bluuebunny/crossref_metadata_2025 huggingface dataset:
Stress-Induced Declines in Soybean N2 Fixation Are Related to Nodule Sucrose Synthase Activity
Authors: Gordon A. J. , Minchin F. R. , Skot L. , James C. L.
Published: October 2016

Soybean (Glycine max L.) plants were subjected to a number of treatments (drought, 10 mM nitrate, 150 mM NaCl, shoot meristem removal, and removal of approximately 50% of the nodules) to test the hypothesis that metabolic responses contribute to the regulation of N2 fixation. Nitrogenase activity was correlated with the activity of nodule sucrose synthase (SS), but not with that of glutamine oxoglutarate amino transferase. Leghemoglobin levels and other enzyme activities were not significantly or consistently affected by the treatments. SS mRNA was greatly reduced in nodules of drought-, salt-, and nitrate-treated plants; however, this was not correlated with changes in soluble carbohydrate, starch, amino acids, or ureides. Leghemoglobin mRNA was only slightly affected by the treatments. The time course of drought stress showed a decline in the SS transcript level by 1 d, but levels of leghemoglobin, glutamine synthetase, and ascorbate peroxidase mRNA were not markedly affected by 4 d. SS activity at 4 d was reduced by 46%. We propose that N2 fixation in soybean nodules is mediated by both the oxygen-diffusion barrier and the potential to metabolize sucrose via SS. The response to environmental perturbation may involve down-regulation of the nodule SS gene.
ZEA3: A Negative Modulator of Cytokinin Responses in Plant Seedlings
Authors: Martin T. , Sotta B. , Jullien M. , Caboche M. , Faure J. D.
Published: October 2016

In Nicotiana plumbaginifolia cytokinins affect seedling development by inhibiting root growth and hypocotyl elongation and by stimulating cotyledon expansion. The zea3.1 mutant was selected for its inability to grow in conditions of low nitrogen and for its ability to grow independently on inhibitory concentrations of zeatin (J.D. Faure, M. Jullien, M. Caboche [1994] Plant J 5: 481–491). The zea3.1 growth response to cytokinins is reflected by an increase in cotyledon expansion due to cell division and by a swelling of the hypocotyl due to cell enlargement. An analysis of the seedling's root length and fresh weight over a wide range of benzyladenine concentrations showed that zea3.1 plants exhibit a higher sensitivity and an amplified response to cytokinins. A similar response of zea3.1 to benzyladenine was also seen in the expression of msr1, a cytokinin-regulated gene. Regulation of msr1 expression by protein phosphorylation was unaffected by the zea3.1 mutation. No significant differences in cytokinin and auxin levels were found between zea3.1 and wild-type seedlings, suggesting that the mutant phenotype is not caused by an alteration of these hormone levels. The data presented suggest that ZEA3 negatively modulates cytokinin responses and may function as a broad regulator of seedling development.
The Effect of Cu2+ on Ion Transport Systems of the Plant Cell Plasmalemma
Authors: Demidchik V. , Sokolik A. , Yurin V.
Published: October 2016

Changes in plasmalemma permeability caused by excessive Cu2+ levels were examined in cells of a freshwater alga (Nitella flexilis) using a conventional microelectrode voltage-clamp technique. A rapid Cu2+-induced increase of plasmalemma conductance starting from 5 [mu]M Cu2+ was shown. Cu2+-induced plasmalemma conductance (ClGm) was nonselective and potential-independent, resembling the conductance of nonselective ionic leakage of the plasmalemma. The K+ channel conductance was shown to be unaltered by Cu2+, and a decrease in plasmalemma Cl- channel conductance at Cu2+ concentrations above 5 [mu]M was found. The depression of Cl- channels and ClGm were time-, dosage-, and Ca2+-dependent processes, revealing a great similarity in all parameters, with Ca2+ causing the preventive effect by shifting the effective Cu2+ concentrations to higher levels. This phenomenon may be explained by the same Cu2+-modified target on the plasmalemma both for ClGm and Cl- channel depression. In addition, a reversible, inhibitory effect of Cu2+ (>10 [mu]M) on the light-stimulated H+-ATPase electrogenic pump in the plasmalemma was demonstrated. This effect was Ca2+- independent, which made it possible to distinguish it from ClGm. Therefore, the Cu2+-induced dramatic alterations in plant cell plasmalemma permeability are caused mainly by nonselective conductance increases and electrogenic pump inhibition.
Characterization of Nitrate Reductase from Light- and Dark-Exposed Leaves (Comparison of Different Species and Effects of 14-3-3 Inhibitor Proteins)
Authors: Lillo C. , Kazazaic S. , Ruoff P. , Meyer C.
Published: October 2016

