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1

Multisite phosphorylation of spinach leaf sucrose-phosphate synthase  

SciTech Connect

Spinach leaf sucrose-phosphate synthase is phosphorylated both in vivo and in vitro on serine residues. Phosphorylation of SPS in vivo yields twelve major phosphopeptides after a tryptic digest and two dimensional mapping. The in vivo labeling of three of these SPS P-peptides is reduced in illuminated leaves where the extracted enzyme is activated relative to that of dark leaves. Two of these inhibitory sites are phosphorylated as well when SPS is inactivated in vitro using ({sup 32}P)ATP. In vivo phosphorylation of two other sites is enhanced during mannose feeding of the leaves (in light or dark) which produces the highest activation state of SPS. Overall, the results confirm that light-dark regulation of SPS activity occurs as a result of regulatory seryl-phosphorylation and involves a balance between phosphorylation of sites which inhibit or stimulate activity. Regulation of the SPS protein kinase that inhibits activity is relatively unaffected by phosphate but inhibited by G1c 6-P (IC{sub 50}{approx}5 mM), which may explain the control of SPS activation state by light-dark signals.

Huber, J.L.; Huber, S.C. (North Carolina State Univ., Raleigh (USA))

1990-05-01

2

Protein phosphorylation as a mechanism for regulation of spinach leaf sucrose-phosphate synthase activity  

Microsoft Academic Search

Protein phosphorylation has been identified as a mechanism for the light-dark regulation of spinach sucrose-phosphate synthase (SPS) activity, previously shown to involve some type of covalent modification of the enzyme. The 120 kD subunit of SPS in extracts of light-treated leaves was labeled with ³²P in the presence of (γ-³²P) ATP. In this in vitro system, ³²P incorporation into light-activated

J. L. A. Huber; S. C. Huber; T NIELSEN

1989-01-01

3

Inactivation of highly activated spinach leaf sucrose-phosphate synthase by dephosphorylation. [Spinacia oleracea  

SciTech Connect

Spinach (Spinacia oleracea L.) leaf sucrose-phosphate synthase (SPS) can be phosphorylated and inactivated in vitro with ({gamma}-{sup 32}P)ATP. Thus, it was surprising to find that SPS, extracted from leaves fed mannose in the light to highly activate the enzyme, could be inactivated in an ATP-independent manner when desalted crude extracts were preincubated at 25{degrees}C before assay. The spontaneous inactivation involved a loss in activity measured with limiting substrate concentrations in the presence of the inhibitor, Pi, without affecting maximum catalytic activity. The spontaneous inactivation was unaffected by exogenous carrier proteins and protease inhibitors, but was inhibited by inorganic phosphate, fluoride, and molybdate, suggesting that a phosphatase may be involved. Okadaic acid, a potent inhibitor of mammalian type 1 and 2A protein phosphatases, had no effect up to 5 micromolar. Inactivation was stimulated about twofold by exogenous Mg{sup 2+} and was relatively insensitive to Ca{sup 2+} and to pH over the range pH 6.5 to 8.5. Radioactive phosphate incorporated into SPS during labeling of excised leaves with ({sup 32}P)Pi (initially in the dark and then in the light with mannose) was lost with time when desalted crude extracts were incubated at 25 C, and the loss in radiolabel was substantially reduced by fluoride. These results provide direct evidence for action of an endogenous phosphatase(s) using SPS as substrate.

Huber, J.L. (North Carolina State Univ., Raleigh (United States)); Huber, S.C. (Dept. of Agriculture, Raleigh, NC (United States) North Carolina State Univ., Raleigh (United States)); Hite, D.R.C.; Outlaw, W.H. Jr. (Florida State Univ., Tallahassee (United States))

1991-01-01

4

Protein phosphorylation as a mechanism for regulation of spinach leaf sucrose-phosphate synthase activity  

SciTech Connect

Protein phosphorylation has been identified as a mechanism for the light-dark regulation of spinach sucrose-phosphate synthase (SPS) activity, previously shown to involve some type of covalent modification of the enzyme. The 120 kD subunit of SPS in extracts of light-treated leaves was labeled with {sup 32}P in the presence of ({gamma}-{sup 32}P) ATP. In this in vitro system, {sup 32}P incorporation into light-activated SPS was dependent upon ATP and magnesium concentrations as well as time, and was closely paralleled by inactivation of the enzyme. The soluble protein kinase involved in the interconversion of SPS between activated and deactivated forms may be specific for SPS as it co-purifies with SPS during partial purification of the enzyme. The kinase appears not to be calcium activated and no evidence has been obtained for metabolite control of SPS phosphorylation/inactivation.

Huber, J.L.A.; Huber, S.C. (North Carolina State Univ., Raleigh (USA))

1989-04-01

5

Transgenic cotton over-producing spinach sucrose phosphate synthase showed enhanced leaf sucrose synthesis and improved fiber quality under controlled environmental conditions.  

PubMed

Prior data indicated that enhanced availability of sucrose, a major product of photosynthesis in source leaves and the carbon source for secondary wall cellulose synthesis in fiber sinks, might improve fiber quality under abiotic stress conditions. To test this hypothesis, a family of transgenic cotton plants (Gossypium hirsutum cv. Coker 312 elite) was produced that over-expressed spinach sucrose-phosphate synthase (SPS) because of its role in regulation of sucrose synthesis in photosynthetic and heterotrophic tissues. A family of 12 independent transgenic lines was characterized in terms of foreign gene insertion, expression of spinach SPS, production of spinach SPS protein, and development of enhanced extractable V (max) SPS activity in leaf and fiber. Lines with the highest V (max) SPS activity were further characterized in terms of carbon partitioning and fiber quality compared to wild-type and transgenic null controls. Leaves of transgenic SPS over-expressing lines showed higher sucrose:starch ratio and partitioning of (14)C to sucrose in preference to starch. In two growth chamber experiments with cool nights, ambient CO(2) concentration, and limited light below the canopy, the transgenic line with the highest SPS activity in leaf and fiber had higher fiber micronaire and maturity ratio associated with greater thickness of the cellulosic secondary wall. PMID:17287885

