bluuebunny/crossref_metadata_2025 huggingface dataset:
Photorespiration is More Effective than the Mehler Reaction in Protecting the Photosynthetic Apparatus against Photoinhibition
Authors: Wu J. , Neimanis S. , Heber U.
Published: February 2014

I. Isolated intact chloroplasts: Photosystem II, but not photosystem I, of the electron transport chain is rapidly photoinactivated even by very low intensities of red light when no large proton gradient can be formed and the electron transport chain becomes over‐reduced in the absence of oxygen and other reducable substrates. Electron acceptors including oxygen provide protection against photoinactivation. Nevertheless, photosystem II is rapidly, and photosystem I more slowly, photoinactivated by high intensities of red light when oxygen is the only electron acceptor available. Increased damage is observed at increased oxygen concentrations although catalase is added to destroy H2O2 formed during oxygen reduction in the Mehler reaction. Photoinactivation can be decreased, but not prevented by ascorbate which reduces hydrogen peroxide inside the chloroplasts and increases coupled electron flow.

II. Leaves: Simple measurements of chlorophyll fluorescence permit assessment of damage to photosystem II after exposure of leaves to high intensity illumination. In contrast to isolated chloroplasts, chloroplasts suffer more damage in situ at reduced than at elevated oxygen concentrations. The difference in the responses is due to photorespiration which is active in leaves, but not in isolated chloroplasts. After photosynthesis and photorespiration are inhibited by feeding glyceraldehyde to leaves, photoinactivation is markedly increased, although oxygen reduction in the Mehler reaction is not affected by glyceraldehyde. In the presence of reduced CO2 levels, photorespiratory reactions, but not the Mehler reaction, can prevent the overreduction of the electron transport chain. Over‐reduction indicates ineffective control of photosystem II activity. Effective control is needed for protection of the electron transport chain against photoinactivation. It is suggested to be made possible by coupled cyclic electron flow around photosystem I which is facilitated by the redox poising resulting from the interplay between photorespiratory carbohydrate oxidation and the refixation of evolved CO2.
The Occurrence of Vascular Cavities and Specialized Parenchyma Cells in the Roots of Cool‐season Legumes
Authors: Rost T. L. , Lu P. , Gladish D.
Published: February 2014

The seeds of 20 legume species were grown in the greenhouse or in growth chambers at different temperatures. Under warm temperature conditions (above 15 °C), six species, pea (Pisum sativum), broadbean (Vicia faba), chickpea (Cicer arietinum), lentil (Lens culinaris), wild lupine (Lupinus latifolius), and soybean (Glycine max), formed cavities in the vascular cylinder of their primary roots, which in turn became filled by the ingrowth of specialized parenchyma cells (SP cells). When these species were grown at low temperature (below 15 °C), however, a “normal” vascular cylinder formed in the primary roots with late‐maturing metaxylem vessel members differentiating in the center. These species were all cool‐season legumes except soybean, a warm‐season legume, which sometimes also formed cavities and SP cell ingrowths. The occurrence of cavities and SP cells therefore was restricted to the cool‐season legumes (except soybean) when they were grown under warm temperature conditions. The position and size of cavities varied among these species. Pea and broadbean usually formed large, axially elongated cavities in the central vascular cylinder, or in the xylem poles. Others formed smaller cavities of various lengths.
Studies of the Mature Pollen of Spinacia oleracea after Freeze Substitution and Observed with Confocal Laser Scanning Fluorescence Microscopy
Authors: Theunis C. H. , Cresti M. , Milanesi C.
Published: February 2014

The three‐dimensional configuration of the nuclei of the trinucleate pollen grain of Spinacia oleracea L. has been examined by means of confocal laser scanning fluorescence microscopy (CLSM). It shows the presence of a male germ unit (MGU) in which all three nuclei are usually positioned in the periphery of the pollen grain. After freeze fixation and freeze substitution, the ultrastructure is better preserved than with standard chemical fixation. It shows the presence inside the pollen grain of mitochondria, dictyosomes, large starch‐containing plastids, endoplasmic reticulum (ER), vacuoles and the MGU. In the sperm cells mitochondria, vesicles, dictyosomes and ER are also found. No microtubules were found in the grain and only very few inside the sperm cells. This is in contrast with earlier published results where fluorescent‐labeled antibodies were used.
Gametophyte Regeneration and Apospory from Archegoniate Protoplasts Under Conditions Devised for Higher Plants*
Authors: Binding H. , Mordhorst G.
Published: February 2014

Developmental pathways from isolated protoplasts were investigated with the moss Funaria hygrometrica, the liverwort Anthoceros crispulus, and the fern Anogramma leptophylla. Gametophytic protoplasts regenerated gametophytes. Apospory was obtained with sporophytic protoplasts of the moss and the fern. The archegoniates also grew in interdivisional co‐cultures with solanaceous species.
p‐CMBS Modifies Extrafacial Sulfhydryl Groups at the Chara Plasma Membrane: Activation of Ca2+ Influx and Inhibition of Two Different K+ Currents
Authors: Thiel G.
Published: February 2014

