bluuebunny/crossref_metadata_2025_split huggingface dataset:
Does Long-Term Elevation of CO2 Concentration Increase Photosynthesis in Forest Floor Vegetation? (Indiana Strawberry in a Maryland Forest)
Authors: Osborne C. P. , Drake B. G. , LaRoche J. , Long S. P. 
Published: October 2016

Abstract
As the partial pressure of CO2 (pCO2) in the atmosphere rises, photorespiratory loss of carbon in C3 photosynthesis will diminish and the net efficiency of light-limited photosynthetic carbon uptake should rise. We tested this expectation for Indiana strawberry (Duchesnea indica) growing on a Maryland forest floor. Open-top chambers were used to elevate the pCO2 of a forest floor habitat to 67 Pa and were paired with control chambers providing an ambient pCO2 of 38 Pa. After 3.5 years, D. indica leaves grown and measured in the elevated pCO2 showed a significantly greater maximum quantum efficiency of net photosynthesis (by 22%) and a lower light compensation point (by 42%) than leaves grown and measured in the control chambers. The quantum efficiency to minimize photorespiration, measured in 1% O2, was the same for controls and plants grown at elevated pCO2. This showed that the maximum efficiency of light-energy transduction into assimilated carbon was not altered by acclimation and that the increase in light-limited photosynthesis at elevated pCO2 was simply a function of the decrease in photorespiration. Acclimation did decrease the ribulose-1,5-bisphosphate carboxylase/oxygenase and light-harvesting chlorophyll protein content of the leaf by more than 30%. These changes were associated with a decreased capacity for light-saturated, but not light-limited, photosynthesis. Even so, leaves of D. indica grown and measured at elevated pCO2 showed greater light-saturated photosynthetic rates than leaves grown and measured at the current atmospheric pCO2. In situ measurements under natural forest floor lighting showed large increases in leaf photosynthesis at elevated pCO2, relative to controls, in both summer and fall. The increase in efficiency of light-limited photosynthesis with elevated pCO2 allowed positive net photosynthetic carbon uptake on days and at locations on the forest floor that light fluxes were insufficient for positive net photosynthesis in the current atmospheric pCO2.
Tissue-Type-Specific Heat-Shock Response and Immunolocalization of Class I Low-Molecular-Weight Heat-Shock Proteins in Soybean
Authors: Jinn T. L. , Chang PFL. , Chen Y. M. , Key J. L. , Lin C. Y. 
Published: October 2016

Abstract
A monospecific polyclonal antibody was used to study the tissue-type specificity and intracellular localization of class I low-molecular-weight (LMW) heat-shock proteins (HSPs) in soybean (Glycine max) under different heat-shock regimes. In etiolated soybean seedlings, the root meristematic regions contained the highest levels of LMW HSP. No tissue-type-specific expression of class I LMW HSP was detected using the tissue-printing method. In immunolocalization studies of seedlings treated with HS (40[deg]C for 2 h) the class I LMW HSPs were found in the aggregated granular structures, which were distributed randomly in the cytoplasm and in the nucleus. When the heat shock was released, the granular structures disappeared and the class I LMW HSPs became distributed homogeneously in the cytoplasm. When the seedlings were then given a more severe heat shock following the initial 40[deg]C -&gt; 28[deg]C treatment, a large proportion of the class I LMW HSPs that originally localized in the cytoplasm were translocated into the nucleus and nucleolus. Class I LMW HSPs may assist in the resolubilization of proteins denatured or aggregated by heat and may also participate in the restoration of organellar function after heat shock.
Effect of Water Stress on Cortical Cell Division Rates within the Apical Meristem of Primary Roots of Maize
Authors: Sacks M. M. , Silk W. K. , Burman P. 
Published: October 2016

Abstract
We characterized the effect of water stress on cell division rates within the meristem of the primary root of maize (Zea mays L.) seedlings. As usual in growth kinematics, cell number density is found by counting the number of cells per small unit length of the root; growth velocity is the rate of displacement of a cellular particle found at a given distance from the apex; and the cell flux, representing the rate at which cells are moving past a spatial point, is defined as the product of velocity and cell number density. The local cell division rate is estimated by summing the derivative of cell density with respect to time, and the derivative of the cell flux with respect to distance. Relatively long (2-h) intervals were required for time-lapse photography to resolve growth velocity within the meristem. Water stress caused meristematic cells to be longer and reduced the rates of cell division, per unit length of tissue and per cell, throughout most of the meristem. Peak cell division rate was 8.2 cells mm-1 h-1 (0.10 cells cell-1 h-1) at 0.8 mm from the apex for cells under water stress, compared with 13 cells mm-1 h-1 (0.14 cells cell-1 h-1) at 1.0 mm for controls.
Overproduction of Ascorbate Peroxidase in the Tobacco Chloroplast Does Not Provide Protection against Ozone
Authors: Torsethaugen G. , Pitcher L. H. , Zilinskas B. A. , Pell E. J. 
Published: October 2016

