bluuebunny/crossref_metadata_2025 huggingface dataset:
Changes in the Carotenoid Pattern During the Synchronous Life Cycle of Scenedesmus
Authors: Senger H. , Schrader Elisabeth , Bishop N. I.
Published: February 2014

The wild type (WT) of Scenedesmus obliquus and a mutant lacking chlorophyll b and the light‐harvesting complexes (WT‐LHC1) were synchronized by a light‐dark regime. Both cultures contained the same type of carotenoids. However, concentrations and patterns of carotenoids were different during their synchronous life cycles. The concentration of total carotenoids followed more or less that of chlorophyll. The WT contained more carotenoids per cell mass, but slightly less per chlorophyll. It is discussed that part of the carotenoids of the mutant, lacking the peripheral antenna of PSII, might be located in the chlorophyll b‐less apoprotein or in an enlarged core antenna of PSII.

During the life cycle of Scenedesmus the carotenes are initially synthesized and most of the α‐carotene is immediately oxidized to lutein which is inserted in the antennae systems of PSII and PSI. The further oxidation of lutein to loroxanthin seems to depend on both the change from dark to light, and on stages of the life cycle itself. Although the major part of β‐carotene appears to be inserted in the reaction centers, a fraction of the total pool is rapidly converted to violaxanthin, following the onset of illumination. The conversion may serve to protect against photooxidation. Further conversion of violaxanthin to neoxanthin occurs to a greater extent in the mutant, WT‐LHC1. The results demonstrate (1) the close connection between the carotenoid pattern and the modulation of the photosynthetic apparatus during the life cycle of Scenedesmus and (2) the flexibility of the organism in compensating for the absence of the light‐harvesting complexes of photosystems II by adjusting the carotenoid distribution.
Photosynthetic Characteristics of the Palisade Mesophyll and Spongy Mesophyll in the CAM/C4 Intermediate Plant, Peperomia camptotricha*
Authors: Nishio J. N. , Ting I. P.
Published: February 2014

Several photosynthetic parameters were examined in the different tissue layers of leaves from the recently characterized crassulacean acid metabolism/C4 intermediate plant, Peperomia camptotricha (Nishio and Ting, 1987). Light appears to control the development of certain photosynthetic characteristics within the tissue layers, while factors other than light seem to dictate others. Analysis of the chlorophyll content (including P700) and chlorophyll‐proteins indicated that more light harvesting chlorophylls were associated with reaction centers in the tissues that were shaded by overlying tissue. Electron transport activity and chlorophyll‐protein analysis indicated that the ratio of photosystem I to photosystem II in the spongy mesophyll (the abaxial tissue type and hence most shaded) was elevated relative to the overlying chlorophyll‐rich median palisade mesophyll. The elevated photosystem I relative to photosystem II in the spongy mesophyll of Peperomia camptotricha may be related to C4 metabolism and an increased requirement for ATP.
Sub‐cellular Localization of Calcium in Azolla‐Anabaena Symbiosis by Chlortetracycline, ESI and EELS
Authors: Canini Antonella , Albertano Patrizia , Caiola Maria Grilli
Published: February 2014

The subcellular localization of calcium in cells of symbiotic partners located within leaf cavities of Azolla was investigated by using chlorotetracycline, ESI and EELS analysis. Loosely membrane‐bound calcium was evidenced by using CTC or EGTA and CTC, in cytoplasmic regions of Azolla hair cells and in cytoplasm of the cyanobiont. Tightly membrane‐bound calcium revealed by CTC, and ESI and EELS analysis, was observed in cyanophycin granules and carboxysomes of the cyanobiont. A third calcium type, revealed by ESI and EELS analysis, was localized at the level of cell walls of simple and branched Azolla hairs, in the envelope of heterocysts, and in the cell walls of the cyanobiont.
Age‐Dependent Modifications and Further Localization of the CX 26‐like Protein from Vicia faba L.
Authors: Hunte Carola , Janßen Martina , Schulz Margot , Traub O. , Willecke K. , Schnabl Heide
Published: February 2014

A strong age dependency together with alterations in the cellular distribution of CX 26 immunorelated protein(s) was found for differently developed leaves of Vicia faba L. With increasing age, an immunoreactive 40 kD band was observed in the soluble and microsomal fraction. In the cell wall protein preparation of young and fully differentiated leaves the 40 kD band was the minor constituent. A 33 kD polypeptide was dominantly localized in the microsomal fractions of all developmental stages and in SDS‐extracts of total cell proteins of young leaves. A 21 kD protein together with a 16 kD polypeptide was associated with the cell wall fraction. The 21 kD protein, assumed to represent a plasmodesmatal constituent, was reduced with age. In SDS extracts, prepared from the different developmental stages of the leaves and of mesophyll protoplasts, the age‐dependent appearance of the several immunostained bands was most obvious. A correlation of the 16, 33, and 40 kD bands to a turnover of the 21 kD protein is suggested. The reduced amount of the 21 kD protein with increasing age may be contemplated as an indication for a relative decrease of symplastic connections between cells of maturing leaves. This is in agreement with the results obtained by immunofluorescence studies using guard cell protoplasts. Here, observations pointed also to a reduction and final loss of CX 26‐related protein at the protoplast surfaces.
The Modified Stomata of the Floral Nectary of Vicia faba L.
Authors: Davis A. R. , Gunning B. E. S.
Published: February 2014