Haigler, Candace H; Singh, Bir; Zhang, Deshui; Hwang, Sangjoon; Wu, Chunfa; Cai, Wendy X; Hozain, Mohamed; Kang, Wonhee; Kiedaisch, Brett; Strauss, Richard E; Hequet, Eric F; Wyatt, Bobby G; Jividen, Gay M; Holaday, A Scott

2007-02-08

6

Transgenic cotton over-producing spinach sucrose phosphate synthase showed enhanced leaf sucrose synthesis and improved fiber quality under controlled environmental conditions  

Microsoft Academic Search

Prior data indicated that enhanced availability of sucrose, a major product of photosynthesis in source leaves and the carbon\\u000a source for secondary wall cellulose synthesis in fiber sinks, might improve fiber quality under abiotic stress conditions.\\u000a To test this hypothesis, a family of transgenic cotton plants (Gossypium\\u000a hirsutum cv. Coker 312 elite) was produced that over-expressed spinach sucrose-phosphate synthase (SPS)

Candace H. Haigler; Bir Singh; Deshui Zhang; Sangjoon Hwang; Chunfa Wu; Wendy X. Cai; Mohamed Hozain; Wonhee Kang; Brett Kiedaisch; Richard E. Strauss; Eric F. Hequet; Bobby G. Wyatt; Gay M. Jividen; A. Scott Holaday

2007-01-01

7

Protein phosphorylation as a mechanism for osmotic-stress activation of sucrose-phosphate synthase in spinach leaves.  

PubMed Central

Experiments were performed to investigated the mechanism of sucrose-phosphate synthase (SPS) activation by osmotic stress in darkened spinach (Spinacia oleracea L.) leaves. The activation was stable through immunopurification and was not the result of an increased SPS protein level. The previously described Ca(2+)-independent peak III kinase, obtained by ion-exchange chromatography, is confirmed to be the predominant enzyme catalyzing phosphorylation and inactivation of dephosphoserine-158-SPS. A new, Ca(2+)-dependent SPS-protein kinase activity (peak IV kinase) was also resolved and shown to phosphorylate and activate phosphoserine-158-SPS in vitro. The peak IV kinase also phosphorylated a synthetic peptide (SP29) based on the amino acid sequence surrounding serine-424, which also contains the motif described for the serine-158 regulatory phosphorylation site; i.e. basic residues at P-3 and P-6 and a hydrophobic residue at P-5. Peak IV kinase had a native molecular weight of approximately 150,000 as shown by gel filtration. The SP29 peptide was not phosphorylated by the inactivating peak III kinase. Osmotically stressed leaves showed increased peak IV kinase activity with the SP29 peptide as a substrate. Tryptic 32P-phosphopeptide analysis of SPS from excised spinach leaves fed [32P]inorganic P showed increased phosphorylation of the tryptic peptide containing serine-424. Therefore, at least part of the osmotic stress activation of SPS in dark leaves results from phosphorylation of serine-424 catalyzed by a Ca(2+)-dependent, 150-kD protein kinase.

Toroser, D; Huber, S C

1997-01-01

8

Expression of a Maize Sucrose Phosphate Synthase in Tomato Alters Leaf Carbohydrate Partitioning  

Microsoft Academic Search

We isolated a complementary DNA sequence for the enzyme sucrose phosphate synthase (SPS) from maize utilizing a limited amino acid sequence. The 3509-bp cDNA encodes a 1068-amino acid polypeptide. The identity of the cDNA was confirmed by the ability of the cloned sequence to direct sucrose phosphate synthesis in Escherichia coli. Because no plant-specific factors were necessary for enrymatic activity,

Ann C. Worrell; Jean-Michel Bruneau; Kristin Summerfelt; Mike Boersig; Toni A. Voelker

1991-01-01

9

Drought effect on nitrate reductase and sucrose-phosphate synthase activities in wheat (Triticum durum L.): role of leaf internal CO2  

Microsoft Academic Search

In order to study the impact of a decline of leaf internal CO2 molar ratio on nitrate reductase (NR) and sucrose- phosphate synthase (SPS) activities, leaves of wheat (Triticum durum) were submitted to different treat- ments: slow or rapid dehydration and decline in ambi- ent CO2 concentration and abscisic acid (ABA) supply. In agreement with the literature, NR activity of

Chantal Fresneau; Jaleh Ghashghaie; Gabriel Cornic

2010-01-01

10

Coarse control of sucrose-phosphate synthase in leaves: Alterations of the kinetic properties in response to the rate of photosynthesis and the accumulation of sucrose  

Microsoft Academic Search

It has been investigated whether diurnal rhythms of sucrose-phosphate synthase (SPS) are involved in controlling the rate of photosynthetic sucrose synthesis. Extracts were prepared from spinach (Spinacia oleracea L.) and barley (Hordeum vulgare L.) leaves and assayed for enzyme activity. The activity of SPS increased in parallel with a rising rate of photosynthesis, and was increased by feeding mannose and

Mark Stitt; Ingo Wilke; Regina Feil; Hans W. Heldt

1988-01-01

11

Abscisic acid accumulation in spinach leaf slices in the presence of penetrating and nonpenetrating solutes  

SciTech Connect

Abscisic acid (ABA) accumulated in detached, wilted leaves of spinach (Spinacia oleracea L. cv Savoy Hybrid 612) and reached a maximum level within 3 to 4 hours. The increase in ABA over that found in detached turgid leaves was approximately 10-fold. The effects of water stress could be mimicked by the use of thin slices of spinach leaves incubated in the presence of 0.6 molar mannitol, a compound which causes plasmolysis (loss of turgor). When spinach leaf slices were incubated with ethylene glycol, a compound which rapidly penetrates the cell membrane causing a decrease in the osmotic potential of the tissue and only transient loss of turgor, no ABA accumulated. Spinach leaf slices incubated in both ethylene glycol and mannitol had ABA levels similar to those found when slices were incubated with mannitol alone. Increases similar to those found with mannitol also occurred when Aquacide III, a highly purified form of polyethylene glycol, was used. When spinach leaf slices were incubated with solutes which are supposed to disturb membrane integrity no increase in ABA was observed. These data indicate that, with respect to the accumulation of ABA, mannitol caused a physical stress rather than a chemical stress.

Creelman, R.A.; Zeevaart, J.A.D.

