bluuebunny/crossref_metadata_2025 huggingface dataset:
Sieve‐Element Characters of the Proteaceae and Elaeagnaceae: Nuclear Crystals, Phloem Proteins and Sieve‐Element Plastids
Authors: Behnke H.‐D.
Published: February 2014

The sieve‐element characters of 34 species from the Proteaceae and Elaeagnaceae have been studied by transmission electron microscopy. While nondispersive protein bodies and dispersive P‐protein are typical components of both families, specific forms and/or their distinctive origin accentuate some taxa. Within the Grevilloideae, subfamily of Proteaceae, a number of Australian species and genera contain protein crystals of nuclear origin arranged into rosette‐like bodies, while in the other members studied from the same subfamily no nondispersive protein bodies were found. Several Australian and South African genera of the Proteoideae contain compound‐spherical nondispersive protein bodies that reside in the cytoplasm from their very beginning. In the Elaeagnaceae three different P‐protein bodies are present of which one is tubular and dispersing, another is nondispersive and of irregular‐stellate form, and a third is globular (resembling a P‐protein from Cucurbita). The great majority of the species studied from the Proteaceae contains form‐Ss sieve‐element plastids, Lomatia ilicifolia and Macadamia ternifolia are distinct in having form‐Pcs plastids. The average diameter of stem sieve‐element plastids in the family is 1.38 μm. The Elaeagnaceae (three species investigated) is a pure form‐So family (average diameter: 0.8 μm). There are no specific sieve‐element characters that would support any relationship between the Proteaceae and Elaeagnaceae. While affinities of the former to pre‐Gondwanan parts of the Rosanae/Myrtanae are discussed, a reconsideration of the Elaeagnaceae as a possible member of the Violanae (identical features with Cucurbitaceae) is proposed.
The Vacuolar ATPase of Red Beet Storage Tissue: Electron Microscopic Demonstration of the “Head‐and‐Stalk” Structure*
Authors: Getz H. P. , Klein M.
Published: February 2014

Tonoplast membranes were prepared from tissue homogenates and from vacuoles isolated from beetroot storage tissue (Beta vulgaris L., ssp. conditiva) for transmission electron microscopic analysis of the structure of the beetroot vacuolar ATPase using the negative staining technique. By comparison of the specific inhibitor sensitivities of the ATPase activity, i.e. ATP hydrolysis and H+‐pumping, the purity of the tonoplast preparations with respect to contamination with mitochondrial inner membranes was assessed to avoid confusion with mitochondrial F1F0‐ATPase. Membranes prepared in Hepes/Tris or BTP/Mes‐containing media rarely showed typical head‐and‐stalk structures although characteristic nitrate‐ and bafilomycin A1‐sensitive ATP‐hydrolysis and H+‐pumping could be measured. However, typical head‐and‐stalk structures were observed regularly when these buffers were replaced by K‐phosphate buffer. Under these conditions, the beetroot vacuolar ATPase is characterized by a large head group with a central cleft, a thin stalk, connecting it to the membrane and by basal components projecting from the base of the stalks near the vacuolar membrane and forming a distinct layer of electron‐light particles between the vacuolar membrane and the layer of non‐stained head groups.
Sugar Transport into Storage Tubers of Stachys sieboldii Miq.: Evidence for Symplastic Unloading and Stachyose Uptake into Storage Vacuoles by an H+‐Antiport Mechanism*
Authors: Niland S. , Schmitz K.
Published: February 2014

Following assimilation of 14CO2 by leaves of Stachys sieboldii, 14C‐stachyose is translocated into the tubers. Stachyose is accumulated and stored in the vacuoles of the pith parenchyma. Protoplasts and vacuoles were isolated and the uptake of sugars was examined. Uptake of sucrose and sucrosyl oligosaccharides of the raffinose family by protoplasts was very low compared to glucose. Transport parameters for glucose indicated a carrier mediated transport in the lower concentration range which was superimposed by diffusion at higher concentrations (> 10 mM). The very low sugar uptake by protoplasts and the sparse enzyme activities of stachyose synthase in the storage parenchyma as well as acid invertase and α‐galactosidase in the cell walls indicated symplastic unloading of stachyose in the tubers. Experiments on 14C‐stachyose uptake by isolated vacuoles confirmed previous observations by Keller (1992).

Isolated vacuoles exhibited ATP and PP hydrolysis and were capable of generating a proton gradient across the tonoplast by a V‐type H+‐ATPase and H+‐PPase. This was demonstrated by fluorescence quenching of quinacrine. Fluorescence could be restored by the addition of gramicidin and partly recovered by the addition of stachyose; mannitol, sorbitol and glucose had no effect. Fluorescence recovery depended on the concentration of stachyose and revealed saturation kinetics (Km = 28 mM). Comparable results have been obtained with tonoplast vesicles by Greutert and Keller (1993).

