.
Molybdenum Metabolism in Plants
Authors: Zimmer W. , Mendel R.
Published: February 2008

Abstract: Among the micronutrients essential for plant growth and for microsymbionts, Mo is required in minute amounts. However, since Mo is often sequestered by Fe‐ or Al‐oxihydrox‐ides, especially in acidic soils, the concentration of the water‐soluble molybdate anion available for uptake by plants may be limiting for the plant, even when the total Mo content of the soil is sufficient. In contrast to bacteria, no specific molybdenum uptake system is known for plants, but since molybdate and sulfate behave similarly and have similar structure, uptake of molybdate could be mediated unspecifically by one of the sulfate transporters. Transport into the different plant organs proceeds via xylem and phloem. A pterin‐bound molybdenum is the cofactor of important plant enzymes involved in redox processes: nitrate reductase, xanthine dehydrogenase, aIdehyde oxidase, and probably sulfite oxidase. Biosynthesis of the molybdenum cofactor (Moco) starts with a guanosine‐X‐phos‐phate. Subsequently, a sulfur‐free pterin is synthesized, sulfur is added, and finally molybdenum is incorporated. In addition to the molybdopterin enzymes, small molybdopterin binding proteins without catalytic function are known and are probably involved in the storage of Moco. In symbiotic systems the nitrogen supply of the host plant is strongly influenced by the availability of Mo in soil, since both bacterial nitrogenase and NADPH‐dependent nitrate reductase of mycorrhizal fungi are Mo enzymes.
A Plastid Sigma Factor Sequence from the C4 Monocot Sorghum bicolor
Authors: Kroll Daniela , Streubel Monika , Westhoff P.
Published: February 2008

Abstract: All plastomes of land plants and alga analyzed to date encode homologues of the core subunits of an eubacteria‐like RNA polymerase. However, the plastomes lack genes for sigma factors which are imperative for proper promoter recognition by this type of RNA polymerase and hence must be encoded by nuclear genes. By searching plant “expressed sequence tags” (EST5) for similarities to eubacterial sigma factors an Arabidopsis EST (155H23T7) was identified which was used for the isolation of a homologous full‐length cDNA from the C4 monocot, Sorghum bicolor. The cDNA sequence encodes a protein exhibiting the typical sequence motives of cs70‐type sigma factors and the corresponding gene was therefore designated Sigi. The SIG1 protein shows the greatest similarity to recently identified plastidial sigma factors of A. thaliana, O. sativa and S. alba. Like these proteins the Sorghum SIG1 protein contains an aminoterminal extension reminiscent of plastidial transit sequences indicating that the SIG1 protein functions as a plastidial sigma factor. Accordingly, Sigi transcripts are found preferentially in leaves and accumulate in a light‐dependent manner. Sigi transcript levels are similar in the mesophyll and bundle‐sheath cells suggesting that at least this sigma factor is not involved in the differential expression of plastid genes in the two cell types. Southern analyses indicate that the Sigl sequence is present as single copy gene in the Sorghum genome.
Seasonality of Glutathione Dynamics in Scots Pine and Bilberry
Authors: Taulavuori E. , Taulavuori K. , Lame K.
Published: February 2008

Abstract: Seasonal changes in the glutathione status of Scots pine (Pinus sylvestris L.) needles and bilberry (Vaccinium myrtillus L.) stems and leaves were investigated during 1995 and 1997–1998, respectively. The glutathione concentration, the proportion of reduced glutathione (GSH%) and glutathione reductase (GR) activity were measured at monthly intervals throughout one year. The glutathione concentration and GSH% in current year's Scots pine needles were highest during late summer, but decreased during autumn. It is suggested that exchange reactions between free and protein‐bound glutathione may be involved in this reduction. Both metabolites decreased towards summer in the previous year's needles. GR activity exhibited the lowest values in summer and the highest values in winter in both needle generations. In bilberry stems, glutathione peaked during midwinter, while GSH% remained high and relatively constant throughout the year. GR activity was highest in August, after which it gradually declined. In bilberry leaves, the total glutathione concentration was high in early summer. This peak was followed by a sharp decrease during midsummer. GR activity in the leaves was very low, but showed a clear increase towards autumn. Obviously, glutathione metabolism showed considerable seasonal variation in Scots pine needles and in bilberry leaves and stems, but the pattern of variation differed between the studied species and organs.
Peculiarities of the Inner Calyx Surface of Caryophylloideae with Special Regard to Sexual Dimorphism in two Dioecious Species1
Authors: Bopp S.
Published: February 2008

Abstract: The structure of the inner calyx surface of several Silene and one Saponaria species with different sex expression have been investigated by scanning electron microscopy. Some of the hermaphroditic and gynodioecious species show peculiarities in the basal parts of their calyces, such as cylindrical trichomes in Si. nutans. Capitate trichomes occur exclusively on the inner calyx surface of the two dioecious species Si. dioica and Si. latifolia ssp. alba. In both species the density of these trichomes is significantly higher in female than in male individuals. The hypothesis is proposed that these trichomes play a role in flower discrimination of specialized pollinators and seed predators.
Life Cycle and Supplementary Comments on the Light Microscopic Morphology of Nannochioris eucaryota
Authors: Tschermak‐Woess Elisabeth
Published: February 2008

