bluuebunny/crossref_metadata_2025_split huggingface dataset:
Photosynthetic Depression at High Thallus Water Contents in Lichens: Concurrent Use of Gas Exchange and Fluorescence Techniques with a Cyanobacterial and a Green Algal Peltigera Species
Authors: Lange O. L. , Green T. G. A. , Reichenberger H. , Meyer A. 
Published: February 2014

Abstract: Lichens, being poikilohydric, have varying thallus water contents (WC) and show a complex interaction between net photosynthesis (NP) and WC. NP can be depressed at low WC (desiccation effects) and, in some species, also at high WC. In the latter case the depression is normally ascribed to increased CO2 diffusion resistances through water blockage. Recently, an earlier explanation, that the depression at high WC is due to recycling of CO2 from increased dark respiration processes (DR), has been given renewed prominence.The two explanations were distinguished by the concurrent use of gas exchange and chlorophyll fluorescence techniques to investigate NP: WC relationships in the lichens Peltigera leucophlebia (green algal) and P. neckeri (cyanobacterial). Both species had a distinct optimal WC for NP with depressed values at low and high WC. The maximal quantum yield for both CO2 fixation (initial slope of light response curves of NP) and photosystem II (fluorescence signals of dark‐adapted thalli) was depressed only at low WC and remained high at optimal and greater WC. In contrast, the relative electron transport rate (ETR, derived from fluorescence signals of thalli in the light) tracked NP and was depressed at low and high WC. The depression of both NP and ETR at high WC (not that at low WC) could be prevented by using elevated external CO2 concentrations. A single, linear relationship was found between all values of gross photosynthesis (NP + DR) and ETR regardless of external CO2 concentration or WC.Our results show that, for these lichens, the depression in NP at high WC is a real fall in photosynthetic rate of the photobionts and is not due to recycling of CO2. The removal of the depression in NP and ETR at high WC by using elevated external CO2 levels allows us to conclude that an additional CO2 diffusion resistance is present.
Water Relations and CO2 Exchange of Tropical Bryophytes in a Lower Montane Rain Forest in Panama
Authors: Zotz G. , Büde B. , Meyer A. , Zellner H. , Lange O. L. 
Published: February 2014

Abstract:For 6 tropical bryophytes, measurements of the diel courses in water status and net CO2 exchange were made in a submontane tropical rain forest in Panama. In addition, the response of gas exchange to changes in photon flux density (PPFD) and thallus water content (WC) was studied under controlled conditions. Diel variation of WC was pronounced, and both low and high WC limited carbon gain considerably. Low PPFD, e.g. during rain storms, was less important in limiting CO2 exchange. More than half of the mean diurnal carbon gain of 2.9 mg C per g thallus carbon was lost during the night as respiration. Assuming that the average 24‐h carbon gain was representative for the entire year, we estimated the net annual primary productivity of the mosses and liverworts to be 45% of the initial plant carbon content.
Seasonal Growth and Photosynthetic Performance of the Antarctic Macroalga Desmarestia menziesii (Phaeophyceae) Cultivated under Fluctuating Antarctic Daylengths
Authors: Gömez I. , Wiencke C. 
Published: February 2014

Abstract:Growth, photosynthesis, dark respiration and pigment contents were monitored in adult sporophytes of the Antarctic brown alga Desmarestia menziesii J. Agardh grown under fluctuating Antarctic daylength conditions. Growth rates were closely coupled to daylength variations with values varying from 0.05% d−1 in winter condition (July‐August) to 0.5% d−1 in early summer (December). Photosynthetic pigments had maximum values of 1.8 mg g−1 FW (chlorophyll a), 0.4 mg g−1 FW (chlorophyll c) and 0.9 mg g−1 FW (fucoxanthin) in summer. These changes were also closely related to individual size and biomass of the plants. Net photosynthesis (Pmax), on a fresh weight basis, showed a clear seasonal pattern with highest rates of 25μmol O2 g−1 FW h−1 in October and minima close to 9μmol O2 g−1 FW h−1 in April. Dark respiration was high in spring (13μmol O2 g−1 FW h−1) approximately coinciding with growth peaks. Likewise, photosynthetic efficiency (α) and the initial saturating light point of photosynthesis (lk) increased significantly in spring [1.3 μimol O2 g−1 FW h−1 (μmol m−2 s−1)−1 and 26μmol photons m−2 s−1, respectively]. In the case of α, no significant differences between fresh weight and Chl a based rates were found. The results of the present study are the first that demonstrate seasonality of physiological parameters in D. menziesii sporophytes and confirm also that phenology and physiology of macroalgae can be simulated in the laboratory. On the other hand this study adds new elements to the explanation of the life strategy of D. menziesii, in particular that algal growth and photosynthesis occur under a programmed seasonal pattern.
The Induction of Contractile Root Activity in Sauromatum guttatum (Araceae)
Authors: Pütz N. , Pieper J. , Froebe H. A. 
Published: February 2014

