bluuebunny/crossref_metadata_2025 huggingface dataset:
High Molecular Weight Organic Compounds in the Xylem Sap of Mangroves: Implications for Long‐Distance Water Transport
Authors: Zimmermann U. , Zhu J. J. , Meinzer F. C. , Goldstein G. , Schneider H. , Zimmermann G. , Benkert R. , Thürmer F. , Melcher P. , Webb D. , Haase A.
Published: February 2014

The rise of sap in mangroves has puzzled plant physiologists for many decades. The current consensus is that negative pressures in the xylem exist which are sufficiently high to exceed the osmotic pressure of seawater (2.5 MPa). This implies that the radial reflection coefficients of the mangrove roots are equal to unity. However, direct pressure probe measurements in xylem vessels of the roots and stems of mangrove (Rhizophora mangle) grown in the laboratory or in the field yielded below‐atmospheric, positive (absolute) pressure values. Slightly negative pressure values were recorded only occasionally. Xylem pressure did not change significantly when the plants were transferred from tap water to solutions containing up to 1700 mOsmol kg−1 NaCl. This indicates that the radial reflection coefficient of the roots for salt, and therefore the effective osmotic pressure of the external solution, was essentially zero as already reported for other halophytes. The low values of xylem tension measured with the xylem pressure probe were consistent with previously published data obtained using the vacuum/leafy twig technique. Values of xylem tension determined with these two methods were nearly two orders of magnitude smaller than those estimated for mangrove using the pressure chamber technique (−3 to −6MPa). Xylem pressure probe measurements and staining experiments with alcian blue and other dyes gave strong evidence that the xylem vessels contained viscous, mucilage‐ and/or protein‐related compounds. Production of these compounds resulting from wound or other artifactual reactions was excluded. The very low sap flow rates of about 20–50 cm h−1 measured in these mangrove plants were consistent with the presence of high molecular weight polymeric substances in the xylem sap. The presence of viscous substances in the xylem sap of mangroves has the following implications for traditional xylem pressure measurement techniques, development of xylem tension, and longdistance water transport: (1) high external balancing pressures in the pressure chamber are needed to force xylem sap to the cut surface of the twig; (2) stable tensions much larger than 0.1 MPa can be developed only occasionally because viscous solutions provide nucleation sites for gas bubble formation; (3) the frequent presence of small gas bubbles in viscous solutions allows water transport by interfacial, gravity‐independent streaming at gas/water interfaces and (4) the increased density of viscous solutions creates (gravity‐dependent) convectional flows. Density‐driven convectional flows and interfacial streaming, but also the very low radial reflection coefficient of the roots to NaCl are apparently the means by which R. mangle maintains water transport to its leaves despite the high salinity of the environment.
Water Relations, CO2 Exchange, Water‐use Efficiency and Growth of Welwitschia mirabilis Hook. fil. in three Contrasting Habitats of the Namib Desert1
Authors: VON Willert D. J. , Wagner‐Douglas Ute
Published: February 2014

CO2 exchange, transpiration and leaf water potential of Welwitschia mirabilis were measured in three contrasting habitats of the Namib desert. From these measurements stomatal conductance, internal CO2concentration and WUE were calculated. In two of the three habitats photosynthetic CO2 uptake decreased and transpiration increased with increasing leaf age while in the third habitat CO2 uptake increased and transpiration decreased with leaf age. Except for the stomata of young leaf sections in this habitat, stomata closed with increasing δw leading to a pronounced midday depression of CO2 uptake. The high stomatal limitation of photosynthetic CO2 uptake of glasshouse‐grown plants was verified in the natural habitat. Photosynthetic CO2 uptake saturated between 800 and 1300 μmol photons m−2 s−1depending on leaf age and habitat. CO2 uptake had a broad temperature optimum declining significantly beyond 32 °C. Predawn leaf water potential reflected water availability and atmospheric conditions in the three habitats and ranged from − 2.5 to − 6.2 MPa. There was a pronounced diurnal course of leaf water potential in all habitats. During the day a gradient in water potential developed along the leaf axis with the lowest potential at the leaf's tip. With respect to whole plant balances of CO2 exchange and transpiration, there were marked differences between Welwitschias in the three habitats. Despite a negative CO2 balance over a period of five months, leaves in the driest habitat grew constantly at the expense of carbon reserves in the plant. Only at the wettest site did carbon gain exceed carbon demand for growth. The WUE of whole plants was insignificant in all habitats. The results were as contrasting as the habitats and plants and did not allow generalisations about adaptational features of Welwitschia mirabilis.
Functional Analysis of the N‐Terminal Prepeptides of Watermelon Mitochondrial and Glyoxysomal Malate Dehydrogenases*
Authors: Lehnerer M. , Keizer‐Gunnik L. , Veenhuis M. , Gietl C.
Published: February 2014