Abstract: Light microscopic characteristics of the extremely small cells of Nannochioris eucaryota allow distinction from other similar or related chlorophycean species. These characteristics are the already well known spherical to slightly ellipsoidal cell form, the form of the chloroplast (being a thick band or plate bending along the cell wall), the presence of oil droplets, the absence of crystalloid bodies, the mode of cytokinesis which starts excentrically, and the peculiarities of cell walls in the course of autosporulation. The nature of two peculiarly located grains within the chloroplasts (possibly of starch) needs electron microscopical verification.
Phylogenetic Information in the Mitochondrial nad5 Gene of Pteridophytes: RNA Editing and Intron Sequences
Authors: Varigerow Sibyl , Teerkorn T. , Knoop V.
Published: February 2008

Abstract: A conserved coding region of the mitochondrial nad5 gene (1098–1107 bp of protein coding sequence) was amplified from 30 pteridophytes (26 ferns and 4 fern allies). A group II intron sequence conserved in all ferns except the eu‐sporangiate genus Ophioglossum is also present in the whisk fern Psilotum nudum and the lycopod Huperzia selogo, but absent from the horsetails (Equisetum), the seed plants and the bryo‐phytes. Phylogenetic trees constructed with different methods consistently suggest several monophyletic units. The conserved group II intron sequence provides valuable additional phylogenetic information. Leptosporangiate ferns are monophyletic with Osmunda as the basal‐most branching genus followed by Trichomanes, Matonia and Lygodium. These genera are set distantly apart from other leptosporangiate ferns, including the tree and water ferns, which branch in close proximity. Species of Polypodiaceae, Dryopteridaceae, Thelypteridaceae, Aspleniaceae and Blechnaceae appear in a monophyletic crown group of derived leptosporangiate ferns with Dryopteridaceae as a paraphyletic taxon. Placement of Psilotum in a class of its own receives no support from the mitochondrial sequences, which rather suggest its inclusion among eusporangiate ferns (Ophioglossales). RNA editing is required to correct the genetic information of the nad5 gene in all species investigated and includes the removal of stop codons from the reading frames. The influence of RNA editing on phylogenetic tree construction is investigated and discussed.
Inulin Occurrence in Sphenoclea (Sphenocleaceae)
Authors: Porembski S. , Koch Marieluise
Published: February 2008

Abstract: Within the angiosperms the Asterales‐Campanulales complex forms a relatively clearly circumscribed dade that is characterized by inulin as storage carbohydrate. The genus Sphenoclea (Sphenocleaceae) is traditionally placed in the Asterales‐Campanulales complex. In testing fresh plant material of S. zeylanica for the first time, the occurrence of inulin as storage carbohydrate could be proven.
Accumulation of Silicon in the Monocotyledons Deschampsia caespitosa, Festuca lemanil and Schoenus nigricans
Authors: Neumann D. , Schwieger W. , Lichtenberger O.
Published: February 2008

Abstract: Conventional and analytical electron microscopy (EDX, ESI, EELS) were used to investigate the silicon accumulation, the chemical nature of the Si deposits and their formation in three species of monocotyledons. In Deschampsia, in particular parts of the outer epidermal cell wall silicon is accumulated as silicic acid. Electron dense, needle‐shaped crystals in the vacuoles of epidermal cells and in the intercellular spaces were also identified as silicic acid. In xylem parenchyma cells, silicon is accumulated as SiO2, which is formed from Sn silicate. In Festuca, crystal‐like deposits of SiO2 occur on the epidermal surface, in the epidermal and parenchyma cell walls, and in vacuoles of bundle sheath cells. Often the deposits disturb the cell walls and penetrate the envelope of plastids and mitochondria. The crystal‐like SiO2 deposits originate from Sn silicate. In the pericarp of ripe nuts of Schoenus, no stainable cell wall components are detected. The inner part of the pericarp consists of silicic acid, while in the outer regions small clusters of silicic acid are embedded in a matrix of SiO2. The silicic acid deposits show an unusual, layered structure, typical for lepidoic silicic acids, which consist of two‐dimensional crystals lying one above the other.
Expression of BifunctionaI Caffeoyl‐CoA 3‐O‐Methyltransferase in Stress Compensation and Lignification
Authors: Grimmig B. , Kneusel R. E. , Junghanns K. T. , Matern U.
Published: February 2008