The effect of the membrane impermeant sulfhydryl group (SH) reagent, p‐chloromercuribenzenesulfonic acid (p‐CMBS), on electrical membrane transport properties of the giant alga, Chara corallina, was determined. In an external medium with a high K+ concentration (5 mM) cells typically exhibited stable membrane potentials close to the K+equilibrium potential. The steady‐state current‐voltage (I‐V) relation could be dissected into two distinct components: an almost linear ohmic leak current and a voltage‐dependent K+ current. Adding 0.5 mM p‐CMBS to the external medium resulted in an immediate, short depolarization transient (resembling the time course of an action potential) and was associated with a slow down of the cytoplasmic streaming velocity. The depolarization, as well as the streaming inhibition, could be abolished by pretreating cells with the Ca2+ channel inhibitor, LaCl3. This suggests that the depolarization transient reflected a p‐CMBS induced Ca2+ influx, a scenario known to trigger membrane excitation and slow down of cytoplasmic streaming. From the I‐V analysis it appeared that p‐CMBS also caused a reversible inhibition of two additional transmembrane currents: (1) a reduction of a leak current and (2) a modification of the deactivation kinetics of the voltage‐dependent K+ channels. From the I‐V difference analysis, the inhibited leak current was identified as a K+ current, because the reversal potential was close to the estimated K+ equilibrium potential. Control experiments have furthermore shown that the mercapto reagent, dithiothreitol, partly reversed the effect of p‐CMBS. This strengthens the view that the action of the mercurial is related to a specific and direct modification of SH groups. The p‐CMBS‐evoked inhibition of K+ currents was not abolished by the LaCl3 pretreatment, which suggests that the effect of the SH reagent is not induced indirectly by p‐CMBS‐triggered Ca2+ influx. Therefore, it is suggested that the mercurial interacts direcly with the K+ transport protein.
Flexibility in CO2 — Fixation Pathway of a Highland Kalanchoë, Kalanchoë petitiana A. Rich.
Authors: Fetene M. , Lüttge U. , Ziegler H.
Published: February 2014

Photosynthetic flexibility and water use efficiency of Kalanchoë petitiana A. Rich., a facultative CAM plant endemic to the highlands of Ethiopia, were investigated to determine the physiological determinants for the ecological success of the plant. Both field measurements of δ13C and greenhouse gas exchange studies showed a shift from C3 photosynthesis to CAM as leaves aged or at the onset of water stress. Recycling of CO2 was observed in developing leaves without concomitant net CO2 uptake. Accumulation of malate was positively correlated with increased cell sap osmolality and improved daily water use efficiency. The importance of flexibility in carbon uptake pathway and of recycling CO2 for the ecological success of the plant is discussed.
Composition of Orchid Scents Attracting Euglossine Bees
Authors: Gerlach G. , Schill R.
Published: February 2014

Fragrance composition of flowers from 101 plant species, especially orchids, were analyzed. Several compounds, including allo‐aromadendrene, β‐bourbonene, α‐copaene, α‐cubebene, 1,2‐dimethoxybenzene, 1,3,5‐trimethoxybenzene, epoxygeranyl acetate, 7,11‐epoxymegastigma‐5(6)‐en‐9‐one, two γ‐lactones, germacradienol, germacrene D, humulene, methoxy‐phenyl‐ethyl acetate, myrcene epoxide, sabinene, styrene, and undecatriene were detected for the first time in orchids. Fragrance composition of flowers pollinated by male euglossine bee species (perfume flowers) of four plant families are compared and contrasted with those of orchid species with other pollination systems.

Melittophilous, but highly specialized orchids, produce fragrances rich in different sesquiterpenes and other rare compounds. In the species that are exclusively pollinated by fragrance‐collecting male euglossine bees, the fragrances are primary attractants that serve both as an attractant and as a reward. The unusually intensely smelling flowers mostly produce esters and monoterpenes. The fragrances of euglossophilous flowers of the three plant families investigated are composed of nearly the same sets of chemical compounds, suggesting convergent evolution.

Typically, euglossophilous plant species produce large amounts of few fragrant substances while melittophilous species often produce rare compounds in small amounts.
Pollination and Breeding System of Vellozia squamata (Liliales: Velloziaceae): A Species of the Brazilian Cerrados
Authors: Oliveira P. E. , Gibbs P. E. , Bianchi Marta
Published: February 2014

The pollination biology and breeding system of Vellozia squamata (Velloziaceae), a species of cerrado vegetation in Central Brazil, were studied. V. squamata is unusual in being pollinated by a few, generalist bee species despite having very large flowers, and having a distinctive pulsed flowering phenology. The species is self‐incompatible but with a late‐acting, post‐fertilization rejection mechanism.
Direct Measurements of the Pressure and Flow in the Xylem Vessels of Nicotiana tabacum and their Dependence on Flow Resistance and Transpiration Rate
Authors: Benkert R. , Balling A. , Zimmermann U.
Published: February 2014