Mitochondrial and glyoxysomal malate dehydrogenase (mMDH; gMDH; L‐malate: NAD+ oxidoreductase; EC 1.1.1.37) of watermelon (Citrullus vulgaris) cotyledons are synthesized with N‐terminal cleavable presequences which are shown to specify sorting of the two proteins. The two presequences differ in length (27 or 37 amino acids) and primary structure. Precursor proteins of the two isoenzymes with site‐directed mutations in their presequences and hybrid precursor proteins with reciprocally exchanged presequences were analyzed for proper import using two approaches, namely in vitro using isolated watermelon organelles or in vivo after synthesis in the heterologous host, Hansenula polymorpha.

The mitochondrial presequence is essential and sufficient to target the mature glyoxysomal isoenzyme into mitochondria (Gietl et al., 1994). As to the function of the mitochondrial presequence a substitution of −3R (considered important for one step precursor cleavage in yeast and mammals) with −3L permitted import into mitochondria but cleavage of the transit peptide and conversion into active mature enzyme was impeded. Substitution of −13R−12S (in a sequence reminiscent of the octapeptide motif serving as a substrate for the mammalian and yeast intermediate peptidase) into −13L12F permitted mitochondrial import and processing like the wild type transit peptide. Purified rat mitochondrial processing protease, which can effect single step cleavage of mitochondrial protein precursors, cleaves in vitro translated watermelon mMDH precursor into its mature form.

The glyoxysomal presequence is essential and sufficient to target the mature mitochondrial isoenzyme into peroxisomes of Hansenula polymorpha, but these peroxisomes lack a processing enzyme to cleave the presequence (Gietl et al., 1994). We here show that isolated watermelon organelles also import the hybrid proteins in vitro and process the glyoxysomal presequence. Site directed mutations within the conserved RI‐X5‐HL‐motif impede efficiency of import and cleavage by watermelon organelles.
Visualization by Freeze‐Fracture Electron Microscopy of Intramembraneous Particles corresponding to the Tonoplast H+‐Pyrophosphatase and H+‐ATPase of Kalanchoë daigremontiana Hamet et Perrier de la Bâthie*
Authors: Mariaux J.‐B. , Becker Andrea , Kemna Inge , Ratajczak R. , Fischer‐Schliebs Elke , Kramer D. , Lüttge U. , Marigo G.
Published: February 2014

The H+‐PPase and the H+‐ATPase of the vacuolar membrane were separated during purification of tonoplast proteins of Kalanchoë daigremontiana Hamet et Perrier de la Bǎthie. Three membrane protein fractions prepared contained firstly, the H+‐PPase protein without any subunits of the H+‐ATPase, secondly, the H+‐PPase protein with only minute traces of the intramembraneous 16 kDa c‐subunit of the H+‐ATPase, and thirdly, the H+‐ATPase subunits without H+‐PPase peptides as verified by SDS‐PAGE. These three preparations were reconstituted into soybean (Glycine max L.)‐phospholipid vesicles, and compared with proteoliposomes obtained by reconstitution of total solubilized tonoplast proteins as well as with native tonoplast vesicles. Analysis of freeze‐fracture replicas prepared from these five different types of vesicles showed that there are two populations of intramembraneous particles, one with a diameter of 6.7‐7.2 nm corresponding to the H+‐PPase, and one with an average diameter of 9.1 nm belonging to the H+‐ATPase. Thus, freeze‐fracture electron microscopy allows one to visualize H+‐PPase particles in addition to H+‐ATPase particles in the tonoplast of Kalanchoë daigremontiana.
Phenotypic Adaptation to Elevated Temperatures of Tonoplast Fluidity in the CAM Plant Kalanchoë daigremontiana is Caused by Membrane Proteins*
Authors: Schomburg M. , Kluge M.
Published: February 2014