Abstract: Caffeate and caffeoyl‐CoA O‐methyltransferases (COMTs and CCoAOMTs) catalyze the formation of ferulic acid and feruloyl‐CoA, respectively, in many plants, and their physiological significance is under investigation. CCoAOMT was proposed to play a pivotal role in cell wall reinforcement during the induced disease resistance response, as exemplified in elici‐tor‐treated parsley cells, as well as in the formation of guaiacyl‐and syringyl‐type lignins. This requires selective substrate and tissue specificities. Parsley CCoAOMT expressed in E. coli methylated caffeoyl‐ or 5‐hydroxyferuloyl‐CoA to feruloyl‐ and sinap‐oyl‐CoA, whereas neither caffeate nor 5‐hydroxyferulate was accepted. Tissue print hybridizations of parsley stem and root sections revealed, furthermore, that CCoAOMT mRNA is consti‐tutively associated with the vascular tissues, but is also expressed in the surface cell layers upon wounding. In order to study the promoter activity of the parsley CCoAOMT gene, tobacco plantlets were transformed with parsley CCoAOMT promoter‐GUS reporter gene constructs; these transformants, at the very young stage, expressed GUS activity in a narrow subapical root zone only extending later to the vascular tissue at the onset of xylem differentiation. GUS activity of the mature transgenic tobacco plants was observed exclusively in the parenchyma lining the differentiated xylem elements and xylem ray cells of root, stem or leaf tissues. Thus, parsley CCoAOMT is a bifunctional enzyme which appears to serve in both stress compensation and lignification. This was supported by the ontogenetic activity profile of tobacco endogeneous CCoAOMT, which correlated closely with the GUS expression under the control of parsley CCoAOMT promoter, while the proportion of CCoAOMT vs. COMT activities varied substantially during growth of the transgenic tobacco plants.
Characterization of Flavin Binding in Flagella of Chiamydomonas
Authors: Dederichs A. , Schäfer A. , Hertel R. , van den Ende H.
Published: February 2008

Abstract: Using an experimental approach similar to that used for Euglena flagella, we found that flagella and flagellar membrane preparations (isoagglutinins) of the unicellular green algae Chlamydomonas moewusii and C. reinhardtii, but not cells without flagella, bind radiolabelled riboflavin with high affinity and specificity. In addition, flagella and isoagglutinins contain high amounts of methanol‐extractable flavins. These results indicate an abundance of proteins with high affinity for riboflavin in the flagella. Since sexual adhesiveness of gametic flagella in C. moewusii is controlled by light, the possibility is discussed that flavoproteins in the flagella are involved in this reaction. Action spectra exhibit maxima at 450 and 600 nm, suggesting–at least for the 450 nm band–a typical blue‐light receptor.
The Ascoma Development in Mycoporum elabens (Mycoporaceae, Dothideales)
Authors: Lumbsch H. T.
Published: February 2008

Abstract: The structure and development of the ascomata in Mycoporum elabens were studied. No pseudoparaphyses or para‐physoids are developed but the asci grow into a network formed by stretched ascostromatic tissue which appears similar to pseudoparaphyses at the mature stage. The ascomata do not open regularly but burst open at several points, thus imitating plurilo‐cularous stromata. This development agrees with that observed for the Dothideales sensu stricto and so it is proposed to place the Mycoporaceae here. Although algal cells were found in the surroundings of the ascomata, they did not have close contact with the fungal hyphae. Thus, Mycoporum elabens is interpreted as being non‐lichenized.
Gynomonoecy in Silene italica (Caryophyllaceae): Sexual Phenotypes in Natural Populations
Authors: Maurice Sandrine
Published: February 2008

Abstract: Some gynodloecious species present not only hermaphrodite and female individuals but also gynomonoecious individuals that produce both female and perfect flowers. In a study of natural populations of Silene italica, we found that gynomonoecious individuals were common in all populations (from 13 to 39%) and that their frequency was independent of the frequency of females. No relationship was found between the number of flowers a plant produced and its sex. The majority of gynomonoecious individuals showed a low proportion of female flowers but all proportions were found. Female flowers of these individuals were well‐developed flowers that set fruit as often as female flowers on pure females. The percentage fruit set was characteristic of the type of flowers (around 56% for perfect flowers and 76% for female flowers) whatever the sex of the individual plant. The determination of sex is not known but data indicate that environmental conditions could be responsible for a shift between the hermaphrodite and the gynomonoecious states rather than between the female and the gynomonoecious states.
Expression of Modes of Photosynthesis (C3, CAM) in Clusia criuva Camb. in a CerradolGallery Forest Transect
Authors: Herzog Britta , Grams T. E. E. , Haag‐Kerwer Angela , Ball Erika , Franco A. C. , Lüttge U.
Published: February 2008

Abstract: The large majority of the Ca. 150 species of the neotropical shrub and tree genus Clusia have the potential to perform Crassulacean acid metabolism (CAM). They are either obligate CAM plants or C3/CAM intermediate plants. Only a very small percentage of the plants studied so far are apparently obligate C3 species. Among these was C. criuva, until recent laboratory studies showed that it may also have a certain CAM capacity under artificial stress conditions. Measurements of stomatal conductance (porometry) and chlorophyll fluorescence variables of C. criuva occurring along a transect from deep shade inside a gallery forest across the semi‐shaded ecotone towards a cerrado and into the exposed cerrado itself in central Brazil now show that it can adapt its photosynthetic apparatus to effective performance of C3 photosynthesis under highly different photosynthetic photon flux densities. In addition, however, it does have a certain potential for CAM and cannot be considered as a strictly obligate C3 plant. Should a basic capacity for performing CAM be a general property of the genus, the quest for CAM traits in other remaining putatively obligate C3 species of the genus ought to be pursued.
Responses of Photosynthetic and Defence Systems to High Temperature Stress in Quercus suber L Seedlings Grown under Elevated CO2
Authors: Faria T. , Vaz M. , Schwanz P. , PolIe A. , Pereira J. S. , Chaves M. M.
Published: February 2008