Experimental data presented here provide circumstantial evidence for symplastic unloading of stachyose in the tubers of Stachys sieboldii and demonstrate that the stachyose concentration in the cytoplasm of storage parenchyma cells is kept low by active stachyose transport into the vacuoles. The results suggest a stachyose/H+‐antiport system.
Pattern of Proteins after Heat Shock and UV‐B Radiation of some Temperate Marine Diatoms and the Antarctic Odontella weissflogii
Authors: Döhler G. , Hoffmann M. , Stappel U.
Published: February 2014

Synthesis of stress proteins after heat shock and different periods of UV‐B radiation were investigated with marine diatom species from the North Sea Ditylum brightwellii, Lithodesmium variabile, Odontella sinensis, Thalassiosira rotula and the Antarctic diatom Odontella weissfloggii from the Weddell Sea. Algae were grown in an artifical sea‐water medium under controlled laboratory conditions: light/dark regime of 12:12 h (7.2 W m−2), normal air (0.035 vol.% CO2) and 18° or 4 °C. All the tested diatom species can produce heat shock proteins (HSPS) of the 70 kDa family by in vivo labelling with [35S]‐methionine. The same results were obtained for Odontella sinensis, Ditylum brightwellii and Odontella weissflogii by estimation of the in vitro translation products with poly‐A‐mRNA isolated from these organisms. However, Odontella weissflogii, a species relatively insensitive to UV‐B irradiance, did not synthesize UV‐induced HSPS, whereas the UV‐sensitive diatom Odontella sinensis, as well as Lithodesmium variabile, produced all the observed HSPS after UV‐B exposure. In addition, a protein of 43 kDa was found after UV‐B irradiance of the temperate Odontella sinensis. The temperate marine diatom Thalassiosira rotula synthesized 70 kDa and 5 7 kDa proteins after a heat shock and a UV‐B exposure of 2 h, but a 40 kDa protein could not be detected, whereas a 60 kDa protein was found after 2 h UV‐B exposure. The results are discussed in view of a possible adaptation of O. weissflogii to an enhanced UV dose.
Root Browning in Pinus banksiana Lamb. and Eucalyptus pilularis Sm. 2. Anatomy and Permeability of the Cork Zone
Authors: McKenzie B. Elizabeth , Peterson Carol A.
Published: February 2014

The periderm in roots of Pinus banksiana Lamb. and the polyderm in roots of Eucalyptus pilularis Sm. originate from the pericycle. This occurs after the roots have turned brown due to deposition of tannins in the walls of cells external to the endodermis. In both species, cork cells form a continuous sheath around the vascular tissues. The cork cell walls are modified by the presence of suberin, lignin and tannin and it is the latter which imparts a brown colour to the tissue. The first layer of cork cells in both species constitutes an apoplastic barrier which prevents the fluorescent dye, berberine, from entering the vascular tissues, despite the absence of an identifiable Casparian band in the cells. Because the roots are still covered with the cortex and epidermis during early stages of periderm and polyderm formation, it is not possible to tell from the external aspect of the root when it makes a transition from the tannin zone to the cork zone.
Salt‐dependent Protein Composition in the Halotolerant Green Alga, Dunaliella parva
Authors: Golldack Dortje , Dietz K.‐J. , Gimmler H.
Published: February 2014

The extremely halotolerant green alga, Dunaliella parva, tolerates salt concentrations from 0.3 to 3.0 M NaCl. Effects of long‐term adaptation to five distinct salinities were analyzed. Salt‐dependent differences of physiological parameters such as growth rate, pigments, quantitative protein contents, and gas exchange were measured; furthermore the qualitative protein composition in salt‐adapted cells was investigated using SDS‐polyacrylamide gel electrophoresis. Proteins of apparent molecular masses of 26, 35, 39, 50, and 63 kDa were induced or intensified with an increase in external sodium chloride concentration whereas proteins of 85 and 101 kDa were diminished in high salt algae. After selective staining, four modifications of glycoproteins were observed. A glycoprotein of 96 kDa was produced exclusively in low salt cells whereas glycosylations of 105, 135, and 260 kDa were induced by high salt concentrations.
Blue and Red Light‐dependent Alterations in the Ratio of two Forms of Glutamine Synthetase in Chlorella kessleri
Authors: Meya Gudrun , Kowallik W.
Published: February 2014

Two forms of glutamine synthetase (EC 6.3.1.2) can be separated in crude extracts of Chlorella kessleri on the basis of their different surface charges. The two enzyme forms (GS1 and GS2) respond differently upon transferring the cells from darkness to autotrophic growth in white light: the activity of GS2 increases, that of GS1 remains unchanged. The increase in GS2 activity is only brought about by blue light; in red light GS2 activity appears to be uninfluenced, while that of GS1 increases.

There are no indications of wavelength‐dependent oligomerization processes as a cause for the observed activity alterations. There is however, a strong influence of inhibitors of protein biosynthesis. Cycloheximide and lincomycin both affect the blue light‐dependent increase in activity of GS2, cycloheximide preventing that of GS1 in red lgiht completely.

Since literature data point to localization of GS2 in the chloroplast, and GS1 in the cytosol, the data are discussed in view of two different photoreceptors involved in the regulation of the amounts of GS1 and GS2 in different compartments of the Chlorella cell.
Plant K+ Channels: Similarity and Diversity
Authors: Hedrich R. , Dietrich Petra
Published: February 2014

In this review we compared the electrophysiological properties of plant K+ uptake channels from different plants and tissues. Taking into account the detailed knowledge of K+ channel properties, which has emerged since the application of the patch‐clamp technique on plant cells, as well as results from our recent studies we were able to extract features common among plant K+ channels. In addition, we focused on the diversity that could create plant or tissue‐specificity. Functional fingerprints for the voltage‐dependent K+ uptake channels were generated on the basis of their voltage‐dependence, kinetics, permeability, conductance and pharmacology as well as regulation of K+ channels studied in their natural environment and cloned channels in heterologous expression systems. Finally, sequence information on plant and animal K+ channels cloned so far was used to identify structural motifs that may be related to functional phenotypes.
The Role of the Cytoskeleton and Dictyosome Activity in the Pulsatory Growth of Nicotiana tabacum and Petunia hybrida Pollen Tubes
Authors: Geitmann Anja , Li Yi Qin , Cresti M.
Published: February 2014