Abstract:Contraction of Sauromatum guttatum roots creates a slow, downward underground corm movement, the corm be‐coming covered by a greater amount of soil, and the geophilous plant surviving the dormancy period at a safer soil position. Corm movement of Sauromatum guttatum is only possible if root contraction results in pulling activity. This pulling activity can be quantified using the lifting technique. Measurements of the pulling activity are shown as working curves over time and as the maximum work of a single contractile root. Our results show that root activity varies in individuals cultivated under different parameter conditions. It can be shown that two factors induce root contraction: first, rapid temperature fluctuations during the preceding growth period; second, illumination of the sheath leaves during the actual growth period. However, light induction is, as found here, more important and hierarchically superior, for the temperature effect is only seen in plants whose sheath leaves are not illuminated. Mobility of S. guttatum plants can thus be described as photo‐movement. If the light effect is not present, the mobility of S. guttatum may become thermo‐movement. However, at present, there is no indication that this movement is oriented to the direction of stimulus.
The Light Harvesting System of the Diatom Cyclotella cryptica. Isolation and Characterization of the Main Light Harvesting Complex and Evidence for the Existence of Minor Pigment Proteins*
Authors: Rhiel E. , Marquardt J. , Eppard M. , Mörschel E. , Krumbein W. E. 
Published: February 2014

Abstract:The main chlorophyll a/c light harvesting complex of the diatom Cyclotella cryptica was isolated by sucrose density gradient centrifugation. It consisted of two polypeptides of Mrs 18000 and 22000. Both polypeptides and fragments thereof, obtained by formic acid treatment, were blocked at their N‐ter‐mini. An antiserum raised against the two subunits selectively immunolabeled the thylakoid within the chloroplasts. The subunits were nuclear encoded and could be immunoprecipitated from poly (A)+ RNA as precursor proteins in the Mr range of 20000 to 24000. The existence of minor chlorophyll protein complexes and their possible function in light climate adaptation processes was investigated in cells adapted to low light and high light conditions. Low light grown cells contained more fucoxanthin and less β‐carotene relative to chlorophyll a than high light adapted cells. The xanthophyll cycle pigments diatoxanthin and diadinoxanthin increased five‐fold relative to chlorophyll a under high light conditions. Western‐immunoblotting experiments with antisera raised against several chlorophyll a/b and chlorophyll a/c antenna complexes demonstrated that, beside the dominating chlorophyll a/c light harvesting complex, minor antenna complexes might exist, which, in part, seem to react to the light climate applied.
Phototropic Response of the Bean Pulvinus: Movement of Water and Ions
Authors: Irving M. S. , Ritter Sigalit , Tomos A. D. , Koller D. 
Published: February 2014