A comparison of developmental features and physiological responses between the modified stomata (MS) of the floral nectary and the stomata of leaves of Vicia faba L. has revealed several significant differences. In mature tissues, the frequency per unit area of MS is three times that of foliar stomata, and when only the distal quarter of nectary projections is considered, it is twelve fold higher. The walls of guard cells (GCs) of MS near the pore were four to five times thinner than those of their foliar counterparts. Average pore widths of the nectary MS remained constant throughout the day and night, contrary to those of leaves; maximal foliar apertures were similar to average pore widths of MS of nectaries. Experiments with plasmolytica demonstrated a higher osmotic potential in nectary MS, and that sister GCs of the nectary only occasionally closed their pores by movements, even when they were plasmolysed, whereas GCs of leaves were found to be plasmolysed only after their pores had shut. Abscisic acid (ABA) was always detected naturally in floral nectar. The results of experiments involving K+‐localization and the secretion of large quantities of ABA in nectar suggested that GCs of the MS lack operational systems involving K+‐influx and ABA‐receptor sites. All information gained is consistent with the earlier conclusion that the MS do not have a regulatory role in nectar secretion by flowers of V. faba.
A Comparative Study by δ13C‐Analysis of Crassulacean Acid Metabolism (CAM) in Kalanchoë (Crassulaceae) Species of Africa and Madagascar
Authors: Kluge M. , Brulfert Jeanne , Lipp J. , Ravelomanana D. , Ziegler H.
Published: February 2014

The carbon isotope ratios (δ13C values) of samples of Kalanchoë species collected in Africa were compared with previous data obtained with species from Madagascar. In contrast to the Malagasy species which cover the whole range of δ13C values from −10 to − 30%o, indicating high inter‐ and intraspecific diversity of CAM performance, in the African species nearly all δ13C values were less negative than −18%0. Thus, in the African species the CAM behaviour is characterized by CO2 uptake proceeding mainly during the night. The distribution of δ13C values among the species clearly mirrors the taxonomic groups and the three sections of the genus Kalanchoë sensu lato. The Kitchingia section comprises only groups having CAM with a high proportion of carbon acquisition by the C3‐pathway of photosynthesis. The same holds true for the first three groups of the Bryophyllum section, whereas in the following groups of the section CAM with CO2 proceeding mainly during the night is common. The latter CAM mode is typical also for the majority of groups and species in the section Eukalanchoë.

The African Kalanchoë species belong to the Eukalanchoë section, whereas in Madagascar all three sections are abundant. The data support the view that the centre of adaptive radiation of the genus is located in Madagascar. They also suggest that high CAM variability is abundant in the more primitive taxa of the genus, whereas the phylogenetically more derived taxa show a stereotype CAM with CO2 uptake taking place only during the night.
X‐Ray Microanalytical Studies on Mineral Concentrations in Vacuoles of Needle Tissues from Larix decidua (L.) Mill.
Authors: Stelze R. , Holste R. , Groth M. , Schmidt A.
Published: February 2014

Elemental concentrations in the vacuoles of mesophyll, endodermis and transfusion parenchyma cells were determined by means of electron probe microanalysis on bulk frozen hydrated needles of an outdoor‐grown larch tree. The investigations were done routinely throughout a life cycle of the deciduous larch needle, starting with bud burst in March and ending with leaf abscission in November. It could be shown that the endodermal vacuoles preferentially accumulate S, CI and Ca while the transfusion parenchyma vacuoles transiently store Mg, K and S. Between May and September the inorganic ion level of mesophyll cells is constantly lower than in the endodermal and transfusion parenchyma vacuoles. In autumn, when the degradation of chlorophylls becomes detectable, the elements Mg, S, CI and Ca are found increasingly in the vacuoles of the mesophyll cells. It is concluded that, in mature and intact larch needles, the vacuoles of the endodermis in cooperation with the transfusion parenchyma vacuoles act as efficient ion storage buffers which maintain a constant low ion level in the vacuoles of mesophyll cells.
Vapour Phase Activation, Intracellular Motility and Germination in the Tripororate Pollen of Epilobium angustifolium
Authors: Heslop‐Harrison J. , Heslop‐Harrison Yolande
Published: February 2014

The germinability of newly released pollen of Epilobium angustifolium in liquid medium is low, but it is enhanced by a short period in an atmosphere of 85–95% RH without access to liquid water or solutes. During this period the thickened pectic layers of the intine at the germination apertures of the grains are eroded and prospective tube tips emerge. Concomitantly polarised movement of organelles begins in the vegetative cells, and wall precursor vesicles (P‐particles) accumulate at the apertures. In pollen held continuously in the humid environment transition to cylindrical growth follows, with the establishment of the inverse‐fountain pattern of circulation in the apical part of the tubes.
Underground Plant Movement
Authors: Pütz N.
Published: February 2014

A special preparation method makes it possible to observe the underground bulb movement of Nothoscordum. This movement is effected by contractile roots. Straight ahead movement, which seems to be typical for many bulbous plants, is only exceptionally seen in Nothoscordum. Bulb movement in Nothoscordum occurs by tilting and twisting, effected by the pulling force of contractile roots on one side of the bulb. Also, vegetative dispersal of lateral bulbs (daughter bulbs) caused by the pulling force of contractile roots can be documented. Finally, starting from the seedling, the overall bulb movement can be demonstrated, showing how the plant penetrates the substratum thus reaching the optimum depth.
Studies on the Sporogenous Lineage in the Moss Timmiella barbuloides
Authors: Gambardella R. , Alfano F. , Gargiulo M. , Squillacioti C.
Published: February 2014