The relationships between xylem tension, velocity of water ascending and transpiration in tobacco plants were measured by means of the “xylem pressure probe technique” (Balling, A. and Zimmermann, U., Planta 182, 325–338, 1990). The flow velocity was determined by suction or injection of fluorescein (or FITC‐labelled dextrans of various molecular weights) from the microcapillary of the pressure probe into the punctured xylem vessel, followed by serial‐sectioning of the stem after a given propagation time. The distance travelled was defined as the distance from the injection point to the uppermost xylem section in which the dye could be detected. For a transpiration rate of 0.52 ± 0.12 ml . h−1, a linear dependence between the flow velocity and the tension gradients was found as expected from the Hagen‐Poiseuille law. The slope of the straight lines decreased with increasing molecular weight of the fluorescent labelled compound, presumably because of (partial) plugging of the pit membranes. The average value of the flow velocity (2.5 . 10−4 ± 0.9 . 10−4 m . s−1) was one magnitude smaller than the value estimated from the geometric dimensions of the xylem vessels, but agreed well with the literature value of 2.8 . 10−4 m . s−1 for herbs (determined by the heat pulse technique; Huber, B. Ber. deutsch. bot. Ges. 50, 89–109, 1932). The average pressure gradient was determined to be 0.39 ± 0.23 MPa . m−1, in agreement with the literature (Begg, J. E. and Turner, N. C. Plant Physiol. 46, 343–346, 1970).

The first response of xylem pressure (or tension) and of flow velocity to a reduction of the transpiration rate (0.14 ± 0.06 ml . h−1) occurred after about 24 h, when an increase of the xylem pressure towards higher values associated with a decrease in flow velocity was observed. In contrast, re‐establishment of the normal transpiration rate brought the pressure (or tension) and the flow velocity back to normal values within half an hour.

Similary, introduction of a transverse cross‐sectional cut into the stem did not lead during the first 10 h to a change in xylem tension (or velocity). However, during the following day the pressure fell to relatively low values (about −0.13 MPa). The velocity increased 10‐fold. In the next two days the xylem pressure increased again to normal values (average +0.03 MPa), whereas the flow velocity assumed higher values than normal.

The data are discussed in terms of the water status and storage of the adjacent tissue cells.
Jasmonates, New Regulators of Plant Growth and Development: Many Facts and Few Hypotheses on their Actions
Authors: Parthier B.
Published: February 2014

Jasmonates, ubiquitous cyclopentanone compounds, are reviewed as new regulators for plant growth and development. They may complement the group of well‐established “classic” phytohormones. Jasmonates influence a multiplicity of plant physiological processes by inhibition, promotion or induction. In many aspects they are similar to abscisic acid, especially in responses to stress. The review contains information on the chemical structures and metabolism of jasmonates, contributes to their biological role and describes possible mode(s) of action at the level of molecular biology and gene expression. In particular, emphasis is placed on the gene expression and accumulation of jasmonate‐induced abundant polypeptides as a stress response of the plant cells. A hypothesis is attempted in which endogenous jasmonates represent an integral part of the signal transduction chain between stress signal(s) and stress response(s).
Osmotic Biosensors. How to Use a Characean Internode for Measuring the Alcohol Content of Beer
Authors: Rüdinger M. , Hierling P. , Steudle E.
Published: February 2014

Isolated internodes of Chara corallina and Nitella flexilis have been used to determine the concentration of one passively permeating solute in the presence of non‐permeating solutes. The technique was based on the fact that the shape of the peaks of the biphasic responses of cell turgor (as measured in a conventional way using the cell pressure probe) depended on the concentration and composition of the solution and on the permeability and reflection coefficients of the solutes. Peak sizes were proportional to the concentration of the permeating solute applied to the cell. Thus, using the selective properties of the cell membrane as the sensing element and changes of turgor pressure as the physical signal, plant cells have been used as a new type of biosensor based on osmotic principles. Upon applying osmotic solutions, the responses of cell turgor (P) exactly followed the P(t) curves predicted from the theory based on the linear force/flow relations of irreversible thermodynamics. The complete agreement between theory and experiment was demonstrated by comparing measured curves with those obtained by either numerically solving the differential equations for volume (water) and solute flow or by using an explicit solution of the equations. The explicit solution neglected the solvent drag which was shown to be negligible to a very good approximation. Different kinds of local beers (regular and de‐alcoholized) were used as test solutions to apply the system for measuring concentrations of ethanol. The results showed a very good agreement between alcohol concentrations measured by the sensor technique and those obtained from conventional techniques (enzymatic determination using alcohol dehydrogenase or from measurement of the density and refraction index of beer). However, with beer as the test solution, the characean internodes did show irreversible changes of the transport properties of the membranes leading to a shift in the responses when cells were treated for longer than 1 h with diluted beer. The accuracy and sensitivity of the osmotic biosensor technique as well as its possible applications are discussed.
Autumn Leaves of Ginkgo biloba L.: Optical Properties, Pigments and Optical Brighteners
Authors: Matile Ph. , Flach Barbara M.‐P. , Eller B. M.
Published: February 2014

Senescent leaves of Gingko biloba accumulate fluorescent compounds which may contribute to the golden luminous appearance of the autumnal foliage. Apart from the putative effect of such optical brighteners, the changes of spectral optical properties associated with senescence are due to the breakdown of chlorophyll in conjunction with a remarkably high retention of carotenoids. Carotenoid esters accumulate concomitant with chlorophyll breakdown. Optical properties in the infrared range of the spectrum illustrate the intactness of leaf tissue to the end of the senescence period.
Production of the Phytoalexin Glyceollin I by Soybean Roots in Response to Symbiotic and Pathogenic Infection
Authors: Schmidt Petra E. , Parniske M. , Werner D.
Published: February 2014