Abstract
Transgenic tobacco (Nicotiana tabacum cv Bel W3) plants were used to test the hypothesis that protection from O3 injury could be conferred by overproduction of ascorbate peroxidase (APX) in the chloroplast. The 10-fold increase in soluble APX activity in the chloroplast was expected to alleviate an implied increase in oxidative potential and prevent damage caused by O3. Three different O3 exposure experiments (one acute and two chronic) with two replicates each were conducted. APX activity in nontransgenic plants increased in response to chronic O3 exposure. However, most responses to O3 were similar between transgenic and nontransgenic plants. These included reductions in net photosynthesis and stomatal conductance, increases in ethylene emission and visible injury, and a decline in the level of the small subunit of ribulose-1,5-biphosphate carboxylase/oxygenase mRNA transcripts observed in response to the air pollutant in the acute and/or chronic experiments. No O3-induced effect on ribulose-1,5-biphosphate carboxylase/oxygenase quantity was observed in the chronic experiments. O3 did not induce acceleration of senescence, as expected from studies with most other species; rather, the tobacco plants rapidly developed necrotic lesions. Thus, overproduction of APX in the chloroplast did not protect this cultivar of tobacco from O3.
Purification and Characterization of Allene Oxide Cyclase from Dry Corn Seeds
Authors: Ziegler J. , Hamberg M. , Miersch O. , Parthier B. 
Published: October 2016

Abstract
Allene oxide cyclase (AOC; EC 5.3.99.6) catalyzes the cyclization of 12,13(S)-epoxy-9(Z),11,15(Z)-octadecatrienoic acid to 12-oxo- 10,15(Z)-phytodienoic acid, the precursor of jasmonic acid (JA). This soluble enzyme was purified 2000-fold from dry corn (Zea mays L.) kernels to apparent homogeneity. The dimeric protein has a molecular mass of 47 kD. Allene oxide cyclase activity was not affected by divalent ions and was not feedback-regulated by its product, 12-oxo-l0,15(Z)-phytodienoic acid, or by JA. ([plus or minus])-cis- 12,13-Epoxy-9(Z)-octadecenoic acid, a substrate analog, strongly inhibited the enzyme, with 50% inhibition at 20 [mu]M. Modification of the inhibitor, such as methylation of the carboxyl group or a shift in the position of the epoxy group, abolished the inhibitory effect, indicating that both structural elements and their position are essential for binding to AOC. Nonsteroidal anti-inflammatory drugs, which are often used to interfere with JA biosynthesis, did not influence AOC activity. The purified enzyme catalyzed the cyclization of 12,13(S)-epoxy-9(Z),11,15(Z)-octadecatrienoic acid derived from linolenic acid, but not that of 12,13(S)-epoxy-9(Z),11- octadecadienoic acid derived from linoleic acid.
Nutrients, Signals, and Photosynthate Release by Symbiotic Algae (The Impact of Taurine on the Dinoflagellate Alga Symbiodinium from the Sea Anemone Aiptasia pulchella)
Authors: Wang J. T. , Douglas A. E. 
Published: October 2016

Abstract
Exogenous concentrations of 10 [mu]M to 1 mM of the nonprotein amino acid taurine stimulated photosynthate release from the dinoflagellate alga Symbiodinium, which had been freshly isolated from the sea anemone Aiptasia pulchella. Photosynthate release, as induced by taurine and animal extract, was metabolically equivalent at both concentrations in that they (a) stimulated photosynthate release to the same extent and (b) induced the selective release of photosynthetically derived organic acids. A complex mixture of amino acids at 75 mM also promoted photosynthate release, but the release rate was reduced by 34% after the omission of taurine (3 mM) from the mixture, suggesting that much of the effect of amino acids was largely attributable to taurine. Exogenous 14C-labeled taurine was taken up by the cells, and more than 95% of the internalized 14C was recovered as taurine, indicating that taurine-induced photosynthate release was not dependent on taurine metabolism. Both taurine uptake and taurine-induced photosynthate release by Symbiodinium exhibited saturation kinetics, but with significantly different Km values of 68 and 21 [mu]M, respectively. The difference in Km values is compatible with the hypothesis that Symbiodinium has a taurine signal transducer that is responsible for photosynthate release and is distinct from the taurine transporter.
A Xyloglucan-Specific Endo-1,4-β-Glucanase Isolated from Auxin-Treated Pea Stems
Authors: Matsumoto T. , Sakai F. , Hayashi T. 
Published: October 2016