1985-01-01

12

Molecular structure and subcellular localization of spinach leaf glycolate oxidase  

Microsoft Academic Search

Glycolate oxidase (E.C. 1.1.3.1) was purified from spinach leaves (Spinacia oleracea). The molecular weight of the native protein was determined by sucrose density gradient centrifugation to be 290,000 daltons (13S), whereas that of the monomeric form was 37,000 daltons. The quaternary structure of the holoenzyme is likely to be octameric, analogous to pumpkin cotyledon glycolate oxidase [Nishimura et al, 1982].

Mikio Nishimura; Yusuf D. Akhmedov; Takashi Akazawa

1983-01-01

13

Purification of Peroxisomes and Mitochondria from Spinach Leaf by Percoll Gradient Centrifugation 1  

PubMed Central

A procedure was developed to purify simultaneously peroxisomes and mitochondria from spinach (Spinacia oleracea L.) leaf under isoosmotic and low viscosity conditions. This method involved differential centrifugation and density gradient centrifugation on four layers of Percoll. Chlorophyll-free preparations of highly intact and active organelles were obtained and cross-contamination was negligible. Both organelles were stable for several hours, even if they remained in Percoll. Purified mitochondria were able to carry out the oxidation of different substrates with excellent respiratory control and ADP:O ratios. The method described in the present work was also suitable to purify mitochondria and peroxisomes from potato (Solanum tuberosum L.) tubers.

Schwitzguebel, Jean-Paul; Siegenthaler, Paul-Andre

1984-01-01

14

Purification of peroxisomes and mitochondria from spinach leaf by percoll gradient centrifugation.  

PubMed

A procedure was developed to purify simultaneously peroxisomes and mitochondria from spinach (Spinacia oleracea L.) leaf under isoosmotic and low viscosity conditions. This method involved differential centrifugation and density gradient centrifugation on four layers of Percoll. Chlorophyll-free preparations of highly intact and active organelles were obtained and cross-contamination was negligible. Both organelles were stable for several hours, even if they remained in Percoll. Purified mitochondria were able to carry out the oxidation of different substrates with excellent respiratory control and ADP:O ratios. The method described in the present work was also suitable to purify mitochondria and peroxisomes from potato (Solanum tuberosum L.) tubers. PMID:16663685

Schwitzguebel, J P; Siegenthaler, P A

1984-07-01

15

NADH-Monodehydroascorbate Oxidoreductase Is One of the Redox Enzymes in Spinach Leaf Plasma Membranes1  

PubMed Central

Amino acid analysis of internal sequences of purified NADH-hexacyanoferrate(III) oxidoreductase (NFORase), obtained from highly purified plasma membranes (PM) of spinach (Spinacia oleracea L.) leaves, showed 90 to 100% homology to internal amino acid sequences of monodehydroascorbate (MDA) reductases (EC 1.6.5.4) from three different plant species. Specificity, kinetics, inhibitor sensitivity, and cross-reactivity with anti-MDA reductase antibodies were all consistent with this identification. The right-side-out PM vesicles were subjected to consecutive salt washing and detergent (polyoxyethylene 20 dodecylether and 3-[(3-cholamido-propyl)-dimethylammonio]-1-propane sulfonate [CHAPS]) treatments, and the fractions were analyzed for NFORase and MDA reductase activities. Similar results were obtained when the 300 mm sucrose in the homogenization buffer and in all steps of the salt-washing and detergent treatments had been replaced by 150 mm KCl to mimic the conditions in the cytoplasm. We conclude that (a) MDA reductase is strongly associated with the inner (cytoplasmic) surface of the PM under in vivo conditions and requires washing with 1.0 m KCl or CHAPS treatment for removal, (b) the PM-bound MDA reductase activity is responsible for the majority of PM NFORase activity, and (c) there is another redox enzyme(s) in the spinach leaf PM that cannot be released from the PM by salt-washing and/or CHAPS treatment. The PM-associated MDA reductase may have a role in reduction of ascorbate in both the cytosol and the apoplast.

Berczi, Alajos; M?ller, Ian M.

1998-01-01

16

Antisense repression of sucrose phosphate synthase in transgenic muskmelon alters plant growth and fruit development  

Microsoft Academic Search

To unravel the roles of sucrose phosphate synthase (SPS) in muskmelon (Cucumis melo L.), we reduced its activity in transgenic muskmelon plants by an antisense approach. For this purpose, an 830bp cDNA fragment of muskmelon sucrose phosphate synthase was expressed in antisense orientation behind the 35S promoter of the cauliflower mosaic virus. The phenotype of the antisense plants clearly differed

Hongmei Tian; Leyuan Ma; Cong Zhao; Hui Hao; Biao Gong; Xiyan Yu; Xiufeng Wang

2010-01-01

17

Spinach or amaranth may represent highest residue of thiophanate-methyl with open field application on six leaf vegetables.  

PubMed

To select representative crop among leaf vegetables which may contain the highest residue after fungicide uses, open field applications with thiophanate-methyl on six crops including pakchoi, rape, crown daisy, amaranth, spinach and lettuce were designed and conducted. In this study, a high-performance liquid chromatography and electrospray ionization-tandem mass spectrometry with selected reaction monitoring was used to simultaneously determine thiophanate methyl and its metabolite carbendazim residue in various samples. The limit of quantification for thiophanate methyl and carbendazim were established in the range of 0.005-0.01 mg kg(-1) for all samples. It was shown that recoveries ranged from 67.8 % to 102.3 % for thiophanate methyl, and 72.0 %-112.6 % for carbendazim at spiked levels of 0.01-0.1 mg kg(-1). It's found that thiophanate methyl converts to carbendazim very quickly. In supervised field trials, the half-lives of thiophanate methyl in six leaf vegetables were in the range of 1.26-2.65 days, and the half-lives of carbendazim were in the range of 2.53-4.28 days. It was also found that thiophanate methyl residue in spinach and amaranth was higher than others after application. It's recommended that spinach or amaranth can be selected as representative crop in leaf vegetables in study of systemic fungicides with similarity as thiophanate methyl. PMID:23242258

Fan, Sufang; Zhao, Pengyue; Zhang, Fengzu; Yu, Chuanshan; Pan, Canping

2012-12-16

18

Sucrose phosphate synthase activity in rice grown at elevated CO sub 2 and temperature  

SciTech Connect

Rice (Oryza sativa L.) was grown at 330 and 660 {mu}L CO{sub 2} L{sup {minus}1} and at 40/33/37, 34/27/31, and 28/21/25{degree}C day/night/paddy water temperatures respectively. Sucrose phosphate synthase (SPS) activity was measured at saturating substrate concentrations at 59 days after planting. SPS activity increased 2 and 3 fold with increasing CO{sub 2} at 28 and 34{degree}C air temperatures respectively. At 40{degree}C SPS activity decreased by 37% at elevated CO{sub 2} and most plants failed to reach maturity. Similar responses were found in leaf samples taken in the dark. These results indicate that SPS, an enzyme involved in the regulation of C partitioning in leaves, increases in activity at elevated CO{sub 2}. This is in contrast to previous results with soybean. The changes in SPS activity will also be discussed in relation to leaf starch/sucrose ratios.