The amount of the phytoalexin glyceollin I in root exudate and root hairs of individual seedlings of Glycine max (L. Merr. cv. Preston) was analysed using a radioimmunoassay. Bradyrhizobium japonicum 110spc4, which is able to form nitrogen fixing nodules with this plant, caused an increase of up to 50‐fold in glyceollin I levels in root exudate relative to uninfected control seedlings. Maximum glyceollin I levels were reached within 10 h of incubation. Elevated glyceollin I levels were also observed after incubation of soybean roots in sterile bacterial supernatant, a suspension of autoclaved bacteria or the supernatant from broken cells of Bradyrhizobium japonicum. Increased glyceollin I production is not due to the process of active root hair penetration by the microsymbiont since living bacterial cells are not necessary for the induction. The observed glyceollin I production in response to Bradyrhizobium japonicum is several times lower than that after pathogenic infection. Infection with zoospores of the phytopathogenic oomycete, Phytophthora megasperma f. sp. glycinea race 1, leads within 20 h to an accumulation of 7 nmol glyceollin I/seedling in the root exudate of the compatible cultivar Kenwood and 48 nmol glyceollin I/seedlings in that of the incompatible cultivar Maple Arrow. These results support the idea that phytoalexins are implicated in determination of compatibility in pathogenic interactions. Crude cell extracts of different symbiotic bacteria (Bradyrhizobium japonicum 110spc4, Rhizobium meliloti 2011, Rhizobium leguminosarum PRE 8, Sinorhizobium fredii HH 103) were found to induce different amounts of glyceollin I in the root exudate. The observed glyceollin I levels could not be correlated with the ability of these rhizobial strains to nodulate Glycine max. Inhibition of flavonoid and phytoalexin synthesis by (R)‐(1‐amino‐2‐phenylethyl)phosphonic acid (APEP), a specific inhibitor of the phenylalanine‐ammonia‐lyase (PAL), during the first 20 h of the symbiotic interaction dramatically decreased the number of nodules formed in root regions that had been in contact with the inhibitor. This effect was observed at concentrations that inhibited neither bacterial nor plant growth. The implications of these findings for the process of nodule initation are discussed.
Changes in the Ultrastructure of Prasiola crispa ssp. antarctica under Salinity Stress
Authors: Jacob A. , Lehmann H. , Kirst G. O. , Wiencke Chr
Published: February 2014

The supralittoral green alga Prasiola crispa, collected in Antarctica, was grown at salinities ranging from 0.35 %o to 175 %o. Its ultrastructure was examined by electron microscopy and compared with the ultrastructure of plants grown under standard conditions (35 %o).

The thalli had very thick cell walls, making up approximately 50% of the thallus volume. Most of the protoplast was occupied by a single chloroplast. Numerous starch granules in the chloroplast were enlarged under hypo‐osmotic conditions and reduced in volume when subjected to hyperosmotic stress indicating a metabolic shift towards low molecular weight organic osmolytes under the latter conditions. Whilst vacuoles were lacking in plants cultured at salinities between 0.35 %o and 35 %o, they developed under hyperosmotic conditions and possibly may serve as compartments accumulating inorganic ions.

Growth, photosynthesis and dark respiration were strongly inhibited under higher salinities, whilst they remained almost unaffected under lower salinities (Jacob et al., 1991).
Developmental Changes in the Anatomy of the Sugarcane Stem in Relation to Phloem Unloading and Sucrose Storage
Authors: Jacobsen Karin Ruth , Fisher D. G. , Maretzki A. , Moore P. H.
Published: February 2014

Transverse sections of immature and mature sugarcane internodes were investigated anatomically with white and fluorescence light microscopy. The pattern of lignification and suberization was tested histo‐chemically. Lignification began in the xylem of vascular bundles and progressed through the sclerenchymatic bundle sheath into the storage parenchyma. Suberization began in parenchyma cells adjacent to vascular bundle sheaths and spread to the storage parenchyma and outer sheath cells. In mature internodes most of the storage parenchyma was lignified and suberized to a significant degree, except in portions of walls of isolated cells. The pattern of increasing lignification and suberization in maturing internodes more or less paralleled an increase of sucrose in stem tissue. In mature internodes having a high sucrose concentration, the vascular tissue was surrounded by thick‐walled, lignified and suberized sclerenchyma cells. The apoplastic tracer dyes triso‐dium 3‐hydroxy‐5,8,10‐pyrenetrisulfonate (PTS) and amido black 10 B, fed into cut ends of the stalk, wereconfined to the vascular bundles in all internodes above the one that was cut — with no dye apparently in storage parenchyma tissue. Thus both structural and experimental evidence is consistent with vascular tissue being increasingly isolated from the storage parenchyma as maturation of the tissue proceeds. We conclude that in mature internodes the pathway for sugars from the phloem to the storage parenchyma is symplastic. The data suggest that an increasingly greater role for a symplastic pathway of sugar transfer occurs as the tissue undergoes lignification/suberization.
The Control of Lateral Root Development in Cultured Pea Seedlings. II. Root Fasciation Induced by Auxin Inhibitors
Authors: Hinchee Maud A. W. , Rost Th. L.
Published: February 2014