Abstract: Growth in elevated CO2 led to an increase in biomass production per plant as a result of enhanced carbon uptake and lower rates of respiration, compared to ambient CO2‐grown plants. No down‐regulation of photosynthesis was found after six months of growth under elevated CO2. Photosynthetic rates at 15°C or 35 °C were also higher in elevated than in ambient CO2‐grown plants, when measured at their respective CO2 growth condition. Stomata of elevated CO2‐grown plants were less responsive to temperature as compared to ambient CO2 plants. The after effect of a heat‐shock treatment (4 h at 45 °C in a chamber with 80% of relative humidity and 800–1000 tmol m‐2 s‐1 photon flux density) on Amax was less in elevated than in ambient CO2‐grown plants. At the photochemical level, the negative effect of the heat‐shock treatment was slightly more pronounced in ambient than in elevated CO2‐grown plants. A greater tolerance to oxidative stress caused by high temperatures in elevated CO2‐grown plants, in comparison to ambient CO2 plants, is suggested by the increase in superoxide dismutase activity, after 1 h at 45 °C, as well as its relatively high activity after 2 and 4 h of the heat shock in the elevated CO2‐grown plants in contrast with the decrease to residual levels of superoxide dismutase activity in ambient CO2‐grown plants immediately after 1 h at 45 °C. The observed increase in catalase after 1 h at 45 °C in both ambient and elevated CO2‐grown plants, can be ascribed to the higher rates of photorespiration and respiration under this high temperature.
The Effect of Isoprene on the Properties of Spinach Thylakoids and Phosphatidyicholine Liposomes
Authors: Logan B. A. , Anchordoquy T. J. , Monson R. K. , Pan R. S.
Published: February 2008

Abstract: Isoprene is emitted from the leaves of some plants. It was recently reported that exogenous isoprene delays the onset of leaf damage during controlled increases in leaf temperature (Singsaas et al. Plant Physiology 115: 1413–1420 [1997[17). Thylakoid membranes are presumed to be the site of action based upon isoprene's hydrophobicity, production in chloroplasts, and effect upon chlorophyll fluorescence at high temperatures. In an attempt to discern the mechanistic basis for isoprene's thermoprotective role, we studied the effect of exogenous isoprene on the peroxidation, permeability, and stability of spinach thylakoids and phosphatidylcholine liposomes. Isoprene, supplied at either 18 or 21 μ1 L1, had no effect upon the rate of liposome peroxidation in the presence of a hydroxyl radical‐generating system. Isoprene also did not affect liposome peroxidation at high temperatures. Neither the proton permeability of thylakoids nor the leakage of a fluorescent probe from liposomes was influenced by exogenous isoprene, when measured at several temperatures. Isoprene did not affect the stability of thylakoid membrane proteins during a temperature increase, as shown by differential scanning calorimetry. Therefore, despite the use of a variety of techniques to investigate fundamental membrane parameters, we were unable to demonstrate an effect of isoprene.
Role of lndole‐3‐acetic Acid in the Interaction of the Phanerogamic Parasite Cuscuta and Host Plants
Authors: Löffler C. , Czygan F. C. , Proksch P.
Published: February 2008

Abstract: During infection with the phanerogamic parasite Cuscuta reflexa the incompatible host plant Lycopersicon esculentum shows characteristic anatomical tissue modifications at the infection sites that are exclusively provoked following contact with Cuscuta ‐ striking cell elongation is observed in the hypo‐dermis and collenchyma of the host plant. Due to the influence of auxins on the process of cell elongation in plants, the role of indole‐3‐acetic acid (IAA) in the interaction of Cuscuta and Lycopersicon was studied using a highly specific enzyme‐linked im‐munosorbent assay for hormone measurement. It was shown that the tissue modifications in the host plant as well as cell elongation in the parasite tissue leading to the formation of an adhesive‐secretory epithelium are correlated with increasing IAA levels in the respective tissues. Both anatomical modifications can also be induced artificially by injection of IAA into control tissue. Based on the obtained data, it can be hypothesized that during the parasitic attack IAA is accumulated in the haus‐toria‐bearing regions of Cuscuta and exuded from the epithelial cells. Due to the close contact between host and parasite, the hormone probably enters the host plant tissue causing the observed anatomical reactions.
Reversible, Water Stress‐Induced Non‐Uniform Chlorophyll Fluorescence Quenching in Wilting Leaves of Potentilla reptans may not be due to Patchy Stomatal Responses
Authors: Osmond C. B. , Kramer D. , Lüttge U.
Published: February 2008

Abstract: After exposure to full sunlight under natural conditions, attached leaves of the common meadow weed Potentilla reptans show non‐uniform (“patchy”) chlorophyll fluorescence quenching in the early stages of fluorescence transients. These areas of bright fluorescence can be readily reproduced in detached leaves that are allowed to wilt on the laboratory bench in weak light. The extent and duration of the patchiness increases with increasing water stress (higher relative saturation deficits). Images captured during saturating flashes show that the patches also display slow development of non‐photochemical quenching, consistent with the possibility that photosynthetic metabolism is impaired in these areas. Wilted Potentilla leaves readily regain full turgor when petioles are placed in water, and uniform chlorophyll fluorescence is recovered with in 30mm. Epidermal impressions reveal closed stomata over areas of both low and high fluorescence in wilted leaves. Because highly fluorescent patches also persist when wilted tissues are exposed to high CO2 (i.e., patchiness is unlikely to be due to local differences in CO2 supply) the data suggest direct effects of water stress on metabolism in wilted leaves. Leaf transverse sections show that although major veins may isolate areas of the lamina, minor veins do not. Relationships to leaf anatomy are discussed.
Influence of Ca2+ and pH on the Stability of Different Boron Fractions in Intact Roots of Vicia faba L.
Authors: Wimmer Monika A. , Goldbach H. E.
Published: February 2008