Nitrate reductase (NR) was extracted and partially purified from leaves of squash (Curcurbita maxima), spinach (Spinacia oleracea), and three transgenic Nicotiana plumbaginifolia leaves in the presence of phosphatase inhibitors to preserve its phosphorylation state. Purified squash NR showed activation by substrates (hysteresis) when prepared from leaves in the light as well as in darkness. A 14–3–3 protein known to inhibit phosphorylated spinach NR in the presence of Mg2+ decreased by 70 to 85% the activity of purified NR from dark-exposed leaves, whereas NR from light-exposed leaves decreased by 10 to 25%. Apparent lack of posttranslational NR regulation in a transgenic N. plumbaginifolia expressing an NR construct with an N-terminal deletion ([delta]NR) may be explained by more easy dissociation of 14–3–3 proteins from [delta]NR. Partially purified [delta]NR was, however, inhibited by 14–3–3 protein, and the binding constant of 14–3–3 protein (4 x 108 M-1) and the NR-inhibiting protein concentration that results in a 50% reduction of free NR (2.5 nM) were the same for NR and [delta]NR. Regulation of NR activity by phosphorylation and binding of 14–3–3 protein was a general feature for all plants tested, whereas activation by substrates as a possible regulation mechanism was verified only for squash.
Phosphoryl Group Exchange between ATP and ADP Catalyzed by H+-ATPase from Oat Roots
Authors: Helguera G. , Beauge L.
Published: October 2016

ATP-ADP exchange was estimated in the presence of plasma membrane H+-ATPase of oat (Avena sativa) roots partially purified with Triton X-100 by measuring [14C]ATP formation from [14C]ADP. Most studies were done at 0[deg]C. At pH 6.0 the exchange showed: (a) Mg2+ requirement with a biphasic response giving maximal activity at 152 [mu]M and (b) insensitivity to ionic strength, [Na+], and [K+]. ATP and ADP dependence were analyzed with a model in which nucleotide-enzyme interactions are at rapid-random equilibrium, whereas E1ATP [left right arrow] E1P-ADP transitions occur in steady state. The results indicated competition between ADP and ATP for the catalytic site, whereas ATP interaction with the ADP site was extremely weak. At 0[deg]C the exchange showed a 3-fold pH increase, from pH 5.5 to 9.0. At an alkaline pH the reaction was not affected by sodium azide and carbonyl cyanide p-trifluometoxyphenyl-hydrazone, had a biphasic response to Mg2+ (maximal at 513 [mu]m), and was insensitive to ionic strength. At 20[deg]C ATP-ADP exchange was pH insensitive. At both temperatures ATP hydrolysis displayed a bell-shaped response, with a maximum around pH 6.0 to 6.5. Because no adenylate kinase activity was detected under any condition, these results demonstrate the existence of an ATP-ADP exchange reaction catalyzed by the plant H+-ATPase.
In Vivo and in Vitro Studies of Glucose-6-Phosphate Dehydrogenase from Barley Root Plastids in Relation to Reductant Supply for NO2- Assimilation
Authors: Wright D. P. , Huppe H. C. , Turpin D. H.
Published: October 2016

Pyridine nucleotide pools were measured in intact plastids from roots of barley (Hordeum vulgare L.) during the onset of NO2- assimilation and compared with the in vitro effect of the NADPH/NADP ratio on the activity of plastidic glucose-6-phosphate dehydrogenase (G6PDH, EC 1.1.1.49) from N-sufficient or N-starved roots. The NADPH/NADP ratio increased from 0.9 to 2.0 when 10 mM glucose-6-phosphate was supplied to intact plastids. The subsequent addition of 1 mM NaNO2 caused a rapid decline in this ratio to 1.5. In vitro, a ratio of 1.5 inactivated barley root plastid G6PDH by approximately 50%, suggesting that G6PDH could remain active during NO2- assimilation even at the high NADPH/NADP ratios that would favor a reduction of ferredoxin, the electron donor of NO2- reductase. Root plastid G6PDH was sensitive to reductive inhibition by dithiothreitol (DTT), but even at 50 mM DTT the enzyme remained more than 35% active. In root plastids from barley starved of N for 3 d, G6PDH had a substantially reduced specific activity, had a lower Km for NADP, and was less inhibited by DTT than the enzyme from N-sufficient root plastids, indicating that there was some effect of N starvation on the G6PDH activity in barley root plastids.
Local and Systemic Responses of Antioxidants to Tobacco Mosaic Virus Infection and to Salicylic Acid in Tobacco (Role in Systemic Acquired Resistance)
Authors: Fodor J. , Gullner G. , Adam A. L. , Barna B. , Komives T. , Kiraly Z.
Published: October 2016

Changes in ascorbate and glutathione levels and in activities of ascorbate peroxidase, catalase, dehydroascorbate reductase (DHAR), glutathione reductase (GR), glutathione S-transferase (GST), and superoxide dismutase (SOD) were investigated in tobacco mosaic virus (TMV)-inoculated lower leaves and in non-inoculated upper leaves of Nicotiana tabacum L. cv Xanthi-nc. In separate experiments the effects of exogenous salicylic acid (SA) were also studied. Symptom appearance after TMV inoculation was preceded by a slight, transient decline of ascorbate peroxidase, GR, GST, and SOD activities in the inoculated lower leaves, but after the onset of necrosis these activities and the glutathione level substantially increased. Ascorbic acid level and DHAR activity declined and dehydroascorbate accumulated in the inoculated leaves. In upper leaves, the glutathione level and the activities of GR, GST, and SOD increased 10 to 14 d after TMV inoculation of the lower leaves, concomitantly with the development of systemic acquired resistance. From the six distinct SOD isoenzymes found in tobacco leaves, only the activities of Cu,Zn-SOD isoenzymes were affected by TMV. SA injection induced DHAR, GR, GST, and SOD activities. Catalase activities were not modified by TMV infection or SA treatment. It is supposed that stimulated antioxidative processes contribute to the suppression of necrotic symptom development in leaves with systemic acquired resistance.
Regulation of Growth Anisotropy in Well-Watered and Water-Stressed Maize Roots (I. Spatial Distribution of Longitudinal, Radial, and Tangential Expansion Rates)
Authors: Liang B. M. , Sharp R. E. , Baskin T. I.
Published: October 2016