Lateral root development in cultured seedlings of Pisum sativum (cv. Alaska) was modified by the application of auxin transport inhibitors or antagonists. When applied either to replace the root tip or beneath the cotyledonary node, two auxin transport inhibitors, 2,3,5‐triiodobenzoic acid (TIBA) and 3,3a‐dihydro‐2‐(p‐methoxyphenyl)‐8H‐pyrazolo[5,1‐α]isoindol‐8‐one (DPX‐1840), increased cell division activity opposite the protoxylem poles. This resulted in the formation of masses of cells, which we are calling root primordial masses (RPMs), 2 to 3 days after treatment. RPMs differed from lateral root primordia in that they lacked apical organization. Some roots however developed both RPMs and lateral roots indicating that both structures were similar in terms of the timing and location of cell division in the pericycle and endodermis leading to their initiation. Removal of the auxin transport inhibitors allowed many of the RPMs to organize later into lateral root primordia and to emerge in clusters. When the auxin, indoleacetic acid (IAA) was added to the growth medium along with DPX‐1840, 3 ranks of RPMs now in the form of fasciated lateral roots emerged from the primary root. The auxin antagonist, p‐chlorophenoxy‐isobutyric acid (PCIB), also induced RPM formation. In contrast to DPX‐1840 treatment, the addition of IAA during PCIB treatment caused normal lateral root development.
Cyanobacterial Picoplankton from Lake Constance*
Authors: Ernst Anneliese , Sandmann G. , Postius Christine , Brass Susanne , Kenter U. , Böger P.
Published: February 2014

Four types of unicellular cyanobacteria were classified by pigment composition and cell size. These originated from the picoplankton fraction of Lake Constance, Germany. β‐Carotene and zeaxanthin were found to be the main carotenoids of three Synechococcus isolates. In this group, coccoid forms with phycocyanin‐rich phycobilisomes also produce caloxanthin and nostoxanthin, which are xanthophylls with 3 and 4 hydroxy groups, respectively. In addition, these rare carotenoids are observed in rod‐forming Synechococcus isolates which contain phycoerythrin‐rich phycobilisomes, but they are very low or absent in the coccoid phycoerythrin‐rich isolates. Due to size and pigment content the coccoid forms are similar to Synechococcus leopoliensis (SAUG B 1402‐1, formerly Anacystis nidulans) and S. rubescens (SAUG B 3.81) while the rod‐forming isolates differ from S. elongatus (PCC 6716) in phycobilisome composition.

The isolate BO 8402 was tentatively assigned to Synechocystis but differs in pigment composition from all strains described as yet. The green cultures exhibited a faint red glow due to an unusual high in vivo autofluorescence from phycocyanin. Neither were phycobilisomes found in a standard preparation nor was allophycocyanin present. The most abundant carotenoids are β‐carotene and caloxanthin, while zeaxanthin, with 12 % of all colored carotenoids, is low.

All forms described in this paper lack complementary chromatic adaptation, indicating that the pigment composition is a reliable parameter to identify these freshwater isolates.
Changes in Sulfur Metabolism During Needle Development of Norway Spruce*
Authors: Schupp R. , Rennenberg H.
Published: February 2014

In a field‐study with approx. 150‐year‐old spruce trees, seasonal changes in thiol composition and content, sulfate content, and oxtractable activities of enzymes of sulfate reduction and assimilation were analyzed in needles and buds and were related to developmental processes during flushing. GSH was the predominant thiol in spruce needles throughout the year, with maximum contents of more than 400nmol g FW−1 during winter and minimum contents of less than 200 nmol g FW−1 during summer. Negative correlation of changes in GSI1 contents during winter and spring with air temperature showed a low correlation coefficient (r =– 0.55), suggesting minor significance of GSH in frost protection. Drastic changes in thiol contents during flushing suggested that GSH accumulated in the previous year's needles during winter supports the growing needles with reduced sulfur. Sulfate and other substrates for sulfate assimilation appeared to be available in buds and the new needles. An external supply with reduced sulfur may still be required because of insufficient activities of enzymes of sulfate reduction and assimilation, esp. ATP‐sulfurylase and APS‐sulfotransferase.
Secondary Carotenoids of Eremosphaera viridis De Bary (Chlorophyceae) Under Nitrogen Deficiency*
Authors: Vecktel B. , Kallmann U. , Ruppel H. G.
Published: February 2014

Under nitrogen deficiency the unicellular chlorococcalean green alga, Eremosphaera viridis De Bary, was able to synthesize secondary carotenoids (SC). Nine SC were identified as six astaxanthin esters, echinenone, canthaxanthin and a lutein ester, previously not described in green algae under nitrogen deficiency. These SC, jS‐carotene and the main part of lutein were located in lipid bodies outside the chloroplasts in the cytosol. The synthesis of SC could be inhibited by the herbicides norflurazon and nicotine. This result supported the idea that SC in cells ot Eremosphaera viridis were synthesized de novo rather than derived from primary carotenoids.
Confocal pH Topography in Plant Cells — Acidic Layers in the Peripheral Cytoplasm and the Apoplast
Authors: Roos W.
Published: February 2014

The distribution of intracellular pH was studied in cultured cells of Gossypium hirsutum by con‐focal pH topography using the fluorescent probe car‐boxy SNARF1 and a ratio imaging procedure. The resulting pH maps can visualize pH differences with an accuracy of 0.1 unit in the investigated range between 7.5 and 5.6. They reveal the following characteristic features of the Gossypium cells:

– the pH of the cytoplasmic core regions ranges from near 7.4 in younger to near 6.0 in older cells;

– vacuoles show the expected acidity with pH < 5.6;

– the cell wall/apoplastic region is acidic with a pH near 5.6 or below, especially in young, growing cells;

– interestingly, acidic areas appear also at the periphery of the cytoplasm, i.e. beneath the plasma membrane. They remain stable in the presence of 5/μmol/I of the protonophore CCCP.