The formation of the sporoderm in the moss Timmiella barbuloides (Brid.) Moenk. (Pottiales) was investigated by electron and fluorescence microscopy. Exine is the first layer formed. It is initiated during late cytokinesis on the distal surface of the tetrad members by centripetal apposition of lamellae just outside the plasma membrane. The exine then extends along the margins of the spore up to the proximal face where it contributes to the formation of the aperture. Exine deposition is closely related to two extensive systems of microtubules that develop sequentially from discrete microtubule organizing centres associated with the plasma membrane at distal and proximal poles of spores. After spore liberation from the tetrads the exine becomes homogeneous. Discontinuous perine ornamentations of extrasporal origin are then deposited onto the outer surface of the exine while the aperture development is completed. The intine is the last and innermost layer formed. Its deposition is restricted to the proximal hemisphere of the spore with thickness decreasing from the pole to equator.
Isolation of Protoplasts from the Coccal Green Alga Eremosphaera viridis De Bary for Patch‐clamp Measurements
Authors: Linz K. W. , Köhler K.
Published: February 2014

A method for enzymatic isolation of protoplasts from the unicellular green alga Eremosphaera viridis for patch‐clamp measurements is described. Viable protoplasts with “patch‐clean” plasma membranes could only be isolated when combining high enzyme concentrations and long incubation times.

In whole‐cell recordings the protoplasts exhibited electrical properties similar to those measured in intact cells. Taken together with the protoplasts' ability for rapid deplasmolysis after transfer into hypotonic solution, this indicates the viability of the isolated protoplasts.
Ultrastructure and Germination Percentage of Crocus biflorus Miller subsp. biflorus (Iridaceae) Pollen
Authors: Caiola Maria Grilli , Banas Malgorzata , Canini Antonella
Published: February 2014

Pollen of Crocus biflorus Miller subsp. biflorus from natural habitats of Tusculum (Frascati, near Rome, Italy) has been studied in order to compare its structure and physiology to pollen of other Crocus species belonging to the Crocus sativus group. Mature pollen grains are rounded, 60 μm in diameter, in‐aperturate (but with surface incisions where exine is lacking). DAPI staining reveals a spindle‐shaped generative nucleus which is intensely fluorescent, and vegetative nucleus which is less fluorescent, and is elongated with numerous lobes. At anthesis the pollen is bicellular, but about 2% of tricellular grains occur among the pollen grains released from the anthers as well as on both naturally or handpollinated stigmas.

Pollen germination is low in vitro, but higher in vivo. The pollen tubes are of normal shape. An electron‐dense surface coat is sometimes visible on the exine, which in many cases, is detached from the exine. The vegetative cytoplasm is very rich in glycolipid bodies surrounded by endoplasmic reticulum. The generative cell has a lobed cell wall and is surrounded by the vegetative nucleus.
The Joint Occurrence of Chloroxanthones in Southern Hemisphere Lecanora Species (Ascomycotina; Lecanoraceae)
Authors: Lumbsch H. T. , Feige G. B. , Elix J. A.
Published: February 2014

Four species belonging to the Lecanora subfusca group (Lecanoraceae, lichenized Ascomycotina) and containing the 2,5,7‐trichloro‐3‐O‐methylnorlichexanthone chemosyndrome are described: L. elixii Lumbsch, L. epibryon Ach., L. mayrhoferi Lumbsch spec. nov. and L. parmelinoides Lumbsch spec. nov. The species, which are interpreted as being closely related, can be distinguished by a combination of subtle morphological and anatomical characters.
Tidal Dependence of Photoinhibition of Photosynthesis in Marine Macrophytes of the South China Sea*
Authors: Hanelt D. , Li J. , Nultsch W.
Published: February 2014

During an expedition in spring 1992 to Hainandao, an island in the tropical zone of the South China Sea, the daily courses of photoinhibition of different brown algal species and of the seagrass Thalassia hemprichii were investigated. Experiments were carried out with the new portable chlorophyll fluorometer PAM 2000 (Walz, Germany). As a measure of photoinhibition Fv/Fm was used and as a measure of the photosynthetic yield ΔF/Fm'. Photoinhibition occurred in all algae floating near the water surface and reached its maximum between noon and the early afternoon. In the evening photosynthesis was always fully recovered. The extent of photoinhibition depended on both the depth of the algae and the course of the irradiance during the day. Algae of the sublittoral zone showed only a low degree of photoinhibition at high fluence rates when they were covered by a water column of more than 1 m, even if the water was clear. The seagrass Thalassia hemprichii grew in the middle and upper intertidal zone and showed a significant photoinhibition at low tide only when it was not water‐covered. Apparently, it is able to cope with extreme high light conditions without downregulation of photosynthesis caused by photoinhibition.
Purification and Characterization of Oxopantoyl Lactone Reductase from Higher Plants: Role in Pantothenate Synthesis
Authors: Julliard J. H.
Published: February 2014

