bluuebunny/crossref_metadata_2025 huggingface dataset:
Photosynthesis of Marine Macroalgae from Antarctica: Light and Temperature Requirements
Authors: Wiencke C. , Rahmel J. , Karsten U. , Weykam G. , Kirst G. O.
Published: February 2014

The photosynthetic performance of macroalgae isolated in Antarctica was studied in the laboratory. Species investigated were the brown algae Himantothallus grandifolius, Desmarestia anceps, Ascoseira mirabilis, the red algae Palmaria decipiens, Iridaea cordata, Gigartina skottsbergii, and the green algae Enteromorpha bulbosa, Acrosiphonia arcta, Ulothrix subflaccida and U. implexa. Unialgal cultures of the brown and red algae were maintained at 0°C, the green algae were cultivated at 10°C. IK values were between 18 and 53 μmol m−2 s−1 characteristic or low light adapted algae. Only the two Ulothrix species showed higher IK values between 70 and 74 μmol m−2 s−1. Photosynthesis compensated dark respiration at very low photon fluence rates between 1.6 and 10.6 μmol m−2 s−1. Values of α were high: between 0.4 and 1.1 μmol O2 g−1 FW h−1 (μmol m−2 s−1)−1 in the brown and red algae and between 2.1 and 4.9 μmol O2 g−1 FW h−1 (μmol m−2 s−1)−1 in the green algal species. At 0°C Pmax values of the brown and red algae ranged from 6.8 to 19.1 μmol O2 g−1 FW h−1 and were similarly high or higher than those of comparable Arctic‐cold temperate species. Optimum temperatures for photosynthesis were 5 to 10°C in A. mirabilis, 10°C in H. grandifolius, 15°C in G. skottsbergii and 20°C or higher in D. anceps and I. cordata. P: R ratios strongly decreased in most brown and red algae with increasing temperatures due to different Q10 values for photosynthesis (1.4 to 2.5) and dark respiration (2.5 to 4.1). These features indicate considerable physiological adaptation to the prevailing low light conditions and temperatures of Antarctic waters. In this respect the lower depth distribution limits and the northern distribution boundaries of these species partly depend on the physiological properties described here.
Somatic Hybrids of Sunflower (Helianthus annuus L.) Identified at the Callus Stage by Isoenzyme Analysis
Authors: Barth S. , Woeste D. , Schnabl Heide
Published: February 2014

Dark grown hypocotyl protoplasts from Helianthus annuus L. cvs. Cerflor and Euroflor were electrically fused to produce somatic hybrids. Following fusion, the protoplasts were cultivated in agarose droplets for four weeks. Macroscopic visible calli (0.1‐0.3 mm) were transferred onto solid medium and calli reaching a size of 3 mm were collected. Their isoenzyme patterns were analysed based on two different isoenzymes that allow discrimination between the two cultivars used for fusion. From the examined calli, about 26 % showed an isoenzyme pattern of putative binary heterokaryocytes. The isoenzyme pattern of the non‐fused control revealed less than 5% of possibly chimeric colonies.
ATPase Activities and Membrane Fine Structure of Rhizodermal Cells from Sorghum and Spartina Roots Grown Under Mild Salt Stress
Authors: Koyro H.‐W. , Stelzer R. , Huchzermeyer B.
Published: February 2014

The study aims at correlations between ultrastructure of rhizodermal membranes and ATPase activities of two gramineous C4‐species effected by salinization of the growth medium.

Comparative investigations were done with drought‐resistant Sorghum and drought‐sensitive, salt tolerant Spartina plants grown under steady‐state conditions without or with 40 mol m−3 NaCl. Both species sustained this treatment and showed marked influences of salt on growth but not on root respiration. Generally, the intramembraneous particle (IMP) frequencies, found on freeze‐fracture replicates of rhizodermal plasmic fracture faces of the plasmalemma (PPF) and tonoplast (TPF), were higher in Sorghum than in Spartina. NaCl leads in both species to an increase of the rhizodermal IMP frequency in the TPF (∼150%) and PPF (∼120%).

The activities of T‐ and P‐ATPase were determined for membrane vesicles from crude extracts and from isolated protoplasts of roots, respectively; the results from both preparations were the same. The vanadate‐sensitive tissue ATPase activities increased under salt stress ∼ 5 times in Sorghum and ∼ 2 times in Spartina whilst the nitrate and azide‐sensitive tissue ATPase activities increased ∼ 6 times only in Sorghum.

The combination of the results from the membrane fine structures with the biochemical tests points out that salt‐effected increases of ATPase activities of Sorghum roots were ∼4 times higher than the increases of IMP frequencies on rhizodermal membranes; in Spartina this effect is less intense.

It is concluded that a salty environment leads to a higher ATPase activity per IMP in both species. The stronger reaction of Sorghum is explainable by the increase in K+/Na+ selectivity of the plasma membrane under salt stress. This is not the case for Spartina because the roots of this species include salt which subsequently is sequestered by the salt glands of the leaves.
Cortical Microtubule Organization and Internodal Cell Maturation in Chara corallina
Authors: Wasteneys G. O. , Williamson R. E.
Published: February 2014