As a system to study the regulation of growth anisotropy, we studied thinning of the primary root of maize (Zea mays L.) occurring developmentally or induced by water stress. Seedlings were transplanted into vermiculite at a water potential of approximately -0.03 MPa (well-watered) or -1.6 MPa (water-stressed). The diameter of roots in both treatments decreased with time after transplanting; the water-stressed roots became substantially thinner than well-watered roots at steady state, showing that root thinning is a genuine response to water stress. To analyze the thinning responses we quantified cell numbers and the spatial profiles of longitudinal, radial, and tangential expansion rates separately for the cortex and stele. The results showed that there was no zone of isotropic expansion and the degree of anisotropy varied greatly with position and treatment. Thinning over time in well-watered roots was caused by rates of radial and tangential expansion being too low to maintain the shape of the root. In response to low water potential, cell number in both tissues was unchanged radially but increased tangentially, which shows that thinning was caused wholly by reduced cell expansion. Water stress substantially decreased rates of tangential and radial expansion in both the stele and cortex, but only in the apical 5 mm of the root; basal to this, rates were similar in well-watered and water-stressed roots. By contrast, as in previous studies, longitudinal expansion was identical between the treatments in the apical 3 mm but in water-stressed roots was inhibited at more basal locations. The results show that expansion in longitudinal and radial directions can be regulated independently.
Growth and N Allocation in Rice Plants under CO2 Enrichment
Authors: Makino A. , Harada M. , Sato T. , Nakano H. , Mae T.
Published: October 2016

The effects of CO2 enrichment on growth and N allocation of rice (Oryza sativa L.) were examined. The plants were grown hydroponically in growth chambers with a 14-h photoperiod (1000 [mu]mol quanta m-2 s-1) and a day/night temperature of 25/20[deg]C. From the 28th to 70th d after germination, the plants were exposed to two CO2 partial pressures, namely 36 and 100 Pa. The CO2 enrichment increased the final biomass, but this was caused by a stimulation of the growth rate during the first week of the exposure to elevated CO2 partial pressures. The disappearance of the initial stimulation of the growth rate was associated with a decreased leaf area ratio. Furthermore, CO2 enrichment decreased the investment of N in the leaf blades, whereas the N allocation into the leaf sheaths and roots increased. Thus, the decrease in leaf N content by CO2 enrichment was not due to dilution of N caused by a relative increase in the plant biomass but was due to the change in N allocation at the whole-plant level. We conclude that the growth responses of rice to CO2 enrichment are mainly controlled by leaf area expansion and N allocation into leaf blades at the whole-plant level.
Distribution of Folate Derivatives and Enzymes for Synthesis of 10-Formyltetrahydrofolate in Cytosolic and Mitochondrial Fractions of Pea Leaves
Authors: Chen L. , Chan S. Y. , Cossins E. A.
Published: October 2016

Leaf extracts of 14-d-old pea (Pisum sativum L. cv Homesteader) seedlings were examined for folate derivatives and for 10-formyltetrahydrofolate synthetase (SYN), 5,10-methenyltetrahydrofolate cyclohydrolase (CYC), and 5,10-methylenetetrahydrofolate dehydrogenase (DHY) activities. Microbiological and enzyme assays showed that leaf folates SYN, CYC, and DHY were predominantly cytosolic. Extracts of Percoll gradient-purified mitochondria contained less than 1% of total leaf folate and less that 1% of each enzyme activity. Fractionation of whole-leaf homogenates resulted in the copurification of DHY and CYC (subunit 38 kD) and the isolation of a SYN protein (subunit 66 kD). Polyclonal antibodies were raised against purified cytosolic DHY-CYC (DHY-CYC-Ab) and cytosolic SYN (SYN-Ab), respectively. Immunoblots showed that DHY-CYC-Ab cross-reacted with a mitochondrial protein band (38 kD). Two mitochondrial protein bands (subunit Mr = 40,000 and 44,000) cross-reacted with SYN-Ab. Immunoaffinity chromatography (DHY-CYC-Ab as the immobile ligand) indicated that the bulk of mitochondrial SYN activity was not associated with mitochondrial DHY or CYC. When 9-d-old etiolated pea seedlings were exposed to light for up to 3 d, the specific enzyme activities of DHY-CYC in whole-leaf extracts rose 2-fold and more DHY-CYC-Ab cross-reacting protein was detected. In contrast, the specific activity of SYN fell from 5 to 1 [mu]mol min-1 mg-1 protein and less SYN-Ab cross-reacting protein was detected. The data suggest that in pea leaves, the bulk of one-carbon-substituted tetrahydrofolates and enzymes for the generation of 10-formyltetrahydrofolate are extra-mitochondrial.
Is the High Basal Level of Salicylic Acid Important for Disease Resistance in Potato?
Authors: Yu D. , Liu Y. , Fan B. , Klessig D. F. , Chen Z.
Published: October 2016