Abstract: An experimental setup was developed which allowed the detection of different boron fractions in intact plant roots. The B fractions were water‐soluble B (WSB), BaCI2‐soluble B (BaSB) and the respective insoluble fractions (WIB and BaIB). In root tips of V. faba seedlings, WSB represents approx. 4%, BaSB 9% of Btot. BaSB consists of (at least) two compounds, the larger of which (65 %) interacts with phosphate and is considered a soluble B complex. Within 2 h of B deficiency, WSB and a large part of BaSB disappear, suggesting that they may be involved in early deficiency reactions in root tips. Concerning insoluble fractions, there was no decline in WIB within the first 6 h of B deficiency. Within the same time frame, BaIB dropped to 35% of the initial B content, indicating a stabilizing effect of Ca on B complexes under in vivo conditions. The concentration of WSB in root tips was lower at pH 3.6 as compared to pH 6.0, indicating that changes in apoplastic pH rapidly alter the equilibrium between free and bound B. WIB was more tightly bound in older root parts, as indicated by a maximum loss of 34% of Btot after 24 h of continuous B removal, as compared to 99.5% in root tips. Our results indicate that different fractions of B (additional to B‐RGII) are affected in the early stages of B deficiency and that Ca is not only a stabilizing agent for B complexes but is also necessary to bind soluble B complexes in the apoplast of intact roots.
Flavin‐Binding Sites in Phycomyces
Authors: Flores R. , Dederichs A. , Olmedo E. Cerdá , Hertel R.
Published: February 2008

Abstract: Riboflavin‐binding proteins could be the photorecep‐tors for tropism in the fungus Phycomyces blakesleeanus. Radio‐labelled riboflavin bound to both membrane‐associated and cy‐tosolic sites. The membrane sites (approximately 0.2–0.6nmol per g fresh material) were highly specific, with decreasing affinities for riboflavin (KD≅ 1 μM under reducing conditions, KD≅μM under oxidizing conditions), FMN, roseoflavin, and FAD. These binding sites, whose properties were similar to those of higher plants, could be solubilized with mild detergents, and were found in all vegetative parts of the fungus, including the spores. Mutants defective for phototropism did not differ from the wild type in the amount of binding sites or their affinity. A completely different binding to riboflavin was observed in the cytosolic supernatant of the sporangiophores; this activity was heat resistant and the binding sites could be partially purified and recognized as a polymerization product of gallic acid. Flavms were abundant in the sporangiophores (4.5 nmol per g fresh mass) and the spores (60 nmol per g fresh mass), but scarce in washed membranes (0.02–0.11 nmol per g fresh spor‐angiophore mass). Autogenous fluorescence, whose absorption and emission wavelengths fit those of riboflavin, was seen by confocal microscopy, in part as clustered particles, in the actively growing parts of the mycelium, in the cytoplasm of sporangiophores, and in the spores.
Fruit‐Set Induced Changes in the Sex of Flowers in Caesalpinia calycina (Leguminosae)
Authors: Gibbs P. E. , Lewis G. P. , Lughadha E. N.
Published: February 2008

Abstract: The proportions of hermaphrodite to staminate flowers in inflorescences of the andromonoecious species Caesalpinb calycina vary. Analysis of fruit position along the flowering rhachis, and also of the sex of floral buds in inflorescences with fruits set in different positions, indicate that fruiting success influences the sex of flowers in distal positions along the rhachis. Other reports of andromonoecy in caesalpinoid species are examined with reference to floral sex lability and the influence of fruit set.
The Response of Petioles of Glechoma hederacea to a Dynamic Light Climate
Authors: Leeflang Lizelotte
Published: February 2008

Abstract: In herbaceous vegetation patterns of light distribution may change over time. Prostrate plants growing in such a dynamic light environment may benefit from petioles that respond plastically to changing light conditions. In an experiment, the response of petioles of Glechoma hederacea to changing light conditions was analyzed. Treatments included continuous shade, continuous high light, a shift from shade to high light and from high light to shade when the plants had formed 10 ramets. In all four treatments, even petioles that had apparently ceased growing, were still able to elongate slightly but the extent of elongation decreased with the age of the petiole. In the oldest petioles relative extension rates were higher in shade than in high light. In plants that were exposed to full daylight in the second half of the experiment, even newly formed petioles were longer than those in plants that grew in full daylight continuously though they had elongated over a shorter period. In plants that were shaded in the second half of the experiment, only the youngest 4 to 5 petioles reached lengths similar to that in continuous shade. This mechanism may enable plants to keep young (productive) leaves in the upper layers of the canopy while other less productive leaves remain at lower levels of the vegetation.
Ecophysiological Studies on the Red Alga Galdieria sulphuraria Isolated from Southwest Iceland
Authors: Gross W. , Oesterhelt Christine
Published: February 2008