Abstract:Segmental analysis of the laminar pulvinus of Phaseolus vulgaris L. showed that its phototropic curvature is accompanied by efflux of inorganic ions and water from its contracting sector and a comparable influx into its expanding one. All the major ions, except Na+, contributed to this transport, suggesting that the response to light involves changes in the driving force, or conductivity of a wide range of solutes. During the curvature, K+ and CI− made the greatest and equivalent contributions to efflux, but only Cl− exhibited a matching influx into the expanding sector, while K+ influx was much less. Use of the cell pressure probe showed that, as the laminar angle of elevation changed between −40° to +40°, turgor pressure in the expanding motor cells increased by 0.48 MPa and decreased in the contracting cells by 0.32 MPa. Picoliter osmometry of single‐cell samples showed that during this movement vacuolar osmotic pressure remained constant. Thus, changes in turgor pressure resulted from changes in apoplastic, rather than the protoplastic osmotic pressure. Volumetric modulus of elasticity of pulvinar motor cells is very low, showing that their walls are very elastic. These properties increase the effectiveness of converting osmotic work into the large‐scale, reversible volume changes responsible for leaf movements.
Gradation in Nutrient Composition and Photosynthetic Pathways Across the Restinga Vegetation of Brazil
Authors: Reinert F. , Roberts A. , Wilson J. M. , De Ribas L. , Cardinot G. , Griffiths H. 
Published: February 2014

Abstract:The restinga comprises coastal vegetation formations which dominate the Atlantic seaboard of Brazil. Exposed sand ridges and associated lagoon systems have poorly developed soils subject to pronounced water deficits. Distinct vegetation zones support a high diversity of life forms, and a comparative study has been undertaken to investigate interactions between degree of exposure, nutrient supply and photosynthetic pathway (C3, or CAM) in selected species across the restinga. A number of species occurring throughout the restinga were chosen as representative species of different life forms, comprising C3 pioneer shrubs (Eugenia rotundifolia and Erythroxylum ovalifolium), impounding (tank) terrestrial bromeliad (Neoregelia cruenta: CAM) and the atmospheric epiphyte (Tillandsia stricta: CAM). Comparisons of plant and soil nutrient composition, and airborne deposition were conducted for each zone. Soil nutrient content and organic matter were closely related, reaching a maximum in zone 4, the seaward face of the inner dune. Salt concentration in leaves was independent of atmospheric deposition for the terrestrial species, in contrast to the atmospheric epiphyte T. stricta. In the slack area, vegetation formed characteristic “islands” with the soil beneath enriched in nutrients, suggesting a complex interplay between plants and soil during the development of vegetation succession. Here, two additional trees were investigated, C3 and CAM members of the Clusiaceae, respectively Clusia lanceolata and C. fluminensis. Stable isotope composition of nitrogen (δ15N) was generally more negative (depleted in 15N) in plants with low total nitrogen content. This was exemplified by the atmospheric bromeliad, T. stricta, with an N content of 2.91 g/kg and δ15N of −12.3 per mil. Stable isotopes of carbon (δ13C) were used to identify the distribution of photosynthetic pathways, and while the majority of bromeliads and orchids were CAM, analysis of the soil organic matter suggested that C3 plants made the major contribution in each zone of the restinga. Since δ13C of plant material also suggested that water supply was optimal in zone 4, we conclude that succession and high diversity in the restinga is dependent on exposure, edaphic factors, and perhaps a critical mass of vegetation required to stabilize nutrient relations of the system.
Sub‐Cellular Element Analysis of a Cyanobacterium (Nostoc sp.) in Symbiosis with Gunnera manicata by ESI and EELS
Authors: Jäger Karin M. , Johansson Christina , Kunz Ulrike , Lehmann H. 
Published: February 2014

Abstract:Element analysis using electron spectroscopic imaging (ESI) and electron energy loss spectroscopy (EELS) was performed in a symbiotic Nostoc sp. strain found in the upper stem tissue of Gunnera manicata, and in Nostoc PCC 9229, a free‐living heterocyst‐forming cyanobacterium able to enter into symbiosis with the angiosperm Gunnera in reconstitution experiments. ESI and EELS unequivocally identified the four elements nitrogen (N), sulphur (S), phosphorus (P) and oxygen (O) in different inclusion bodies of these biological specimens. High amounts of nitrogen were solely detected in huge cyanophycin granules in vegetative cells of the symbiotic Nostoc strain, whereas large polyphosphate bodies, containing high amounts of phosphorus, sulphur and oxygen, could be seen in the free‐living Nostoc PCC 9229. The latter were usually not present or, when found, very small in vegetative cells of the cyanobiont.
Modifications of Cortical Cell Walls in Roots of Seedless Vascular Plants
Authors: Damus M. , Peterson R. L. , Enstone Daryl E. , Peterson Carol A. 
Published: February 2014