Pollen tubes of Nicotiana tabacum and Petunia hybrida show pulsatory growth. Phases of slow growth lasting minutes are interrupted by pulse‐like elongations lasting 10–20 seconds involving an increase of growth rate by up to 24‐fold. Inhibition of dictyosome activity with brefeldin A or monensin did not result in an inhibition of pulsatory growth but eventually stopped pollen tube elongation. In contrast to this the inhibition of the cytoskeletal elements with cytochalasin D and colchicine caused the pollen tubes to abandon the pulse‐like elongations. It was concluded that the activity of the dictyosomes does not have a controlling function in the mechanism of pulsatory growth, even though it is necessary for pollen tube elongation, since cell wall material is provided by secretory vesicles deriving from the Golgi apparatus. In contrast the cytoskeletal elements, actin and microtubules, seem to play an important regulatory role in the pulse‐like elongations. In addition, it was observed that during the experiments several pollen tubes burst upon the completion of a pulse‐like expansion, indicating on the one hand that the internal turgor is the driving force of the pulse‐like expansions. On the other hand, the bursting shows that the pollen tube cell wall is rather weak at the end of a pulse, indicating that at this point of time it is either thinner or less stable than during the slow growth phase or at the beginning of a pulse.
Carotenoids and Reaction Center II‐D1 Protein in Light Regulation of the Photosynthetic Apparatus in Aphanocapsa*
Authors: Nonnengießer K. , Schuster A. , Koenig F.
Published: February 2014

A new cyanobacterial isolate, morphologically closely resembling Aphanocapsa, was characterized for its growth requirements, as well as pigmentation, photosynthetic activity and dynamics of the D1 protein in the reaction center (RC) of photosystem II (PSII). It was shown to be able to grow on glucose in the dark in the presence of DCMU. The cyanobacterium turned light yellow at high light intensity in the absence, and dark emerald green in high light in the presence of sublethal concentrations of the DCMU‐type inhibitor atrazine. While total carotenoids per cell slightly decreased with increasing light intensity during growth, the cells still turned pale yellow due to decreased levels of chlorophyll and phycocyanin. In contrast to β‐carotene, zeaxanthin and echinenone which decreased with increasing light intensity during growth, the carotenoid glycoside, myxoxanthophyll, continuously increased in concentration.

Extremely high rates of light‐saturated O2 evolution were recorded for the high light cultures after a 0.5 h recovery period in the dark. The recovery measured after 2.5 h was shown to be less effective in darkness than in dim light and was prohibited by chloramphenicol. The degree of recovery was dependent on the light intensity during growth. A fast light intensity‐dependent RC II‐D1 protein turnover was found for the bleached yellow cells rich in myxoxanthophyll. The half‐life of the RC II‐D1 protein, plotted against the light intensity during growth and experimentation, yielded a curve the slope of which was considerably steeper for Aphanocapsa than for Anacystis. Apparently, the isolated strain of Aphanocapsa reacts more vigorously to changes in the environment than other strains tested and may, therefore, turn out to be a suitable organism in the attempt to elucidate the molecular mechanism of light intensity adaptation.
A Remarkable Case of Ornithophily in Calceolaria: Food Bodies as Rewards for a Non‐nectarivorous Bird*
Authors: Sérsic A. N. , Cocucci A. A.
Published: February 2014

In southernmost South America, the pollination biology of Calceolaria uniflora Lam. (Scrophulariaceae) was studied in the field. One of the most striking features of the flower of this species is a corolla appendage folded against the outside of the lower lip. This massive and fleshy structure is pecked off by Thinocorus rumicivorus (Thinocoridae, Charadriiformes) as a food body. The percentage of damaged flowers averaged 64% and was as high as 81% in one study site. Pollen is placed on the front of the bird's head by the exserted stamens with large versatile anthers. This pollination syndrome is unique for the bird involved and exceptional in the kind of reward offered. This Calceolaria species, and probably a second one endemic to the Falkland Islands (Islas Malvinas), are the only ornithophilous species in a mostly oil‐bee pollinated genus. Their reproduction strategy appears to be adapted to an environment lacking in oil‐collecting bees.
Characterization of an Isoprene Synthase from Leaves of Quercus petraea (Mattuschka) Liebl.
Authors: Schnitzler J.‐P. , Arenz R. , Steinbrecher R. , Lehning Andrea
Published: February 2014

Biogenic emission of isoprene (2‐methyl‐1,3‐butadiene) by many plant species plays an important role in atmospheric chemistry. Its rapid breakdown in the atmosphere substantially affects the oxidation potential of the atmosphere. Leaves of Quercus petraea were found to contain an enzyme which catalyses the conversion of dimethylallyl pyrophosphate (DMAPP) to isoprene. A standard enzyme assay was established and the isoprene synthase activity was characterized in purified leaf extracts. Optimum enzyme activity was observed at pH 8.5. The enzyme had an apparent Km of 0.97 mM for its substrate DMAPP, but isopentenyl pyrophosphate (IPP), the isomeric form of DMAPP, was not converted to isoprene by the enzyme extract. The temperature optimum of the enzyme activity was 35 °C. Isoprene synthase activity was strictly dependent on the presence of bivalent cations, with magnesium being most effective. Molecular weight determination by FPLC revealed the presence of a single protein with a native molecular weight of approximately 90–100 kDa.
Taxonomic Studies in Foliicolous Species of the GenusPorinaI. ThePorina rufulaAggregate
Authors: Lücking R.
Published: February 2014