Oxopantoyl lactone reductase has been purified to homogeneity from a crude extract of spinach leaves (Spinacia oleracea L.) using affinity chromatography on Red‐Agarose and several subsequent ion exchange steps. The enzyme is monomeric with a relative molecular mass between 33,000 to 36,000. Affinity‐purified antibodies directed against the homogenous enzyme have been used to determine the amount of oxopantoyl lactone reductase in the crude leaf extract as well as the chloroplast stroma. The overall purification factor has been determined to be 22,000. The subcellular location of the enzyme is chloroplastic. The final specific activity (strictly NADPH‐dependent) is 4.5 μmole . min−1 . mg−1. The enzyme is also able to reduce isatin, bornanedione and acenaphthenequinone. The enzyme activity is strongly and uncompetitively inhibited by 2‐keto‐4‐hydroxybutyrolactone and substituted 4,5‐dioxopyrrolidines. An oxopantoate reductase associated with acetohydroxy acid isomeroreductase could be detected in the plant extract. Using a specific inhibitor of this latter enzyme or oxopyrrolidines, complementation studies with branched chain amino‐acids and pantothenate have shown that oxopantoyl lactone reductase is likely to be involved in pantothenate biosynthesis. Furthermore, pantoyl lactone, the putative product of the reaction, together with β‐alanine and ATP, has been shown to be the substrate of pantothenate synthase using a novel assay for pantothenate.
The Use of DNA Fingerprinting in Ecological Studies of Phragmites australis (Cav.) Trin. ex Steudel
Authors: Zeidler A. , Schneider S. , Jung C. , Melchinger A. E. , Dittrich P.
Published: February 2014

A number of reed populations (Phragmites australis) from natural locations on the shore of Lake Ammersee in the south of Bavaria as well as artificially grown reed plants were analyzed for restriction fragment length polymorphisms (RFLPs) in order to evaluate for further ecological studies the dynamics of the restriction pattern within the genome of plants which propagate themselves asexually. The artificially grown reed plants were raised in four ponds supplemented with different phosphate concentrations (8 μg, 16 μg, 50 μg, and 200 μg/l) from rhizomes taken from a neighbouring fish pond. The genomic DNA of 25 of these plants and the DNA from 37 plants out of 18 stands from the lakeshore was isolated and restricted with the enzyme EcoRI, EcoRV, XbaI and HindIII and hybridized to three probes from a shot‐gun cloned reed plasmid library. The probes gave between 15 and 26 bands (DNA fingerprints) of high polymorphic frequency (68% − 100%) after hybridization with repetitive sequences of restricted DNA. A cluster analysis based on the banding pattern as a measure of genetic similarity (GS) was performed with the two sets of reed plants. The plants from the lakeshore exhibited a clear formation of clusters with GS up to 100%; the 20 plants grown from rhizomes, in contrast, did not show any clear correlation among themselves, neither to the phosphate concentration they grew in, nor to the five plants tested from the pond their rhizomes came from. The value of genetical investigations of the plant genome in context with environmental impact on plants is being discussed.
Structural Aspects of the Lichen‐Rock Interface Using Back‐scattered Electron Imaging
Authors: Ascaso C. , Wierzchos J.
Published: February 2014

The profound knowledge of the structural and chemical characteristics of the interface between lichen thallus and rock, seems to be indispensable for the process of understanding the lichen symbiosis as well as the significance of the weathering action of lichens. One of the most promising techniques to be used in this investigation is the Scanning Electron Microscopy (SEM) in the back‐scattered electron (BSE) emission mode. In the present work thalli of Parmelia conspersa, Aspicilia intermutans and Lecidea auriculata growing in granitic rock were examined by SEM in BSE mode with (Energy Dispersive Spectroscopy) EDS. In the case of the foliose thalli the observation of the interface permits detection of the rhizine/hyphae adherence and determination of the origin of the minerals which adhere to the rhizine/hyphae. In the case of the crustose thalli BSE permits investigation within the ultrastructure of the crustose thallus and crustose lichen‐rock contact zone and also allows observations of the penetration and filling of the fissures and cracks of the underlying rock by components of the thallus and other living organisms. The BSE images could contribute to a better knowledge of the cytological state of the rock‐inhabiting organisms and also to the understanding of the action of the chemical treatments used in the removal of lichen from building materials.
“Pollen Buds” in Ophiorrhiza (Rubiaceae) and their Role in Pollenkitt Release
Authors: Weber Martina , Igersheim A.
Published: February 2014

Pollen buds are apertural protrusions formed by the ectintine. In their wall unesterified and methyl‐esterified pectins are detected by immunogold labeling. During pollenkitt formation pollen buds become adpressed and connected to the tapetum wall. The following expansion of the endothecium causes the mechanical rupture of the tapetum at the binding sites of the pollen buds. These events are accompanied by the release of the pollenkitt.
Pre‐adaptation of Arctic Plants to Climate Change*
Authors: Crawford R. M. M. , Abbott R. J.
Published: February 2014

Re‐appraisal of high latitude ice cover during the Weichselian and the recent discovery of pre‐Holocene plant communities in Novaya Zemlya and Northern Norway suggests that the contemporary Arctic flora may have had a longer time span in its occupation of high latitude sites than has hitherto been recognised. The present‐day Arctic flora in some regions may therefore have derived at least some of its genetic inheritance from populations that survived in ice‐free refugia in the high Arctic polar deserts during the latter stages of the Weichselian glaciation. Increasing evidence for sudden changes in climate at high latitudes in the past, suggests that Arctic vegetation would have been subjected to rapid climatic warming if it had maintained a presence in these regions during the late Weichselian. A review of what is known about plant survival in the high Arctic since pre‐Holocene times, coupled with an examination of some of the physiological properties of modern populations in these regions is presented in an attempt to ascertain if high Arctic plants possess mechanisms which facilitate their capacity to respond either phenotypically or physiologically to climatic change.
Field Measurements of Water Relations and CO2Exchange of the Tropical, Cyanobacterial BasidiolichenDictyonema glabratumin a Panamanian Rainforest*
Authors: Lange O. L. , Büdel B. , Zellner H. , Zotz G. , Meyer A.
Published: February 2014