Hussain, W.; Rowland-Bamford, A.J.; Baker, J.T.; Allen, L.H. Jr.; Bowes, G. (Univ. of Florida, Gainesville (USA) USDA-ARS, Gainesville, FL (USA))

1990-05-01

19

Photosynthesis-related infrared light transmission changes in spinach leaf segments  

SciTech Connect

The time courses of infrared light transmission changes and fluorescence induced by light in spinach leaf segments were measured. The illumination by red light exhibited a complex wave pattern. The transmission approached the baseline after repeating decreases and increases. Illumination by far-red light decreased the transmission. One of the differences between the two responses was the difference between the two amplitudes of the first increasing component. The component in the red light response was larger than the component in the far-red light response. The transmission decrease by far-red light is supposed to correspond to ''red drop.'' The transmission decrease by far-red light was suppressed by red light. This is due to an activation of a transmission-increasing component. This probably corresponds to ''enhancement.'' A proportional correlation existed between the intensity of far-red light and the minimum intensity of red light that suppressed the transmission decrease induced by far-red light. The component which made Peak D in the time course of fluorescence yield and the first increasing component in the transmission changes were suppressed by intense light.

Akimoto, T.

1985-10-01

20

gamma-Irradiation dose: effects on baby-leaf spinach ascorbic acid, carotenoids, folate, alpha-tocopherol, and phylloquinone concentrations.  

PubMed

Ionizing radiation of fruits and vegetables, in the form of gamma rays or electron beams, is effective in overcoming quarantine barriers in trade and prolonging shelf life, but a void of information persists on ionizing radiation effects of vitamin profiles in individual foods. Baby-leaf spinach from commercial cultivars, flat-leafed 'Lazio' and crinkled-leaf 'Samish', was grown, harvested, and surface sanitized according to industry practices. Baby-leaf spinach of each cultivar was packaged under air or N(2) atmosphere, representing industry practices, then exposed to cesium-137 gamma-radiation at 0.0, 0.5, 1.0, 1.5, or 2.0 kGy. Following irradiation, leaf tissues were assayed for vitamin (C, E, K, B(9)) and carotenoid (lutein/zeaxanthin, neoxanthin, violoxanthin, and beta-carotene) concentrations. Atmospheres by irradiation had little consistent effect, but N(2) versus air was associated with elevated dihydroascorbic acid levels. Four phytonutrients (vitamins B(9), E, and K and neoxanthin) exhibited little or no change in concentration with increasing doses of irradiation. However, total ascorbic acid (vitamin C), free ascorbic acid, lutein/zeaxanthin, violaxanthin, and beta-carotene all were significantly reduced at 2.0 kGy and, depending on cultivar, were affected at lesser doses of 0.5 and 1.5 kGy. Dihydroascorbic acid, the most affected compound and an indicator of stress, likely due to irradiation-generated oxidative radicals, increased with increasing irradiation doses >0.5 kGy. PMID:20329797

Lester, Gene E; Hallman, Guy J; Prez, Juliana A

2010-04-28

21

Changes in chloroplast number per cell during leaf development in spinach  

Microsoft Academic Search

The amounts of chlorophyll and nitrogen and the numbers of cells per unit area change as the green leaves of spinach plants grow and increase in size in the light. The changes in the numbers of chloroplasts per cell were measured by a new method. A 5-fold increase in the numbers of chloroplasts per cell took place in both palisade

J. V. Possingham; W. Saurer

1969-01-01

22

Measurement of the ascorbate content of spinach leaf protoplasts and chloroplasts during illumination  

Microsoft Academic Search

Protoplasts prepared from spinach leaves in May and June contained substantial amounts of ascorbate (1.330.28 mol mg-1 chlorophyll), of which 3040% was localised in the chloroplasts. During illumination, the ascorbate content was maintained at approximately the same concentration as in the dark in both protoplasts and chloroplasts, even in the absence of CO2 when pseudocyclic electron flow would be expected

Christine Foyer; Jackie Rowell; David Walker

1983-01-01

23

Short-term water stress leads to a stimulation of sucrose synthesis by activating sucrose-phosphate synthase  

Microsoft Academic Search

The aim of this work was to identify which aspects of photosynthetic metabolism respond most sensitively to leaf water deficit. Spinach (Spinacia oleracea L.) leaf discs were floated on sorbitol concentrations of increasing molarity and changes of the protoplast volume were estimated using [14C]sorbitol and 3H2O penetration. Detached leaves were also wilted until 10% of their fresh weight was lost.

Paul Quick; Gabi Siegl; Ekkehard Neuhaus; Regina Feil; Mark Stitt

1989-01-01

24

Spinach leaf chloroplast CO sub 2 and NO sub 2 sup minus photoassimilations do not compete for photogenerated reductant  

SciTech Connect

Potential competition between CO{sub 2} and NO{sub 2}{sup {minus}} photoassimilation for photogenerated reductant (e.g. reduced ferredoxin and NADPH) was examined employing isolates of mesophyll cells and intact chloroplasts derived from mature source spinach leaves. Variations in the magnitude of incident light energy were used to manipulate the supply of reductant in situ within chloroplasts. Leaf cell and plastid isolates were fed with saturating CO{sub 2} and/or NO{sub 2}{sup {minus}} to produce the highest demand for reductant by CO{sub 2} and/or NO{sub 2}{sup {minus}} assimilatory processes (enzymes). Even in the presence of CO{sub 2} fixation, NO{sub 2}{sup {minus}} reduction in intact leaf cell isolates as well as plastid isolates was maximal at light energies as low as 50 to 200 microeinsteins per second per square meter. Simultaneously, 500 to 800 microeinsteins per second per square meter were required to support maximal CO{sub 2} assimilation. Regardless of the magnitude of the incident light energy, CO{sub 2} assimilation did not repress NO{sub 2}{sup {minus}} reduction, nor were these two processes mutually repressed. These observations have been interpreted to mean that reduced ferredoxin levels in situ in the plastids of mature source leaf mesophyll cells were adequate to supply the concurrent maximal demands exerted by enzymes associated with CO{sub 2} as well as with inorganic nitrogen photoassimilation.