An analysis of character variation in species of thePorina rufulaaggregate, i.e.P. rufula(Kremp.) Vain.,P. limbulata(Kremp.) Vain.,P. rubentior(Stirt.) Müll. Arg., andP. pseudofulvellaSérus., showed that the hitherto applied concepts of species delimitation ‐ based on perithecial size and colour ‐ are not appropriate and should be replaced by a concept which primarily regards perithecial colour and shape as specific characters. Revision of type specimens proved the identity ofP. rufulaandP. pseudofulvella, whereasP. limbulatasensu Santesson had to be split intoP. limbulatas. str. andP. leptospermoidesMüll. Arg. Evolutionary tendencies are seen in reduction of thallus morphology and perithecial pigments as an adaptation to shady habitats, indicatingP. leptospermoidesas a more primitive andP. rufulaas a more advanced taxon. Judging from species distribution, the phylogenetic origin of theP. rufulaaggregate might be in the Neotropics.
Apoptosis in Plants
Authors: Havel L. , Durzan D.J.
Published: February 2014

Apoptosis is a feature of animal cells that explains some aspects of programmed cell death in plants. Differences between plant and animal cell development require that concepts be reexamined to signify how plant cells have evolved the need for cell elimination in the meristematic growth habit, life cycle, and alternation of generations. Central to this theme is the regulation of divisional cycles for mitosis, meiosis, apomeiosis, and their related sexual and asexual reproductive processes. Apoptosis depends on the coordinated expression of genes regulating divisional cycles and apoptotic pathways so that irreversible nuclear and cytoplasmic elimination occurs. Cellular degradation products are salvaged to sustain adaptation, viability, structural function, and ontogeny. The cell wall is usually retained and further differentiated or eliminated. A model of factors predisposing apoptosis and comprising checkpoints in cell divisional cycles is presented for comparisons among plant and animal cells.
The Role of Starch in the Gravitropic Response of the Lentil Root
Authors: Aarrouf J. , Perbal G.
Published: February 2014

It is well accepted that the amyloplasts of the cap are responsible for gravisensing in primary roots. However, roots with starch‐depleted plastids are able to respond to gravistimulus, but their curvature is slower than that of roots containing amyloplasts. The goal of our experiment was to analyse the effects of natural variations of statolith starch in the gravitropic response of lentil roots to a stimulation in the horizontal position. In lentil seedlings grown in the vertical position for 26 h, the volume of the amyloplasts in the statocytes differed between individual roots. The amount of starch in the cap was determined parallel to the rate of gravitropic curvature. There was no statistical correlation between the intensity of the gravitropic response and the starch content in the statocytes. Lentil roots were treated with gibberellic acid (GA3) at 32°C in order to reduce the volume of starch in the statoliths. There was 53% less starch in the cap of GA3treated roots as compared to the cap of control roots. But there was no relationship between starch content in the cap and the responsiveness of the root to a gravistimulus, except when the amount of starch was small.
The Arabidopsis thaliana AtSUC2 Gene is Specifically Expressed in Companion Cells
Authors: Stadler Ruth , Sauer N.
Published: February 2014

Polyclonal antisera against a fusion protein of β‐galactosidase and the 20 C‐terminal amino acids of the Arabidopsis thaliana sucrose carrier AtSUC2 were used to determine the cellular localization of the AtSUC2 protein. Using fluorescence‐labelling on sections from different organs of Arabidopsis the AtSUC2 protein was immunolocalized exclusively in companion cells. The presented data indicate that phloem loading in Arabidopsis may be catalyzed by the AtSUC2 sucrose carrier which transports sucrose into the companion cells. No evidence for a participation of the second Arabidopsis sucrose transporter AtSUC1 has been obtained.
Population Size, Pollination and Breeding System of Silene stockenii Chater (Caryophyllaceae), an Annual Gynodioecious Species of Southern Spain
Authors: Talavera S. , Arista M. , Salgueiro F. J.
Published: February 2014

The distribution area, phenology, sex polymorphism, floral characteristics and breeding system of Silene stockenii (Caryophyllaceae), a narrowly endemic annual species of southern Spain, were studied. Only five populations were found in a total area of 2 ha. Silene stockenii is a gynodioecious species with fully female, fully hermaphrodite and intermediate plants bearing hermaphrodite, male‐sterile, and partially male‐sterile flowers. Male‐sterile flowers are typically smaller than hermaphrodites. Nectar production was significantly higher in hermaphrodite plants and during the female phase of hermaphrodite flowers. The red flowers appear during the spring (March‐May) and are pollinated by long‐tongued Bombyliidae. Hand pollinations revealed that the species is self‐compatible; however, natural self‐pollination is rare due to marked protandry. Hand pollination significantly increased the number of seeds per fruit and seed set, indicating limited pollination in the field. In controlled pollinations female plants of S. stockenii produced higher seed set than hermaphrodite plants, but in freely pollinated plants fruit set and seed production was similar in both morphs, indicating that pollinators do not discriminate in favour of hermaphrodite plants.
Evidence for Symplastic Phloem Unloading with Concomitant High Activity of Acid Cell Wall Invertase in Agrobacterium tumefaciens‐Induced Plant Tumors*
Authors: Pradel Katja S. , Rezmer Claudia , Krausgrill Silke , Rausch T. , Ullrich Cornelia I.
Published: February 2014