Comparative electron paramagnetic resonance spectroscopic studies on spin‐labeled native and protein‐free purified tonoplast membranes in the CAM plant Kalanchoë daigremontiana showed that the phenotypic decrease in tonoplast fluidity occurring upon acclimation to elevated temperature is brought about by specific protein‐lipid interaction. However, there are indications that, to some extent, the properties of the bulk tonoplast lipids may also be affected by acclimation to high temperature. In contrast to heat acclimated individuals and for still unknown reasons, in plants grown at normal temperature depletion of the tonoplast membrane of its proteins had no effect on membrane fluidity. The results are considered as evidence for the occurrence of homeoviscous adaptation in the tonoplast of CAM plants towards changes in the temperature climate during growth.
K+ Gradients in the Pulvinus of Phaseolus coccineus during Leaf Movement*
Authors: Ruge W. A. , Hampp R.
Published: February 2014

We used quantitative histochemistry to investigate the tissue‐specific compartmentation of potassium in the laminar pulvinus of Phaseolus coccineus L. at day and night positions of diurnal leaf movement. The assay was based on the potassium‐dependent activation of pyruvate kinase. Total potassium levels of pulvini were higher in the light than in the dark [0.88 and 0.57mol (kg dry weight)−1, respectively]. Transverse compartmentation of potassium was studied on three tissue slices, representing the middle part, petiolar and laminar sides of individual pulvini. These were dissected further into 10 distinct subsamples (bundle; motor tissues: extensor, flexor; flanks). In the day position the amount of potassium in the extensor was higher than in the night position [1.92 and 1.50 mol (kg dry weight)−1, respectively]. Flexor changes were opposite [1.13 and 1.65 mol (kg dry weight)−1, respectively]. In the day position there was a steep and consistent increase in potassium content from the innermost to the outermost zones of the extensor. In the night position this was much more variable. Comparable gradients were not detected in flexor samples. Here highest amounts of potassium were recovered from the middle of the motor tissue. The data specify distinct tissue regions involved in osmotic adjustment during leaf movement in Phaseolus coccineus.
The Casparian Strip of Clivia miniata Reg. Roots: Isolation, Fine Structure and Chemical Nature*
Authors: Schreiber L. , Breiner H.‐W. , Riederer M. , Düggelin M. , Guggenheim R.
Published: February 2014

The root endodermis of Clivia miniata Reg. was successfully isolated using the cell wall degrading enzymes cellulase and pectinase. The enzymes did not depolymerize those regions of the primary cell walls of anticlinal endodermal root cells where the Casparian strips were located. Since the endodermis of C. miniata roots remained in its primary developmental state over the whole root length, endodermal isolates essentially represented Casparian strips. Thus, sufficient amounts of isolated Casparian strips could be obtained to allow further detailed investigations of the isolates by microscopic, histochemical and analytical methods. Scanning electron microscopy revealed the reticular structure of the Casparian strips completely surrounding the central cylinder of the roots. Whereas in younger parts of the root only the anticlinal cell walls of the endodermis remained intact in the isolates, in older parts of the root the periclinal walls also restricted enzymatic degradation due to the deposition of lignin. Extracts of the isolates with organic solvents did not reveal any wax‐like substances which might have been deposited within the cell wall forming a transport barrier, as is the case with cutin and suberin. However, several histochemical and analytical methods (elemental analysis and FTIR spectroscopy) showed that the chemical nature of the Casparian strips of C. miniata roots can definitely be a lignified cell wall. These findings are in complete agreement with studies carried out at the beginning of this century on the chemical nature of the Casparian strips of several other plant species. The implications of these results concerning apoplasmatic transport of solutes and water across Casparian strips are discussed.
Source‐sink Characteristic of Photoassimilate Transport in Fertile and Sterile Plants of Chara vulgaris L.*
Authors: Schulte C. , Kirst G. O. , Winter U.
Published: February 2014