Robinson, J.M. (Dept. of Agriculture, Beltsville, MD (USA))

1988-12-01

25

Physical and Kinetic Evidence for an Association between Sucrose-Phosphate Synthase and Sucrose-Phosphate Phosphatase.  

PubMed Central

The possible formation of a multienzyme complex between sucrose (Suc)-phosphate synthase (SPS) and Suc-phosphate phosphatase (SPP) was examined by measuring the rates of Suc-6-phosphate (Suc-6-P) synthesis and hydrolysis in mixing experiments with partially purified enzymes from spinach (Spinacia oleracea) and rice (Oryza sativa) leaves. The addition of SPP to SPS stimulated the rate of Suc-6-P synthesis. SPS inhibited the hydrolysis of exogenous Suc-6-P by SPP when added in the absence of its substrate (i.e. UDP-glucose) but stimulated SPP activity when the SPS substrates were present and used to generate Suc-6-P directly in the reaction. Results from isotope-dilution experiments suggest that Suc-6-P was channeled between SPS and SPP. A portion of the SPS activity comigrated with SPP during native polyacrylamide gel electrophoresis, providing physical evidence for an enzyme-enzyme interaction. Taken together, these results strongly suggest that SPS and SPP associate to form a multienzyme complex.

Echeverria, E.; Salvucci, M. E.; Gonzalez, P.; Paris, G.; Salerno, G.

1997-01-01

26

Expression, purification and preliminary crystallographic analysis of sucrose phosphate synthase (SPS) from Halothermothrix orenii  

PubMed Central

This is the first report of the crystallization of a sucrose phosphate synthase (SPS; EC 2.4.1.14). It also constitutes the first study of a sucrose phosphate synthase from a non-photosynthetic thermohalophilic anaerobic bacterium, Halothermothrix orenii. The purified recombinant spsA protein has been crystallized in the monoclinic space group C2, with unit-cell parameters a=154.2, b = 47.9, c = 72.3?, ? = 103.16, using the hanging-drop vapour-diffusion method. The crystal diffracts X-rays to a resolution limit of 3.01?. Heavy-metal and halide-soaking trials are currently in progress to solve the structure.

Huynh, Frederick; Tan, Tien-Chye; Swaminathan, Kunchithapadam; Patel, Bharat K. C.

2005-01-01

27

Bifunctional sucrose phosphate synthase/phosphatase is involved in the sucrose biosynthesis by Methylobacillus flagellatus KT.  

PubMed

The aerobic obligate methylotroph Methylobacillus flagellatus KT was shown to synthesize sucrose in the presence of 0.5-2% NaCl in the growth medium. In the genome of this bacterium, an open reading frame (ORF) encoding a predicted 84-kD polypeptide homologous to the plant and cyanobacterial sucrose phosphate synthases (SPSs) was found. Using heterologous expression of the putative sps gene in Escherichia coli, followed by affinity chromatography, pure recombinant protein SPS-His6 was obtained. The enzyme catalyzed two reactions: conversion of fructose 6-phosphate and UDP-glucose into sucrose 6-phosphate and hydrolysis of sucrose 6-phosphate to sucrose. The bifunctional sucrose phosphate synthase/phosphatase (SPS/SPP) was a 340kDa homotetrameric Mg(2+) -dependent enzyme activated by fructose 1,6-phosphate2 and ATP but inhibited by glucose 6-phosphate, fructose 1-phosphate, AMP and inorganic phosphate. The amino acid sequence of the protein had a C-terminal domain homologous to SPPs. This correlated with the absence of the spp gene in the M.flagellatus chromosome. The ORFs homologous to the M.flagellatus SPS were found in the genomes of another obligate methylotroph Methylovorus glucosetrophus as well as the lithoautotrophic bacteria Acidithiobacillus ferrooxidans, Nitrosomonas europaea and Nitrosospira multiformis whose genomes lacked the spp genes. Thus, data extending the knowledge of biochemical properties of bacterial SPSs have been obtained. PMID:23865613

But, Sergey Y; Khmelenina, Valentina N; Reshetnikov, Alexander S; Trotsenko, Yuri A

2013-08-12

28

Relationship between Steady-State Fluorescence Yield and Photosynthetic Efficiency in Spinach Leaf Tissue 1  

PubMed Central

The relationship between steady-state photosynthetic efficiency, as moles CO2 per mole of incident visible photons under 2% O2, and chlorophyll fluorescence quenching has been investigated in intact leaf tissue of Spinacia oleracia. Fluorescence yield was measured using a pulse amplitude modulation technique that permitted rapid and sensitive resolution and quantitation of photochemical and nonphotochemical quenching coefficients. A highly linear relationship was observed between photosynthetic efficiency and the ratio of photochemical:nonphotochemical quenching coefficients for values of the latter less than 1.6. This relationship applied whether irradiance or CO2 concentration was varied. The observed relationships between photochemical yield and fluorescence yield were compatible with the photosystem II model proposed by Butler and Kitajima (1975 Biochim Biophys Acta 376: 116-125). The results are discussed with respect to the proposed role of nonphotochemical quenching in regulating radiant energy utilization and also the applicability of fluorescence measurements as a means of estimation of the rate of photosynthetic electron transport.

Peterson, Richard B.; Sivak, Mirta N.; Walker, David A.

1988-01-01

29

Spinach or Amaranth Contains Highest Residue of Metalaxyl, Fluazifop-P-butyl, Chlorpyrifos, and Lambda-cyhalothrin on Six Leaf Vegetables upon Open Field Application.  