Abstract: The acido‐ and thermophilic red alga, Galdieria sulphuraria, was isolated from three volcanic areas of the Reykjanes peninsula (southwest Iceland). These sites showed pH values of 1.5 to 3, low concentrations of dissolved organic carbon, and were apparently exclusively colonized by the red alga. No other eucaryotes were observed by light or electron microscopy. The isolated Galdieria strains grew heterotrophically on various sugars and polyols. At all three sites, Galdieria occupied terrestrial habitats. Extensive endolithic growth of the alga was only observed at one site where cell layers were found as deep as 3 cm within rocks of geyserite, a soft white siliceous mineral. Light is apparently insufficient for photosynthesis >10 mm below the stone surface. It is proposed that cells deep within the rock make use of metabolites released by decaying cells in the surroundings. Cells isolated from these algal layers exhibited sugar uptake rates indicative for a low‐level heterotrophic state. Therefore, the extraordinary heterotrophic capabilities of Galdieria seem to be especially important in endolithic habitats.
The Size of Cells and Organisms in Relation to the Evolution of Embryophytes
Authors: Raven J. A.
Published: February 2008

Abstract: The earliest O2‐‐evolvers were marine cyanobacteria (3.5 billion years ago) with marine eukaryotic phototrophs from 2.0 billion years ago. These organisms were, and are, poikilo‐hydric, i.e., cannot remain hydrated when exposed to a desiccating atmosphere (as can occur for intertidal benthic algae and cy anobacteria at low tide). The smallest marine primarily poikilo‐hydric O2‐‐evolvers are close to the lower size limit imposed by non‐scaleable components such as minimum genome size and constant membrane thickness, with cyanobacterial unicells 0.65 μn in diameter and eukaryotic unicells 0.95 μm in diameter. The largest (multicellular) marine primarily aquatic poikilohydric O2‐‐evolvers are brown algae at least 60 m long and over 100 kg fresh mass; there are no obvious constraints on the max imum size of such organisms. In freshwaters the size range for primarily poikilohydric O2‐‐evolving organisms is smaller, due to the absence of very large organisms. An even smaller size range characterizes terrestrial algae and cyanobacteria which have occurred for about 1 billion years. Desiccation‐tolerant cyanobacterium and algae (intertidal, freshwater, terrestrial) are at the lower end of the size ranges.

Embryophytic terrestrial O2‐‐evolvers arose some 450 million years ago and were than all poikilohydric and (probably) desiccation‐tolerant. Embryophytic defining structural features re quire organisms of at least 100 μm equivalent spherical diameter for both gametophyte and sporophyte phases. Primarily poi kilohydric embryophytes are not more than 1 m tall as a result of a mechanistically mysterious size limit for desiccation‐tolerant organisms. Homoiohydric embryophytes evolved some 420 mil lion years ago in the sporophyte phase (later to become the dominant terrestrial vegetation) and possibly in the gameto phyte phase (although no such homoiohydric gametophytes are known today). The homoiohydric features of gas spaces, stomata, cuticle, endohydric water conducting system and water and nutrient uptake structures require an organism at least 5 mm high; this has implications for the minimum size of mega‐spores and seeds. The tallest homoiohydric plants are (or were within historic times) 130 m high, with height constrained by re source costs of the synthesis and maintenance of the mechanical and water conduction systems, andbr of xylem water trans port. Secondarily poikilohydric embryophytes in aquatic, or very damp terrestrial, habitats are derived from homoiohydric plants; they retain most homoiohydric features but are not functionally homoiohydric. The smaller secondarily poikilohydric plants are less than one tenth of the size of the smallest functionally homoiohydric plants.
Control of Leaf Growth and its Role in Determining Variation in Plant Growth Rate from an Ecological Perspective
Authors: Bultynck L. , Fiorani F. , Lambers H.
Published: February 2008

Abstract: Plants vary widely in their relative growth rate (RGR), be it dependent on environmental conditions or due to their genetic background. In a comparison of the RGR of grasses growing under different environmental conditions, variation in RGR tends to correlate with that in the leaf elongation rate (LER). When different species or genotypes thereof are compared under identical growing conditions, variation in LER may or may not correlate with that in RGR, depending on the comparison. However, since RGR is described by an exponential equation, whereas LER is mainly a linear process, we conclude that any correlation between RGR and LER must be fortuitous. That is, exponential growth must be due to increases with time in plant traits such as 1) leaf dry mass per unit leaf length invested per unit time, and/or 2)E̊, i.e., the total LER of all the growing leaves at one point in time. The latter can be achieved as follows: 1) each subsequent leaf has a higher LER than the preceding one; 2) leaves appear at an increasing rate; 3) the duration of the process of leaf elongation increases for subsequent leaves. In this review, we only explore possible factors that account for changes in E̊ with time, in different genotypes and under different environmental conditions. Inherent variation in LER of individual leaves and variation due to environmental factors may reflect variation in the rate of cell division and/or in cell elongation.
Integration of Controlled Intracellular Pressure Microinjection, lontophoresis, and Membrane Potential Measurement
Authors: Kempers R. , Prior D. A. M. , Oparka K. J. , Knoblauch M. , van Bel A. J. E.
Published: February 2008