In stems of Ricinus communis and leaves of Kalanchoë daigremontiana, rapidly growing tumors were induced by the wild type strains of Agrobacterium tumefaciens C58 and A281 (p35 Sgusint). Transformed cells, monitored by histochemical β‐glucuronidase (GUS) staining, showed GUS activity in K. daigremontiana tumors in up to 100% of the tissue. In R. communis tumors, however, GUS activity was patchy, probably due to interference in gus expression from highly active phenolic compounds. Functionality of the sieve elements within the vascular bundles of the tumor and their connection with host stem bundles were shown by applying fluorescein to source leaves as a tracer of phloem‐mobile solutes. The transport pathway within the tumor and the mechanism of phloem unloading were investigated by iontophoretic injection of Lucifer yellow CH into sieve tubes. Apparent symplastic solute unloading into parenchyma cells was confirmed by localizing common primary pit fields by staining them with aniline blue. In spite of the evidence for symplastic unloading, the activity of acid cell wall invertase (CWI) was about tenfold higher in tumor than in the adjacent host stem tissue. These results indicate primary independence of phloem unloading of CWI in tumors.
Structural and Functional Evidence for Xylem‐Mediated Water Transport and High Transpiration in Agrobacterium tumefaciens‐Induced Tumors of Ricinus communis*
Authors: Schurr U. , Schuberth Bettina , Aloni R. , Pradel Katja S. , Schmundt D. , Jähne B. , Ullrich Cornelia I.
Published: February 2014

Tumors induced by the wild‐type strain C58 of Agrobacterium tumefaciens in hypocotyls of Ricinus communis L. were investigated structurally and functionally with respect to xylem differentiation, cuticle and stomata development, water pathway and transpiration. Clearing of tissue with lactic acid and staining with lacmoid revealed a continuation of stem xylem into differentiated bundles in the tumor. Under the influence of tumors the host xylem below the tumors increased considerably in size. Transport of negatively‐charged dyes, amido black, acid fuchsin and the fluorescent pyrenetrisulfonate demonstrated a continuous water flow through the vessels from the stem into the tumor, and up to its surface. Infrared thermography and quantitative measurements of transpiration revealed that transpiration was about 15 times and 7.5 times higher at the tumor surface in comparison to host leaves and to leaves of non‐infected plants, respectively. Leaf CO2 assimilation rate remained unaffected by tumorisation. Tumor growth caused disruption of the epidermis, which did not regenerate and hence no cuticle developed to protect against water loss. Stomata located at the tumor rim hypertrophied and lost their function. Tumors are thus characterised as being structurally and functionally strong pathological water sinks on their host plant.
Frequency Resonances of the Circadian Rhythm of CAM Under External Temperature Rhythms of Varied Period Lengths in Continuous Light*
Authors: Lüttge U. , Grams T. E. E. , Hechler Bettina , Blasius B. , Beck F.
Published: February 2014

Net CO2 exchange (Jco2) of leaves of the CAM plant Kalanchoë daigremontiana Hamet et Perrier de la Bǎthie was studied in continuous light under the influence of temperature jumps of different period lengths. Each period consisted of two equal time intervals at a lower and a higher temperature, i.e. ≅24 and ≅29 °C respectively. At a period length of the imposed external temperature rhythm of 8 h the free running endogenous rhythm of Jco2 with a period length of 21.7 h was expressed. Under external rhythms of 12–28 h period length there was entrainment of Jco2. Under external rhythms of 40 and 56 h the time course of Jco2 became arrhythmic. In power spectra of the Jco2 time series obtained by Fourier analysis, besides the dominant frequency, there were other frequency peaks with lower Fourier amplitudes of Jco2. It was noted that these are natural number multiples of the major frequencies. A comparison shows that these frequencies correspond to the harmonic overtones of the basic oscillation of the free running endogenous rhythm of Jco2 at 24°C, viz. 1/22.5 h−1. The overall power of the enforced oscillations shows a typical resonance behaviour around the natural, free running frequency. The intriguing observation that external temperature jump rhythms lead to resonance, not only of the basic oscillation but also of its harmonic overtones, is discussed in relation to earlier findings suggesting the occurrence of paths between order and deterministic chaos in the CAM rhythm.
Experimental Studies on the Competitive Balance Between two Central European Roadside Grasses With Different Growth Forms
Authors: Beyschlag W. , Ryel R.J. , Ullmann I. , Eckstein J.
Published: February 2014

Monocultures and 1:1 mixtures of the highly competitive grass Elymus repens (L.) Gould and the low competitive grass Puccinellia distans (Jacq.) Parl. were grown under controlled conditions in a growth chamber at four different soil depths and under various water and nutrient conditions in order to evaluate whether shallow soil depth could be the determining factor in causing a stable coexistence of the two species, or dominance of P. distans, as recently observed in the shallow soil areas of Middle European road shoulders. As expected, above‐ and belowground biomass production of monocultures of both species was strongly reduced by shallow soils under all treatments. However, with decreasing soil depth, the aboveground biomass fraction of P. distans was found to markedly increase relative to that of E. repens in the mixtures, particularly if the plants were grown under water‐stress conditions. Although biomass production of both species increased with high nutrient supply, nutrient levels did not affect the competitive relationship on shallow soils. Apparently, P. distans which naturally develops a rather extensive fine root system in the top 10–15 cm of soil is better able to effectively use the limited resources of shallow soil than the normally deeper rooted E. repens. In consequence, E. repens cannot produce enough aboveground biomass to effectively shade and ultimately exclude P. distans. Hydroculture experiments with both species at four different salinity levels revealed that biomass production of E. repens was more affected by salt stress than that of the facultative halophyte P. distans. Experiments are also presented which show that allelopathic effects of E. repens, which have been equivocally discussed in the literature, do not seem to affect biomass production of P. distans. It is concluded that shallow soil conditions are sufficient to create the observed patterns of co‐occurrence at the roadside, but that common road treatments like winter salt application or frequent mowing of the road shoulders further enhance the competitive ability of P. distans in the shallow soil areas close to the pavement.
Photoinhibition of Photosynthesis in Plants Growing in Natural Tropical Forest Gaps. A Chlorophyll Fluorescence Study
Authors: Krause G.H. , Winter K.
Published: February 2014