Diel time courses of microclimate, hydration, and CO2exchange of the basidiolichenDictyonema glabratumand its responses to experimentally changed conditions were measured for 14 days in a clearing of a premontane, tropical rainforest (Panama).

Net photosynthesis (NP) was adapted to high temperatures and there was no depression of CO2uptake at the highest thallus hydration. The presence of a CO2concentrating mechanism was demonstrated. Decreased NP occurred after desiccation, and apparent photon yield of CO2fixation was also sensitive to water loss.

Natural NP was controlled by the interplay of thallus hydration and radiation. Regular, daily desiccation and dense cloud cover suppressed production. On average, 72 % of the diurnal photosynthetic gain was lost during the night, and there were days with negative carbon balance. Nevertheless, total carbon gain of the lichen was extremely high. A tentative estimation suggests that annual carbon gain amounts to 228 % of initial thallus carbon content.

Because of their strong effect on net production, increased nocturnal temperatures as given at lower elevation, would lead to a negative carbon balance. This might explain the lack of abundance of this and other macrolichens in warmer, lowland rainforests.
Quantification of the Daily Cytokinin Transport from the Root to the Shoot of Urtica dioica L.*
Authors: Beck E. , Wagner B. M.
Published: February 2014

Cytokinins are predominantly root‐born phytohormones which are distributed in the shoot via the xylem stream. In the hormone message concept they are considered as root signals mediating the transport of the photosynthates to the various sinks of a plant. In this paper the cytokinin relations of Urtica dioica L., the stinging nettle, are described, based on the daily flux from the roots to the shoot. Trans‐zeatin‐type cytokinins predominate in the various tissues of Urtica (Wagner and Beck, 1993), and accordingly trans‐zeatin riboside and trans‐zeatin are the forms transported by the xylem sap. The daily time‐course of cytokinin concentration in root pressure exudates and in xylem sap collected from a petiole after pressurizing the root bed showed high concentrations in the morning, followed by a substantial drop to a level of 15–30% of the initial concentration which was then maintained during the afternoon. This time‐course is interpreted as resulting from continuous synthesis and exudation of cytokinins into the xylem fluid of the roots whose cytokinin concentration is then modified by the dynamics of the transpiration stream. Loading of cytokinins into the xylem sap could be enhanced several times by increasing the flux rate of the xylem stream to the maximal transpiration rate when a maximum export rate was reached. The total daily cytokinin gain by the shoot depended on the nitrogen status of the plant. Roots of Urtica plants grown on a sufficient nitrogen supply had a significantly higher cytokinin content and exuded more cytokinins into the shoot than those of plants raised under nitrogen shortage. A positive correlation was found between the steady rates of cytokinin export measured during the afternoon and the shoot to root‐ratios of biomass which, in turn, corresponded to the nitrogen status of the plants.
Micromorphological and Phytochemical Research on Teucrium scorodonia and Teucrium siculum from the Italian Flora
Authors: Servettaz O. , Pinetti A. , Bellesia F. , Maleci L. Bini
Published: February 2014

Micromorphology and distribution of trichomes in different plant parts of Teucrium scorodonia and Teucrium siculum from five populations in Italy are described. The composition of volatile compounds in the same plants has also been studied. The micro‐morphological characters of the two taxa differ only in the calyces. T. siculum from the Euganean hills shows a great shape variability in the bracts. As far as the volatile compounds are concerned, this taxon reveals a somewhat special position, particularly for the presence of monoterpenes, which are lacking in T. siculum from Central and Southern Italy.
Physical Interactions of two Rhizomorph‐forming Lichens with their Rock Substrate
Authors: Sanders W. B. , Ascaso Carmen , Wierzchos J.
Published: February 2014

Samples of a calcareous conglomerate rock colonized by Squamarina cartilaginea and a siliceous schist colonized by Acarospora scotica were cut and examined with SEM‐backscattered electron imaging. Both species produce extensive rhizomorphs (sensu lato), whose component hyphae interpenetrated, separated, and incorporated substrate particles in the course of development. Rhizomorph expansion and contraction associated with hydration cycles could also detach adherent fragments within the substrate. In S. cartilaginea, rhizomorphs and associated hyphae also directly penetrated the calcareous substrate matrix, probably by chemical dissolution. Those of A. scotica appeared to penetrate the schist mainly by forcing their way between the fine, angular, somewhat flattened particles which comprises the substrate. The orientation of these particles influenced the form of developing rhizomorphs and the subsequent pattern of substrate exfoliation. Lichen compounds of potential biode‐teriorative significance occurred within the squamules of both species but were not detectable in their rhizomorphs. Lichenized photobionts were abundant within the substrate; their developmental relationship to epilithic squamules could be demonstrated in the case of A. scotica.
New Insights into the Protein Import Machinery of the Chloroplast's Outer Envelope
Authors: Soll J.
Published: February 2014

