bluuebunny/crossref_metadata_2025 huggingface dataset:
Drought‐induced Short Roots in Arabidopsis thaliana: Structural Characteristics
Authors: Couot‐Gastelier Jeanne , Vartanian Nicole
Published: February 2014

In Arabidopsis thaliana, as in other Brassicaceae species, a progressive drought stress induced changes in root morphogenesis: from a threshold plant water deficit, the new emerging roots remain short, hairless and often take a tuberized shape at their base while drought persists. The organization of these drought‐induced roots was examined in light microscopy in Arabidopsis thaliana, Columbia wild‐type ecotype, and compared to the normal, well‐watered lateral roots. The main structural traits were the absence of elongation zone, the arrest of cell cap expansion, the lack of root hairs (despite epidermal differentiation in trichoblasts and atrichoblasts) and the radial enlargement of epidermal and cortical cells. The early differentiation, close to the short root apex, of large and highly lignified metaxylem elements, the absence of starch accumulation in hypertrophied cortical cells appeared to be characteristic of the species Arabidopsis, as compared to other Brassicaceae. These structural alterations are discussed in terms of drought‐induced changes in gene expression with regard to similar modifications described in root morphogenesis and root hair‐defective Arabidopsis mutants.
Responses of Calcicole and Calcifuge Poaceae Species to Iron‐Limiting Conditions
Authors: Gries D. , Runge M.
Published: February 2014

Six differently distributed Poaceae species were compared in order to identify morphological and/or physiological properties that ensure calcicole species but not calcifuge species a sufficient Fe supply on CaCO3 rich soils.

When grown at a range of FeEDTA supply from deficient to adequate, the calcicole species had higher Fe productivities and relative yields at low Fe supply than the calcifuges. Specific root surface and Fe uptake requirements were lower in calcicoles than in calcifuges.

Root exudation of Fe‐mobilizing compounds was monitored in plants grown either with or without added FeEDTA in hydroponic culture. Under Fe deficiency, typically more than 80% of soluble root exudates of Poaceae are phytosiderophores (Marschner et al., 1989; Römheld, 1987). Maximum exudation rates of Fe mobilizing compounds were 6.6 to 11.5 μmol g−1 root dry wt 2 hr−1 in calcicoles and 0.48 to 1.64 in calcifuges. If Fe requirement is defined as mean Fe uptake rate required for 90 % of the maximal relative growth rate, the exudation rates of Fe mobilizing compounds were at least 11.7 to 31.9 times higher than Fe requirements in calcicoles and 0.38 to 5.36 times higher in calcifuges.

Growth response to a precipitated versus a chelated Fe source was determined. The relative ability to grow with Fe(OH)3 precipitate was correlated with the Fe mobilization rate of the species. The present results give evidence for the importance of Fe efficiency in wild plants. Calcicoles are able to live on calcareous soils partly because they produce larger amounts of Fe mobilizing compounds and have lower tissue Fe requirements than calcifuges.
Net Uptake of Sulfate and its Transport to the Shoot in Spinach Plants Fumigated with H2S or SO2: Does Atmospheric Sulfur Affect the “Inter‐Organ” Regulation of Sulfur Nutrition?*
Authors: Herschbach Cornelia , De Kok L. J. , Rennenberg H.
Published: February 2014

Spinach plants (Spinacea oleracea L. cv. Estivato) were grown on nutrient solutions under deficient, normal and excess sulfate supply. In both young and mature plants net uptake of sulfate and its transport to the shoot increased with increasing sulfate supply, but both processes proceeded at a higher rate in young as compared to mature plants. The relative sulfate transport, i.e. the relative amount of the sulfate taken up that is transported to the shoot, decreased with increasing sulfate supply. Apparently, net uptake of sulfate is not strictly controlled by the sulfur demand of the shoot, but xylem loading appears to counteract excess transport of sulfate to the shoot.

Fumigation with H2S or SO2 reduced net uptake of sulfate by the roots in sulfur‐deficient plants and absolute as well as relative sulfate transport to the shoot independent of the three sulfate levels supplied to the plant. At the same time thiol contents of the shoot and the root were enhanced by fumigation with H2S and SO2. These findings are consistent with the idea that thiols produced in the leaves can mediate demand‐driven control of sulfate uptake by the roots and its transport to the shoot.
The Function of Phloem Connections in Regenerating In Vitro‐Grafts*
Authors: Schöning U. , Kollmann R.
Published: February 2014

In order to answer the question whether functioning phloem connections exist between graft partners, phloem transport has been studied in cultured explant‐grafts after application of 14C‐sucrose and carboxyfluorescein (CF) to the scion. Autografts of Lycopersicon esculentum and Helianthus annuus were investigated at various regeneration periods. Ungrafted internodes served as controls.

A segmental analysis was used to determine the tissue distribution of 14C‐sucrose in a graft. The 14C‐profiles obtained show that sucrose translocation across the graft interface started 4 days after grafting and increased later. The observed translocation appears to occur via wound phloem, since at this time the first complete wound‐phloem bridges (shown as files of aniline‐blue‐positive sieve plates) traverse the graft interface. In 7‐d‐old autografts, sucrose transport across the graft interface returned to normal again, as indicated by the distribution of the label. In addition, 14C‐profiles reveal accumulation of label in sink tissues. Here the basal callus of the stock, and temporarily the graft union itself, represent the main sinks for labelled sucrose.