Abstract: A novel device for intracellular microinjection was designed to integrate controlled pressure microinjection and electrical microinjection (iontophoresis) with membrane poten tial recording and a limited capacity for turgor measurement. The validity of the device was verified by microinjection of a mixture of the fluorescent probes, Texas Red sulfonyl chloride and 10 kDa‐LYCH‐dextran conjugate, into epidermal cells of var iegated Coleus blumei leaves. Continuous monitoring of the fluorochrome movement by confocal laser scanning microscopy evidenced that the novel device succeeded in differential micro‐injection of the fluorescent probes by pressure and iontophor esis. The multifunctionality of the microinjection system was further demonstrated by showing that both microinjection methods functioned in parallel with cellular membrane poten tial measurements in Vicia faba stem tissue. Advantages and prospective applications of the integrated microinjectionjmem‐brane potential measurement system are briefly discussed.
Development of Vacuoles and Vacuolar H+‐ATPase Activity under Extremely High CO2 Conditions in Chiorococcum littorale Cells
Authors: Sasaki T. , Pronina Natalia A. , Maeshima M. , Iwasaki I. , Kurano N. , Miyachi S.
Published: February 2008

Abstract: The number and cross‐sectional area of vacuoles in Chlorococcum littorale cells visualized with a differential interfer ence fluorescence microscope increased after their transfer from air to 40% CO2. An immunological observation indicated that the level of subunit B of vacuolar H*ATPase also increased under 40% CO2 conditions. The activity of nitrate‐sensitive ATP‐ase associated with the vacuolar membrane was 2–fold higher in 40% CO2‐‐grown cells than in air‐grown cells. The effects of inhi bitors on the ATPase activity confirmed that these activities were derived from vacuolar‐type H‐ATPase. These results sug gest that vacuole development associated with that of vacuolar H+‐ATPase occurred during the acclimatization of C. littorale cells to extremely high CO2 conditions.
Identification and Characterization of Activating and Conjugating Enzymes of the Ubiquitin System from the Unicellular Alga Chiamydomonas reinhardtii
Authors: Schunn G. , von Kampen J. , NieIänder U. , Wettern M.
Published: February 2008

Abstract: Using a biochemical approach we identified families of ubiquitin‐activating and ubiquitin‐conjugating enzymes in Chiamydomonas reinhardtii. The family of ubiquitin‐activating enzymes, characterized by their ability to form thioesters with ubiquitin and eluting off a ubiquitin affinity column by ATP‐depletion probably consists of at least four members. Whereas one of these enzymes is active under a broad range of pH values, thioesterof the other UBAs with ubiquitin is restricted to pH 7.5. Two ubiquitin‐activating enzymes are metabolically phosphory‐lated which is assumed to be an activity control mechanism. Most of the 7 ubiquitin‐conjugating enzymes detected in this study were found to bind rather tightly to an anion exchange column, and eluted off the column at specific salt concentra tions. Two of the ubiquitin‐conjugating enzymes described here did, however, not bind to this column. These enzymes can, as all other C. reinhardtii ubiquitin‐conjugating enzymes, perform thioester formation with ubiquitin regardless of the source (plant/animal) of the ubiquitin‐activating enzyme.
The Role of Hypocotyl and Roots in Photoperiodic Floral Induction of Chenopodium rubrum
Authors: Vondráková Zuzana , Krekule J.
Published: February 2008

Abstract: Hypocotyls and roots of Chenopodium rubrum were tested as possible receptors of photoperiodic signals inducing flowering. The hypocotyl was found to be responsive to such a signal. Its role as the locus of synthesis andjor the transport sys tem of a florigenic stimulus is discussed. The roots respond to light/dark conditions solely by changing their growth rate but they do not seem to be involved in induction of flowering.
Functional Compartments During Sporangium Development in the Pteridophyte Cyrtomium falcatum (L.f.) Presl as Expressed in Tapetum Function
Authors: Oldenhof H. , Willemse M. I. M.
Published: February 2008

Abstract: The tapetum surrounds the developing sporogenous tissue, and therefore is suggested to have an important role during sporogerlesis. In pteridophytes details about tapetum development and function during sporangium development are poorly known. The current article analyses the leptospor‐angiate development of the pteridophyte Cyrtomium falcatum in terms of functional compartmentalization related to tapetum function. Morphology, development and localization of different compounds during sporangium development are studied. Dur ing C. falcatum leptosporangiate development phases of initia tion, division, differentiation, and maturation are identified. Functional compartments are distinguished by the presence of a callose culture sac during the division and differentiation phase, and a callose spore sac during the differentiation and ma turation phase.
Effects of Sexual Reproduction on Growth and Vegetative Propagation in the Perennial Geophyte Arum italicum (Araceae)
Authors: Méndez M.
Published: February 2008

Abstract: The influences of sexual reproduction on growth and vegetative propagation were analysed in three populations of the geophyte Arum italicum Miller (Araceae). In an observational study using multiple regression, a negative influence of repro duction on tuber mass was detected for two populations. In an experimental study, “control” and “inflorescence removal” treatments were imposed on plants from one of the popula tions. Tuber growth was significantly lower in “control” plants than in “removal” plants, indicating the existence of a somatic cost of reproduction. The somatic cost of reproduction was de creased by an increasing degree of temporal coincidence be tween leaves and reproductive structures on the l)laflt. Neither the observational nor the experimental studies showed any neg ative effect of sexual reproduction on vegetative propagation.
Effects of Nutrient Addition on Community Productivity and Structure of Serpentine Vegetation
Authors: Chiarucci A. , Maccherini S. , Bonini I. , Dominicis V. De
Published: February 2008