Potato (Solanum tuberosum) plants contain a high basal level of salicylic acid (SA), the role of which in disease resistance is currently unclear. Here we report that, in spite of a drastic reduction in total SA levels in transgenic potato plants expressing the bacterial salicylate hydroxylase gene (nahG), there was no significant increase in disease severity when infected by Phytophthora infestans. Therefore, the high basal level of SA does not lead to constitutive resistance in healthy potato plants. However, in contrast to control plants, arachidonic acid failed to induce systematic acquired resistance (SAR) in nahG plants against P. infestans, indicating an essential role of SA in potato SAR. These results suggest that in potato the development of SAR against P. infestans may involve increased sensitivity of the plant to SA.
Solubilization and Separation of a Plant Plasma Membrane NADPH-O2- Synthase from Other NAD(P)H Oxidoreductases
Authors: Van Gestelen P. , Asard H. , Caubergs R. J.
Published: October 2016

Solubilization and ion-exchange chromatography of plasma membrane proteins obtained from bean (Phaseolus vulgaris L.) seedlings resulted in a single NAD(P)H-O2--synthase protein peak. This enzyme showed a high preference toward NADPH as a substrate (reaction rate, 27.4 nmol O2- produced min-1 mg-1 protein), whereas NADH reactions ranged from 0 to maximally 15% of the NADPH reactions. The protein functions as an oxidase and it was clearly resolved from NAD(P)H dehydrogenases identified with commonly used strong oxidants (ferricyanide, cytochrome c, DCIP, and oxaloacetate). The involvement of peroxidases in O2- production is excluded on the basis of potassium-cyanide insensitivity and NADPH specificity. The NADPH oxidase is only moderately stimulated by flavins (1.5-fold with 25 [mu]M flavine adenine dinucleotide and 2.5-fold with 25 [mu]M flavin mononucleotide) and inhibited by 100 [mu]M p-chloromercuribenzenesulfonic acid, 200 [mu]M diphenyleneiodonium, 10 mM quinacrine, 40 mM pyridine, and 20 mM imidazole. The presence of flavins was demonstrated in the O2-synthase fraction, but no b-type cytochromes were detected. The effect of these inhibitors and the detection of flavins and cytochromes in the plant O2- synthase make it possible to compare this enzyme with the NADPH O2- synthase of animal neutrophil cells.
Estimation of Polymer Rigidity in Cell Walls of Growing and Nongrowing Celery Collenchyma by Solid-State Nuclear Magnetic Resonance in Vivo
Authors: Fenwick K. M. , Jarvis M. C. , Apperley D. C.
Published: October 2016

When the growth of a plant cell ceases, its walls become more rigid and lose the capacity to extend. Nuclear magnetic resonance relaxation methods were used to determine the molecular mobility of cell wall polymers in growing and nongrowing live celery (Apium graveolens L.) collenchyma. To our knowledge, this is the first time this approach has been used in vivo. Decreased polymer mobility in nongrowing cell walls was detected through the 13C-nuclear magnetic resonance spectrum by decreases in the proton spin-spin relaxation time constant and in the intensity of a sub-spectrum corresponding to highly mobile pectins, which was obtained by a spectral editing technique based on cross-polarization rates. Flexible, highly methyl-esterified pectins decreased in relative quantity when growth ceased. A parallel increase in the net longitudinal orientation of cellulose microfibrils was detected in isolated cell walls by polarized Fourier-transformed infrared spectrometry.
Changes in Mitochondrial Respiratory Chain Components of Petunia Cells during Culture in the Presence of Antimycin A
Authors: Wagner A. M. , Wagner M. J.
Published: October 2016

When petunia (Petunia hybrida Vilm, cv Rosy Morn) cells are cultured in the presence of 2 [mu]M antimycin A (AA), respiration proceeds mainly via the cyanide-resistant pathway. Cyanide-resistant respiratory rates were higher in mitochondria from AA cells than in control mitochondria. Compared with control cells, an increase in alternative oxidase protein was observed in AA cells, as well as an increase in ubiquinone (UQ) content. A change in the kinetics of succinate dehydrogenase was observed: there was a much higher activity at high UQ reduction in mitochondria from AA cells compared with control mitochondria. No changes were found for external NADH dehydrogenase kinetics. In AA cells in vivo, UQ reduction was only slightly higher than in control cells, indicating that increased electron transport via the alternative pathway can prevent high UQ reduction levels. Moreover, O2 consumption continues at a similar rate as in control cells, preventing O2 danger. These adaptations to stress conditions, in which the cytochrome pathway is restricted, apparently require, in addition to an increase in alternative oxidase protein, a new setup of the relative amounts and/or kinetic parameters of all of the separate components of the respiratory network.
Partial Purification and Characterization of Red Chlorophyll Catabolite Reductase, a Stroma Protein Involved in Chlorophyll Breakdown
Authors: Rodoni S. , Vicentini F. , Schellenberg M. , Matile P. , Hortensteiner S.
Published: October 2016