Translocation of CF was analyzed in hand sections of the grafts. The beginning of translocation into the stock was confirmed with the dye. Moreover, effective phloem translocation across the graft interface, visualized with CF, could undoubtedly be assigned to wound‐phloem bridges reconnecting the cut vascular bundles of scion and stock. Thus, the function of phloem connections in regenerated in vitro‐grafts is directly shown.
Changes in Chloride Fluxes and Cytosolic pH Induced by Abscisic Acid in Elodea densa Leaves
Authors: Beffagna Nicoletta , Romani Giulia , Gatti Lucia
Published: February 2014

The effects of ABA on intracellular pH, net H+ extrusion, Cl− fluxes and Em values were studied in Elodea densa leaves, and the possible relationships between the ABA‐induced changes of cytosolic pH and of Cl− and H+ fluxes were investigated. Cytosolic and vacuolar pH were calculated by the weak acid and weak base distribution method. The data show that, also in this material (a water plant without stomata), ABA induces a decrease in both net H+ extrusion and intracellular pH, and strongly inhibits Cl− efflux. No significant effect of ABA is detectable on Em values, either at short or long intervals in the presence or absence of K+. Cl− efflux is apparently independent of the activity of the plasmalemma H+ pump and of the Em values. Conversely, it strongly depends on the value of cytosolic pH, a larger efflux occurring for the lower pH values both in the presence and in the absence of ABA. These results indicate that the ABA‐induced cytosolic acidification cannot be the cause but, possibly, a consequence of the decrease in Cl− efflux, and are consistent with the hypothesis of a primary role of ABA in regulating Cl− efflux, presumably by directly affecting a class of Cl−‐permeable channels.
Root Browning in Pinus banksiana Lamb. and Eucalyptus pilularis Sm. 1. Anatomy and Permeability of the White and Tannin Zones
Authors: McKenzie B. Elizabeth , Peterson Carol A.
Published: February 2014

Growing tree roots are characteristically brown with white tips. The browning process, which occurs as the white region matures, has often been attributed to the deposition of suberin in various tissues. However, in pouch‐grown tree seedlings of jack pine (Pinus banksiana Lamb.) and eucalyptus (Eucalyptus pilularis Sm.), browning was not linked to suberization but was caused by the deposition of condensed tannins in the walls of all cells external to the stele. Therefore, we propose using the term “tannin zone” to refer to this region of the root. Vitality tests indicated that the cells of the epidermis and cortex were alive in white regions but were dead in brown regions. Following sequential treatment with berberine hemisulfate and potassium thiocyanate, the cortical walls external to the endodermal Casparian band were full of berberine thiocyanate crystals, indicating that they were permeable to berberine. These walls should also be permeable to water and ions, which have smaller molecular dimensions than the tracer dye. Based on the anatomy and permeability of the tannin zone, we predict that its capacity for ion uptake would be reduced compared to the white zone because of a reduced absorptive plasmalemma surface area. In jack pine, some uptake could be effected by the passage cells of the endodermis. The tannin zone should be even less absorptive in eucalyptus because the exodermis remains an apoplastic barrier and the endodermis lacks passage cells. It is difficult to predict the difference between the tannin and white zones with respect to water uptake. Death of the cells external to the endodermis would reduce the resistance of the root to water movement, but deposition of tannins would increase it. The deposition of suberin lamellae in increasing numbers of endodermal cells may also retard water flow. The anatomy and physiological properties of the tannin zone are unique from those of the distal, white zone and the proximal, cork‐clad zone.
Calcium, Calcium Oxalate Crystals, and Leaf Differentiation in the Common Bean (Phaseolus vulgaris L.)*
Authors: Zindler‐Frank Elisabeth
Published: February 2014

Young plants of Phaseolus vulgaris were grown in nutrient solutions at different levels of calcium concentration. When the calcium concentration was low more palisade parenchyma and less extended bundle sheath was formed at the adaxial side of minor veins of the leaves as compared to leaves of plants grown with higher calcium supply. The number of calcium oxalate crystals in the bundle sheath extensions was positively correlated to the amount of calcium fed to the plants. The ion induces additional cell divisions in the bundle sheath extensions. A high supply of calcium leads to the formation of a second type of crystal in the bundle sheath.
Flagellar Photoresponses of Chlamydomonas Cells Held on Micropipettes: III. Shock Response
Authors: Rüffer Ursula , Nultsch W.
Published: February 2014

Using high‐speed microcinematography flagellar shock responses of a great number of Chlamydomonas cells, free‐swimming as well as immobilized on micropipettes, were investigated in this study. Responses were elicited by flashes, by blue, red or white light steps or occurred “spontaneously”. A large variety of shock responses has been found, in part due to various kinds of flagellar deactivations. Typical courses of flagellar responses are described in detail. The major part of the analyzed responses consists of a transition back from undulatory beats, characteristic for shock responses, to the normal breaststroke beats, probably as a result of a decreasing Ca++ concentration at the axoneme. It is known that undulatory beats are triggered by a transient strong influx of Ca++ ions into the flagella. Responses are initiated simultaneously in the two flagella but are finished independently. Differences in cis (= next to the stigma) and trans (= far from it) flagella were observed but were not consistent. The origin of the deactivations during the shock responses is discussed, as well as an involvement of basal body‐associated structures in flagellar beating and in the change between the two beating modes. The comparison of the two fundamentally different types of beating and a close study of transitional beats may convey insight into the complexity of flagellar beating in Chlamydomonas.
Effects of Ri T‐DNA from Agrobacterium rhizogenes on Growth and Hyoscyamine Production in Datura stramonium Root Cultures
Authors: Piñol M. T. , Palazón J. , Cusidó R. , Serrano M.
Published: February 2014