PubMed

To select representative leaf vegetables which may contain the highest residue, field experiments of metalaxyl, fluazifop-P-butyl, chlorpyrifos, and lambda-cyhalothrin on six crops including pakchoi, rape, crown daisy, amaranth, spinach, and lettuce were designed and conducted. In this study, a high-performance liquid chromatograph and electrospray ionization tandem mass spectrometer with multiple reaction monitoring was used to simultaneously determine metalaxyl and fluazifop-P-butyl residue in various samples, and a gas chromatograph with electron capture detector was used to detect chlorpyrifos and lambda-cyhalothrin. The limits of quantification (LOQ) of metalaxyl, fluazifop-P-butyl, chlorpyrifos, and lambda-cyhalothrin were in the range of 0.001-0.01 mg kg(-1) for all samples, and the average recoveries of all pesticides ranged from 67.6 to 119.1% at spiked levels of 0.01-0.1 mg kg(-1). In supervised field trials, the half-lives of metalaxyl, fluazifop-P-butyl, chlorpyrifos, and lambda-cyhalothrin were in the range of 1.11-3.79 days, 1.11-2.27 days, 1.13-5.17 days, and 1.77-6.24 days. It was also found that all pesticide residues in spinach and/or amaranth were higher than others after application. It is recommended that spinach or amaranth can be selected as a representative crop of leaf vegetables in studying systemic fungicide, insecticides, and herbicides with similarity as metalaxyl, fluazifop-P-butyl, chlorpyrifos, and lambda-cyhalothrin. PMID:23387923

Fan, Sufang; Zhang, Fengzu; Deng, Kailin; Yu, Chuanshan; Liu, Shaowen; Zhao, Pengyue; Pan, Canping

2013-02-22

30

Activation of SPS from darkened spinach leaves by an endogenous protein phosphatase  

SciTech Connect

Sucrose-phosphate synthase from darkened spinach leaves has a low activation state but can undergo a time-dependent activation in desalted leaf extracts that is inhibited by Pi, molybdate, okadaic acid and vanadate, but stimulated by fluoride. SPS labeled in vivo with ({sup 32}P)Pi in excised leaves in the dark loses incorporated {sup 32}P with time when extracts are incubated at 25{degree}C. This loss is largely prevented by vanadate, suggesting that an endogenous protein phosphatase can use SPS as substrate. Changes in phosphorylation state are closely paralleled by changes in SPS activation state. The spontaneous activation achieved in the extracts can be reversed by addition of 2 mM MgATP. Feeding okadaic acid to darkened leaves prevents light activation of SPS suggesting that the endogenous protein phosphatase is similar to the type-1 enzyme of animal tissues. Overall, the results are consistent with the notion that light activation of SPS involves dephosphorylation of inhibitory phosphorylation site(s). Regulation of the protein phosphatase by Pi may be of physiological significance.

Huber, S.C.; Huber, J.L. (North Carolina State Univ., Raleigh (USA))

1990-05-01

31

Tissue-specific differences of the mitochondrial protein import machinery: in vitro import, processing and degradation of the pre-F1? subunit of the ATP synthase in spinach leaf and root mitochondria  

Microsoft Academic Search

In this study we report the first comparison of the mitochondrial protein import and processing events in two different tissues from the same organism. Both spinach leaf and root mitochondria were able to import and process the in vitro transcribed and translated Neurospora crassa F1 subunit of ATP synthase to the mature size product. Temperature optimum for protein import, 20

Carina Knorpp; Marie Hugosson; Sara Sjling; AnnaCarin Eriksson; Elzbieta Glaser

1994-01-01

32

Nodule-enhanced expression of a sucrose phosphate synthase gene member (MsSPSA) has a role in carbon and nitrogen metabolism in the nodules of alfalfa (Medicago sativa L.).  

PubMed

Sucrose phosphate synthase (SPS) catalyzes the first step in the synthesis of sucrose in photosynthetic tissues. We characterized the expression of three different isoforms of SPS belonging to two different SPS gene families in alfalfa (Medicago sativa L.), a previously identified SPS (MsSPSA) and two novel isoforms belonging to class B (MsSPSB and MsSPSB3). While MsSPSA showed nodule-enhanced expression, both MsSPSB genes exhibited leaf-enhanced expression. Alfalfa leaf and nodule SPS enzymes showed differences in chromatographic and electrophoretic migration and differences in V (max) and allosteric regulation. The root nodules in legume plants are a strong sink for photosynthates with its need for ATP, reducing power and carbon skeletons for dinitrogen fixation and ammonia assimilation. The expression of genes encoding SPS and other key enzymes in sucrose metabolism, sucrose phosphate phosphatase and sucrose synthase, was analyzed in the leaves and nodules of plants inoculated with Sinorhizobium meliloti. Based on the expression pattern of these genes, the properties of the SPS isoforms and the concentration of starch and soluble sugars in nodules induced by a wild type and a nitrogen fixation deficient strain, we propose that SPS has an important role in the control of carbon flux into different metabolic pathways in the symbiotic nodules. PMID:19898977

Aleman, Lorenzo; Ortega, Jose Luis; Martinez-Grimes, Martha; Seger, Mark; Holguin, Francisco Omar; Uribe, Diana J; Garcia-Ibilcieta, David; Sengupta-Gopalan, Champa

2009-11-08

33

Extraction and characterization of mixed phase KNO2-KNO3 nanocrystals derived from flat-leaf green spinach  

NASA Astrophysics Data System (ADS)

Naturally available green spinach, which is a rich source of potassium, was used as the key ingredient to extract mixed-phase ferroelectric crystals of nitrite and nitrate derivatives (KNO2 + KNO3). The KNO3 phase was found to be dominant for higher pH values, as revealed by the x-ray diffraction patterns. The characteristic optical absorption spectra exhibited intra-band ?-?* electronic transitions, whereas Fourier transform infrared spectra exhibited characteristic N-O stretching vibrations. Differential scanning calorimetry revealed a broad endothermic peak at 121.8 C, highlighting a transition from phase II to I via phase III of KNO3. Obtaining nanoscale ferroelectrics via the adoption of green synthesis is economically viable for large-scale production and possible application in ferroelectric elements/devices.

Hazarika, S.; Mohanta, D.