Red chlorophyll (Chl) catabolite (RCC) reductase, which catalyzes the reaction of an intermediary Chl catabolite (RCC) in the two-step cleavage reaction of pheophorbide (Pheide) a into primary fluorescent catabolites (pFCCs) during Chl breakdown, was characterized and partially purified. RCC reductase activity was present at all stages of barley leaf development and even in roots. The highest specific activity was found in senescent leaves, which were used to purify RCC reductase 1000-fold. Among the remaining three proteins, RCC reductase activity was most likely associated with a 55-kD protein. RCC reductase exhibited saturation kinetics for RCC, with an apparent Michaelis constant of 0.6 mM. The reaction depended on reduced ferredoxin and was sensitive to oxygen. Assays of purified RCC reductase with chemically synthesized RCC as a substrate yielded three different FCCs, two of which could be identified as the stereoisomeric pFCCs from canola (Brassica napus) (pFCC-1) and sweet pepper (Capsicum annuum) (pFCC-2), respectively. In the coupled reaction with Pheide a oxidase and RCC reductase, either pFCC-1 or pFCC-2 was produced, depending on the plant species employed as a source of RCC reductase. Data from 18 species suggest that the stereospecific action of RCC reductase is uniform within a plant family.
Purification and Characterization of Phosphoribosylpyrophosphate Synthetase from Rubber Tree Latex
Authors: Gallois R. , Prevot J. C. , Clement A. , Jacob J. L.
Published: October 2016

Phosphoribosylpyrophosphate synthetase (PRS; EC 2.7.6.1) from Hevea brasiliensis Mull. Arg. latex was located in the cytosol. After purification, its apparent molecular weight under nondenaturing conditions was estimated at 200,000 [plus or minus] 10,000; a single band at 57,000 [plus or minus] 3,000 was detected after sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The enzyme seemed to be a homotetramer. Its affinity constants were estimated at 200 [plus or minus] 30 [mu]M for adenosine triphosphate and 40 [plus or minus] 2 [mu]M for ribose-5-phosphate. The purified enzyme proved to be functional in a paraphysiological medium (cytosol deproteinized by ultrafiltration). Optimum pH was 7.5 in buffer and 6.5 in a paraphysiological medium. No PRS activity was detected in the absence of the Mg2+ ion. Of the numerous compounds tested, only Mn2+, phosphoribosylpyrophosphate, and inorganic phosphate affected the enzymatic reaction. Mn2+ (inhibitor constant = 20 [mu]M) and phosphoribosylpyrophosphate (inhibitor constant = 30 [mu]M) were inhibitors. PRS responded allosterically (Hill's coefficient = 2.3) to ribulose-5-phosphate in the presence of a physiological concentration of inorganic phosphate (10 mM). These results are set in the physiological context of laticifers.
Evidence for Chewing Insect-Specific Molecular Events Distinct from a General Wound Response in Leaves
Authors: Korth K. L. , Dixon R. A.
Published: October 2016

The timing of transcript accumulation of several wound-induced genes is different in insect-damaged and mechanically damaged leaves. Transcripts for the proteinase inhibitor II and 3-hydroxy-3-methylglutaryl-coenzyme A reductase genes accumulate more rapidly in potato (Solanum tuberosum L.) leaves chewed on by caterpillars than in leaves damaged mechanically. The timing of maximum transcript accumulation was not affected by the degree of damage inflicted by the insect larvae. When applied to a mechanical wound site, regurgitant isolated from Manduca sexta larvae causes transcript accumulation profiles to shift to parallel those in insect-damaged tissue. Whether obtained from larvae fed either potato leaves or a nonplant diet, insect regurgitant fed through the petiole of detached leaves also induces accumulation of these transcripts. The transcript accumulation-inducing activity of regurgitant is enhanced by heating at 100[deg]C. Our data suggest that a heat-stable, insect-derived elicitor functions to induce the rapid accumulation of transcripts that may be involved in plant defense against herbivores. Distinct signal transduction pathways that can distinguish between insect damage and abiotic damage might therefore exist in plants.
Evidence from Polygene Mapping for a Causal Relationship between Potato Tuber Dormancy and Abscisic Acid Content
Authors: Simko I. , McMurry S. , Yang H. M. , Manschot A. , Davies P. J. , Ewing E. E.
Published: October 2016

In previous studies polygene mapping of a backcross population derived from haploid potato (Solanum tuberosum) and a diploid wild species (Solanum berthaultii) showed at least eight quantitative trait loci (QTLs) associated with tuber dormancy. The same population was mapped for abscisic acid (ABA) content in tubers so that any QTLs identified could be compared with those detected previously. At least three distinct loci on three chromosomes (2, 4, and 7) were associated with variation in ABA content. One of the QTLs was detected only as a main (single locus) effect, and two QTLs were found through two-locus interaction analysis (epistasis). Interaction between QTLs at markers TG234 (chromosome 2) and TG155 (chromosome 4) explained 20% of total phenotypic variance for this trait. The interaction closely resembled one previously detected for dormancy, suggesting an association between high ABA content and long tuber dormancy. Although relationships between ABA level and dormancy could be demonstrated through polygene mapping, there was no indication of a relationship between these traits when they were subjected to a conventional correlation test. This illustrates the usefulness of polygene mapping as a tool to identify possible associations between hormone levels and plant development.
Visualization of Freezing Behaviors in Leaf and Flower Buds of Full-Moon Maple by Nuclear Magnetic Resonance Microscopy
Authors: Ishikawa M. , Price W. S. , Ide H. , Arata Y.
Published: October 2016