A large number of plastid localized proteins are post‐translationally imported as precursor proteins from the cytosol into the organelle. Recognition and translocation is accomplished by a subset of chloroplast envelope proteins, which were identified by different but complementary methods. The outer envelope proteins OEP 86, OEP 75, OEP 70 (a heat shock cognate 70 homologue) and OEP 34 are clearly involved in the import event and can be isolated as one functionally active translocation unit. For three of these proteins cDNA clones have been very recently obtained, namely OEP 86, OEP 75 and OEP 34. OEP 86 seems to be a precursor protein receptor which could be regulated by GTP binding and ATP‐dependent phosphorylation‐dephosphorylation. OEP 75 is part of the translocation pore traversing the membrane in multiple β‐sheets. OEP 34 is tightly associated with OEP 75. It represents a new type of GTP‐binding protein which possesses endogenous GTPase activity. Multiple GTP binding and hydrolysis cycles as well as protein phosphorylation‐dephosphorylation events might, therefore, regulate the interaction of a precursor protein with the translocation machinery of the outer envelope, making it very distinct from the mitochondrial outer membrane system. Further proteins of the inner envelope membrane, namely IEP 97 and IEP 36, have been implied to function in the translocation event. These recent data allow not only identification of the players in the game but also speculation about mechanisms and regulation of translocation.
Reproductive Biology of the Distylous Manettia luteo‐rubra (Rubiaceae)
Authors: Passos Luciana , Sazima Marlies
Published: February 2014

The reproductive biology of Manettia luteo‐rubra was studied in the coastal montane Atlantic rain forest of southeastern Brazil. This Rubiaceae is a perennial vine that flowers all the year round, but has a flowering peak during the dry season. It presents reciprocal herkogamy, thus the plants are morphologically distylous. The morphs occur in a 1:1 ratio, and pollen diameter and corolla length vary between short and long‐styled flowers. Manettia luteo‐rubra displays typical heterostylous self‐incompatibility and sets almost no fruits from self‐ or intramorph pollinations. The flowers are tubular, red with yellow lobes, and odourless. Anthesis is asynchronous, and the flowers last about four days. Concentration of sugars in nectar is similar in both morphs, ca. 24%, this concentration being typical for hummingbird flowers. Three species of hummingbirds are the major pollinators of the flowers of M. luteo‐rubra at the study site: the hermits Phaethornis eurynome and P. squalidus, and the trochiline Thalurania glaucopis. Three species of Heliconius butterflies act as minor pollinators. Both morphs of M. luteo‐rubra exhibit natural fruit‐set of about 80%, this reproductive output being maintained throughout the year by the pollinators' constancy to the flowers.
Seasonal Changes of the Antioxidative Systems in Foliar Buds and Leaves of Field‐grown Beech Trees (Fagus sylvatica, L.) in a Stressful Climate
Authors: Polle Andrea , Morawe Birgit
Published: February 2014

The activities of superoxide dismutase, ascorbate peroxidase, monodehydroascorbate radical reductase, and dehydroascorbate reductase and the contents of ascorbate, chlorophyll and soluble protein were determined in beech (Fagus sylvatica, L.) foliage over two or three seasons. Four important stages of leaf development were distinguished: resting buds, emerging, mature and senescent leaves. Foliar buds in spring, prior to the emergence of new leaves, contained a lower chlorophyll content but a higher protein content and higher activities of ascorbate peroxidase and monodehydroascorbate radical reductase than mature leaves in summer. By contrast, superoxide dismutase and glutathione reductase activities and ascorbate contents were higher in mature leaves than in swollen foliar buds. Dehydroascorbate reductase activity was low in all developmental stages. Resting buds in winter contained activities of superoxide dismutase, ascorbate peroxidase and monodehydroascorbate radical reductase that were similar to those found in mature leaves in summer, whereas the contents of total and reduced ascorbate were 6‐ and 20‐times lower, respectively, in buds than in mature leaves. The low foliar concentration of reduced ascorbate in resting buds, despite high monodehydroascorbate radical reductase activity, suggests that the regeneration of ascorbate might be limited by the availability of reductant. High antioxidative capacity was conferred by mature beech leaves and may be an important protection measure for coping with the large fluctuations in temperature and exposure to elevated ozone concentrations in summer.
Low Molecular Weight Carbohydrate Patterns in Geographically Different Isolates of the Eulittoral Red Alga Bostrychia tenuissima from Australia
Authors: Karsten U. , Bock Chr , West J. A.
Published: February 2014

Sixteen isolates of the red alga, Bostrychia tenuissima King et Puttock, from New South Wales, Victoria and South Australia were cultured in the laboratory and analysed for low molecular weight carbohydrates using 13C‐NMR and HPLC techniques. All populations south of 34 °S contain D‐sorbitol in combination with the heteroside digeneaside. The isolates north of 34° S lack digeneaside, but contain D‐sorbitol and, in addition, an isomeric form D‐dulcitol. Moreover, the 13C‐NMR spectra showed an unknown metabolite which was only measured in combination with digeneaside. While in the strains south of 34 °S digeneaside and the unknown compound occur in small quantities and remained unchanged with increasing salinities (5–60 ppt), the relatively high D‐sorbitol contents strongly increased under hypersaline conditions. In the populations north of 34 °S both the concentrations of D‐sorbitol and D‐dulcitol increased with increasing salinity. These data demonstrate the important role of polyols in the osmotic acclimation of B. tenuissima. The ecological and/or biological factors controlling this geographical pattern of metabolite content are not known. However, the different carbohydrate patterns within B. tenuissima are considered as indicators of the development of physiological ecotypes.
Transient Expression Activity of RbcS Promoter Regions from Brassica napus in Mesophyll Protoplasts from Nicotiana tabacum*
Authors: Beck I. , Wittig C. , Link G.
Published: February 2014