Acidic layers of peripheral cytoplasm were also detected in protoplasts of Penicillium cyclopium, i.e. eukaryotic cells of simpler structure, which served as a reference object. This ronfirms earlier findings obtained with classical fluorescence microscopy and another fluoroprobe (fluorescein diacetate). Though additional experimental support is needed, low pH regions at the cytoplasm/plasma membrane interface should be considered a real contribution to the pH control of plant and fungal cells, facilitating e.g. the maintenance of cytosolic pH in acidic environments.
Selective Reconstitution of the Tonoplast H+‐ATPase of the Crassulacean‐Acid Metabolism Plant Kalanchoë daigremontiana
Authors: Behre Barbara , Ratajczak R. , Lüttge U.
Published: February 2014

IA detergent removal technique was used to reconstitute solubilized tonoplast proteins of mesophyll cells of the CAM plant Kalanchoë daigremontiana into phosphatidylcholine liposomes. The proteoliposomes were able to hydrolyse ATP and to pump protons across the vesicle membrane. Both activities were inhibited by nitrate, an inhibitor of V‐type ATPases. Freeze‐fracture micrographs confirmed the incorporation of membrane proteins into liposomes. Increase of specific ATP‐hydrolysis activity compared to solubilized tonoplast proteins and SDS‐PAGE analysis of reconstituted proteins in comparison with the polypeptide pattern of the purified tonoplast H+‐ATPase from the same plant source indicated a highly selective reconstitution of the tonoplast H+‐ATPase.
Travelling Pattern of Acidity in the Epidermis of Tulip Leaves
Authors: Hejnowicz Z.
Published: February 2014

Many growing leaves of tulips show subtle undulations of their surface, oriented mostly transversely to the leaf axis. The undulations move acropetally with respect to cells. The epidermal peels from the leaves with the undulations placed on agar plates containing a pH indicator dye produce band patterns of more acid and less acid zones. Similar patterns also appear when the agar‐indicator is applied to the abraded leaf surface. This indicates that there is spatially variable H+ efflux from the epidermis into agar. No variation of the colour appears when the agar‐indicator is applied to the mesophyll surface formed by peeling off the epidermis, which indicates that the pH pattern is a feature of the epidermis only. The pattern of pH bands correlates closely with the pattern of undulation; more acid bands correspond to the convex zones of the surface. The movement of the undulations also indicates that the pH pattern moves, which means that in the epidermal apoplast the pH oscillates at a particular location.
Photoinhibition of Photosynthesis and its Recovery in Red Algae
Authors: Hanelt D. , Huppertz K. , Nultsch W.
Published: February 2014

In different marine red algae (Chondrus crispus, Delesseria sanguinea, Membranoptera alata, Phycodrys rubens, Phyllophora truncata, Polyneura hilliae) photoinhibition of photosynthesis has been investigated by means of both fluorescence and oxygen measurements. Measurements of absolute oxygen production show that photoinhibition causes a decline in the initial slope and in the rate of bending of the fluence rate‐response curve (i.e. the photosynthetic efficiency at non‐saturating fluence rates), as well as a decline in the photosynthetic capacity (Pm) at saturating fluence rates. Fluorescence data (Fv/Fm) were consistent with the results of oxygen measurements. Under excessive light photoinhibition protects photosynthesis against photo‐damage in red algae. However, an increase in the initial fluorescence (Fo) after photoinhibitory treatment indicates that it could not prevent photodamage entirely.

Action spectra of photoinhibition demonstrate that the main photoinhibition site in Polyneura hiliae is PS II, because far red light absorbed by PS I was ineffective. The strong increase of Fo in the blue wavelength range and the slight and partial recovery in weak blue light indicate that blue light especially causes photodamage.

Recovery of photosynthesis requires dim white light conditions. Experiments with monochromatic light also show a wavelength dependence of recovery. Moreover, the recovery of photosynthesis after a photoinhibitory treatment is strongly temperature dependent, indicating participation of enzymatic processes. The comparison of fluorescence and oxygen measurement of the recovery shows different results in some species. The rate of oxygen production in red control light increased immediately after photoinhibited algae were exposed to weak light conditions. Surprisingly, the ratio of variable to maximum fluorescence (Fv/Fm) of Phyllophora truncata and the maximum fluorescence (Fm) of Polyneura hilliae show first a delay of the recovery under weak light conditions. Thus, in recovery experiments fluorescence and oxygen data are not quite consistent.
Experimental and Modelling Studies of Competition for Light in Roadside Grasses
Authors: Beyschlag W. , Ryel R. J. , Ullmann I.
Published: February 2014