The arrangement of cortical microtubules, as documented by immunofluorescence and immunogold‐silver enhancement, changes during the growth and maturation of giant internodal cells of Chara corallina, a process taking approximately 45 days. Transverse microtubules are found throughout growth along with a subset of distinctly non‐transverse microtubules. During the second half of the growing period, when relative growth rates are diminishing, these non‐transverse microtubules become more abundant but a few days prior to growth cessation, they are mostly absent. At about the time of growth cessation the microtubules, while retaining their locally parallel alignment, begin to show increasing deviation from the transverse axis. Eventually, a mosaic of locally parallel yet variably oriented fields of microtubules forms. Many days after growth stops, microtubules become shorter and less numerous and lose parallel alignment, leading to the formation of a random MT pattern.
Involvement of Ubiquitin in Phosphoenolpyruvate Carboxylase Degradation
Authors: Schulz Margot , Klockenbring T. , Hunte Carola , Schnabl Heide
Published: February 2014

Western immunoblot analysis of protein extracts prepared from epidermal peels, whole leaves, and mesophyll protoplasts with ubiquitin and PEPCase antibodies indicated ubiquitinated PEPCase bands and degradation products only in crude extracts which have been obtained in the presence of the proteolysis inhibitors leupeptin and hemin. After ammonium sulfate precipitation and further purification, PEPCase forms were stable and not ubiquitinated. It is assumed, that only a certain part of PEPCase is degraded via the ubiquitin‐dependent proteolysis.
Modulation of Gene Activity During Photomorphogenesis of Gametophytes of the Fern, Onoclea sensibilis
Authors: Raghavan V.
Published: February 2014

Gametophytes of the sensitive fern, Onoclea sensibilis grow as filaments in the dark and in red light and assume planar morphology in blue light. RNA content and the synthesis of different RNA fractions as monitored by [3H]‐uridine incorporation and chromatography on oligo(dT)‐cellulose column, were consistently low in the dark‐grown gametophytes, high in blue light and intermediate in red light. No new mRNAs were detected in the translation products primed by poly(A)+ RNA isolated from gametophytes grown under any conditions. Of the nearly 30 polypeptide bands identified in the in vitro profile, some increased in intensity in blue light, while most continued to decay in the dark and in red light. An increase in the intensity of the polypeptide bands was detected when dark‐ or red light‐grown gametophytes were returned to blue light. Abundance of mRNA of the gene for the large subunit of maize ribulose‐1,5‐bis‐phosphate carboxylase/oxygenase (rbcL) remained more or less unchanged during growth of gametophytes in blue light but declined to very low or undetectable levels in red light and in the dark. Transfer of gametophytes from the dark or red light to blue light led to the reappearance of rbcL mRNA. Within the limits of detectability, these observations indicate that light quality or dark condition does not affect the expression of the genome, but modifies its relative transcriptional activity. Overall, the results support the hypothesis that changes in the rate of synthesis or degradation of certain mRNAs are associated with the growth patterns of gametophytes of O. sensibilis in the different environments.
Analysis of the Growth Response of Air‐Grown Rice Coleoptiles to Submergence
Authors: Kutschera U. , Hoss R. , Fröhlich M. , Hoson T.
Published: February 2014

The effect of submergence of air‐grown rice seedlings (Oryza sativa L. var. Sasanishiki) on coleoptile growth and ultrastructure, extensibility and chemical composition of the cell walls was investigated. The lag‐time between start of submergence and the onset of the enhancement of growth was less than 4 h. The growth response was associated with a drastic thinning of the cell walls and an increase in wall extensibility. At the outer epidermal wall of both air‐grown and submerged coleoptiles electron‐dense (osmiophilic) particles were detected. During submergence, the net accumulation of cellulose and hemicellulose was reduced, but the increase in pectic substances was unaffected. Submergence caused an 80% inhibition of the net accumulation of wall‐bound phenolics (ferulic‐ and diferulic acid) compared with air‐grown controls. The osmotic concentration of the tissue saps was not affected by submergence. Our results support the hypothesis that rapid coleoptile elongation under water is caused by an inhibition of the formation of phenolic cross‐links between matrix polysaccharides via diferulate, which results in a mechanical stiffening of the cell walls in the air‐grown coleoptile.
Variation and Evolution of Karyotype Characters in Palm Subfamily Coryphoideae s.l.
Authors: Röser M.
Published: February 2014

Karyological data are presented for 13 genera of palm subfamily Coryphoideae s.l. Chromosome numbers of 4 species and of genus Guihaia (G. argyrata, 2n = 36) are new. Apart from the prevailing chromosome number of 2n = 36, subfam. Coryphoideae s.l. shows extreme heterogeneity with respect to chromosome size and morphology, organization of constitutive heterochromatin (C‐banding, fluorochrome staining), interphase nucleus structures and prophase condensation patterns. Five karyologically differing groups of genera can be distinguished (Coccothrinax‐group, Guihaia, Livistona‐group incl. Sabal, Phoenix, and Bismarckia). Chromosome evolution probably has gone from medium sized to very small chromosomes with an average length of less than 1.5 μm; hc‐distribution from evenly distributed throughout the karyotype to accumulated in few chromosomes; from simple banding patterns to complicated ones (hc‐elaboration). Karyotypes with chromosomes of continuously decreasing size, similar morphology, and uniform prophase condensation probably gave rise to almost bimodal karyotypes with non‐uniform, heteropycnotic chromosomal structures. Changes in the organization of interphase nuclei are corresponding. Karyotype differentiation is compared to major evolutionary events in floral and vegetative morphology of subfam. Coryphoideae s.l. Karyologically, genera Phoenix and Bismarckia are isolated and the relations to the remaining part of the subfamily are not clear.
Reconstitution into Liposomes of the Tonoplast ATP‐ and Pyrophosphate‐Dependent Proton Pumps from Rubus hispidus Cell Cultures
Authors: Perotti E. , Chanson A.
Published: February 2014