Photoinhibition of photosynthesis was monitored by means of chlorophyll a fluorescence in leaves of plants growing in 60–80 m2 light gaps in a moist tropical lowland forest located on Barro Colorado Island in central Panama. In these forest gaps, photon flux density was low (less than 100 μmol photons m−2 s−1) during most of the day, but increased on clear days to 1.7‐1.8 mmol photons m−2 s−1 for 1–2 h during midday. Nine species representing different taxa and life‐forms were examined. Leaves of all species exhibited substantial photoinhibition in situ during high light exposure, as manifested by a decrease in the ratio of variable to maximum fluorescence emission, FV/FM. Recovery (reversion of fluorescence quenching) took place in the shade following high light exposure. The major part of recovery occurred in a fast phase within about 1 h after the high light period. A slow phase of recovery proceeded for another 4–5 h until sunset. After 30–60 min of recovery in the shade, calculated rates of PSII electron transport remained significantly (5–15%) reduced in comparison to rates obtained prior to high light exposure; after about 2 h of recovery, inhibition was negligible. All species responded to the high light periods and following shade periods in a very similar manner. It is concluded that photoinhibition and recovery exhibited by these gap leaves reflect a dynamic regulatory mechanism of thermal energy dissipation that allows plants of different life‐forms to cope with periods of high light in tropical forest gaps.
Origin of the Woody Macaronesian Sempervivoideae and the Phylogenetic Position of the East African Species of Aeonium
Authors: Mes T. H. M. , van Brederode J. , Hart H. ‘t
Published: February 2014

Evolutionary relationships among the genera of Macaronesian Sempervivoideae, Aeonium, Aichryson, Greenovia, and Monanthes, were studied using sequence variation of the chloroplast DNA trnL (UAA) ‐ trnF (GAA) spacer and the nuclear ribosomal Internal Transcribed Spacer 2 (ITS2). Phylogenetic analysis indicates that the Moroccan Sedum sect. Monanthoidea is the sister taxon of the Macaronesian Sempervivoideae. In combination with the terminal position in the Macaronesian Sempervivoideae of the East African A. leucoblepharum, which has formerly been assumed to be the sister taxon of the other species of Macaronesian Sempervivoideae (i.e. Aichryson and Monanthes), a recent remigration to Africa is suggested. Statistical support for the terminal position of A. leucoblepharum using only spacer sequences is without homoplasy but not high since only single mutations in both the chloroplast and nuclear sequence characterize the clade containing A. leucoblepharum. A. leucoblepharum and the Canarian species with a similar growth‐form share 50% of the RAPDs. Within a clade comprising woody species with yellow flowers and a herbaceous rosette, the highest genetic divergence, as determined with RAPDs, is found between A. simsii and the woody Macaronesian and African species. The extremely close genetic ties among the woody and branched (sub)shrubs indicate that, when compared to the other species of the genus, the woody, African Aeonium species are not the sister group of the Macaronesian Sempervivoideae and substantiate the view that an ancestor of A. leucoblepharum recently migrated from the Canary Islands to East Africa and Arabia through long distance dispersal, rather than being a relict of an African Aeonium flora from the Tertiary.
Rearrangements of F‐actin during Stomatogenesis Visualised by Confocal Microscopy in Fixed and Permeabilised Tradescantia Leaf Epidermis
Authors: Cleary Ann L. , Mathesius Ulrike
Published: February 2014

Abstract: New details of F‐actin organisation in leaf epidermal and stomatal cells were revealed by rhodamine — and fluorescein — phalloidin staining of fixed epidermal peels of Tradescantia virginiana and visualisation by confocal microscopy. Non‐specialised epidermal cells contain highly organised arrays of fine cortical actin filaments aligned in transverse or oblique orientations. In interphase guard mother cells (GMCs), the arrangement of cortical F‐actin changes on the periclinal and anticlinal cell walls at different times during differentiation. Initially, cortical F‐actin on the periclinal surfaces is oriented transversely and F‐actin is evenly distributed around the anticlinal walls. Following polarisation of the adjacent subsidiary mother cells (SMCs), actin in GMCs concentrates on the lateral anticlinal walls, but not on the transverse walls. Subsequently, F‐actin on the periclinal walls reorients to radial and then longitudinal. Organisation of F‐actin in SMCs appears to be influenced by the adjacent GMCs and co‐ordination in F‐actin arrangements in cells of the stomatal complex continues through to the formation of the guard cell pair. Our studies indicate that actin bands marking the division site in prophase cells, and detected in microinjected living material, are a particularly labile subset of F‐actin. Actin bands were difficult to preserve, even when aldehyde fixation was avoided, in contrast to all interphase and mitotic F‐actin.
A New Turgor/Membrane Potential Probe Simultaneously Measures Turgor and Electrical Membrane Potential
Authors: Zhu Guo Li
Published: February 2014