Equiproportional mixtures and monocultures of two roadside grass species (Elymus repens (L.) Gould and Puccinellia distans (L.) Pari.) were grown in experimental field plots under non‐limiting water and nutrient conditions. During the course of the season, E. repens increasingly overgrew and shaded plants of P. distans which eventually died. A multispecies canopy photosynthesis model was parameterized using measurements of structural and physiological characteristics from three different stages of canopy development. Results of simulations clearly revealed that canopy photosynthesis of P. distans was highly dependent on the degree of light competition caused by E. repens. Since P. distans has recently invaded stands of roadside vegetation throughout Central Europe where it has replaced the native and highly competitive E. repens, it is hypothesized that this success is due to disturbance factors that keep E. repens from growing tall and shading P. distans.
In Vitro Ovary Culture of some Apogon Garden Irises (Iris pseudacorus L., I. setosa Pall., I. versicolor L.)
Authors: Laublin Geneviève , Cappadocia M.
Published: February 2014

Various organs of immature inflorescences from 32 selected genotypes of Iris versicolor, 6 of I. pseudacorus and 7 of I. setosa were cultured in vitro on two induction media supplemented with 45 μM 2, 4‐D or 4.5 μM each of 2, 4‐D and kinetin. Among the explants tested, peduncle sections showed a very limited response, and only ovary sections cultured under low light intensity consistently produced calluses and/or meristematic nodules on both media. This occurred in all genotypes of I. pseudacorus, whereas only a fraction of the genotypes belonging to the other species responded at the induction phase. Responding explants with callus and/or meristematic nodules were cut into halves and transferred onto a regeneration medium containing 22 μM benzyladenine, which induced shoot formation. Once again, large differences in response were noted among genotypes of each species. Those belonging to I. pseudacorus all gave a positive response producing vigorous shoots. Cytological analyses performed on 62 regenerated plants did not reveal changes in chromosome number.
Phenotypic Similarity and Genetic Relationship Among Populations of Microseris bigelovii (Asteraceae: Lactuceae)
Authors: Bachmann K.
Published: February 2014

Twelve inbred strains have been derived from 10 representative populations of the North American annual M. bigelovii. The distribution and correlation of 21 phenotypic characters distinguishing these strains has been studied. The genetic similarity of these strains has been previously determined using nu clear DNA polymorphisms. Genetically similar strains (always geographic near neighbors) share phenotypic character states but these involve different characters in different cases. A few character state differences are correlated across all strains via early rosette growth rate, timing of reproduction, or overall capitulum size. Most character states recombine freely. This is evidence for effective gene flow (probably by achene dispersal) among these isolated populations.
Changes in the Constitution of Thylakoid Membranes in Spruce Needles During an Open‐top Chamber Experiment
Authors: Flammersfeld U. , Wild A.
Published: February 2014

The goal of the presented paper was to study the emission effects of natural air pollutants on the protein complexes of the thylakoid membrane. The tests were carried out in the frame of a long‐term experiment in which spruce trees kept in open‐top chambers with unfiltered ambient‐air were compared to spruce trees in chambers with purified‐air. The reaction centres of photosystem I (P‐700), cytochrome f, cytochrome b‐563, cytochrome b‐559, as well as the oxidation speed of the antennae chlorophylls were quantified.

The concentrations of the cytochromes f and b‐563 indicate a marked annual rhythm with decreased concentrations during the summer months. The spruce trees in chambers with ambient‐air showed a smaller amount of the studied redox components in relation to 1000 molecules of chlorophyll than did the spruce trees in chambers exposed to purified‐air. In addition, increased oxidation speed of antennae chlorophylls could be observed on the isolated thylakoid membranes of the spruce trees in chambers with ambient‐air conditions. A relationship between the oxidation speed and the ozone concentration of the ambient air could be observed, i.e. with increasing ozone levels the oxidation of the antennae chlorophylls accelerated. However, the damage occurred only with a temporary delay (the so‐called memory effect).

In case of the cytochromes f and b‐563 (components of the cytochrome b6f‐complex), a chamber effect related to changed light conditions became obvious when comparing spruce trees kept in chambers to trees left in their natural surrounding. The reduced photosynthetically active radiation — it is reduced in the chambers by 10 − 30% — led to a decrease of both cytochromes.

In spite of the effects due to the chambers, the results indicate that ozone could be an effective damage factor and this will be of importance with regard to the situation in the low mountain range of Germany.
The Specific Mineral Metabolism of Selected Plant Species and its Ecological Implications
Authors: Kinzel H. , Lechner Ilse
Published: February 2014

In order to assess and compare the species‐specific mineral metabolism of various plants, we raised eight selected species from different families under identical nutritional conditions. Five different nutrient solutions with varying Ca/K ratios were used. After two months of growth, the leaves were harvested, arranged according to age, and analyzed with respect to their K, Ca, and Mg contents. The ion ratios, the changes of ion contents with increasing age, the differences in water‐ and acid‐soluble Ca (calcium oxalate), and the dependence of ion uptake on variations of ion concentrations in the solutions revealed a species‐specific (“physiotypic”) feature of mineral metabolism. These features are discussed taking into consideration the ecological demands of the investigated species, and assuming that the physiological peculiarities of a species should affect its ecological behavior.
A Comparative Study of Internal Light Environment in Bifacial Leaves of Different Plants
Authors: Remisotosku A. Martinez v. , McClendon J. H. , Fukshansky L.
Published: February 2014