The ATP‐ and pyrophosphate‐dependent proton pumps from tonoplast‐enriched vesicles prepared from Rubus hispidus cell cultures were solubilized in the presence of polyoxyethylene(9,10)p‐t‐octylphenol (Triton X‐100) and reconstituted into liposomes of soybean phospholipids, using Bio‐Beads SM‐2 to remove the detergent. The specific activity of the two pumps was greatly increased by the solubilization‐reconstitution procedure. Identical characteristics were found for pyrophosphate‐dependent proton transport in native and reconstituted vesicles. On the other hand, the ATP‐dependent proton transport of the reconstituted vesicles was no longer inhibited by KNO3.
Paxillus involutus — Pinus sylvestris Mycorrhizae from Heavily Polluted Forest.
Authors: Turnau K. , Kottke I. , Oberwinkler F.
Published: February 2014

The electron‐opaque granules localized in vacuoles of Paxillus involutus hyphae associated with Pinus sylvestris mycorrhizae, collected from heavily polluted sites were analysed by electron spectroscopic imaging (ESI) and electron energy loss spectroscopy (EELS) connected with the electron microscope (TEM 902, Zeiss). On the basis of the elemental composition two kinds of granules were distinguished. The first, similar in appearance to polyphosphate granules, described already for several fungi, was characterized by high contents of phosphorus accompanied by sulphur, calcium and often aluminium. More common, however, was the second sort of granules containing more nitrogen, sulphur and cadmium, while the amount of phosphorus was much lower. The data reveal accumulation of cadmium inside fungal vacuoles and suggest the possibility of detoxification of heavy metal by the symbiotic fungus.
Effect of Root Cooling on Photosynthesis of Artemisia tridentata Seedlings under Different Light Levels
Authors: BassiriRad H. , Caldwell M. M. , Mott K. A.
Published: February 2014

Root chilling has been shown to inhibit shoot photosynthesis yet the mechanism for such an action is not clearly understood. A study was designed to elucidate the mechanism by which root cooling may affect net photosynthesis. Roots of Artemisia tridentata seedlings were cooled from 20°C to 5°C while their shoot temperature remained at 20°C. This was conducted at two light levels (700 and 1300 μmol m−2 s−1). The time course of shoot net photosynthesis (A), stomatal conductance to water vapor (gs), intercellular CO2 concentration (Ci) and root respiration (Rs) were determined on a whole‐plant basis. Root cooling caused a 25% reduction in A at high PPFD, which was preceded by more than 50% reduction of gs and about 10% reduction in Ci. A versus Ci curves for single branches showed no difference between cold and warm soil temperatures, although stomatal conductance was lower for the lower soil temperature. This suggests that a stomatal limitation may have been involved in the inhibition of A. Furthermore, a concomitant decrease of as much as 23% in leaf relative water content (RWC) indicated that root cooling affected stomatal closure due to decreased water supply to the foliage. At lower PPFD, root cooling did not cause a decrease in A of the whole plant despite a moderate drop in gs, Ci and RWC. Cold soil also led to a substantial and rapid reduction in root respiration rate (Rs) regardless of the light level.
The Effect of Nitrogen Supply to Urtica dioica L. Plants on the Distribution of Assimilate Between Shoot and Roots
Authors: Fetene M. , Möller Ina , Beck E.
Published: February 2014

In this study the influence of nitrogen nutrition on the patterns of carbon distribution was investigated with Urtica dioica. The nettles were grown in sand culture at 3 levels of NO−3, namely 3 (low), 15 (medium) and 22 (high) mM. These levels encompassed a range within which nitrogen did not affect total biomass production. The ratio of root: shoot biomass of the low nitrogen plants was, however, significantly higher than that of the nettles grown at medium and high N supply. Carbon allocation from one leaf of each pair of leaves was examined after a 14CO2‐pulse and a subsequent 14C distribution period of one night. Only the youngest two leaf pairs did not export assimilates. Carbon (14C) export to the shoot apex and to the roots, as measured at the individual nodes responded to the nitrogen status: At medium and high nitrogen supply the 3rd, 4th and 5th leaf pairs exported to the shoot apex, while lower leaves exported to the root. At low nitrogen supply only the 3rd leaf exported towards the shoot apex. The results illustrate the plastic response of carbon distribution patterns to the nitrogen supply, even when net photosynthesis, carbon export from the source leaves and biomass production were not affected by the nitrogen supply to the plant.
Some Critical Remarks on the Suitability of the Concept of the Photosynthetic Unit in Photosynthesis Research and Phytoplankton Ecology
Authors: Wilhelm C.
Published: February 2014

Based on the classical definition of the photosynthetic unit after Emerson and Arnold, new definitions are presented and their consistency subjected to critical reflection. Modern molecular approaches to determine the physiological condition or even the efficiency of the photosynthetic machinery via determination of the magnitude of the photosynthetic unit are discussed against the background of new data on the dynamics of the thylakoid membrane.
Wax as a Mechanism for Protection against Photoinhibition — A Study of Cotyledon orbiculata
Authors: Robinson Sharon A. , Lovelock Catherine E. , Osmond C. B.
Published: February 2014

The leaves of the Crassulacean acid metabolism plant Cotyledon orbiculata have a waxy coating which is highly reflective but can be easily removed by brushing. This provided an ideal system in which to investigate the role of epidermal wax as a possible photoprotectant. Removal of the wax, prior to exposure to natural sunlight, resulted in substantial decreases in Fv/Fm and in severe cases evidence of photoinhibitory damage, as indicated by a rise in Fo. Leaves from which wax had been removed also showed higher conversion of violaxanthin to zeaxanthin than waxed leaves. Recovery of brushed leaves over a 12 day period was correlated with an increase in the total pool of xanthophyll cycle components. This study suggests that the presence of highly reflective wax on the epidermis may confer significant photoprotection to plants exposed to high solar radiation environments.
Expression of P‐Enolpyruvate Carboxylase and other Aspects of CAM during the Development of Peperomia camptotricha Leaves
Authors: Ting I. P. , Hann Janet , Sipes Deborah , Patel Asmita , Walling Linda L.
Published: February 2014