In cuttings of Chara vulgaris consisting of 3–4 internodal cells with whorls (branchlets) transport of photoassimilates was investigated by 14C‐labelling. The distribution of radioactivity in different component parts of the plant was shown as percentage and calculated in relation to fresh weight. Sucrose was identified as the main transported carbohydrate. In fertile Ch. vulgaris plants, developing oogonia and antheridia were important sinks for transported carbohydrates. Polarity of transport in the internodal cells (nutrients and assimilates) remains constant, as the main characteristic, from base to apex in fertile as well as in sterile plants. In sterile plants, the branchlets being the main source for photoassimilates and the apex the sink, transport from branchlets is mainly in the direction of the internodes. In the case of fertile plants gametangia are additional sinks redirecting transport of assimilates into the branchlets.
Cyanobacteria of Rocks and Soils of the Orinoco Lowlands and the Guayana Uplands, Venezuela
Authors: Büdel B. , Lüttge U. , Stelzer R. , Huber O. , Medina E.
Published: February 2014

The occurrence of 23 cyanobacterial species, belonging to 9 different genera and 5 cyanobacterial lichen species of 5 different genera on exposed, open rock surfaces of inselbergs and on soil in savannas of the Orinoco lowlands and the Guayana uplands is described. Their distribution patterns and frequency within the different habitats are given. The filamentous procaryotic blue‐green algae/cyanobacteria Stigonema ocellatum and Scytonema crassum, together with the unicellular cyanobacterium Gloeocapsa sanguinea were the most frequent species on rocks, whereas the filamentous cyanobacterium, Schizothrix telephoroides, dominated in cyanobacterial mats on the savanna soil. All species showed intensively coloured sheaths, either brown or yellow in the case of Stigonema ocellatum and Scytonema crassum, or red in Gloeocapsa sanguinea and Schizothrix telephoroides. In addition, a number of cyanobacterial lichens occurred.
Precursors of the Cocoa‐Specific Aroma Components are Derived from the Vicilin‐Class (7S) Globulin of the Cocoa Seeds by Proteolytic Processing
Authors: Voigt J. , Biehl B.
Published: February 2014

Essential precursors of the cocoa‐specific aroma components are formed during fermentation of cocoa seeds in the tropics. During the past decades, indications have accumulated that these aroma precursors are derived from seed proteins by acid‐induced proteolysis. This has been recently corroborated by in vitro studies on the formation of the aroma‐related components. It has been shown that the essential proteolysis products are derived from the vicilin‐class (7S) globulins of the cocoa seeds by the cooperative action of an endogenous aspartic endoprotease and a carboxypeptidase.
Electrophoretic Analysis of Genetic Variation within and between Populations of Quercus cerris, Q. pubescens, Q. petraea and Q. robur (Fagaceae) from Eastern Austria
Authors: Samuel R. , Pinsker W. , Ehrendorfer F.
Published: February 2014

Allozyme variation at 14 loci was studied electrophoretically in 19 population samples of Quercus cerris, Q. pubescens, Q. petraea, and Q. robur. Genetic variation, measured as mean heterozygosity, was found to be high within populations but low among populations. A significant deficit of heterozygotes was observed in most of the populations of Q. pubescens, Q. petraea, and Q. robur. At the species level, Q. cerris (sect. Cerris) appears to be clearly separated from the rest (sect. Quercus). Q. pubescens, Q. petraea, and Q. robur form a cluster of closely‐related species. The degree of genetic differentiation among these species is low, i.e. in the range normally found among con‐specific populations. Nevertheless, allozyme data allow the elaboration of a dendrogram which is in reasonable accordance with the taxonomic classification, but also supports the importance of hybridization and introgression. This is also underlined by the fact that the allelic differentiation at the Got‐2 locus corresponds with the phenotypic classification (petraea‐like, hybrids, and robur‐like) in samples from mixed populations.
Atomic Force Microscope Information on Pollen Exine Substructure in Nuphar
Authors: Rowley J. R. , Flynn J. J. , Takahashi M.
Published: February 2014

Images of individual exine units from the tectum of Nuphar luteum (L.) Sm. pollen were made using atomic force microscopy. These units were recorded as being 120 to 160 nm wide. Exine‐units sectioned transversally were circular and had a central circular (core) zone 40 nm or more in diameter. Exine unit‐structures in Nuphar have an outer (binder) substructure coiled around a core zone.
Mitochondrial DNA and its Inheritance in Pleurotus ostreatus and P. pulmonarius
Authors: Fischer M. , Seefelder St.
Published: February 2014

Six stocks each of the basidiomycetes Pleurotus ostreatus and P. pulmonarius were checked for intraspecific polymorphism and inheritance of mitochondrial DNA (mtDNA). Polymorphisms were extensive in both species after digestion with the endonucleases Hae III and Hind III, and they were stock‐specific with one exception. The range of mtDNA sizes was similar for both taxa, lying between approximately 56 kb and 70 kb for P. ostreatus and 60 kb and 78 kb for P. pulmonarius.