Abstract
A xyloglucan-specific endo-1,4-β-glucanase was isolated from the apoplast fraction of auxin-treated pea (Pisum sativum) stems, in which both the rate of stem elongation and the amount of xyloglucan solubilized were high. The enzyme was purified to apparent homogeneity by sequential cation-exchange chromatographies, affinity chromatography, and gel filtration. The purified enzyme gave a single protein band on sodium dodecyi sulfate-polyacrylamide gel electrophoresis, and the molecular size was determined to be 77 kD by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and 70 kD by gel filtration. The isoelectric point was about 8.1. The enzyme specifically cleaved the 1,4-β-glucosyl linkages of the xyloglucan backbone to yield mainly nona- and heptasaccharides but did not hydrolyze carboxymethylcellulose, swollen cellulose, and (1-&gt;3, 1-&gt;4)-β-glucan. By hydrolysis, the average molecular size of xyloglucan was decreased from 50 to 20 kD with new reducing chain ends in the lower molecular size fractions. This suggests that the enzyme has endo-1,4-β-glucanase activity against xyloglucan. In conclusion, a xyloglucan-specific endo-1,4-β-glucanase with an activity that differs from the activities of cellulase and xyloglucan endotransglycosylase has been isolated from elongating pea stems.
The Mechanism of Amino Acid Efflux from Seed Coats of Developing Pea Seeds as Revealed by Uptake Experiments
Authors: de Jong A. , Koerselman-Kooij J. W. , Schuurmans JAMJ. , Borstlap A. C. 
Published: October 2016

Abstract
The uptake of amino acids by excised seed coat halves of developing seeds of pea (Pisum sativum L.) was characterized. The influx of L-valine and L-glutamic acid was proportional to their external concentration, with coefficients of proportionality (k) of 11.0 and 7.1 [mu]mol g-1 fresh weight min-1 M-1, respectively. The influx of L-lysine could be analyzed into a component with linear kinetics (k = 8.1 [mu]mol g-1 fresh weight min-1 M-1) and one with saturation kinetics (Michaelis constant = 6.5 mM), but the latter may have resulted from the mutual interaction between the influx of the cationic lysine and the membrane potential. The influx of the amino acids was not affected by 10 [mu]M carbonylcyanide m-chlorophenylhydrazone, but was inhibited by about 50% in the presence of 2.5 mM p-chloromercuribenzene sulfonic acid. Conservative estimates of the permeability coefficients of the plasma membrane of seed coat parenchyma cells for lysine, glutamic acid, and several neutral amino acids were all in the range of 4 x 10–7 cm s-1 to 9 x 10–7 cm s-1, which is 4 to 5 orders of magnitude greater than those reported for artificial lipid bilayers. It is concluded that nonselective pores constitute a pathway in the plasma membrane for passive transport of amino acids. It is argued that this pathway is also used for the efflux of endogenous amino acids, the process by which nitrogen becomes available for the embryo.
Blue-Light-Induced Shrinking of Protoplasts from Maize Coleoptiles and Its Relationship to Coleoptile Growth
Authors: Wang X. , Iino M. 
Published: October 2016

Abstract
Protoplasts isolated from red-light-grown maize (Zea mays L.) coleoptiles shrank transiently upon brief exposure (e.g. 30 s) to blue light under background irradiation with red light. The maximal volume reduction (about 4% at a saturating fluence) occurred about 5 min after blue-light stimulation. The response was prevented by the anion-channel blocker 5-nitro-2-(3-phenylpropylamino)-benzoic acid. Red light and far-red light did not induce any comparable response. Protoplasts of different sizes and those isolated from different coleoptile positions showed similar responses. After treatment with a saturating blue-light pulse, the protoplasts became responsive to a second pulse and gained full responsiveness within 5 min, suggesting that the photoreceptor system involves a dark-reversible component. The response to continuous blue light was also found to be transient. The protoplast volume was reduced during about 6 to 9 min of irradiation and returned within the next 30 min to the control level. The response to continuous blue light was saturated at 30 [mu]mol m-2 s-1. However, when the fluence rate was enhanced 10-fold after a period of irradiation at 30 [mu]mol m-2 s-1, the protoplasts showed another shrinking response. These and other kinetic results indicate that the photoreceptor system undergoes a photosensory adaptation. Growth in different zones of the coleoptile was inhibited by blue light transiently after pulse stimulation, as well as during continuous stimulation. It was concluded that the observed protoplast shrinking is related to the blue-light-induced inhibition of coleoptile growth.
Differential Localization of Antioxidants in Maize Leaves
Authors: Doulis A. G. , Debian N. , Kingston-Smith A. H. , Foyer C. H. 
Published: October 2016