During the development of Peperomia camptotricha leaves, metabolism changes from C3‐photosynthesis to Crassulacean acid metabolism (CAM). The youngest leaves showed no diurnal fluctuation of organic acids or P‐enolpyruvate carboxylase (PEPc) activity. There was little evidence for PEPc protein using PEPc antibodies prepared from the CAM form of PEPc, nor was there evidence for PEPc mRNA when tested using a cDNA probe made from CAM P. scandens. As leaves matured, there was a parallel increase in titratable acidity, PEPc activity, PEPc protein, and PEPc mRNA. In leaf whorls 1 through 6, there was a significant linear correlation between the diurnal fluctuation of organic acids and PEPc activity indicating a functional relationship. The specific activity of PEPc increased as leaves matured and the Km (PEP) decreased indicating that the enzyme was becoming more active. The ratio of PEPc protein to PEPc mRNA decreased as leaves matured. During the expression of CAM, the spongy mesophyll where most of the CAM activity occurs increased in thickness and per cent air space, whereas the palisade mesophyll where most of the C3 activity occurs did not increase in size dramatically. The diurnal fluctuation of organic acids and the expression of PEPc activity, protein, and mRNA increased as the thickness of the spongy mesophyll increased. During the expression of CAM in Peperomia camptotricha, there appears to be coordinated expression of PEPc mRNA, protein, and activity, the commencement of diurnal organic acid fluctuation, and the development of the CAM‐like spongy mesophyll. Thus the evidence suggests that CAM in this species is expressed during normal development and not in response to environmental signals.
Quantitative Evaluation of Erotactin Secretion in Eggs of Hormosira banksii (Fucales, Phaeophyceae)
Authors: Maier I. , Clayton M. N.
Published: February 2014

The release of the C11‐hydrocarbon spermatozoid attractant hormosirene by eggs of the Australian fucoid Hormosira banksii has been determined quantitatively using a closed‐loop extraction technique. The eggs secrete erotactin for more than 2 weeks with an exponentially decreasing rate. The initial secretion rate was estimated to be 75 fmol h−1 egg−1 and the total amount of hormosirene produced per egg to be 2.35 pmol (0.35 ng). The results were used to calculate the threshold range for spermatozoid chemotaxis in the pheromone gradient around eggs.
Studies on the Sporogenous Lineage in the Moss Timmiella barbuloides
Authors: Gambardella R. , Duckett J. G. , Alfano F. , Gargiulo M. , Squillacioti C.
Published: February 2014

This correlated immunofluorescence and electron microscope study reveals that the microtubule arrays during meiosis in Timmiella barbuloides mirror those in other mosses but the organization of the metaphase I spindle is quite different. In other mosses the sagittiform metaphase I spindle initially contains four bands of microtubules derived from the tetrahedral system present at prophase. These bands converge towards the division axis and each half spindle contains two focal points of microtubules straddling a cleavage furrow. In Timmiella the sagittiform spindle also contains four microtubular foci derived from the preprophasic tetrahedron. However, one of these contributes to one half spindle, the other half deriving from the three remaining foci orientated at approximately 120° to each other. In contrast to other mosses the sporocytes in Timmiella are hardly lobed, the cleavage‐furrows ill‐defined, the prophasic plastid positioning in the lobes is also more variable and the organelle band in meiocytes comprises mitochondria alone.
Studies on the Localization and Spectral Characteristics of the Fluorescence Emission of Differently Pigmented Wheat Leaves
Authors: Stober1 F. , Lichtenthaler H. K.
Published: February 2014

Intensity, spectral characteristics and localization of the UV‐laser (337 nm) induced blue‐green and red fluorescence emission of green, etiolated and white primary leaves of wheat seedlings were studied in a combined fluorospectral and fluoromicroscopic investigation. The blue‐green fluorescence of the green leaf was characterized by a maximum near 450 nm (blue region) and a shoulder near 530 nm (green region), whereas the red chlorophyll fluorescence exhibited maxima in the near‐red (F690) and far‐red (F735). The etiolated leaf with some carotenoids and traces of chlorophyll a, in turn, showed a higher intensity of the blue‐green fluorescence with a shoulder in the green region and a strong red fluorescence peak near 684 to 690 nm, the far‐red chlorophyll fluorescence maximum (F735) was, however, absent. The norfluorazone‐treated white leaf, free of chlorophylls and carotenoids, only exhibited blue‐green fluorescence of a very high intensity. In green and etiolated leaves the blue‐green fluorescence primarily derived from the cell walls of the epidermis and the red fluorescence from the chlorophyll a of the mesophyll cells. In white leaves the blue‐green fluorescence emanated from all cell walls of epidermis, mesophyll and leaf vein bundles. The shape and intensity of the blue‐green and red fluorescence emission is determined by the reabsorption properties of chlorophylls and carotenoids in the mesophyll, thus giving rise to quite different values of the various fluorescence ratios F450/F690, F450/F530, F450/F735 and F690/F735 in green and etiolated leaves.
The Stimulating Effect of a Cold Dark Pretreatment on the Accumulation of Components of Light‐Harvesting Chlorophyll a/b Complexes and on Photosynthetic Activity in Wheat (Triticum aestivum)
Authors: Zwicker H.‐G. , Schulz R. , Schönbohm E.
Published: February 2014

Recently we reported on the stimulating effect of a cold dark pretreatment (cold‐dp) on the chlorophyll accumulation (Schönbohm et al., 1988) and on the CO2‐ and O2‐gas exchange (Schönbohm and Czeska‐Werner, 1990) during de‐etiolation of wheat leaves under white light.