Transformed root lines of Datura stramonium were established following infection of aseptic stem segments with Agrobacterium rhizogenes strain A4. These root lines were examined for their alkaloid productivity in relation to growth rate and the presence in the nuclear genome of rol(A, B and C) and tms genes. The amount of polypeptides coded by rolB and rolC genes, and the transcript levels of rolA, rolB and rolC genes were also investigated. Southern blot analysis using [32P]‐la‐belled fragments of the T‐DNA as probes, revealed the lack of tms genes and the presence of the three rol genes in the genome of the all root lines. The growth rates of these transformed root lines were not always correlated with their hyoscyamine biosynthesis ability. However, all transformed root lines, showed a positive correlation between hyoscyamine production and the level of polypeptide coded by rolC gene.
Population‐specific Traits and their Implication for the Evolution of a Drought‐adapted Ecotype in Armeria maritima
Authors: Köhl Karin
Published: February 2014

Traits contributing to drought resistance of Armeria maritima were investigated by comparing six populations of this species from sandy grasslands, heavy metal mines and salt marsh sites. The sandy soil ecotype that is influenced by periodic drought was found to allocate constitutively a higher proportion of biomass to the root system, especially to the fine roots, than the other two ecotypes. The selective advantage of this lower shoot‐root ratio is presumably the delayed onset of the critical water saturation deficit because of the ability to take up additional water from deeper soil layers. Under water stress, all populations of A. maritima showed a decrease in the shoot‐root ratio. Additionally, under moderate long‐term water stress a decrease in (= more negative) osmotic potential was found in leaves of plants from all populations. Lowest osmotic potentials were shown by the salt marsh ecotype and the highest by one of the heavy metal populations. Osmotic adjustment was achieved passively by a reduction in osmotic volume. Accumulation of osmotically active compounds was seen only under severe water stress, when the considerable betaine contents found in all populations of A. maritima even under control conditions were further increased by severe drought. The evolution of traits related to drought adaptation in the sandy soil ecotype of A. maritima is discussed.
Pollen in Bee‐Flower Relations Some Considerations on Melittophily*
Authors: Westerkamp Ch.
Published: February 2014

Pollen and nectar are usually lumped together as floral rewards for pollinating bees, but they play totally different roles for flowers and bees (Table 1), as well as in the relationship between them. While flowers are specialized for certain pollinators via nectar, bees specialize on certain flowers via pollen. While flowers need pollen as a prerequisite for pollination, it is the essential larval food in bees. Thus, there is a strong competition between them for pollen. Foraging for pollen must be divided into three phases: uptake in the flower, reloading into and homeward transport within a carrying container. Bees have specializations for transport but hardly any for pollen uptake ‐ and thus for pollination. Bees actively harvesting pollen usually do not pollinate. This only happens as a consequence of contamination of the bee by pollen. From these data a scenario is provided for the evolution of bees and bee flowers. Specialized bee flowers are often characterized by their ability to hide pollen from the bees and at the same time use them as optimal pollinators. If the relationship of bees and flowers is mutualistic at all it is best described as a balanced mutual exploitation.
Form‐Pfs Plastids, Stem Anatomy and Systematic Affinities of Stylobasium Desf. (Stylobasiaceae)
Authors: Behnke H.‐D. , Kiritsis Ute , Patrick Susan J. , Kenneally K. F.
Published: February 2014

The vascular system of the stem of Stylobasium was investigated during its primary and secondary phases with both light and electron microscopic methods. It contains collateral bundles arranged in a ring, separated by rays which undergo regular cambial growth. The phloem consists of short sieve elements connected to sieve tubes by simple sieve plates, companion cells of the same length, and phloem parenchyma cells. During their autophagy‐like differentiation and maturation, typical of all angiosperms, the sieve elements of Stylobasium have a peculiar feature, whereby they develop and retain form‐Pfs plastids (containing protein filaments and starch). The sieve‐element plastids of the two Stylobasium species, and of some 100 species belonging to taxa of which Stylobasium had been considered to be a possible member, have been studied by transmission electron microscopy. With the exception of a few species with form‐Pcs plastids (containing a single small protein crystal in addition to starch), the great majority of taxa studied are characterized by S‐type sieve‐element plastids (containing starch only). The presence of form‐Pfs plastids in Stylobasium supports its separation into the unigeneric Stylobasiaceae and the placement of this family close to other form‐Pfs or form‐Pcfs‐containing taxa. While other characters would exclude an affiliation to the Magnolianae (form‐Pfs plastids in Canella) or Caryophyllales (form‐Pfs plastids in Microtea), an association with the form‐Pcfs families Connaraceae and Mimosaceae is positively considered and corresponds to their frequent allocation close to the Rutales and Sapindales. Within the Rutales/Sapindales the sizes of sieve‐element plastids (average diameter) range from very large (e.g. in the Julianaceae) to comparatively small (e.g. in Aceraceae) and are used to group the families. The sieve element characters of the Coriariaceae (tiny plastids with almost no starch, wide sieve plate pores, copious P‐protein) suggest their removal from Rutales/Sapindales into the neighbourhood of the Cucurbitaceae.
Distribution of the Character States “Early Sympetaly” and “Late Sympetaly” Within the “Sympetalae Tetracyclicae” and Presumably Allied Groups*
Authors: Erbar Claudia , Leins P.
Published: February 2014