Abstract
The aim of this work was to determine the compartmentation of antioxidants between the bundle-sheath and mesophyll cells of maize (Zea mays L.) leaves. Rapid fractionation of the mesophyll compartment was used to minimize modifications in the antioxidant status and composition due to extraction procedures. The purity of the mesophyll isolates was assessed via the distribution of enzyme and metabolite markers. Ribulose-1,5 bisphosphate and ribulose-1,5-bisphosphate carboxylase/oxygenase were used as bundle-sheath markers and phosphoenolpyruvate carboxylase was used as the mesophyll marker enzyme. Glutathione reductase and dehydroascorbate reductase were almost exclusively localized in the mesophyll tissue, whereas ascorbate, ascorbate peroxidase, and superoxide dismutase were largely absent from the mesophyll fraction. Catalase, reduced glutathione, and monodehydroascorbate reductase were found to be approximately equally distributed between the two cell types. It is interesting that, whereas H2O2 levels were relatively high in maize leaves, this oxidant was largely restricted to the mesophyll compartment. We conclude that the antioxidants in maize leaves are partitioned between the two cell types according to the availability of reducing power and NADPH and that oxidized glutathione and dehydroascorbate produced in the bundle-sheat tissues have to be transported to the mesophyll for re-reduction to their reduced forms.
Maternal, Single-Gene Regulation of Assimilate Partitioning in Pea
Authors: Kelly M. O. , Spanswick R. M. 
Published: October 2016

Abstract
Assimilate partitioning has been identified as a key process in the control of yield. Although the role of reproductive structures in this process has received intensive study, our understanding of the role of the maternal plant is limited. We suggest that the Sn gene of pea (Pisum sativum L.) is a potentially valuable genetic tool for studying maternal regulation of partitioning. In this study, nearly isogenic lines differing at the Sn locus were compared with respect to seed-filling characteristics and carbon assimilation. Lines with the Sn gene had a slower rate and shorter duration of seed growth than the line recessive for this gene, and these traits could not be ascribed to reduced carbon assimilation. Flowers of the two nearly isogenic lines were manually pollinated to control the genotype of the developing embryo independently of the maternal genotype. The final dry weight of the seed was determined by the genotype of the maternal plant and not by the genotype of the embryo, supporting the hypothesis that the Sn gene acts in the vegetative plant to regulate the partitioning of assimilates between vegetative and reproductive growth. Although the Sn gene has been noted for delaying apical senescence, it also delayed leaf senescence in this study; leaves of the Sn line continued to photosynthesize long past the time that leaves of the recessive line had senesced and after the seeds and pods were dry.
Increased Expression of Vacuolar Aquaporin and H+-ATPase Related to Motor Cell Function in Mimosa pudica L
Authors: Fleurat-Lessard P. , Frangne N. , Maeshima M. , Ratajczak R. , Bonnemain J. L. , Martinoia E. 
Published: October 2016

Abstract
Mature motor cells of Mimosa pudica that exhibit large and rapid turgor variations in response to external stimuli are characterized by two distinct types of vacuoles, one containing large amounts of tannins (tannin vacuole) and one without tannins (colloidal or aqueous vacuole). In these highly specialized cells we measured the abundance of two tonoplast proteins, a putative water-channel protein (aquaporin belonging to the [gamma]-TIPs [tonoplast intrinsic proteins]) and the catalytic A-subunit of H+-ATPase, using either high-pressure freezing or chemical fixation and immunolocalization. [gamma]-TIP aquaporin was detected almost exclusively in the tonoplast of the colloidal vacuole, and the H+-ATPase was also mainly localized in the membrane of the same vacuole. Cortex cells of young pulvini cannot change shape rapidly. Development of the pulvinus into a motor organ was accompanied by a more than 3-fold increase per length unit of membrane in the abundance of both aquaporin and H+-ATPase cross-reacting protein. These results indicate that facilitated water fluxes across the vacuolar membrane and energization of the vacuole play a central role in these motor cells.
Wound-Induced Changes of Membrane Voltage, Endogenous Currents, and Ion Fluxes in Primary Roots of Maize
Authors: Meyer A. J. , Weisenseel M. H. 
Published: October 2016