The goal of the present paper was to study the effect of a cold‐dp on the accumulation of chloroplast pigments, on the kinetics of fluorescence quenching, on the synthesis of Cab‐proteins and on the amounts of cab‐transcripts during de‐etiolation under white light.

The following results were obtained:

Not only the chlorophyll synthesis but also the synthesis of xanthophylls and of β‐carotene is highly increased by a cold‐dp.

The kinetics of the PAM‐fluorescence curves demonstrate that the activity and co‐operation of the two photosystems start earlier and with higher efficiency during de‐etiolation in cold‐dp than in warm‐dp wheat leaves.

The amount of cab‐transcripts can be elevated by a cold‐dp.

The amount of Cab‐proteins during de‐etiolation is much higher in cold‐dp than in warm‐dp wheat leaves.

The presented data are in accordance with our earlier published results. Consequences of these results on seedlings growing under natural conditions with fluctuating temperatures during day and night are pointed out.
Peroxisomal Degradation of 2‐Oxoisocaproate. Evidence for Free Acid Intermediates
Authors: Gerbling Heidrun
Published: February 2014

Peroxisomes from mung bean hypocotyl (Vigna radiata L.) degrade 2‐oxoisocaproate, the transamination product of leucine, via isobutyryl‐CoA and propionyl‐CoA to acetyl‐CoA. The methyl group at the C‐3 position forms a barrier to β‐oxidation. This barrier is overcome in the peroxisomes by several enzymatic steps. Senecioate (3‐methylcrotonate), 2‐hydroxyisovalerate, and 2‐oxoisovalerate were detected as free acid intermediates. Senecioate, formed from 3‐methylcrotonyl‐CoA, is transformed by enzymatic hydrolysis to 2‐hydroxyisovalerate. 2‐Hydroxyisovalerate is then oxidized to 2‐oxoisovalerate in an H2O2‐producing reaction, exhibiting 1:1 stoichiometry of the products, by a 2‐hydroxyacid oxidase which is different from the peroxisomal marker enzyme glycollate oxidase. 2‐oxoisovalerate is activated by an NAD‐dependent oxidative decarboxylation to isobutyryl‐CoA. Accumulation of 2‐oxoisovalerate in the presence of arsenite, an inhibitor of oxidative decarboxylations, is a feature of this latter pathway of degradation of isovaleryl‐CoA or senecioate. It is concluded that the barrier caused by the methyl group of 2‐oxoisocaproate is surmounted in higher plant peroxisomes in a manner different to that in mammalian mitochondria.
The Protonema of Chara fragilis Desv.: Regenerative Formation, Photomorphogenesis, and Gravitropism
Authors: Hodick D.
Published: February 2014

When exposed to constant white light for four weeks, isolated nodes of Chara fragilis Desv. regenerated side branches, rhizoids, and multicellular protonemata, the latter being similar to those germinated from oospores. When kept in darkness the nodes developed protonemata exclusively. These were single‐celled, colourless, and tip‐growing and, with the light microscope, they looked like rhizoids. Upon exposure to blue light, but not to red or far‐red, the growth rates of the protonemata rapidly declined, the cell apices swelled, and the nucleus migrated acropetally. Within 24 h the cells went through the first of a series of divisions resulting in the formation of multicellular protonemata. When returned to darkness after a blue light pulse of 5 h the cell divisions proceeded normally, but the protonemata showed etiolated growth. While growth of the internode was drastically promoted, the development of the multicellular apex and the lateral initial were suppressed. Both uni‐ and multicellular etiolating protonemata showed negative gravitropism but were phototropically insensitive. It is argued that the single‐celled protonema is an organ specialized for the penetration of mud covering the nodes or oospores of Chara and thus serves to search for light, comparable to etiolated hypocotyls and stems in seedlings of higher plants.
Cellular Dimorphism in the Maize Root Cortex: Involvement of Microtubules, Ethylene and Gibberellin in the Differentiation of Cellular Behaviour in Postmitotic Growth Zones
Authors: Baluška F. , Brailsford R. W. , Hauskrecht M. , Jackson M. B. , Barlow P. W.
Published: February 2014

Detailed morphometric analysis of cell shapes and an immunofluorescent study of microtubules were carried out on primary roots of Zea mays L. Two types of cells were found to be formed within the postmitotic isodiametric growth (PIG) region of the root cortex that were differentially responsive to low level of exogenous ethylene. The innermost and central cell rows of the cortex were sensitive to ethylene treatment and showed a disturbed distribution of cortical microtubules (CMTs) as well as changed polarity of cell growth, whereas the 2–3 outermost cell rows were less sensitive in this respect. This suggests that post‐mitotic cells of the inner cortex are specific targets for ethylene action. These properties of the inner cortex are compatible with its cells being involved in the formation of aerenchyma; they may also favour root growth in compacted soil. By contrast, the specific properties of the outer cortex indicate that this tissue domain is necessary for the gaseous impermeability and the mechanical strengthening of subjacent aerenchymatous cortex, especially in the mature region of the root.