Within the Asteridae (“Sympetalae Tetracyclicae”) two main developmental patterns can be distinguished as regards the formation of corolla tubes, namely “early” and “late sympetaly”. Since the character “ontogeny of sympetaly”, after intensive studies, proved to be valuable for systematic considerations, we now recognize two blocks of orders within the Asteridae (and related groups): the Asteridae A‐block and the Asteridae B‐block (Figs. 82 and 83). By and large this bipartition referring mainly to the corolla tube development corresponds well with major lineages indentified by recent molecular data (see, e.g., Chase et al., 1993). Asteridae A‐block is characterized predominantely by “late sympetaly” the “early sympetaly” in Rubiales and Oleales can be interpreted as derived within this block or can be linked with that in Asteridae B‐block. Asteridae B‐block is uniform throughout in its “early sympetaly”. In this block it is a primitive character, as judged from its occasional occurrence in the choripetalous Cornales and Apiales (Apiaceae, Araliaceae, Pittosporaceae), which can be regarded as ancestral for block B.
Experimental Studies on the Competitive Balance Between two Central European Roadside Grasses With Different Growth Forms
Authors: Ryel R. J. , Beyschlag W. , Heindl B. , Ullmann I.
Published: February 2014

The weakly‐competitive grass, Puccinellia distans (Jacq.) Parl., and the highly competitive grass, Elymus repens (L.), coexist on roadsides in Central Europe which are regularly mowed. The effect of mowing on this existence was evaluated in situ at the roadside and in experimental field plots under non‐limiting water and nutrient conditions. In four experimental garden plots, tussocks of P. distans were transplanted into monocultures of E. repens early in the growing season. After establishment, two of the plots were mowed and two left unmowed. In the unmowed plots, P. distans was quickly overtopped and died, while in mowed plots, P. distans was able to persist throughout the growing season. Despite persistence in the mowed plots, the number of tillers of P. distans declined throughout the growing season as numbers of tillers of E. repens increased. It was concluded that mowing could enhance coexistence in situations of unlimited nutrients and water where the faster growing and aggressive E. repens would exclude P. distans without mowing. At the roadside, six plots were established at a site containing both species early in the growing season. Weekly mowing was performed on three of the plots while the others were left unmowed. In mid‐July, when the grasses were beginning to senesce and had produced seed‐heads, foliage area for P. distans was significantly higher in the mowed than the unmowed plots while the reverse was true for E. repens. While P. distans had higher foliage area in the mowed plots, it was able to persist to seedhead production in the unmowed plots. Simulations conducted with a multispecies canopy photosynthesis model indicated that reductions in carbon gain for P. distans due to shading by foliage of E. repens did not correspond well with foliage area for P. distans at the start of experiment or in the mowed and unmowed plots in mid‐July. In both the mowed and unmowed plots, the portion of foliage consisting of P. distans increased with closeness to the roadway and corresponded inversely with soil depth. At soil depths of greater than 15 cm, P. distans did not occur. More effective exploitation of shallow soil may shift the competitive balance toward P. distans and be a significant factor in the coexistence of these two species in the shallow soils at the roadside. Differences in leaf temperatures at the roadside that might result from different leaf widths were also evaluated. The narrower‐leaved P. distans was hypothesized to have lower midday leaf temperatures at sites close to the asphalt and perhaps be closer to the temperature optimum for photosynthesis during warm summer days. In situ leaf temperature measurements made with small thermocouples attached to intact leaves, however, were not significantly different for the two species, and coexistence was not likely to be affected by leaf temperatures.
Rapid Effects of Boron Deficiency on Cell Wall Elasticity Modulus in Cucurbita pepo Roots
Authors: Findeklee P. , Goldbach H. E.
Published: February 2014

Rinsing roots of Cucurbita pepo with an essentially boron‐free nutrient solution results in a significant reduction of the cell wall elasticity modulus as determined by the cell presure probe (measuring always in the same cells). This points to a role of boron in crosslinking cell wall macromolecules. Longer exposure to boron deficient conditions, however, increased again and above the initial values. This trend became visible between 20 and 30 minutes after starting the deficiency treatment. There is no indication for a loss of turgor during the time course of the experiments, suggesting that boron primarily affects cell wall physical properties and that membrane leakiness, as observed by other groups, is a secondary event. Several testable hypotheses for the action of boron are presented.
Protein Synthesis in Euglena gracilis is Light‐and Temperature‐Dependent, Oscillating in a Circadian, Temperature‐Compensated Manner
Authors: Künne A. , De Groot E. J.
Published: February 2014

Abstract: Incorporation of radiolabelled amino acids into proteins of Euglena gracilis revealed that the amount of labelled protein depends on the conditions of illumination and temperature of cultivation. Protein synthesis was generally lower under dark conditions except at 37 °C. The largest amounts of labelled protein were measured at 21 °C and decreased at higher and lower temperatures. By separating the labelled proteins of the membraneous cell fraction from subcultures under a range of culture conditions, the synthesis of some specific proteins was found to be light‐ and/or temperature‐dependent. On incubating cells taken at different times during a light/dark cycle and under constant conditions, a circadian rhythm of 35S‐methionine‐ as well as 35S‐cysteine‐incorporation was detected. Thereby the cells incorporated ten‐times less cysteine than methionine. Protein synthesis always peaked during the last quarter of the daily light phase, confirming the rhythmic rise in total protein. The length of the rhythm period, approximately 24 h, was nearly independent of the applied temperature in the range of 16 to 27 °C.
Flow Cytometric Analysis of the Different Ploidy Levels Observed in the Genus Ulex L. Faboideae‐Genisteae in Brittany (France)
Authors: Misset M. T. , Gourret J. P.
Published: February 2014