1H-Nuclear magnetic resonance (NMR) microscopy was used to study the freezing behavior of wintering buds of full-moon maple (Acer japonicum Thunb.). The images obtained predominantly reflected the density of mobile (i.e. non-ice) protons from unfrozen water. A comparison of NMR images taken at different subfreezing temperatures revealed which tissues produced high- and low-temperature exotherms in differential thermal analyses. In leaf and lower buds of A. japonicum, the scales and stem bark tissues were already frozen by -7[deg]C, but the primordial inflorescence and terminal primordial shoots remained supercooled at -14[deg]C, and the lateral primordial shoots were unfrozen even at -21[deg]C. The freezing of these supercooled tissues was associated with their loss of viability. The size of the supercooled primordial shoots and inflorescences was gradually reduced with decreasing temperature, indicating extraorgan freezing in these tissues. During this process the formation of dark regions beneath the primordia and subsequent gradual darkening in the basal part of supercooled primordia were visible. As the lateral shoot primordia were cooled, the unfrozen area was considerably reduced. Since the lateral primordia remained viable down to -40[deg]C, with no detectable low-temperature exotherms, they probably underwent type I extraorgan freezing. Deep supercooling in the xylem was clearly imaged. NMR microscopy is a powerful tool for noninvasively visualizing harmonized freezing behaviors in complex plant organs.
Properties of Two Outward-Rectifying Channels in Root Xylem Parenchyma Cells Suggest a Role in K+ Homeostasis and Long-Distance Signaling
Authors: Wegner L. H. , De Boer A. H.
Published: October 2016

Xylem parenchyma cells (XPCs) control the composition of the transpiration stream in plants and are thought to play a role in long-distance signaling as well. We addressed the regulation, selectivity, and dependence on the apoplastic ion concentrations of two types of outward rectifiers in the plasma membrane of XPCs, to assess the physiological role of these conductances. In whole-cell recordings, the membrane conductance at depolarization was under the control of cytosolic Ca2+: at physiological Ca2+ levels (150 nM) the K+ outward-rectifying conductance (KORC) predominated, whereas at elevated Ca2+ levels (5 [mu]M), only the nonselective outward-rectifying conductance (NORC) was active. No such regulatory effect of Ca2+ was observed in inside-out experiments. The voltage dependence of whole-cell KORC currents strongly depended on apoplastic K+ concentration: an increase in apoplastic K+ resulted in a positive shift of the current-voltage curve, roughly following the shift in Nernst potential of K+. KORC is impermeable to Na+, but does translocate Ca2+ in addition to K+. In contrast to KORC, NORC selected poorly among monovalent cations and anions, the relative permeability PC+/PA- being about 1.9. Gating of NORC was largely unaffected by the level of K+ in the bath. Under all ionic conditions tested, NORC tail currents or single-channel currents reversed close to 0 mV. Using an in vivo xylem-perfusion technique, tetraethylammonium (an inhibitor of KORC) was shown to block K+ transport to the shoot. These data support the hypothesis that release of K+ to the xylem sap is mediated by KORC. The molecular properties of these two conductances are discussed in the light of the distinct physiological role of XPCs.
Nuclear incorporation of iron during the eukaryotic cell cycle
Authors: Robinson Ian , Yang Yang , Zhang Fucai , Lynch Christophe , Yusuf Mohammed , Cloetens Peter
Published: October 2016

Scanning X-ray fluorescence microscopy has been used to probe the distribution of S, P and Fe within cell nuclei. Nuclei, which may have originated at different phases of the cell cycle, are found to show very different levels of Fe present with a strongly inhomogeneous distribution. P and S signals, presumably from DNA and associated nucleosomes, are high and relatively uniform across all the nuclei; these agree with X-ray phase contrast projection microscopy images of the same samples. Possible reasons for the Fe incorporation are discussed.
Nanox: a miniature mechanical stress rig designed for near-field X-ray diffraction imaging techniques
Authors: Gueninchault N. , Proudhon H. , Ludwig W.
Published: October 2016

Multi-modal characterization of polycrystalline materials by combined use of three-dimensional (3D) X-ray diffraction and imaging techniques may be considered as the 3D equivalent of surface studies in the electron microscope combining diffraction and other imaging modalities. Since acquisition times at synchrotron sources are nowadays compatible with four-dimensional (time lapse) studies, suitable mechanical testing devices are needed which enable switching between these different imaging modalities over the course of a mechanical test. Here a specifically designed tensile device, fulfilling severe space constraints and permitting to switch between X-ray (holo)tomography, diffraction contrast tomography and topotomography, is presented. As a proof of concept the 3D characterization of an Al–Li alloy multicrystal by means of diffraction contrast tomography is presented, followed by repeated topotomography characterization of one selected grain at increasing levels of deformation. Signatures of slip bands and sudden lattice rotations inside the grain have been shown by means ofin situtopography carried out during the load ramps, and diffraction spot peak broadening has been monitored throughout the experiment.
Finite element analysis and improved design of large-scale belt-conveyor drums
Authors: Mihailidis Athanassios , Savaidis George , Bouras Emmanouil , Athanasopoulos Emmanouil , Ganavaras Nikolaos , Topalidis Ioannis , Karageorgos Dimitrios , Rampidis Ilias
Published: October 2016

Purpose

Large-scale belt-conveyor systems are extensively used in open mines to continuously transport bulk material. Conveyor pulleys are critical components and failures have significant financial consequences due to extended downtime. Aiming at increasing their durability, two critical spots are identified: the drum and the welds between end-plates and drum. Alternative designs have been evaluated. The paper aims to discuss these issues.