Ethylene affected neither the pattern of cortical cell expansion in the meristem nor the position of the PIG region with respect to the root tip. This contrasts with gibberellin‐deficiency which affected these parameters in both parts of the cortex. These observations indicate a fundamental difference between the role of these two phytohormones in the morphogenesis and development of maize roots.
The Determination of Phaseic Acid by Monoclonal Antibody‐Based Enzyme immunoassay
Authors: Gergs U. , Hagemann K. , Zeevaart J. A. D. , Weiler E. W.
Published: February 2014

A monoclonal antibody PA3‐2‐B3, IgG1 (Λ) is described which specifically recognizes phaseic acid and shows very little cross‐reactivity (0.14%) with abscisic acid or dihydrophaseic acid (0.88%). Based on this antibody, an enzyme immunoassay was developed which displays a linearity range from 15 pg to 3 ng of phaseic acid. Results obtained with this assay agree with those obtained by gas chromatography‐electron capture detection. Using the novel enzyme immunoassay, as well as an established immunoassay for abscisic acid, levels of these two compounds in leaves of Phaseolus vulgaris were determined as a function of plant age, water stress, recovery from stress, and feeding of abscisic acid through the transpiration stream. The production of phaseic acid in a microsomal system from bean leaves was demonstrated. The results show a regulation of the plant's capacity to metabolize abscisic acid to phaseic acid as a function of water stress.
The Effect of Lateral Root Outgrowth on the Structure and Permeability of the Onion Root Exodermis
Authors: Peterson Carol A. , Moon Greg J.
Published: February 2014

Lateral root development in onion is accompanied by a variety of anatomical and permeability changes in some cells of the adventitious root. The endodermal Casparian band of the parent root is disrupted early in the development of the lateral but later extends so as to be continuous with the developing Casparian band of the new root. The lateral root emerges through a longitudinal split in the adventitious root exodermis and epidermis. Following this, the cell walls and intercellular air spaces adjacent to the lateral become incrusted with suberin and a small amount of lignin, forming a collar of modified tissue around the lateral. Subsequent radial expansion of the lateral distorts the adjacent cells of the adventitious root and forces a tight association between it and the lateral. The apoplastic permeability of lateral/parent root junctions was tested using Cellufluor, an apoplastic fluorescent dye which binds to cellulose. Prior to lateral root emergence, no dye enters the parent root cortex due to the Casparian band of the exodermis. Immediately after emergence, dye often penetrates through the break in the exodermal Casparian band and diffuses into the first cortical cell layer. However, when the collar of suberized cells develops (two days after lateral root emergence), movement of the dye into an undisturbed adventitious root is usually prevented (i.e., in 77% of the cases examined). In contrast, only 17% of the root systems which were transplanted just prior to treatment excluded the dye. This indicates that the apoplastic seals around the laterals are sensitive to movement and we recommend that only undisturbed root systems be used for permeability studies.
Uptake, Transport and Storage of Cardenolides in Foxglove. Cardenolide Sinks and Occurrence of Cardenolides in the Sieve Tubes of Digitalis lanata1
Authors: Christmann J. , Kreis W. , Reinhard E.
Published: February 2014

Cardiac glycoside transport was investigated on the organ and whole plant level. Uptake experiments were carried out with shoot and root cultures of Digitalis lanata. In both systems primary cardenolides, i.e., those with a terminal glucose in their oligosaccharide side chain, were taken up against their concentration gradient, whereas the glucose‐free secondary cardenolides were not. Active uptake of primary cardenolides was further evidenced by KCN inhibition of uptake. Using plantlets grown in vitro the long‐distance transport of primary cardenolides from the leaves to the roots was demonstrated. Cardenolides were also detected in etiolated leaves, induced on plants with green leaves, which are supposed to be unable to synthezise cardenolides de novo, providing further evidence for long‐distance transport. Several primary cardenolides were detected in the honeydew excreted by aphids fed on Digitalis lanata leaves, indicating that the phloem is a transporting tissue for cardenolides. On the other hand, the xylem sap obtained by applying the pressure‐chamber technique was cardenolide‐free. It was concluded that in Digitalis primary cardenolides serve as both the transport and the storage form of cardenolides. After their synthesis they are either stored in the vacuoles of the source tissue or loaded into the sieve tubes, from which they are unloaded at other sites where they are trapped in the vacuoles of the respective sink tissue.
Glutamine and Glutamate Transport in Cyanophora paradoxa
Authors: Kloos K. , Schlichting R. , Zimmer W. , Bothe H.
Published: February 2014

The present investigation showed that isolated cyanelles from Cyanophora paradoxa selectively enriched glutamine from the external medium, whereas glutamate poorly penetrated into these organelles. Glutamine uptake proceeded in two phases, presumably involving a low and a high affinity system. The uptake of glutamine was significantly enhanced by 2‐oxoglutarate and light. Inhibitor experiments indicated that glutamine and 2‐oxoglutarate were converted to glutamate by a ferredoxin‐dependent glutamate synthase (GOGAT) reaction inside the cyanelles, and the glutamate formed at best slowly left these organelles. Such results were obtained independently of each other by measuring either the 14C‐glutamine uptake or the 2‐oxoglutarate and glutamine‐dependent O2 evolution. Glutamine is suggested to be the N‐compound which is supplied to the eukaryotic host. Glutamine could be exported jointly with 2‐oxoglutarate, possibly employing a common carrier. Cyanelles have apparently evolved glutamine (and oxoglutarate) carrier(s) with properties not yet described for any other organism.
The Life Cycle of Cryptochlora perforans (Chlorarachniophyta)
Authors: Beutlich A. , Schnetter R.
Published: February 2014