2013-01-01

34

Testing models of fatty acid transfer and lipid synthesis in spinach leaf using in vivo oxygen-18 labeling  

SciTech Connect

Oxygen-18 labeling has been applied to the study of plant lipid biosynthesis for the first time. [{sup 13}C{sub 2}{sup 18}O{sub 2}]Acetate was incubated with spinach (Spinacia oleracea) leaves and the {sup 18}O content in fatty acid methyl esters isolated from different lipid classes measured by gas chromatography-mass spectrometry. Fatty acids isolated from lipids synthesized within the plastid, such as monogalactosyldiacylglycerol, show an {sup 18}O content consistent with the exogenous acetate undergoing a single activation step and with the direct utilization of acyl-acyl carrier protein by the acyl transferases of the chloroplast. In contrast, fatty acids isolated from lipids assembled in the cytosol, such as phosphatidylcholine, show a 50% reduction in the {sup 18}O content. This is indicative of export of the fatty acyl groups from the plastid via a free carboxylate anion, and is consistent with the acyl-acyl carrier protein thioesterase:acyl-coenzyme A (CoA) synthetase mediated export mechanism. If this were not the case and the acyl group was transferred directly from acyl-acyl carrier protein to an acyl acceptor on the cytosolic side, there would be either complete retention of {sup 18}O or, less likely, complete loss of {sup 18}O, but not a 50% loss of {sup 18}O. Thus, existing models for fatty acid transfer from the plastid and for spatially separate synthesis of prokaryotic and eukaryotic lipids have both been confirmed.

Pollard, M.; Ohlrogge, J.

1999-12-01

35

Testing models of fatty acid transfer and lipid synthesis in spinach leaf using in vivo oxygen-18 labeling.  

PubMed

Oxygen-18 labeling has been applied to the study of plant lipid biosynthesis for the first time. [(13)C(2)(18)O(2)]Acetate was incubated with spinach (Spinacia oleracea) leaves and the (18)O content in fatty acid methyl esters isolated from different lipid classes measured by gas chromatography-mass spectometry. Fatty acids isolated from lipids synthesized within the plastid, such as monogalactosyldiacylglycerol, show an (18)O content consistent with the exogenous acetate undergoing a single activation step and with the direct utilization of acyl-acyl carrier protein by the acyl transferases of the chloroplast. In contrast, fatty acids isolated from lipids assembled in the cytosol, such as phosphatidylcholine, show a 50% reduction in the (18)O content. This is indicative of export of the fatty acyl groups from the plastid via a free carboxylate anion, and is consistent with the acyl-acyl carrier protein thioesterase:acyl-coenzyme A (CoA) synthetase mediated export mechanism. If this were not the case and the acyl group was transferred directly from acyl-acyl carrier protein to an acyl acceptor on the cytosolic side, there would be either complete retention of (18)O or, less likely, complete loss of (18)O, but not a 50% loss of (18)O. Thus, existing models for fatty acid transfer from the plastid and for spatially separate synthesis of "prokaryotic" and "eukaryotic" lipids have both been confirmed. PMID:10594108

Pollard, M; Ohlrogge, J

1999-12-01

36

Coordinate control of sucrose formation in soybean leaves by sucrose-phosphate synthase and fructose-2,6-bisphosphate  

Microsoft Academic Search

Net photosynthesis (CER), assimilate-export rate, sucrose-phosphate-synthase (EC 2.4.1.14) activity, fructose-2,6-bisphosphate content, and 6-phosphofructo-2-kinase (EC 2.7.1.105) activity were monitored in leaves of soybean (Glycine max (L.) Merr.) plants during a 12:12 h day-night cycle, and in plants transferred, at regular intervals throughout the diurnal cycle, to an illuminated chamber for 3 h. In the control plants, assimilate-export rate decreased progressively during

Phillip S. Kerr; Steven C. Huber

1987-01-01

37

Phytochrome A affects stem growth, anthocyanin synthesis, sucrose-phosphate-synthase activity and neighbour detection in sunlight-grown potato  

Microsoft Academic Search

. Phytochrome action in fully de-etiolated sunlight-grown potato (Solanum tuberosum L.) was studied by comparing wild-type (WT) plants and transgenic plants with either a sense or an anti-sense phytochrome\\u000a A (phyA) construction. Radial stem growth, anthocyanin levels, and sucrose-phosphate-synthase activity were directly related\\u000a to the levels of phyA (severely reduced in transgenics with anti-sense phyA, normal in WT and increased

Marcelo J. Yanovsky; Teresa M. Alconada-Magliano; Mara A. Mazzella; Christiane Gatz; Brian Thomas; Jorge J. Casal

1998-01-01

38

The regulation of exogenous NAD(P)H oxidation in spinach (Spinacia oleracea) leaf mitochondria by pH and cations.  

PubMed Central

Essentially chlorophyll-free mitochondria were isolated from green leaves of spinach (Spinacia oleracea L. cv. Viking II). Uncoupled oxidation of exogenous NADPH (1 mM) to oxygen had an optimum at pH 6.0, and activity was relatively low at pH 7.0, even in the presence of 1 mM-CaCl2. There was a proportional increase in the apparent Km for NADPH with decreasing H+ concentrations, suggesting that NADPH protonated on the 2'-phosphate group was the true substrate. Exogenous NADH was oxidized by oxygen with an optimum at pH 6.9. Under low-cation conditions, EGTA or EDTA (both 1 mM) had no effect on the Vmax. of NADH oxidation, although the removal of bivalent cations from the membrane surface by the chelators could be observed by use of 9-aminoacridine fluorescence. In contrast, under high-cation conditions, chelators lowered the Vmax. by about 50%, probably due to a better approach of the negatively charged chelators to the negative membrane surface than under low-cation conditions. In a low-cation medium, the Vmax. of NADH oxidation was increased by about 50% by the addition of cations. This was caused by a lowering of the size of the negative surface potential through charge screening. In contrast with other cations, La3+ inhibited NADH oxidation, possibly through binding to lipids essential for NADH oxidation. The apparent Km for NADH varied 6-fold in response to changes in the size of the surface potential, suggesting that the approach of the negatively charged NADH to the active site is hampered by the negative surface potential. The results demonstrate that the spinach leaf cell can regulate the mitochondrial NAD(P)H oxidation through several mechanisms: the pH; the cation concentration in general; and the concentration of Ca2+ in particular. The results also emphasize the importance of electrostatic considerations when investigating the kinetic behaviour of membrane-bound enzymes.