Abstract: A controversy arose in the last decade concerning the identity of U. gallii and the ploidy of gorses in Brittany. To determine, for a wide number of samples, the ploidy levels of indigenous or recently introduced gorses in Brittany, we used the flow cytometric method on DAPI fluorescent nuclear suspensions, together with size measurements of stomata and dry pollen grains. All plants belonged to the section Neowillkommia of the genus Ulex. They were found to form a polyploid series with 2x, 4x and 6x levels. All U. minor were diploid. All U. europaeus ssp. europaeus and all U. gallii, except a single specimen out of 65, were hexaploid. This specimen had cell dimensions very close to that of U. europaeus ssp. latebracteatus which is a tetraploid. Tissue‐specific augmentation was found in Rhizobium‐containing cells of root nodules and within the endosperm of immature seeds. The 2C DNA content of U. europaeus ssp. europaeus was estimated at 90% that of Pisum sativum, so weighing about 7.7 pg/2C. Neither U. gallii nor U. europaeus ssp. europaeus showed any difference in their ploidy level between erect and prostrate ecotypes. The taxonomic and nomenclatural consequences are discussed.
Induction of a new Lipoxygenase Form in Cucumber Leaves by Salicylic Acid or 2,6‐Dichloroisonicotinic Acid*
Authors: Feussner I. , Fritz I. G. , Hause B. , Ullrich W. R. , Wasternack C.
Published: February 2014

Changes in lipoxygenase (LOX) protein pattern and/or activity were investigated in relation to acquired resistance of cucumber (Cucumis sativus L.) leaves against two powdery mildews, Sphaerotheca fuliginea (Schlecht) Salmon and Erysiphe cichoracearum DC et Merat. Acquired resistance was established by spraying leaves with salicylic acid (SA) or 2,6‐dichloroisonicotinic acid (INA) and estimated in whole plants by infested leaf area compared to control plants. SA was more effective than INA. According to Western blots, untreated cucumber leaves contained a 97 kDa LOX form, which remained unchanged for up to 48 h after pathogen inoculation. Upon treatment with SA alone for 24 h or with INA plus pathogen, an additional 95 kDa LOX form appeared which had an isoelectric point in the alkaline range. For the induction of this form, a threshold concentration of 1 mM SA was required, higher SA concentrations did not change LOX‐95 expression which remained similar between 24 h and 96 h but further increased upon mildew inoculation. Phloem exudates contained only the LOX‐97 form, in intercellular washing fluid no LOX was detected. dichloroisonicotinic localization revealed LOX protein in the cytosol of the mesophyll cells without differences between the forms.
Mitochondrial DNA in Mon‐Mon and Di‐Mon Pairings of Pleurotus ostreatus
Authors: Fischer M. , Wolfrath H.
Published: February 2014

Based on enzymatically amplified regions of the mitochondrial DNA (mtDNA), stock‐specific markers were obtained for two stocks of Pleurotus ostreatus. A length mutation was detected within a region encoding for DNA of the mitochondrial ribosomes. The inheritance of mtDNA was uniparental both in Mon‐Mon and Di‐Mon interstock pairings. Replacement of the recipient mtDNA to a large extent was finished 3 to 4 months after hyphal contact of paired mycelia. Dissolution of mitochondrial mosaics was somewhat faster in Di‐Mon than in Mon‐Mon pairings. As became evident in Di‐Mon pairings, the spread of the dominating mtDNA is independent from nuclear migration, and these processes could go in opposite directions. While in compatible Di‐Mon pairings two different types of nuclear background develop with respect to the mating type factors, only one certain mtDNA phenotype remained after dissolution of the mitochondrial mosaic. The spread of the mtDNA occurred at a distinctly slower rate than nuclear migration. Three weeks after hyphal contact the dominating mtDNA had not reached the growing edge of the recipient mycelium, whereas clamp formation was noted after 11 days at the latest. The data presented in this study indicate that no apparent correlation exists between mtDNA and nuclear background.
Micro‐Foraging Routes of Bicolletes pampeana (Colletidae) and Bee‐Induced Pollen Presentation in Cajophora arechavaletae (Loasaceae)
Authors: Schlindwein C. , Wittmann D.
Published: February 2014