Observations on the behaviour of different life cycle stages, gamete fusions, and measurements of nuclear DNA contents in Cryptochlora perforans resulted in a first concept concerning life histories in Chlorarachniophyta: the life cycle of Cr. perforans is diplohaplontic (gamete fusion with karyogamy ‐ mitosis ‐ meiosis ‐ mitosis). In the haploid as well as in the diploid life cycle phases amoeboid and coccoid stages occur. The isomorphic gametes are modified amoebae frequently without filopodia. Only haploid flagellate stages are known representing mito‐ or meiozoospores. Diploid coccoid stages have a granular cytoplasmic structure and may be somewhat larger than haploid ones. Nevertheless, positive identification of haploid (gametophytic) and diploid (sporophytic) stages is only possible on the basis of nuclear DNA contents.
Selenium in Plants: Uptake, Functions, and Environmental Toxicity
Authors: Läuchli A.
Published: February 2014

Selenium (Se) has chemical properties similar to sulfur, but slight differences can lead to altered tertiary structure and dysfunction of proteins and enzymes, if selenocysteine is incorporated into proteins in place of cysteine.

In some areas of California with irrigation agriculture elevated Se concentration in drainage and shallow groundwaters caused bioaccumulation of Se in wetlands and Se toxicity to wildlife. Among higher plants Se accumulators are tolerant to high Se concentrations whereas non‐accumulators are Se‐sensitive. Algae show a requirement of Se for growth and development, but no Se essentiality has been demonstrated for higher plants, possibly with the exception of Se accumulators. Higher plants take up Se preferentially as selenate via the high affinity sulfate permease. Contents of Se in agricultural crops are usually below 1 mg kg−1 DW, and hence such crops are considered safe for human and animal consumption even when grown on moderately high Se soils. Sulfate salinity inhibits uptake of selenate by many plant species.

Assimilation of selenate by non‐accumulators leads to synthesis of selenocysteine and selenomethionine; Se‐cysteine is readily incorporated into proteins. High Se can interfere with S and N metabolism in non‐accumulators. In contrast, Se accumulators sequester Se mainly in non‐protein selenoamino acids. Among several selenoenzymes identified in bacteria and mammals, Se‐dependent glutathione peroxidase which catalyses the reduction of organic peroxides and H2O2 has been demonstrated convincingly in algae; in higher plants, however, the experimental evidence regarding its occurrence is controversial. All organisms including higher plants contain Se‐cysteyl‐tRNAs that decode UGA. Selenocysteine is proposed to function as 21st proteinaceous amino acid and thus is suggested to have a biological role in higher plants.

Biogeochemical cycling of Se involves significant volatilization of methylated selenides such as dimethyl selenide to the atmosphere from higher plants as well as freshwater algae, but Se exchange between oceans and the atmosphere appears to proceed as net flux to the oceans.
Cytological Characterization of a Giant Strain of Euglena gracilis Obtained from Dark‐starved Cultures
Authors: Mares D. , Romagnoli C. , Rubini M. , Fasulo M. P.
Published: February 2014

Euglena gracilis green cells were dark‐starved for four months. After this period almost the entire population died, while a few giant, viable cells appeared in the culture. The giantism was maintained after repeated subcultures in growth medium in light or dark conditions. However, the phenomenon was not permanent, and the morphological characteristics of the wild‐type Euglena were gradually restored.

In giant cells nuclei enlarged greatly, DNA content increased and the Golgi apparatus greatly proliferated. Chloroplasts and mitochondria increased in number and size and often presented structural modifications when compared with normal Euglena. Importantly, in the giant cells that were maintained in darkness in resting or growth conditions chloroplasts persisted as structured organelles which appeared red‐fluorescent under UV illumination.

Whether giantism is a phenotypic or a genotypic change is still debated. In our case, the evolution of this phenomenon, chiefly the enhanced DNA content, suggests that teratism is a multiploid mutation with the possibility of a return to the normoploid condition. Constitutive chloroplasts are present in most algae, except for a few species, among which is Euglena gracilis. The persistence of differentiated plastids in darkness in giant Euglena is considered to be a return to an ancestral condition and may, therefore, be phylogenetically important.
Sieve‐Element Plastids, Nuclear Crystals and Phloem Proteins in the Zingiberales
Authors: Behnke H.‐D.
Published: February 2014

The sieve‐element characters of 40 species from all families making up the monocotyledon order Zingiberales have been studied by transmission electron microscopy. While phloem‐proteins are a typical component of all eight families, the Zingiberaceae are characterized by nondispersive protein bodies derived from nuclear crystals. The sieve‐element plastids are of the form‐P2cs, i.e. contain cuneate protein crystals (as typical of all monocotyledons) and starch grains, those of the family Musaceae have protein filaments in addition (form‐P2cfs). The exclusiveness of the form‐P2c(f)s plastids contributed to the homogeneity of the order and its distinctness among other monocotyledon taxa. When diameters of the sieve‐element plastids from leaf phloem are compared, in the “banana group” the family averages of the Strelitziaceae and the Lowiaceae have, respectively, maximum and minimum values and are clearly different from those in the Musaceae, the family in which they have been included previously. In the “ginger group”, the family averages of the Zingiberaceae, Costaceae, and Marantaceae are close to the order average, with only Cannaceae having minimum values. A comparison of species averages, however, reduces the size differences between families: the value for Ravenala (Strelitziaceae) is close to those of the five Musaceae tested, and that of Globba (Zingiberaceae) even slightly lower than the species average of Canna.
Chloroplast Development in Rye Coleoptiles
Authors: Fröhlich M. , Kutschera U.
Published: February 2014