Abstract:Forty‐three species of seedless vascular plants were assessed for modifications to root cortical cell walls. All species except Lycopodium had an endodermis with distinct Casparian bands. Experiments with the apoplastic tracer berberine hemisulfate showed that walls of all root cortical cells in the two Lycopodium species tested were permeable to this tracer. Although most species examined lacked a hypodermis several Equisetum species had a hypodermis with modified walls. Three Selaginella species had distinct Casparian bands in this cortical cell layer. This layer, therefore, is an exodermis in Selaginella and its presence limited the inward diffusion of the apoplastic tracer berberine hemisulfate.
Immunochemical Studies on the Clp‐protease in Chloroplasts: Evidence for the Formation of a CIpC/P Complex*
Authors: Desimone M. , Weiß‐Wichert C. , Wagner E. , Altenfeld Ursula , Johanningmeier U. 
Published: February 2014

Abstract:Chloroplasts contain a proteolytic system whose activity is ATP‐dependent. The presence of genes encoding homologues of the ATP‐dependent E. coli CIpA/P protease on the plastome and nuclear genome suggests that a similar protease is located in chloroplasts. Antibodies raised against a recombinant chloroplast‐encoded proteolytic ClpP subunit detect this polypeptide in chloroplasts prepared from barley leaves or the eukaryotic algae Chlamydomonas reinhardtii and Euglena gracilis. Co‐immunoprecipitation experiments using the anti‐ClpP antibody and an antibody against the nuclear encoded regulatory CIpC component (a ClpA homologue) provide direct evidence for the existence of a CIpC/P complex in the chloroplast stroma. These results suggest that at least a part of the ATP‐dependent proteolytic reactions in the chloroplast is catalyzed by an enzyme complex similar to the E. coli CIpA/P protease.
Seasonal Pattern of Isoprene Synthase Activity in Quercus robur Leaves and its Significance for Modeling Isoprene Emission Rates
Authors: Schnitzler J.‐P. , Lehning Andrea , Steinbrecher R. 
Published: February 2014

Abstract:Biogenic emission of hydrocarbons plays an important role in the interactions between plants, especially trees, and the atmosphere. Among these volatile organic compounds isoprene (2‐methyl‐1,3‐butadiene) is the predominant component emitted by many photosynthesizing leaves. Its rapid atmospheric breakdown substantially affects the oxidation potential of the atmosphere. An enzyme, isoprene synthase, extracted from leaves of European oak (Quercus robur L.) was previously found to catalyse the Mg 2+–dependent elimination of diphosphate from dimethylallyldiphosphate to form isoprene. The present paper describes the seasonal variation of this enzyme acitivity in Quercus robur (L.) leaves in 1995. The enzymatic data obtained were used to create an additional term for the isoprene emission algorithm (ISOC93). The addition of this correction term for the seasonality of isoprene synthase to the emission model improved considerably the simulation of seasonal isoprene emission rates in oaks, avoiding over‐ and underestimations in the current modeling approach.
Sexual and Asexual Reproduction in Natural Stands of Populus nigra
Authors: Legionnet Agnès , Faivre‐Rampant Patricia , Villar M. , Lefèvre F. 
Published: February 2014

Abstract:The balance between sexual and asexual propagation in the establishment of natural stands of Populus nigra was assessed from the genotypes of trees sampled in different natural stands. One site was completely sampled and genotyping proceeded using STS and RAPD markers. Among 118 trees, only four were vegetative copies of other trees of the site. Isozymes were used in four stands, and a method to detect the presence of vegetative copies in a sample is proposed for these markers. No vegetative copies were found in two cases, and a low number of copies was detected in the other two. Observations are reported for seedlings as well as for different modes of vegetative propagation in natural stands. We conclude that sexual and asexual propagation play complementary roles in the dynamics of this species, and that in most cases the adults originate from seedlings.
Importance of Cycling and Recycling of Mineral Nutrients within Plants for Growth and Development
Authors: Marschnert H. , Kirkby E. A. , Engels C. 
Published: February 2014