In flowers of Cajophora arechavaletae Urb. the stamens are hidden from flower visitors in naviculate petals. In the male phase the stamens successively migrate at irregular intervals to the centre of the flower where they present pollen. Therefore, non‐specialised pollinators cannot predict the time of pollen presentation. The oligolectic females of Bicolletes pampeana are effective pollinators of Cajophora arechavaletae. Females and males can elicit stamen movements by pressing the scales of the nectaries outwards with their head while taking up nectar. If this stimulus is responded to, up to 3 stamens move and reach the centre of the flower on average after 2.4 min. Experiments showed that the stimulus of nectar scale pressing was responded to maximally when the inter‐stimulus interval was at least 14 min. B. pampeana females have evolved a foraging strategy which is adapted to the unique pollen presentation of C. arechavalete flowers. On microforaging routes they trapline 30–60 flowers and, therefore, most frequently come back to the same flower after intervals of about 3 min. This is exactly the period after which a female can expect pollen in the centre of the flower if her previous stimulus was responded to. Competition between the females causes them to return to the flowers at such short intervals.
Physiological, Biochemical, and Molecular Characters for the Taxonomy of the Subgenera of Scenedesmus (Chlorococcales, Chlorophyta)
Authors: Kessler E. , Schäfer Michaela , Hümmer Carola , Kloboucek Annette , Huss V. A. R.
Published: February 2014

Biochemical and physiological properties of 16 Scenedesmus species representing the three subgenera Scenedesmus, Acutodesmus, and Desmodesmus are not suitable for species differentiation. All Scenedesmus species studied thus far produce secondary carotenoids, e.g. astaxanthin and canthaxanthin, under nitrogen‐deficient conditions. In addition, with the exception of one strain, hydrogenase activity under anaerobic conditions is generally present. Sequence analyses of ribosomal 18S RNAs indicate that the subgenus Desmodesmus is phylogenetically well separated from the other subgenera, whereas the separation of Scenedesmus and Acutodesmus appears less convincing and is dismissed in favour of a single subgenus, Scenedesmus. Three taxa formerly assigned to the genus Chlorella are shown to be unicellular species of the genus Scenedesmus. “Chlorella” fusca var. vacuolata and “C.” fusca var. rubescens, which is closely related to S. obliquus, belong to the Scenedesmus/‘Acutodesmus group. “C.” fusca var. fusca is closely related to S. communis and thus belongs to the subgenus Desmodesmus. Inclusion of Kermatia pupukensis into the genus Scenedesmus is also strongly supported by the RNA data which furthermore indicate a relationship with the subgenus Desmodesmus.
The Impact of Molecular Methods on the Systematics of Angiosperms
Authors: Wagenitz C.
Published: February 2014

A comparison is made between the systematics of selected orders and families based on morphology and other “classical” characters on the one hand, and the results of molecular methods on the other hand. It can be shown that taxa defined by a broad array of characters from morphology, anatomy, embryology and phytochemistry usually are confirmed by molecular results. On the other hand a family like the Saxifragaceae s.l. delimited solely on the basis of floral morphology has been shown to be grossly polyphyletic. Some quite surprising results of the molecular analyses usually agree with some embryological or phytochemical characters, and sometimes even with characters of vegetative morphology and anatomy. As a special case “unequal ancient splits” are discussed, where one clade contains few genera and species usually retaining many primitive characters, and the other shows great diversity and contains the more advanced members.
Impact of Atmospheric Sulfur Deposition on Sulfur Metabolism in Plants: H2S as Sulfur Source for Sulfur Deprived Brassica oleracea L.
Authors: De Kok L. J. , Elisabeth C. , Stuiver E. , Rubinigg M. , Westerman Sue , Grill D.
Published: February 2014

Brassica oleracea L. was rather insensitive to atmospheric H2S: growth was only negatively affected at ≥0.4 μl I−1. Shoots formed a sink for H2S and the uptake rate showed saturation kinetics with respect to the atmospheric concentration. The H2S uptake rate was high in comparison with other species, which may reflect the high sulfur need of Brassica. The net uptake of sulfate by roots of hydroponically grown plants was substantially reduced after one week of exposure to 0.25 μl l−1 H2S, indicating that plants switched in part from sulfate to H2S as sulfur source for plant growth. Plants were sulfur deficient after two weeks of sulfur deprivation, illustrated by reduced growth, which was more pronounced for shoots than for roots, and in enhanced shoot dry matter content. The latter could for the greater part be attributed to enhanced levels of soluble sugars and starch. Sulfur deficiency was further characterized by a low pigment content, extremely low levels of sulfate and water‐soluble non‐protein thiols, and by enhanced levels of nitrate and free amino acids, particularly in the shoots. Furthermore, sulfur deficient plants contained a lower total lipid content in shoots, whereas its content in roots was unaffected. The level of sulfolipids was decreased in both roots and shoots. When sulfur deprived plants were exposed to 0.25 μl I−1 H2S for one week, all sulfur deficiency symptoms were abolished and growth was restored. Furthermore, plants were able to grow with 0.4 μl I−1 H2S as the sole sulfur source. Water‐soluble non‐protein thiol content was enhanced in both shoots and roots of H2S exposed plants, irrespective of the sulfate supply to the roots, whereas plants grown with H2S as sole sulfur source contained very low sulfate levels. The interaction between atmospheric and pedospheric sulfur nutrition in plants is discussed.
Microscopic Study of Mature Seed Coats and Aborted Structures of Interspecific Cotton Hybrids
Authors: Shimony C. , Sass N. , Yucha R. , Saranga Y.
Published: February 2014