In the parenchyma cells of 1‐d‐old dark‐grown rye coleoptiles (Secale cereale) proplastids occurred which sometimes contained starch grains. During coleoptile growth in darkness starch‐filled amyloplasts are formed from the preexisting proplastids. No prolamellar bodies were observed in the stroma of the plastids of the etiolated coleoptile. After irradiation of 3‐d‐old etiolated coleoptiles with continuous white light three different types of plastids occurred. In the epidermal cells proplastids were observed. The parenchyma cells below the stomata of the outer epidermis (above the two vascular bundles) contained mature, spindle‐shaped chloroplasts with a well‐developed thylakoid system. In the parenchyma cells that surround the vascular bundles amyloplasts with some thylakoid membranes (chloroamyloplasts) occurred. The mesophyll cells of the primary leaves of dark‐grown seedlings contained etioplasts with large prolamellar bodies. In the primary leaves of irradiated plants chloroplasts similar to those of the parenchyma cells of the coleoptile were observed. Our results show that the rye coleoptile, which grows underground as a heterotrophic organ, is capable of developing mature chloroplasts upon reaching the light above the soil surface. The significance of this expression of photosynthetic capacity for the carbon economy of the developing seedling is discussed.
Paxillus involutus/Pinus sylvestris Mycorrhizae from Heavily Polluted Forest II. Ultrastructural and Cytochemical Observations
Authors: Turnau K. , Kottke I. , Dexheimer J.
Published: February 2014

Paxillus involutus/Pinus sylvestris mycorrhizae, collected from experimental plots (situated in a Pino‐Quercetum forest) treated with cadmium dust, were previously reported to accumulate metals like Cd, P, S, N, Al and Si in vacuolar bodies. The Gomori‐Swift test was applied to the same material to reveal if cysteine‐rich proteins might be involved in element detoxification. Vacuolar deposits of high and low phosphate level were both stained. Higher intensity of the Swift reaction was found in the fungal mycelium from mycorrhizae sampled from polluted plots than in mycorrhizae from unpolluted sites. In both cases a higher intensity of the test was revealed in the host cytoplasm close to the Hartig net than in internal parts of roots. Different intensities of the Gomori‐Swift reaction were also observed when the Hartig net was compared to the fungal mantle. A PATAg test was additionally processed and revealed an accumulation of glycogen in rosettes and net‐like structures when samples from cadmium dust treated plots were observed.
Displacement and Return Movement of Chloroplasts in the Marine Dinophyte Pyrocystis noctiluca. Experiments with Optical Tweezers
Authors: Leitz G. , Greulich K. O. , Schnepf E.
Published: February 2014

Infrared laser traps (optical tweezers) were used to study laser‐induced organelle movements in the marine alga Pyrocystis noctiluca (Dinophyta). These cells are highly suitable for optical micromanipulation due to their large size and extensive vacuole. Experiments were done with plastids held by optical tweezers and moved from the nuclear area into the vacuole. The subsequent retraction movement was analysed for speed. The displaced organelles remained connected to their original position by a thin cytoplasmic strand, often less than 1 μm in diameter. When the organelles were released they rapidly returned at an initial rate of 81.7 ± 7.8 μm . s−1 (overall displacement 50 μm, measured distance 20 μm, 25 °C ± 1 °C, number of cells 22), slowing down with progressive retraction of the connecting strand. The return movement was reduced to 4.2 ± 0.2 μ .s−1 (n = 10) when the organelles were displaced and held for 1 min. Displacement to a longer distance increased the rate of return movement. A change from a high to a low environmental temperature significantly reduced movement from 94.5 ± 9.0 . s−1 (30 °C ± 1 °C, n = 22) to 34.5 ± 2.7 μm .s−1 (5°C ± 1 °C, n = 22). Nocodazole and N‐ethylmaleimide (NEM), inhibitors of microtubules and acto‐myosin, respectively, did not affect the retraction of the connecting strand, but at high concentrations of NEM it became increasingly difficult to move organelles away from the nuclear area. We suggest that the return movement of organelles within laser‐induced artificial strands mainly depends on the viscoelastic properties of the tonoplast. The quantification of these properties by optical tweezers allows determination of reactions of plant cells to temperature changes.
The Non‐Ionic Detergent Brij 58 Conserves the Structure of the Tonoplast H+‐ATPase of Mesembryanthemum crystallinum L. During Solubilization and Partial Purification
Authors: Ratajczak R.
Published: February 2014

The effects of solubilization with Triton X‐100 or Brij 58 on the polypeptide composition and the substrate affinity of the tonoplast H+‐ATPase of plants of Mesembryanthemum crystallinum performing C3 photosynthesis or crassulacean acid metabolism (CAM) have been compared. Although all known subunits of the tonoplast H+‐ATPase were present in the fraction of solubilized proteins after treatment with Brij 58 or Triton X‐100, with Triton X‐100 the apparent KM value for ATP hydrolysis was increased by a factor of 1.8 and 1.5 in preparations from C3 and CAM plants, respectively, even at low concentrations in contrast to treatment with Brij 58. This is explained by structural changes of the tonoplast H+‐ATPase due to the Triton X‐100 treatment.

After solubilization with Brij 58 the tonoplast H+‐ATPase was partially purified by Superose‐6 size‐exclusion FPLC. When Brij 58 was present, addition of lipids to the chromatography buffer was not necessary to conserve enzyme activity in contrast to previously described purification methods using Triton X‐100. The substrate affinity of the partial purified H+‐ATPase was similar to the substrate affinity obtained for ATP‐hydrolysis of native tonoplast vesicles, indicating that the enzyme structure during partial purification was conserved by using Brij 58. The results underline that the lipid environment of the tonoplast H+‐ATPase is important for enzyme structure and function.