Abstract
The effects of mechanical wounding on membrane voltage, endogenous ion currents, and ion fluxes were investigated in primary roots of maize (Zea mays) using intracellular microelectrodes, a vibrating probe, and ion-selective electrodes. After a wedge-shaped wound was cut into the proximal elongation zone of the roots, a large inward current of approximately 60 [mu]A cm-2 was measured, together with a change in the current pattern along the root. The changes of the endogenous ion current were accompanied by depolarization of the membrane voltage of cortex cells up to 5 mm from the wound. Neither inhibitors of ion channels nor low temperature affected the large, wound-induced inward current. The fluxes of H+, K+, Ca2+, and Cl- contributed only about 7 [mu]A cm-2 to the wound-induced ion current. This suggests the occurrence of a large mass flow of negatively charged molecules, such as proteins, sulfated polysaccharides, and galacturonic acids, from the wound. Natural wounding of the root cortex by developing lateral roots caused an outwardly directed current, which was clearly different in magnitude and direction from the current induced by mechanical injury.
De Novo Biosynthesis of Volatiles Induced by Insect Herbivory in Cotton Plants
Authors: Pare P. W. , Tumlinson J. H. 
Published: October 2016

Abstract
In response to insect feeding on the leaves, cotton (Gossypium hirsutum L.) plants release elevated levels of volatiles, which can serve as a chemical signal that attracts natural enemies of the herbivore to the damaged plant. Pulse-labeling experiments with [13C]CO2 demonstrated that many of the volatiles released, including the acyclic terpenes (E,E)-α--farnesene, (E)-β-farnesene, (E)-β-ocimene, linalool, (E)-4,8-dimethyl-1,3,7-nonatriene, and (E/E)-4,8,12-trimethyl-1,3,7,11-tridecatetraene, as well as the shikimate pathway product indole, are biosynthesized de novo following insect damage. However, other volatile constituents, including several cyclic terpenes, butyrates, and green leaf volatiles of the lipoxygenase pathway are released from storage or synthesized from stored intermediates. Analysis of volatiles from artificially damaged plants, with and without beet armyworm (Spodoptera exigua Hubner) oral secretions exogenously applied to the leaves, as well as volatiles from beet armyworm-damaged and -undamaged control plants, demonstrated that the application of caterpillar oral secretions increased both the production and release of several volatiles that are synthesized de novo in response to insect feeding. These results establish that the plant plays an active and dynamic role in mediating the interaction between herbivores and natural enemies of herbivores.
Differential Gene Expression in Response to Auxin Treatment in the Wild Type and rac, an Adventitious Rooting-Incompetent Mutant of Tobacco
Authors: Lund S. T. , Smith A. G. , Hackett W. P. 
Published: October 2016

Abstract
Histological analyses of auxin-treated cuttings from the wild type and the rac mutant of tobacco (Nicotiana tabacum cv Xanthii) previously revealed that some rac phloem parenchyma or inner cortical parenchyma cells form callus in response to exogenous auxin treatment but these cells never undergo the organized divisions associated with adventitious root initiation in the wild type. Here we report the effect of the rac mutation on the temporal and spatial expression patterns of three genes previously shown to be associated with adventitious root meristems, HRGPnt3, iaa4/5, and gh3. Using histochemical staining analyses of HRGPnt3-GUS transformant cuttings, we determined that the rac mutation blocks auxin activation of the HRGPnt3 promoter. Thus, activation of the HRGPnt3 promoter occurs specifically during adventitious root initiation in tobacco cuttings. Histochemical staining analyses of iaa4/5-GUS and gh3-GUS transformant cuttings revealed that the rac mutation does not repress the auxin activation of the iaa4/5 and gh3 promoters. Based on our histochemical staining analyses, we conclude that differential gene expression occurs in response to auxin treatment during adventitious root initiation in the wild type compared with callus formation in rac cuttings. We also determined that HRGPnt3 mRNA accumulation occurs in response to components of our root-induction protocol other than auxin, indicating that HRGPnt3 expression is regulated both developmentally and environmentally.