Parameters of light propagation in plant leaves — absorption and scattering coefficients, asymmetry of scattering — have been estimated on the basis of measured transmission and emission as well as internal fluxes. This estimation has been carried through by solving the inverse problem of the 4‐flux radiative transfer — a theory considering forward and backward diffuse as well as directed components of the overall radiation in a multiple scattering sample. Using the gained parameters, light flux gradients in a two‐layered model leaf have been calculated at different wavelengths. Monte Carlo simulation of absorption spectra performed with the parameters obtained with this treatment is in a good agreement with experimental spectra, thus substantiating the theory. Parallel calculations with the two‐flux (Kubelka‐Munk) theory provide an estimation of the accuracy and applicability of this more simple treatment. Calculations have been performed for three different plants: Catalpa bignonioides, Tilia americana and Vitis riparia.
Peroxidase Catalyzed Dimerization and Demethylation of Protoberberine Alkaloids*
Authors: Bauer W. , Stadler R. , Zenk M. H.
Published: February 2014

A peroxidase which catalyzes, in essentially quantitative yield, the dimerization of jatrotthizine to 4,4′‐bisjatrorrhizine was isolated and partly characterized from Berberis stolonifera cell cultures. This peroxidase also mediates the demethylation of a variety of 10‐ or 3‐O‐CH3 substituted tetrahydroprotoberberines and their quarternary analogues. A survey of more than 30 cell culture species, using seven different alkaloids, demonstrated the presence of this catalytic activity mainly in the plant families Berberidaceae and Ranunculaceae, while it was absent in the Papaveraceae. Caution is justified when employing alkaloids labelled at their [‐O‐CH3] groups for enzymatic assays except when peroxidases (even without addition of H2O2) are not present.
Quantification of Visible Structural Changes of the V0V1‐ATPase in the Leaf‐tonoplast of Mesembryanthemum crystallinum by Freeze‐fracture Replicas Prepared During the C3‐Photosynthesis to CAM Transition*
Authors: Klink Rebecca , Lüttge U.
Published: February 2014

Plants of the annual facultative halophyte and facultative CAM‐plant, Mesembryanthemum crystallinum L., were irrigated with a solution containing NaCl when they had developed 3 leaf pairs. This treatment induced CAM and the plants were then watered with 400 mM NaCl until the end of the experiment of 37 days. A separate set of plants was simultaneously maintained as non‐salt treated controls. Tonoplast vesicles were prepared from the leaves at regular intervals during the time‐course of the experiment. Three samples of each preparation were freezed fractured, and carbon/platinum‐replicas taken. On a total of 1400 fracture faces the diameters and densities per unit area of intramembraneous particles were measured. The results show an increase in the average diameter of particles from 6.5 nm to 8.5 nm and an increase of the relative amount of fracture faces with high particle densities related to the total of fracture faces obtained; both of which kinetically correlated to CAM induction. This increase in size and density of particles, which are known to belong to the H+‐transporting ATPase of the tonoplast. shows independently of and in addition to protein analyses, that an increased amount of ATPase‐protein is incorporated into the membrane during CAM induction. Some possible explanations for the increase in ATPase particle size are discussed.
Ion‐selective Microelectrodes: Their Use and Importance in Modern Plant Cell Biology
Authors: Felle H. H.
Published: February 2014

The exact ion gradients across cellular membranes and their changes due to metabolic or transport processes can be best studied with the use of ion‐selective microelectrodes. The last decade of research using ion‐selective microelectrodes in intact cells has proven this technique to be indispensable for the investigation of a variety of physiological questions of regulatory processes, membrane transport, cellular signalling, developmental biology and plant nutrition. Their application to selected problems has led to numerous exciting observations, many of which have changed our view concerning cellular responses to environmental stimuli and in many instances have led to a new understanding of plant cell physiology. Since, with these electrodes, intracellular as well as extracellular free ion concentrations can be simultaneously detected with electrical transport parameters such as membrane potential and membrane conductance, they can be powerful tools in the hands of many plant cell biologists.
NPA Inhibits Secretion of Amylases by Barley Aleurone Cells and Auxins can Overcome this Inhibition
Authors: Klämbt D.
Published: February 2014

Polar cell growth is regulated by auxin (Klämbt et al., 1992). It is essentially dependent upon exocytosis. Is exocytosis directly regulated by auxin?

Aleurone cells secrete amylases, as well as other hydrolases, by exocytosis. In preliminary experiments, with 22 h of incubation, increasing concentration of N‐1‐naphthylphthalamic acid (NPA) parallels the inhibition of amylase secretion.

A model system for secretion was designed. Barley aleurone layers, previously incubated in 1 μM GA3 for 16 h, then washed extensively in the presence of 10 μM NPA for 10 min, were incubated finally for 2 h in GA3, NPA and/or auxins. NPA inhibits amylase secretion. Auxins completely abolished secretion inhibition at the optimal concentration of 1 μM.

Aleurone layers contain 1.5 to 3 μM endogenous indole‐3‐acetic acid (IAA) and have a high capacity to accumulate and retain IAA. A 7‐fold accumulation occurred within 3 h after application of 20 μM radiolabeled IAA. A loss of about 10% could be measured within the following 4 h period in fresh media, independent of the presence of NPA.

The inhibition of amylase secretion by NPA is not due to an inhibition of protein biosynthesis which was tested by the use of [35S]‐methionine.