Seed coats and fibers of aborted structures (termed “motes”) and mature seeds from an interspecific hybrid (ISH) of cotton (Gossypium hirsutum x G. barbadense) were studied by microscopy to determine (a) the developmental stages at which motes of various sizes stop growing and (b) the origin of lint‐contaminating fragments. Small motes (1–2 mm wide, up to 3 mm long) were identified as ovules whose growth had been arrested before anthesis or soon afterwards, medium‐size motes (1–3 mm wide, 3–5 mm long) as those whose growth had been arrested up to 10 days post‐anthesis, and large motes (3–5 mm wide, 5–8 mm long) as those which had stopped growing about 20 days post‐anthesis. Microscopic examination of lint‐contaminating fragments showed that they derive mainly from medium‐size motes and partly from mature seed coats. Reducing the number of medium‐size motes by breeding can, therefore, improve the lint quality of ISHs of cotton.
Biomechanics of Isolated Plant Cuticles
Authors: Wiedemann P. , Neinhuis C.
Published: February 2014

The mechanical properties of isolated cuticles of leaves (Yucca aloifolia, Clusia fluminensis, Nerium oleander, Hedera helix) and one fruit (Lycopersicon esculentum) were investigated by means of a tensile test. Samples of the leaves and the fruit were cut to identical size (12.5 × 50 mm) and the cuticles were enzymatically isolated, cleaned, and air dried. The morphology of the isolated cuticular membranes (CM) was investigated by scanning electron microscopy (SEM) and showed considerable differences. The thickness of the CM was determined by a digital image analysis system and ranged between 2.4 and 13.4 μm. The CM were subjected to a tensile test and the results are presented as stress‐strain diagrams. From the latter, Young's moduli were calculated, a measure for the stiffness which allows the direct comparison of different materials. The obtained values ranged between 0.1 and 1.3 CPa. Hydration of CM caused a decrease of Young's moduli of about 35–50%. A possible role of the cuticle as a factor for the stabilization of plant organs is discussed.
Effect of a Treatment with Naphthaleneacetic Acid on the Arrangement of Lateral Roots in Onion (Allium cepa L): General Pattern and Coordination between Ranks
Authors: Lloret P. G. , Pulgarín A. , Casimiro I. , Molina M. , Casero P. J.
Published: February 2014

Lateral roots in Allium cepa arise in longitudinal rows opposite the protoxylem poles of adventitious roots. The number, spacing within ranks and positional relationship to laterals in different ranks were analysed in control roots and those treated with an auxin (α‐naphthaleneacetic acid). Treatment increased numbers of laterals per rank and distributed the more evenly in all ranks. Laterals of control roots were concentrated in two neighbouring ranks. Auxin‐treated roots showed a more regular distribution of laterals between ranks and close spacing of laterals along each rank. Comparisons with theoretical random distributions suggest a dispersed spacing model for lateral root arrangement with mutual repulsion between successive lateral roots within each rank both in control and auxintreated roots. On the other hand, there is some interaction between laterals in different ranks in 0.1 mM NAA‐treated roots.
Disruption of a spe‐like Open Reading Frame Alters Polyamine Content and psbA‐2 mRNA Stability in the Cyanobacterium Synechocystis sp. PCC 6803
Authors: Mulo Paula , Eloranta Terho , Aro Eva‐Mari , Maenpää Pirkko
Published: February 2014

In Synechocystis 6803, transcripts of the psbA‐2 gene encoding the reaction‐center protein D1 of photosystem II are short‐lived in light but stable in darkness. No dark‐stabilization was observed if the genomic region downstream from the psbA‐2 gene was disrupted. The deleted fragment was found to include an open reading frame (ORF) with striking similarity to the spe gene encoding arginine decarboxylase (L‐arginine carboxylase, EC 4.1.1.19), which is involved in the biosynthesis of polyamines. The spermidine content of the mutants with a disrupted ORF was observed to be lower than in the wild‐type suggesting that polyamines may play a role in the stability of the psbA‐2 mRNA.
A phi Layer in Roots of Ceratonia siliqua L
Authors: Pratikakis E. , Rhizopoulou Sophia , Psaras G. K.
Published: February 2014

The central cylinder of the primary root of the carob tree (Ceratonia siliqua) is encircled by a layer of cells with wall thickenings, known as a phi (φ) cell layer. The development of the φ layer and the chemical composition of the cell wall thickenings have been studied in roots of C. siliqua. The results reveal the presence of condensed tannins in the mature phi thickenings and that the development of the φ layer is asynchronous: at 0–1 cm from the root tip φ thickenings appear before endodermis differentiation at the sites opposite phloem, at 1–4 cm new φ thickenings are developed at the sites opposite xylem, at 4–7 cm the φ layer consists of two layers of cells and it completely encloses the central cylinder.
Localization of Pyrophosphatase and V‐ATPase in Chlamydomonas reinhardtii
Authors: Robinson D. G. , Hoppenrath Mona , Oberbeck K. , Luykx P. , Ratajczak R.
Published: February 2014