Design/methodology/approach

Loads on the driving drum are determined from measurements of the bearing force and the motor power. The friction interaction between belt and drum is described by the creep model and its impact is evaluated by comparing the results obtained for low and typical values of friction coefficient. Alternative designs are analysed using finite element method with optimised variable density mesh. The stress field and the deformations are calculated and evaluated.

Findings

Friction affects the torque transmission capacity and force distribution, but it is shown that in this case it has almost no impact on the maximum von Mises stress which occurs on the inside surface of the drum; therefore fatigue cracks initiated there, cannot be visually detected. A reinforcing diaphragm is added at the mid-plane to reduce the stress. A new, improved design is proposed to eliminate welds between the end-plates and the drum.

Research limitations/implications

The new proposed design has to be tested in the field to ultimately validate its higher durability.

Originality/value

The impact of the friction of the belt on the drum is demonstrated. The reinforcement resulting from a mid-plane diaphragm is quantitatively evaluated and assessed. A new improved pulley design is proposed aiming at significantly increased operational life compared to the one of the current design.
Cutting forces prediction and thermal distribution considering various cutting parameters and wear progression in drilling
Authors: Mirisidis Ioannis
Published: October 2016

Purpose

The purpose of this paper is to develop a finite element method (FEM) supported simulation of drilling process applied to superficially hardened steels and assess the heat treatments effect on the optimum drilling conditions (feed rate, speed, etc.).

Design/methodology/approach

A three-dimensional model was developed simulating the drilling procedure while experimental data, concerning the chip geometry and force components, were used to validate the model. The developed simulation will allow systematically insight on the tools wear progression induced by the developed temperature and stress fields. Two different cases of simulation were examined. A typical simulation was investigated, which erected with all the standard features found in the FEM simulation software. In the second case, all the experimental data were introduced.

Findings

The simulation results revealed that the advanced developed FEM model describes sufficiently the real chip geometry. Moreover, the FEM calculations provide an effective tool for predicting occurring temperatures, strain and stresses and thus for approaching the real loads of the cutting tool during drilling.

Originality/value

This paper fulfills an identified need to study the drilling simulation.
Effects of business school student’s study time on the learning process
Authors: Tetteh Godson Ayertei
Published: October 2016

Purpose

This paper aims to clarify the relationship between the student’s study time and the learning process in the higher education system by adapting the total quality management (TQM) principles-process approach. Contrary to Deming’s (1982) constancy of purpose to improve the learning process, some students in higher education postpone their studies till the last few weeks of an examination.

Design/methodology/approach

The paper opted for an experimental study with three different classes of business school students. The experimental research question was “Do student’s study time (massed or distributed spacing) has an impact on the learning process?”

Findings

Results indicated that students in the “Strictly supervised study time” group improved on their learning process more than the “Not Strictly Supervised study time” and the control group. It is important for students to manage their own learning activities and follow a regular study time and constantly improve their learning process as proposed by Deming (1982).

Research limitations/implications

This study used restricted to undergraduate business school students in a university in Ghana, and may not necessarily be applicable universally. One other limitation was that the authors did not control for lecturer’s expectancies and how these may have influenced the students’ learning process. Another potential limitation was that TQM was the only subject area used for this study.

Practical implications

This objective of the study is to use the TQM principles of process approach, the Learning Theory and the Learning Strategies from the Motivated Strategies for Learning Questionnaire (MSLQ) – Pintrichet al.(1991) – to support theoretical and practical implications of the relationship between the student’s study time and the learning process. The results imply that students must take a more active role in their learning by having a regular study time.

Originality/value

Currently, to the best of the authors’ knowledge, there are not many experiment-based studies on a student’s study time using the MSLQ-Pintrichet al.(1991) approach. This study contributes to the literature by examining how a student’s study time (massed or distributed spacing) has an impact on the learning process.
Segmenting students based on study abroad motivations, attitudes, and preferences
Authors: Janda Swinder
Published: October 2016

Purpose

The purpose of this paper is to create a segmentation scheme to better understand different student groups based on their motivations, attitudes and preferences related to studying abroad.

Design/methodology/approach

The study uses a two-step approach – in phase one, a series of 15 semi-structured interviews are conducted with students in an effort to uncover depth information related to key motivations, attitudes and preferences related to study abroad. This is followed up by phase two which uses the data from phase one to develop and administer an online survey to collect quantitative data related to student study abroad perceptions.

Findings

Results indicate that there are two broad segments of students based on their study abroad motivations, attitudes and preferences. The larger segment, termed the “externally-motivated familiarity seekers”, represents 62 per cent of students, while the smaller segment, labeled the “internally-motivated adventure seekers” represents 38 per cent of students. Further results show that the majority of students are interested in short-term study abroad.

Research limitations/implications

The study was conducted at one University in the Midwestern region of the USA. Further research using samples from different geographic areas would help improve efficacy of the results.

Practical implications

The results have significant value for higher education institutions focused on optimizing their study abroad offerings to bring about a program-student fit that will create additional value for a variety of students.

Originality/value

This study is intended to understand key student motivations and preferences related to study abroad and as such provide higher educational institutions with practical insights that they can use to offer the right types of study abroad programs that will enhance value for a variety of students.
Intraspecific trait variation across multiple scales: the leaf economics spectrum in coffee
Authors: Martin Adam R. , Rapidel Bruno , Roupsard Olivier , Van den Meersche Karel , de Melo Virginio Filho Elias , Barrios Mirna , Isaac Marney E.
Published: October 2016

Understanding species differences in plant functional traits has been critical in developing a mechanistic understanding of terrestrial ecological processes. Greater attention is now being placed on understanding the extent, causes and consequences of intraspecific trait variation (ITV).