Abstract: A new combined turgor/membrane potential probe (T‐EP probe) monitored cell turgor and membrane potential simultaneously in single giant cells. The new probe consisted of a silicone oil‐filled micropipette (oil‐microelectrode), which conducted electric current. Measurements of turgor and hydraulic conductivity were performed as with the conventional cell pressure probe besides the membrane potential. In internodal cells of Chara corallina, steady state turgor (0.5‐0.7 MPa) and resting potentials (‐200 to −220 mV) in APW, and hydraulic conductivity (0.07 to 0.21 × 10∼5 m s−1 MPa−1) were measured with the new probe, and cells exhibited healthy cytoplasmic streaming for at least 24 h during measurements. When internodal cells of Chara corallina were treated with 30, 20, 10, and 5 mM KCI, turgor responded immediately to all concentrations, and the osmotic changes in the medium were measured. Action potentials, which brought the membrane potential to a steady depolarization that measured the concentration difference of K+ in the medium, were induced in a concentration — dependent delay and occurred only 30, 20, and 10 mM of KCl. When the solution was changed back to APW, the repolarization of membrane potential consisted of a quick and a following slow phase. During the quick phase, which took place immediately and lasted 1 to 3 min, the plasma membrane remained activated. The membrane was gradually deactivated in the slow phase, and entirely deactivated when the membrane potential recovered to the resting potential in APW. Although the activated plasma membrane was permeable to K+, no major ion channels were activated on the tonoplast, and therefore, internodal cells of Chara corallina did not regulate turgor when osmotic potential changed in the surrounding medium.
Maternal Effect on Embryogenesis in Tobacco Overexpressing Rice Phytochrome A*
Authors: Emmler K. , Schäfer E.
Published: February 2014

When analyzing tobacco lines overexpressing various types of rice phytochrome A, we observed seedlings with fused cotyledons. Phytochrome A is a member of the phytochrome family of plant red/far‐red absorbing photoreceptors. Reciprocal crossings with wild‐type tobacco indicated that this abnormal phenotype was maternally inherited. Mother plants that were expected to produce abnormal seedlings, were raised under different conditions and seeds collected separately from individual capsules. The frequency of abnormal seedlings increased in seeds from later flowers but decreased when mother plants were raised under continuous white light. The interaction of the overexpressed phytochrome A proteins with endogenous plant hormones might be responsible for cotyledon fusion. The abnormal phenotype could partially be recovered by application of gibberellic acid to intact flowers at the time of pollination. In contrast, the synthetic auxin NAA slightly enhanced the degree of cotyledon fusion. Even wild‐type tobacco seedlings exhibited partial fusion of cotyledons if flowers were treated with 2,4‐D and occasionally the shoot apex was replaced by a second root. Application of GA3 to the flowers, in contrast, impaired the development of the radicule. These observations are discussed with respect to maternal effects in plant embryogenesis.
Regulation of CAM and Respiratory Recycling by Water Supply in Higher Poikilohydric Plants — Haberlea rhodopensis Friv. and Ramonda serbica Panč, at Transition from Biosis to Anabiosis and Vice Versa
Authors: Markovska Y. , Tsonev T. , Kimenov G.
Published: February 2014

In this paper the expression of C3 and CAM in the resurrection plants Haberlea rhodopensis Friv. and Ramonda serbica Panč, during the transition from biosis to anabiosis and Wee versa is reported for the first time. The transition from predominantly C3 metabolism to net dark fixation of CO2 occurred in leaves of R.serbica during desiccation. Desiccated plants of H. rhodopensis react by reducing light assimilation of CO2. When watering was resumed night time fixation of CO2 by R. serbica was observed within 24 hours. The recovery of CO2 fixation by H. rhodopensis was not seen until the 8 th day. Desiccated and rehydrated plants of H. rhodopensis recapture a higher proportion of respiratory CO2 than well‐watered plants. Since both species have little capacity for water conservation in their tissues, the early onset of high recycling of CO2 following drought could be an important mechanism for potentially saving water.
Gas Exchange, Water Loss and Biomass Production in Rice and Wild Oryza Species in Well‐Watered and Water‐Limiting Growth Conditions
Authors: Yeo M. E. , Cuartero J. , Flowers T. J. , Yeo A. R.
Published: February 2014

A major reason for the drought susceptibility of cultivated rice is the inability to regulate water loss as effectively as other cereals. We report studies of growth and gas exchange under well‐watered and water‐limiting conditions on selected species of Oryza and seek to relate this physiological information to the ecology of the genus. The immediate ancestor of the Oryza sativa cultigen is native to swamps and marshes, and wet habitats are typical for the genus as a whole. However, the ecological range of some species does extend to habitats that dry out seasonally. In all species studied growth was reduced by water deficit. In all species studied leaves had small absolute water contents and began to roll at a relative water content above 90%. However, there were species differences in leaf rolling and the response of stomatal conductance to an increase in vapour pressure deficit. Following re‐watering, there were persistent reductions in stomatal conductance in most of the species tested, but the assimilation rate was not reduced in all of these cases. Where there was a persistant reduction in assimilation rate, there was also a reduction in carboxylation efficiency. It was a frequent observation that plants had a stomatal conductance greater than expected for their carbon assimilation rate; that is in the range where substantial changes in conductance have little effect upon photosynthesis. It is suggested that a reason for this may be the cooling of leaves which have a small thermal capacity in environments which often combine high temperature, humidity and irradiance. Large conductances combined with small water contents may be no disadvantage in the natural habitats of Oryza, but provide some reasons for the poor regulation of water loss in cultivated rice. Although there were significant differences in gas exchange amongst species the advantages that were observed over O. sativa were not of a magnitude likely to justify wide hybridisation. This implies that improvement in the drought resistance of rice is more likely to come from increasing water acquisition than from decreasing water loss.
Multiple Effects of Lysophosphatidylcholine on the Activity of the Plasma Membrane H+‐ATPase of Radish Seedlings*
Authors: De Michelis Maria Ida , Papini R. , Pugliarello Maria Chiara
Published: February 2014