Microsomal membranes of Chlamydomonas reinhardtii possess PPase and V‐ATPase activities. By immunogold labelling we have shown that H+‐pyrophosphatase (PPase) is localized to membranes of lytic and contractile vacuoles of Chlamydomonas, in which the density of antigen in the latter is much higher. In addition, PPase is conspicuously present in trans cisternae and transpole elements of the Colgi apparatus. Such a distribution for PPase has hitherto not been reported. A positive in situ identification for PPase at the plasma membrane, including the flagellar membrane, was also made, and has also been confirmed by Western blotting and activity measurements on isolated plasma membranes. V‐ATPase antisera which cross react with polypeptides of this transport complex from maize roots failed to recognize anything in Western blots of Chlamydomonas microsomal membranes. Thus immunogold labelling for V‐ATPase was not possible with Chlamydomonas. On the other hand, surfaces of contractile vacuole membranes as revealed by deepetching were covered by conspicuous 9 − 11.5 nm diameter smooth particles which had a central hole. These were very similar to those previously identified by Heuser et al., (1993) as the V,‐head of V‐ATPase in Dictyostelium contractile vacuoles. Another type of membrane image, designated “intermediate‐sized vesicle”, was found associated with the contractile vacuole. It was characterized by densely‐packed 6 − 7.5nm diameter polygonal particles, which upon rotation analysis showed both 5‐ and 6‐fold symmetries, also with a central hole. These particles are interpreted as representing either PPase complexes or the V0 body of the V‐ATPase in etched fractured membrane surfaces. We have incorporated these findings into a model of contractile vacuole function.
Tracing the Path of Oxygen into Birdsfoot Trefoil and Alfalfa Nodules using Iodine Vapor
Authors: Jacobsen Karin Ruth , Rousseau R. A. , Denison R. F.
Published: February 2014

Although physiological control of nodule 02 permeability is an active area of research, the gas diffusion pathway between the atmosphere and the infected zone has not been firmly established. Previous studies have used infiltration of ink or dyes to identify points of entry, but such water‐soluble tracers could give a misleading picture of gas diffusion pathways. We therefore used iodine vapor (and its reaction with starch) to trace gas‐phase pathways into the infected zone of determinate birdsfoot trefoil (Lotus corniculatus) and indeterminate alfalfa (Medicago sativa) nodules. We also used histochemical methods to identify suberized or lignified layers that could act as barriers to gas diffusion. Birdsfoot trefoil nodules were surrounded by a suberized periderm, but nonsuberized cells and intercellular spaces were observed in the periderm between lenticels and their associated vascular bundles. Iodine entered birdsfoot trefoil nodules only through lenticels. The periderm appears to provide a significant barrier to gas diffusion. Although airspaces were rare in the nodule parenchyma (also referred to as the “inner cortex”), we found some evidence that a few air‐filled pathways cross this secondary barrier, also in the vicinity of vascular bundles. Alfalfa nodules were cylindrically surrounded by a suberized endodermis which ended near the meristematic tip; iodine entered principally at the end of the endodermis near the meristem. Future research on physiological control of nodule O2 permeability should concentrate on strategic “choke points”, associated with lenticels in determinate nodules, or in the zone proximal to the meristem in indeterminate nodules.
Cytological Characterization of Multicellular Structures in Embryogenic Microspore Cultures of Brassica napus L.
Authors: Hause G. , Hahn H.
Published: February 2014

We investigated an embryogenic microspore culture from Brassica napus L. cv. “Topas”, 3 days after induction of embryogenesis, using light and electron microscopical techniques. According to our observations, 6 groups of uni‐ or multicellular structures could be distinguished by differences in size, wall structure, structure and distribution of organelles and the degree of vacuolisation. Only one multicellular group represents real proembryos which are able to form embryos and to regenerate plants. These 6 groups could be detected in living cultures using an inverted microscope. The cell size and the degree of vacuolization are especially useful markers to distinguish the groups. Separate cultivation of the multicellular complexes of the 6 groups in culture plate inserts from the third day of culture proved that only one group contains real proembryos.
Growth and Alkaloid Patterns of Roots of Tabernaemontana pachysiphon and Rauvolfia mombasiana as Influenced by Environmental Factors
Authors: Höft M. , Verpoorte R. , Beck E.
Published: February 2014

The influence of environmental factors on the indole alkaloid content and biomass of the roots of Tabernaemontana pachysiphon and Rauvolfia mombasiana, two species of considerable local medicinal use in tropical East Africa, was investigated. Both species, belonging to the Apocynaceae, are frequent constituents of the residual tropical forests, prefering sites of different ecological conditions. Experimental plants, raised from seeds, were grown for 16 months in a temperature‐ and humidity‐controlled greenhouse. Environmental factors at variance were water and nutrient supply, and light intensity. At sufficient water and nutrient supply, the more drought and nutrient shortage‐tolerating heliophilous Rauvolfia mombasiana showed increased alkaloid accumulation, concurrently with reduced root biomass. Under the same conditions, the drought‐sensitive and higher levels of nutrient‐requiring ombrophilous Tabernaemontana pachysiphon produced more root biomass but accumulated less alkaloids in the roots. The results indicate that the accumulation of indole alkaloids in the roots, as well as biomass allocation to the roots, is influenced in an opposite manner by the nutrient and water supply to the heliophilous and the ombrophilous species.
Misconceptions About the Relation Between Plant Growth and Respiration
Authors: Hansen L. D. , Breidenbach R. W. , Smith B. N. , Hansen J. R. , Criddle R. S.
Published: February 2014

Abstract: The relation between plant growth rate and respiration rate is readily derived from the overall chemical reaction for aerobic metabolism. The derived relation can be used to show that separation of respiration into growth (g) and maintenance (m) components is not a useful concept. g and m cannot be unambiguously measured or defined in terms of biochemical processes. Moreover, because growth yield calculations from biochemical pathway analysis, from biomass molecular composition, from biomass heat of combustion, and from biomass elemental composition have not included all of the energy costs for biosynthesis, they are not accurate measures of the carbon cost for plant growth. Improper definitions of growth‐respiration relations are impeding the use of physiological properties for prediction of plant growth as a function of environmental variables.