The inheritance of mtDNA was uniparental throughout. In pairings of monokaryons exhibiting specific mtDNA types, only one parental mtDNA type was recovered in the resulting dikaryons; while the mitochondria of the donor mycelium spread out, the mitochondria of the recipient mycelium apparently are lost. Certain mtDNA types were more often inherited than others. By examining this dominance of mtDNA types one could establish parentage for both species.
Light‐dependent Proton Excretion of Wheat (Triticum aestivum L.) and Maize (Zea mays L.) Roots
Authors: Gorr G. , Obst G. , Döring O. , Böttger M.
Published: February 2014

We investigated the change of root net proton excretion of seedlings of Triticum aestivum L. and Zea mays L. with daily variation of illumination using a multi‐channel pH‐stat system. We found an increase of net proton excretion during darkness and a drop after the beginning of illumination. Inhibition of carotenoid biosynthesis by norflurazone and photooxidation of chlorophylls did not change the periodicity or its induction. The induction of diurnal periodicity was possible with blue, green and red light. After induction the oscillation of net proton excretion continued for at least two cycles under constant light. We conclude that net H+ excretion of wheat and maize roots may be regulated by an endogenous clock or by a signal from the leaves. The nature of such a hypothetical signal remains unknown.
Oxygen Dependence of Elongation Growth and Oxygen Uptake in Maize Coleoptiles
Authors: Ding Bao‐Lian , Schopfer P.
Published: February 2014

Auxin‐mediated elongation growth of maize coleoptile segments is inhibited by reducing the O2 concentration in the incubation medium to GT 100 μmol . 1−1. The half‐maximal elongation rate is reached at 40 μmol . 1−1 O2, i.e. about two orders of magnitude higher than with mitochondrial respiration. O2 uptake of the segments measured under similar conditions with an O2 electrode shows a very similar dependence on O2 concentration. Auxin increases O2 uptake by 5–10% when it induces growth. About 40% of the O2 uptake is insensitive to inhibition by KCN. Auxin has no effect on O2 uptake in the presence of KCN. The possibility that auxin‐mediated elongation growth depends on a KCN‐sensitive oxidative process, other than cytochrome c oxidase‐catalyzed respiration, is discussed.
Developmental Regulation of Susceptibility and Tolerance to Fusarium Root Rot in Beans
Authors: Vögeli‐Lange Regina , Mohr U. , Wiemken A. , Düggelin M. , Guggenheim R. , Boller T.
Published: February 2014

The soil‐borne fungus, Fusarium solani f. sp. phaseoli, attacks roots and hypocotyls of bean (Phaseolus vulgaris) plants causing a devastating disease called root and foot rot. In a study of the host‐pathogen relationship it was found that young bean roots, with the radicle just emerging, were highly tolerant to the pathogen, whereas older bean seedlings, with a fully developed root system, were completely susceptible. Investigations by low‐temperature scanning electron microscopy demonstrated that significantly fewer spores and hyphae were present on the root surface of young bean seedlings as compared to older ones. A similar pattern of attachment was found when bean roots were inoculated with spores of F. solani f. sp. pisi, a related pathogen causing disease on peas but not on beans. Light microscopic studies showed that F. solani f. sp. pisi did not penetrate the root but rapidly formed thick‐walled resting spores on the root surface. F. solani f. sp. phaseoli on the other hand quickly penetrated the root and formed an extensive network of fungal hyphae. These results demonstrate that the ability of fungal propagules to adhere to and to penetrate host tissues are two distinct processes. Furthermore, the data indicate that young bean roots lack a surface component necessary for attachment of fungal spores which may help explain their tolerance to Fusarium root rot.
A Flow Cytometric Analysis of the Nuclear 2C DNA Content in 17 Phaseolus Species (53 Genotypes)
Authors: Nagl W. , Treviranus A.
Published: February 2014