Abstract:Cycling of mineral nutrients, i.e. retranslocation in the phloem from the shoot to the roots, and recycling, i.e. translocation of cycled nutrients back in the xylem to the shoot can contribute substantially to the fluxes of phloem‐mobile nutrients between roots and shoot. Cycling and recycling of nutrients serves several well defined functions. These include supplying the root with nutrients assimilated in the shoot (nitrate and sulphate reduction), maintenance of cation‐anion balance, providing additional driving force for solute flow in the xylem and phloem, and acting as a shoot signal to convey nutrient demand to the roots. Cycling of mineral nutrients like K is also required to cover the demand for growth of apical root zones and to smooth out fluctuations that occur spatially and with time in the external nutient supply of soil‐grown plants. Cycling and recycling of mineral nutrients is also closely related to the process of phloem loading and export of photosynthates from source leaves. This is particularly true for potassium, magnesium and phosphorus. Nutrient deficiency‐induced shifts in dry matter partitioning between shoot and roots are therefore closely related to the solute flow in the phloem not only of photosynthates but also mineral nutrients from source leaves to roots. More research is needed, however, to elucidate in greater detail the contribution of cycling and recycling of mineral nutrients in the integration of growth processes at the whole plant level.
Phototropic Stimulation can Shift the Gradient of Crown Root Emergence in Maize
Authors: Nick P. 
Published: February 2014

Abstract:The crown roots in the coleoptilar node of maize emerge asymmetrically: emergence at the dorsal flank of the node (opposite to the caryopsis) precedes emergence at the ventral flank (facing the caryopsis). This asymmetry can be altered by phototropic stimulation: emergence of crown roots is delayed in the lighted flank and promoted in the shaded flank causing an inversion of the endogenous asymmetry. The curvature induced by the phototropic stimulation is transient, the effect on crown root emergence, in contrast, persists. This stable effect is not a consequence of curvature per se and becomes irreversibly fixed between one and two hours after stimulation. The emergence of crown roots depends on directional signalling from the coleoptile to the node. The data are discussed in terms of a stable blue light induced transverse polarity of the coleoptile that can imprint a stable asymmetry upon the coleoptilar node guiding the emergence of crown roots.
Root Anatomy and Mycotrophy of the Achlorophyllous Voyria tenella Hook. (Gentianaceae)
Authors: Imhof S. 
Published: February 2014

Abstract:The central cylinder of the root of Voynet tenella consists of up to ten central, non‐lignified, tracheidal xylem elements surrounded by some parenchymatic tissue and 5–7 groups of phloem. A pericycle could not be discerned. Even though the endodermis carries a faint suberin lamella it cannot be discerned anatomically without special staining. The cells of the 1–3 cortex layers next to the endodermis are elongated longitudinally, the subsequent cortex parenchyma is multi‐layered and consists of isodiametric cells. The cells of the 2–3 layered outer dermal tissue are smaller than those of the adjacent cortex, their walls carry a suberin lamella and the outermost of them constantly scale off. The dermal tissue is interpreted as a multilayered exodermis. The fungal colonization in roots of Voyria tenella remarkably differs from any known mycorrhizal pattern. After having penetrated the dermal tissue, the always intracellularly‐growing hyphae head straight towards the inner cortex layers, where they spread along the central cylinder. Ramifications from these inner‐spreading hyphae then colonize the cortex parenchyma from the inside and they develop dense hyphal coils. Eventually, the coiled hyphae swell and collapse, resulting in amorphous clumps of fungal material. This mycorrhizal pattern is referred to as an intraradical fungus garden. Arguments are given to call the mycorrhiza in Voyria tenella a specialized arbuscular mycorrhiza. Phylogenetic and ecological implications of the observations and the results are discussed.
Photosynthetic Capacity Increases with Plant Size
Authors: Zotz G. 
Published: February 2014

Abstract:The photosynthetic capacity of mature leaves of the epiphytic orchid, Dimerandra emarginata, was studied in plants of different size. There was a linear increase of both area‐based and dry weight‐based rates of O2‐evolution with size by more than 100% from the smallest (1 cm tall) to the largest (50 cm tall) individual. Similar size‐related changes were observed in the leaf nitrogen content but not in the chlorophyll content. The results are discussed in the context of the optimal partitioning theory.