The 5′ upstream DNA of RbcS genes from Brassica napus contains sequence elements that specifically interact with DNA‐binding proteins of the transcription apparatus in vitro. To clarify if these sequences are functional in vivo, we have studied them in transient expression experiments. Fragments generated by successive deletions of the 5′ upstream regions of two RbcS genes were fused in frame to the β‐glucuronidase (gusA) reporter gene and GUS activity was monitored fluorometrically after polyethylene glycol (PEG)‐mediated DNA uptake in mesophyll protoplasts from Nicotiana tabacum SR1. The results indicate modular organization of cis‐elements that together account for full promoter activity. Whereas the TATA‐box region alone resulted in basal expression levels, enhanced GUS activity was observed in the presence of additional further‐upstream sequences, including the G‐box and the Gs‐box. For maximal activity, the presence of a region containing the I‐box was required. In addition to these putative activating DNA regions, evidence was obtained for regions that negatively affected GUS activity and hence may contain silencer element(s).
Anatomy and Phenylpropanoid Metabolism in the Incompatible Interaction of Lycopersicon esculentum and Cuscuta reflexa
Authors: Sahm Antje , Pfanz H. , Grünsfelder Maria , Czygan F.‐C. , Proksch P.
Published: February 2014

A time‐dependent correlation of anatomical and chemical defence reactions was shown during the incompatible reaction of tomato against the phanerogamic parasite Cuscuta reflexa. Microscopical analysis of the infection sites at the tomato stem revealed the elongation of epidermal, hypodermal and collenchymatic cells beneath the parasitic prehaustorium. After 9–11 days of infection the elongated cells had collapsed forming a visible brownish plaque at the tomato stem followed by a scalariform tissue with lignified and suberized cell walls. Concomitantly, an enhanced accumulation of soluble phenolic compounds (chlorogenic acid and an unidentified hydroxycinnamic acid derivative), as well as a stimulation of peroxidases, was observed. In contrast, PAL activity was not increased. Whereas the stimulation of phenylpropanoid metabolism could also be induced by artificial wounding, the described anatomical changes were only observed during attack of Cuscuta.
Auxin‐Binding Protein (ABP1) is not Confined to the Outer Epidermis of Maize (Zea mays L.) Coleoptiles
Authors: Kayser B. , Klämbt D.
Published: February 2014

Maize seedlings were studied for their expression patterns of ABP1‐mRNA and ABP1. In situ hybridization did not reveal hot spots of ABP1‐mRNA accumulation. This result was supported by northern hybridization. In coleoptiles the ABP1‐mRNA remains constant during day 1 to day 5 and is of low abundance (1.3 pg/μg total RNA). Northern blots indicated that in primary roots the mRNA level is even 10 times lower. Neither ABP1‐mRNA nor ABP1 was found to be concentrated within the outer epidermis of the coleoptile. Analysis of immunostained western blots did not reveal pronounced differences in ABP1 content on the basis of equal amounts of fresh weight or total protein. We therefore assume ABP1 to be more or less equally distributed among the cells of the shoot tissues of maize seedlings.
Water Potential Modulates Extensibility of Rye Coleoptile Cell Walls
Authors: Edelmann H. G.
Published: February 2014

Extensibility of walls of frozen/thawed rye (Secale cereale) coleoptile segments as a function of the water potential of the incubation solution (Ψ0) was analyzed employing the creep test method. Negative Ψ0exerts an inhibiting effect on extension of isolated walls. The lower the Ψ0of polyethylene glycol 6000 (PEG), the less the walls of frozen/thawed segments extended under load. This inhibiting effect of Ψ0on wall creep was reversible and independent of the preincubation temperature of the segments. An increase in Ψ0resulted in increased extension rate within 2–4 min, whereas a decrease in Ψ0resulted in gradually decreasing extension rate after 8–12 min. This finding implies that wall extension changes during growth induced by changes of Ψ0in vivoare not only due to changes of turgor pressure but also due to a direct influence by negative Ψ0on physical wall properties. The results are discussed with respect to the regulation of extension growth during conditions of water stress.
Carotenoid Mutants of Mucor circinelloides
Authors: Ruiz‐Hidalgo María José , López‐Matas María Angeles , Velayos A. , Fraser P. D. , Bramley P. M. , Eslava A. P.
Published: February 2014