The genus Phaseolus is characterized by a highly stable karyotype of 2n = 22. Despite this constancy, the size of the chromosomes varies, and crossing of species is possible only in a few cases. We determined the 2C nuclear DNA content of a number of Phaseolus species, cultivars and genotypes by flow cytometry, in order to realize the interspecific and intraspecific variation of the 2C value. The data range from 1.03 pg to 2.18 pg without any clear correlation to systematic relationships. The mean DNA values of wild and cultivated forms, as well as those of Andean and Mesoamerican genotypes, do not differ significantly. The variation is interpreted in terms of some nucleotypic adaptations. The data may be useful for molecular biological analyses, as well as for biotechnological and classical breeding programmes.
Phenotypic Plasticity in the Annual Weed Polygonum aviculare
Authors: Meerts P.
Published: February 2014

Reaction norms of fourteen life history and morphological traits were investigated in four tetra‐ and two hexaploid genotypes of the annual weed species complex, Polygonum aviculare. The plants were cultivated in six treatments consisting of factorial combinations of three pot sizes and two fertility levels. All characters, except life span, were plastic but the relative importance of genotype (G), treatment (T) and interaction (G × T) to total variance was strongly trait‐specific. Consistent genetic differentiation, not correlated with ploidy level, was found in metamer size and life history: genotypes originating from trampled sites had smaller metamers and shorter shoots while those originating from sites with a short growing season, due to weeding activities, had a shorter life span, an earlier flowering date and a higher biomass allocation to reproduction compared to genotypes from less disturbed sites. Significant variation was found in reaction norms for all characters, including a lower amount of plasticity in metamer size in genotypes with numerous metamers and a lower amount of plasticity in total weight in shortlived genotypes. This suggested that variation in phenotypic plasticity reflected developmental constraints imposed by contrasting life span and metamer size in different genotypes. There was no evidence for niche differentiation along the soil resource gradient, suggesting that the species is comprised of “general purpose” genotypes with respect to soil fertility. It is concluded that the Polygonum aviculare complex has evolved a “dual” adaptive strategy i.e. a combination of genetic polymorphism and high phenotypic plasticity.
Molecular Cloning of emip, a Member of the Major Intrinsic Protein (MIP) Gene Family, Preferentially Expressed in Epidermal Cells of Barley Leaves
Authors: Hollenbach Beate , Dietz K. ‐J.
Published: February 2014

Cloning and characterization of a barley gene named emip is reported that encodes a member of the major intrinsic protein family. A λ‐unizap cDNA library synthesized from poly A+−mRNA of leaf epidermis was screened differentially with epidermis‐versus mesophyll‐derived probes. One of the clones epi 3‐2 was sequenced and further analyzed. The open reading frame of the full length clone codes for a polypeptide of 288 amino acids with a molecular mass of 30,634 Da exhibiting a high degree of homology with members of the major intrinsic protein family. Hydropathy analysis predicts six potential membrane‐spanning helices. mRNA levels were high in the growing zone of barley leaves and declined towards the tip of the fully expanded leaf blade. Expression was high in epidermal strips, lower in roots and very low in the leaf mesophyll. In order of decreasing response, wilting, salt shock and heat shock resulted in stimulated expression. mRNA levels remained low during slow salting up experiments. The expressional pattern suggests a role of EMIP in turgor regulation, particularly under stress.
Consumption of Carbonyl Sulphide by Chlamydomonas reinhardtii with Different Activities of Carbonic Anhydrase (CA) Induced by Different CO2 Growing Regimes
Authors: Protoschill‐Krebs G. , Wilhelm C. , Kesselmeier J.
Published: February 2014

The green alga, Chlamydomonas reinhardtii, was grown under high and low CO2 regimes inducing significantly different activities of the extracellular carbonic anhydrase (CA). In close relation to the CA activities, the algae exhibited different consumption rates of the climatically relevant atmospheric trace gas, carbonyl sulphide (COS), thus indicating that CA is responsible for uptake of COS from the medium.
Primary and Lateral Root Development of Dark‐ and Light‐Grown Cotton Seedlings under Salinity Stress*
Authors: Reinhardt D. H. , Rost T. L.
Published: February 2014