We analyzed the effect of lysophosphatidylcholine (lysoPC) on the activity of the plasma membrane (PM) H+‐AT‐Pase measured at pH 6.3 or 7.5 in inside‐out PM vesicles isolated from germinating radish seeds. LysoPC stimulated PM H+‐ATPase at both pHs, but the dependence of the effect on lysoPC concentration was different: at pH 6.3 maximal stimulation was observed with 40 to 200 μg ml−1 lysoPC, while at pH 7.5 a sharp peak of activation was observed at about 50 μg ml−1 lysoPC, higher concentrations becoming dramatically inhibitory; this inhibitory effect was considerably reduced in the presence of 10% (v/v) glycerol. In trypsin‐treared PM lysoPC stimulated the H+‐ATPase activity assayed at pH 6.3, but only marginally that assayed at pH 7.5. LysoPC increased both Vmax (from 190 to 280nmol min−1 mg−1 prot) and apparent KM (from 0.15 to 0.3 mM) of the H+‐ATPase at pH 6.3, while it increased Vmax (from 120 to 230 nmol min−1 mg−1 prot) and decreased apparent Km (from 0.8 to 0.4 mM) at pH 7.5. Low concentrations of Nacetylimidazole (10 to 50 mM), which modifies tyrosine residues, abolished the stimulation by lysoPC of the PM H+‐ATPase activity at pH 7.5, but not that observed at pH 6.3. These results indicate that lysoPC influences the PM H+‐ATPase through different mechanisms, and that its effect can only partly be ascribed to its ability to hamper the inhibitory interaction of the regulatory C‐terminal domain with the catalytic site. N‐acety‐limidazole did not affect the stimulation of PM H+‐ATPase by controlled trypsin treatment or by fusicoccin, indicating that the requirement for the tyrosine residue(s) modified by low Nacetylimidazole concentrations is specific for lysoPC‐induced displacement of the C‐terminal domain.
Changes in the CO2 Concentrating Mechanism During the Cell Cycle in Dunaliella tertiolecta
Authors: Sültemeyer D.
Published: February 2014

Synchronised cells of Dunaliella tertiolecta were used to investigate the expression of the CO2 concentrating mechanism over the cell cycle during growth in either ambient air (low Ci cells) or air enriched with 5% CO2 (high Ci cells). The cultures were analysed for extracellular carbonic anhydrase activity, affinity of photosynthesis for inorganic carbon (Ci) and the ability to accumulate Ci. In high Ci cells, carbonic anhydrase activity changed between 2 − 4 units mg−1 Chi during the light‐dark rhythm showing no clear periodicity. Similarly, the apparent affinity for Ci remained rather constant over the cell cycle. This was judged from the Ci concentrations required for half maximum rate of photosynthesis (K1/2(Ci)) of 72 − 80μM. In the same cells the accumulation ratio of internal Ci versus external Ci ranged between 5 and 9.5 without a clear rhythm. In contrast, these parameters showed distinct periodical changes in synchronised low Ci cells. Carbonic anhydrase activity changed from 10 to 350 units mg−1 Chl with maximum and minimum activities occurring in the middle and at the end of the light period, respectively. The K1/2(Ci) values showed similar periodicity ranging between 13 − 36μM. In addition the accumulation ratio increased up to 30 in the middle of illumination and decreased to its lowest level of 12 at the end of the light period. These results indicate the presence of a common step in regulating the induction of the measured parameters and that light is not an absolute requirement for the induction of the CO2 concentrating mechanism in synchronous low CO2 grown cells of Dunaliella tertiolecta.
Indigenous Medicinal Plants in Mexico: the Example of the Nahua (Sierra de Zongolica)
Authors: Weimann Claudia , Heinrich M.
Published: February 2014

As in most peasant cultures medicinal plants are a very important resource for the Nahua of the Sierra de Zongolica (Mexico). Documentation of the current indigenous medicinal uses of 203 plants in this region was conducted during 18 months of fieldwork. The 816 individual reports documented were divided into nine groups of indigenous uses. The frequency of usage of the individual plants reported was employed in the analysis of the ethnobotanical importance of the respective plants. Plants cited more frequently in a group of indigenous uses are regarded as of greater ethnobotanical importance than those cited only by a few informants. Data on phytochemistry, pharmacology and ethnobotany from the scientific literature were used to evaluate possible biological or pharmacological and toxicological effects of some particularly important plants. For most plants detailed studies on these actions are still lacking, which would allow a conclusive evaluation. This ethnobotanical evaluation forms the basis for such studies which have been started on some plants, and for better understanding their potential as minor economic products of the region. These uses may also give incentives to the conservation of the local biodiversity.