Abstract: The effects of a nutrient addition experiment on the plant biomass of garigue vegetation on ultramafic (serpentine) soils in Tuscany, Italy, were investigated. Although community composition was not significantly changed, fertilization had a significant positive influence on biomass production. The most affected species groups were woody species (chamaephytes and phanerophytes), annual grasses and annual forbs; the bio mass increase of the perennial grasses and perennial forbs was statistically not significant. Soil extractable elements differed for calcium and potassium in the plots where they were added; sodium and nickel extractabilities were reduced by calcium ad dition due to the increased soil pH. Biomass production was linked more to major nutrient addition than to reduced nickel extractability, confirming that serpentine vegetation of Tuscany is mainly affected by nutritional stress rather than soil heavy metal content. The addition of calcium had a low effect on pri mary production of these ultramafic soils.
Flow Cytometric Determination of Genome Size in some Old World Lupinus Species (Fabaceae)
Authors: Obermayer Renate , Świecicki W. K. , Greilhuber J.
Published: February 2008

Abstract: Genome size determinations using propidium iodide flow cytometry were conducted in Lupinus anatolicus, L. pilosus, L. luteus, L. hispanicus ssp. hispanicus and L. hispanicus ssp. hispa‐nicus × L. luteus (a complex hybridization product ofL. hispanicus ssp. hispanicus and L. luteus). Using Glycine max“Ceresia” (1C = 1.134pg) and an accession of L. pilosus (1C = 0.649pg) as internal standards the following 1C values were obtained: L. anatolicus: 0.606 pg; L. pilosus: 0.620–0.678 pg; L. luteus: 1.173 pg; L. hispanicus: 1.043 pg; L. hispanicus ssp. hispanicus × L luteus: 1.036 pg. Lupinus anatolicus is a newly described taxon with smooth seeds whose genome is approximately as small as the smallest genomes measured in the related L. pilosus, a taxon with rough seeds. The genomes in the related smooth‐seeded taxa L. luteus, L. hispanicus and L. hispanicus ssp. hispanicus × L. luteus are considerably larger. There is a 1.13‐fold difference between L. luteus (crop) and L. hispanicus (wild). The genome size of L. hispanicus ssp. hispanicus × L. luteus, however, is not intermediate, it is close to L. hispanicus.
Dispersal Patterns of some Phyteuma Species (Campanulaceae)
Authors: Maler A. , Emig W. , Leins P.
Published: February 2008

Abstract: In the genus Phyteurna spadix‐shaped spikes or capitula are composed of xerochasic poricidal capsules, holding unspecialized seeds. Phyteurna betonicifoliurn VILL., Phyteuma hemisphaericum L, Phyteurna scheuchzeri ALL., and Phyteurna spica‐turn L. were examined in wind tunnel experiments to determine the minimum wind speed necessary for seed release, and the relationship between wind speeds and dispersal distances. In a simplified practical simulation the dispersal strategies of these species were described with a leptokurtic curve. The short‐distance seed dispersal of Phyteuma hernisphaericurn allows a limited enlargement of the occupied area, while the seeds of P. scheuchzeri are dispersed more remotely from the mother plant. P. spicaturn and P. betonicifoliurn mainly disperse closely around the mother plant but provide a certain percentage of seeds for colonization of more distant areas. It is demonstrated that the dispersal modes are determined by the characteristics of fruits, infructescences, and seeds. It is also shown that plants with similar morphological organization show different dispersal patterns, which must be interpreted as a fine‐tuned adaptation to the habitat with all its biotic and abiotic factors.
Acclimation of Maximal Quantum Yield of Photosynthesis in the Brown Alga Alaria esculenta under High Light and UV Radiation
Authors: Bischof K. , Hanelt D. , Wiencke C.
Published: February 2008

Abstract: Macroalgae of the upper sublittoral zone of Arctic coastal ecosystems are subjected to darkness or low light for several months during winter and have to withstand large changes in irradiance after the breakup of sea ice in the Arctic spring. Changes in photosynthetic response to high PAR (pho‐tosynthetically active radiation) and UV‐B radiation (UV‐B) in the cold temperate brown alga A/aria esculenta were monitored with a PAM fluorometer to study photoinhibition, recovery and acclimation of maximal quantum yield of photochemistry. Plants collected in the field, as well as specimens raised in the laboratory, were exposed to various radiation conditions including different levels of PAR and UV radiation (UV‐A + UV‐B). Measurements of variable chlorophyll fluorescence of photosystem II revealed that the photosynthetic apparatus in A. esculenta was able to acclimate to the respective high light and UV treatments within several days. However, two different mechanisms of acclimation seem to be involved. Initially, the rate of recovery of maximal quantum yield increased after only a few exposures to high light or UV. Second, after several exposure cycles, the degree of inhibition was reduced. Data on fluorescence induction kinetics and quenching analysis showed that exposure to the respective UV radiation resulted in an increase of non‐photochemical quenching, while effective quantum yield of photochemistry was hardly affected.