Primary root growth dynamics and lateral root development of dark‐ and light grown cotton seedlings (Gossypium hirsutum L., cv. Acala SJ‐2) were studied under control and salinity stress conditions. The seedlings were grown by two methods: A) in paper‐lined, vermiculite‐filled beakers with the plants growing between the paper and the glass wall (Gladish and Rost, 1993), and B) in hydroponics after germination and initial growth in germination paper rolls saturated with the treatment solutions (Kent and Läuchli, 1985). After germination, daily primary root elongation rate gradually incrased to a maximum, then gradually declined to close to zero for dark‐grown seedlings, or to sustained rates of about 10 mm per day for light‐grown control plants. Salinity stress delayed primary root growth and reduced peak elongation rates, without changing the general primary root growth pattern. These results suggest that salinity changed the time‐scale, but did not modify the normal developmental sequence. Lateral root growth was more inhibited by salinity than primary root growth. In addition, elongation of lateral roots was more inhibited by salinity than their initiation and emergence. Light exposure of the shoot favored both sustained primary root growth from 7 days after planting, and lateral root emergence and growth. Salinity effects were more severe on seedlings germinated and grown in hydroponics (method B) than on vermiculite‐grown plants (method A). These results emphasize the importance of growing conditions for the NaCl‐induced effects on cotton root development. In addition, the differential effects of salinity on primary and lateral roots became evident, pointing to diverse control mechanisms for the development of these root types.
Cytological Investigations of Lithobiontic Microorganisms in Granitic Rocks
Authors: Ascaso C. , Wierzchos J. , de los Ríos A. A.
Published: February 2014

This paper shows the ultrastructure of lithobiontic organisms in a granitic rock from the exterior to the interior, where fissures are found 1–2 mm from the surface. There is clear differentiation at cell level between mycobiont and photobiont cells located on the rock surface which forms part of the lichen thallus and prokaryotic and eukaryotic cells (algae and fungi) found in the fissures. As well as the observations at the ultrastructural level of the microorganisms which live in fissures and cavities, immunolabelling techniques with colloidal gold have been applied to obtain an immunolocalization of Rubisco enzyme in some of the cells. The technique applied here permits Rubisco enzyme to be identified in algae‐like cells belonging to fissures where it is difficult to identify the pyrenoid. The mineral environment of the cells situated inside the fissures is investigated by Energy Dispersive Spectrometry (EDS). The biotite particles present in the fissure walls, as well as some lithobiont microorganisms, show a depletion of potassium from interlayer positions.
Photoautotrophic Cell Suspension Cultures from Mesembryanthemum crystallinum and their Response to Salt Stress
Authors: Willenbrink M. E. , Hüsemann W.
Published: February 2014

For the first time, photoautotrophic cell suspension cultures of Mesembryanthemum crystallinum have been established. The cells are growing in a sugar‐free culture medium in the presence of 2 % (v/v) CO2 as the sole carbon source. A 16 h light photoperiod is applied. Increase in fresh and dry weight during a 21 days growth cycle was more than 3‐fold. Treatment of the cells with 200 mM NaCl from day 10 to day 21 of subculture stimulated cell culture growth, enhanced CO2 fixation and elicited an increase in the extractable activities of enzymes related to CO2 fixation (RubisCO; PEP carboxylase) and malic acid metabolism (NAD / NADP dependent malic enzyme and malic acid dehydrogenase). The cells performed osmotic adjustment to high salinity by uptake of K+, Na+, Cl− and formation of proline as well as by a reduction in cell size. Although sugar and starch content of the cells changed during light/dark transition, a CAM‐related diurnal fluctuation of malic acid was not observed.
Nucleus Basal Body Connector of Dunaliella: Threshold Concentration of Calcium Necessary for in vitro Contraction*
Authors: Merten P. , Lechtreck K.‐F. , Melkonian M.
Published: February 2014