The wild‐type of the filamentous fungus Mucor circinelloides accumulates the yellow pigment β‐carotene. At a continuous blue‐light fluence rate of 0.1 W/m2 the β‐carotene content increases about eight fold over the dark controls. Among the mutants isolated after exposure of spores to either N‐methyl‐N'‐nitro‐N‐nitrosoguanidine or ICR‐170, a red mutant accumulating lycopene, white mutants accumulating phytoene and white mutants without carotenoids were found. The biosynthesis of carotenoids in M. circinelloides shows similarities with that of the fungus Phycomyces blakesleeanus such as the presence of mutants in the same structural genes and the induction by light of the pathway. However, negative end‐product regulation by β‐carotene on the biosynthetic pathway, as in Phycomyces, is absent in M. circinelloides. In contrast to Phycomyces carB and carR mutants, carotenoids in corresponding mutants of M. circinelloides are photoinduced.
Carbohydrate Accumulation Affects the Redox State of Ascorbate in Detached Tobacco Leaves
Authors: Polle Andrea , Eiblmeier Monika
Published: February 2014

A decreased utilization of NADPH for CO2 fixation as a result of carbohydrate accumulation in chlorotic leaves is generally believed to be associated with an increase in oxidative stress. Molecular oxygen may serve as an alternative electron acceptor of photosynthesis under these conditions. In order to test this hypothesis mature leaves of tobacco plants (Nicotiana tabacum) were detached, fed with glucose (50 mM) via the petiole, and used to study the effect of carbohydrate accumulation on the pigment content and the components of the superoxide dismutase‐ascorbate‐glutathione cycle. During a period of five days the concentration of total soluble carbohydrates increased substantially in leaves supplied with glucose in comparison with control leaves supplied only with water. This increase was accompanied by a twofold decrease in the chlorophyll content. In detached water‐fed leaves the levels of most of the antioxidative components increased, whereas glucose feeding had no or only little additional effect on the activities of the protective enzymes, but caused a 1.6‐ and 4‐fold increase in the contents of glutathione and ascorbate, respectively. In relation to the total foliar ascorbate pool, the amount of reduced ascorbate increased from about 30 % to 60 % upon feeding with glucose. These results do not support the idea that the accumulation carbohydrates per se cause an increased rate of superoxide production which necessitates increased activities of antioxidative enzymes. It rather appears that glucose‐fed leaves have an increased reductive capacity that can be released via glutathione into the ascorbate pool, thereby, regulating the redox state of ascorbate.
Allopolyploid Origin of Arabidopsis suecica (Fries) Norrlin: Evidence from Chloroplast and Nuclear Genome Markers
Authors: Mummenhoff K. , Hurka H.
Published: February 2014

The origin of the presumed allopolyploid Arabidopsis suecica has been explored through isozyme electrophoresis and mutational analysis of chloroplast (cp) DNA. Nuclear encoded isozymes are inherited biparentally and were used to indicate A. thaliana and Cardaminopsis arenosa as parental species. Analysis of the maternally inherited cpDNA provided strong evidence for A. thaliana as maternal parent. The isozyme data suggest multiple origin of A. suecica, because the alloploid shows polymorphisms at the same loci that are polymorphic in its progenitors. The molecular data are in agreement with the hypothesized recent origin of A. suecica at the Late glacial/Holocene boundary in Fennoscandia, in areas opened up by retreating glaciers.
The Involvement of Protein Synthesis Elongation Factor 1α in the Organization of Microtubules on the Perinuclear Region during the Cell Cycle Transition from M Phase to G1 Phase in Tobacco BY‐2 Cells
Authors: Kumagai F. , Hasezawa S. , Takahashi Y. , Nagata T.
Published: February 2014

Association of the organization of microtubules (MTs) in the perinuclear region with a 49‐kDa protein, that is immunologically cross‐reactive to a 51‐kDa protein isolated from sea urchin centrosomes and has been shown to play some roles in the organization of MTs in animal cells (Toriyama et al.: Cell Motil. Cytoskeleton 9, 117–128, 1988), was examined during the cell cycle transition from M phase to G1 phase using the highly synchronized tobacco BY‐2 cells under confocal laser scanning microscopy (CLSM). After double staining with an antibody against the 51‐kDa protein and with an antibody against tubulin, it was revealed that the 49‐kDa protein was closely associated with the organization of MTs on the perinuclear regions during this stage under the CLSM. Notably, microfilaments (MFs) were not associated with the organization of MTs in the perinuclear region. This observation suggests that the 49‐kDa protein plays a specific role in the organization of MTs on the perinuclear regions during the cell cycle transition from M phase to G1 phase. To understand the molecular characteristics of the 49‐kDa protein further, the search for cDNA encoding the 49‐kDa protein was conducted in a cDNA expression library prepared from rapidly growing tobacco BY‐2 cells using monoclonal antibodies against the 51‐kDa protein. Determination of the base sequence of the isolated clone revealed that it encodes protein synthesis elongation factor (EF)‐1α. Thus the significance of the involvement of the 49‐kDa protein as EF‐1α in the organization of MTs on the perinuclear regions is discussed in relation to other cellular functions.
Multiple Stress Factors affecting Growth of Rock‐inhabiting Black Fungi
Authors: Sterflinger Katja , Krumbein W. E.
Published: February 2014

Black fungi, belonging to the Dematiaceae, with yeast‐like growth patterns, were isolated from rock surfaces in the Mediterranean. They tolerate high temperatures and sodium chloride stress although they are neither thermophilic nor halophilic organisms. Environmental stress factors not only affect growth velocity of the fungi but also the colony shape. A shift of the smooth and flat colonies developed under optimal culture conditions to more clump‐like growth similar to the colony shape on the natural rock substratum is caused by both high temperature and osmotic stress. The “principle of uniformity” is proposed as a new term to interpret specific morphotypes of pleomorphic fungi of different taxonomic assignment.