ITV is especially important in governing ecological processes in cropping systems, where only a small number of species or genotypes exist in high abundances. However, it remains unclear if key principles of trait‐based ecology – namely the leaf economics spectrum (LES) – also describe intraspecific variation in crop functional biology. There also remains a need to understand whether ITV within crops is random, or structured across environmental, management‐related or biological levels of organization in agroecosystems.

We employed a nested design field survey to evaluate ITV in leaf traits in coffee (Coffea arabica), one of the world's most widespread tropical crops. We evaluated ITV in eight physiological, morphological and chemical leaf traits, across five nested categorical levels (sites, management systems, spatial location, plant identity, branch identity). We compared patterns of LES trait covariation in coffee, to interspecific patterns observed across over 700 wild plant species.

Patterns of bivariate and multivariate ITV in coffee were broadly consistent with, but considerably weaker than, interspecific patterns associated with the LES, indicating that crops may systematically diverge from global patterns of trait trade‐offs observed in wild plants.

Physiological traits varied most widely (coefficient of variation (cv) 42–107%), followed by morphological traits (cv = 15–38%) and chemical traits (cv = 3–11%). Physiological ITV was best explained by the site in which a coffee plant was growing (17–55% explained), while ITV for chemical traits was best explained by management treatments within sites (25–36%); morphological ITV was higher even at the individual tree level or branch level and remained largely unexplained.

Our results support the hypothesis that artificial selection and high‐resource agricultural environments lead crops to systematically deviate from patterns of leaf trait covariation observed across wild plants species. Coupled with an understanding of how different traits vary systematically across multiple levels of biological organization, these findings help integrate ITV into future analyses of agroecosystem structure and function.

A lay summary is available for this article.
Plant communication in a widespread goldenrod: keeping herbivores on the move
Authors: Morrell Kimberly , Kessler André
Published: October 2016

Plant communication has been documented in over 35 plant species spanning 16 families to date; however, the underlying mechanisms through which it shapes plants' ecological interactions remain less clear.

Using a combination of field/laboratory bioassays, headspace volatile and leaf chemical analyses in tall goldenrod (Solidago altissima), we tested the hypothesis that plant‐to‐plant communication affects the performance, feeding and movement behaviour of herbivores by changing plants' chemical phenotypes.

We found that plant communication accelerates herbivore movement between host plants while simultaneously reducing herbivory. This suggests that plant communication can limit herbivore loads by keeping herbivores on the move between host plants.

We demonstrate that volatile chemicals emitted from herbivore‐attacked plants are sufficient to explain metabolic responses in and ecological consequences for the exposed neighbour plant. Volatile profiles of beetle (Trirhabda virgata)‐damaged and undamaged plants show substantial compositional differences, especially in sesquiterpene emission, indicating that these differences have the potential to provide neighbouring plants with specific information about herbivores in the vicinity.

Despite qualitative and phenological differences in plants' metabolic responses to herbivory‐induced volatile organic compounds (VOCs) and feeding herbivores, herbivores nonetheless respond similarly to directly damaged plants and plants exposed to VOCs from damaged neighbours as if they were of equivalently poor quality.

This study suggests that by enlarging the spatial scale at which induced resistance affects the distribution of plant chemical phenotypes in plant populations, VOC‐mediated plant communication alters the movement behaviour and performance of herbivores.

A lay summary is available for this article.
Solid or Flexible? Social Trust from Early Adolescence to Young Adulthood
Authors: Abdelzadeh Ali , Lundberg Erik
Published: October 2016

The belief that people are generally fair and trustworthy has generated plenty of scholarly attention in recent decades, particularly in the Scandinavian countries, which are often known for high levels of social trust. This article draws attention to the current discussion in the literature on whether social trust is a stable cultural trait marked by persistence or is based on experiences and subject to change throughout life. Based on unique longitudinal data from five different cohorts of young people in Sweden, ranging in age from 13 to 28 years, this article provides an empirical contribution on how social trust develops over time. The results show that there is a greater degree of instability in social trust between 13 and 15 years of age than in other age groups, and that social trust appears to stabilize with age. Findings also indicate that there are substantial inter‐individual differences in social trust among young people within the same age group, both in initial levels and in the rates of change over time. The article concludes that although social trust is relatively stable it tends to crystallize in early adulthood, highlighting the relevance of the impressionable‐years hypothesis.
Divine Healing in Australian Protestantism, 1870–1940
Authors: Adams Damon S.
Published: October 2016

The topic of divine healing was not at the forefront of the Protestant movement during its first three centuries as it reacted to what was seen as an exaggerated and often fallacious miraculous supernaturalism in Roman Catholicism. By the middle of the nineteenth century the Protestant churches in Britain, America, Europe and Australia had to consider divine healing in light of a newly emerging holiness movement. This article examines the developments in practice and theological perspective of the Protestant churches in Australia, particularly as they responded to the clear claims of the growing Pentecostal movement in the nation and the sacramental perspective on healing supported by the High Anglican sector of the Australian Church of England.