Detergent‐isolated flagellar apparatuses of the flagellate green alga Dunaliella bioculata retain remnants of the nucleus (the karyoskeleton) which are linked to the basal bodies by the centrin‐containing nucleus basal body connectors (NBBC). Such complexes were subjected to different calcium concentrations (1 × 10−9 M − 5 × 10−4 M Ca2+) and the distance between the basal bodies and the karyoskeleton was measured by light microscopy. The threshold concentration of Ca2+ for NBBC contraction was determined to be around 5 × 10−8 M Ca2+. At > 10−7 M Ca2+ NBBC were maximally contracted and the distance between the basal bodies and the karyoskeleton was only about 50% of the initial distance. Using a polyclonal antibody generated against centrin (Salisbury et al., 1984), the NBBC were visualized by indirect immunofluorescence in both the extended and contracted state. Our results demonstrate that in vitro contraction of centrin‐containing filaments in green algae is initiated at about the same free Ca2+ concentration in three different centrin‐containing basal apparatus components (i.e. the distal connecting fibre, the flagellar transitional region and the NBBC).
Proton Efflux from the Outer Layer of the Peduncle of Tulip in Gravitropism and Circumnutation*
Authors: Hejnowicz Z. , Sievers A.
Published: February 2014

Epidermal plus hypodermal peels from tulip peduncles produced bands of acidity on agar containing bromocresol purple. Peels from horizontally oriented peduncles gave rise to an acidity band which corresponded to the lower side of the peduncle. The band began 3–6 cm beneath the flower and extended basipetally within the region of gravitropic bending. No corresponding band appeared in an agar layer laid on the cortical surface exposed by peeling. Peduncles growing in the normal vertical position showed circumnutations with a period in the range of 4 h. The peels from these stalks produced one or two bands more acid than the remaining part of the peel. Since the acidity band in horizontally positioned stalks corresponds to the zone of faster growth causing gravitropic bending, we infer that the band(s) produced by vertical stalks also correspond to zones of differential growth involved in circumnutation. On the basis of a previous finding that tulip leaves give rise to an oscillating acidity pattern, we infer that vertical stalks also show such a pattern. This inference fits the model proposing the involvement of an internal oscillator in circumnutation. However, the ratio of the circumnutation period to the gravitropic lag phase in tulip peduncles is such as predicted by the gravitropic‐feedback model of circumnutation.
Regulation of Glutathione Synthesis in Suspension Cultures of Parsley and Tobacco*
Authors: Schneider St. , Bergmann L.
Published: February 2014

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

Electron microscopical investigations of primary haustoria of Orobanche crenata parasitizing the roots of the highly compatible host, Vicia narbonensis, reveal an uninterrupted phloem system connecting both partners. Individual sieve elements belonging to the host and parasite could be identified by the cell markers: plastids, mitochondria and P‐protein, which in the present system turned out to have species‐specific fine structure.

Sieve pores of normal structure interconnect the sieve elements of host and parasite. They originate from interspecific plasmodesmata.
Concanamycin 4‐B: A Potent Inhibitor of Vacuolar pH Regulation in Chara Cells
Authors: Tazawa M. , Okazaki Y. , Moriyama Y. , Iwasaki N.
Published: February 2014

Concanamycin 4‐B, a macrolide antibiotic with an 18‐membered lactone ring, is known as a specific inhibitor of the vacuolar type of H+‐ATPase, as is bafilomycin A1. The drug was tested for its effect on regulation of the vacuolar pH (pHv) of internodal cells of a fresh water characean alga, Chara corallina, under normal conditions and under salt stress. The pHv was measured either on isolated vacuolar sap with a conventional pH electrode or directly by inserting a pH‐sensitive glass microelectrode into the vacuole. Proton‐pumping into tonoplast vesicles was almost completely inhibited by concanamycin 4‐B at 1 nM.

Concanamycin 4‐B at 1 μM significantly increased pHv while bafilomycin A1 was ineffective when applied at 1 μM. Concanamycin 4‐B did not affect pHv when applied at 0.1 μM and increasing the concentration to 10 μM did not amplify the degree of alkalization.

Concanamycin 4‐B also inhibited pHv regulation under NaCl stress. When Chara cells were treated with 100 mM NaCl, pHv promptly increased and then recovered to the original level. The reacidification was completely inhibited by concanamycin 4‐B (1 μM), suggesting that the reacidification was achieved by the H+‐ATPase of the tonoplast.
Characterization of the Carotenoidless Strain of Scenedesmus obliquus, Mutant C‐6E, a Living Photosystem I Model*
Authors: Römer Susanne , Senger H. , Bishop N. I.
Published: February 2014

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

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

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

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

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

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

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