Edman, K; Ericson, I; M?ller, I M

1985-01-01

39

A high-performance liquid chromatography-based radiometric assay for sucrose-phosphate synthase and other UDP-glucose requiring enzymes  

SciTech Connect

A method for product analysis that eliminates a problematic step in the radiometric sucrose-phosphate synthase assay is described. The method uses chromatography on a boronate-derivatized high-performance liquid chromatography column to separate the labeled product, (14C)sucrose phosphate, from unreacted uridine 5{prime}-diphosphate-(14C)glucose (UDP-Glc). Direct separation of these compounds eliminates the need for treatment of the reaction mixtures with alkaline phosphatase, thereby avoiding the problem of high background caused by contaminating phosphodiesterase activity in alkaline phosphatase preparations. The method presented in this paper can be applied to many UDP-Glc requiring enzymes; here the authors show its use for determining the activities of sucrose-phosphate synthase, sucrose synthase, and uridine diphosphate-glucose pyrophosphorylase in plant extracts.

Salvucci, M.E.; Crafts-Brandner, S.J. (University of Kentucky, Lexington (USA))

1991-05-01

40

Variation of plastid types in spinach  

Microsoft Academic Search

Summary During growth in the light the plastids of cultured leaf discs of spinach divide, increase in size, and differentiate in a similar manner to those in intact leaves. By contrast when l'eaf discs are grown in the dark prolamellar bodies begin to develop in partially differentiated chloroplasts within 2 hours. After 7 days growth in the dark the plastids

D. G. Cran; J. V. Possingham

1972-01-01

41

Sucrose-Phosphate Synthase from Synechocystis sp. Strain PCC 6803: Identification of the spsA Gene and Characterization of the Enzyme Expressed in Escherichia coli  

Microsoft Academic Search

The first identification and characterization of a prokaryotic gene (spsA) encoding sucrose-phosphate synthase (SPS) is reported for Synechocystis sp. strain PCC 6803, a unicellular non-nitrogen-fixing cyanobac- terium. Comparisons of the deduced amino acid sequence and some relevant biochemical properties of the enzyme with those of plant SPSs revealed important differences in the N-terminal and UDP-glucose binding site regions, substrate specificities,

LEONARDO CURATTI; EDUARDO FOLCO; PAULA DESPLATS; GUSTAVO ABRATTI; VERONICA LIMONES; LUIS HERRERA-ESTRELLA; GRACIELA SALERNO

1998-01-01

42

Conversion of L-sorbosone to L-ascorbic acid by a NADP-dependent dehydrogenase in bean and spinach leaf. [Phaseolus vulgaris L. ; Spinacia oleracea L  

SciTech Connect

An NADP-dependent dehydrogenase catalyzing the conversion of L-sorbosone to L-ascorbic acid has been isolated from Phaseolus vulgaris L. and Spinacia oleracea L. and partially purified. It is stable at {minus}20{degree}C for up to 8 months. Molecular masses, as determined by gel filtration, were 21 and 29 kilodaltons for bean and spinach enzymes, respectively. K{sub m} for sorbosone were 12 {plus minus} 2 and 18 {plus minus} 2 millimolar and for NADP{sup +}, 0.14 {plus minus} 0.05 and 1.2 {plus minus} 0.5 millimolar, for bean and spinach, respectively. Lycorine, a purported inhibitor of L-ascorbic acid biosynthesis, had no effect on the reaction.

Loewus, M.W.; Bedgar, D.L.; Saito, Kazumi; Loewus, F.A. (Washington State Univ., Pullman (USA))

1990-11-01

43

Delineating the structural, functional and evolutionary relationships of sucrose phosphate synthase gene family II in wheat and related grasses  

PubMed Central

Background Sucrose phosphate synthase (SPS) is an important component of the plant sucrose biosynthesis pathway. In the monocotyledonous Poaceae, five SPS genes have been identified. Here we present a detailed analysis of the wheat SPSII family in wheat. A set of homoeologue-specific primers was developed in order to permit both the detection of sequence variation, and the dissection of the individual contribution of each homoeologue to the global expression of SPSII. Results The expression in bread wheat over the course of development of various sucrose biosynthesis genes monitored on an Affymetrix array showed that the SPS genes were regulated over time and space. SPSII homoeologue-specific assays were used to show that the three homoeologues contributed differentially to the global expression of SPSII. Genetic mapping placed the set of homoeoloci on the short arms of the homoeologous group 3 chromosomes. A resequencing of the A and B genome copies allowed the detection of four haplotypes at each locus. The 3B copy includes an unspliced intron. A comparison of the sequences of the wheat SPSII orthologues present in the diploid progenitors einkorn, goatgrass and Triticum speltoides, as well as in the more distantly related species barley, rice, sorghum and purple false brome demonstrated that intronic sequence was less well conserved than exonic. Comparative sequence and phylogenetic analysis of SPSII gene showed that false purple brome was more similar to Triticeae than to rice. Wheat - rice synteny was found to be perturbed at the SPS region. Conclusion The homoeologue-specific assays will be suitable to derive associations between SPS functionality and key phenotypic traits. The amplicon sequences derived from the homoeologue-specific primers are informative regarding the evolution of SPSII in a polyploid context.

2010-01-01

44

Sucrose Phosphate Synthase and Acid Invertase as Determinants of Sucrose Concentration in Developing Muskmelon (Cucumis melo L.) Fruits 1  

PubMed Central

Fruits of orange-fleshed and green-fleshed muskmelon (Cucumis melo L.) were harvested at different times throughout development to evaluate changes in metabolism which lead to sucrose accumulation, and to determine the basis of differences in fruit sucrose accumulation among genotypes. Concentrations of sucrose, raffinose saccharides, hexoses and starch, as well as activities of the sucrose metabolizing enzymes sucrose phosphate synthase (SPS) (EC 2.4.1.14), sucrose synthase (EC 2.4.1.13), and acid and neutral invertases (EC 3.2.1.26) were measured. Sucrose synthase and neutral invertase activities were relatively low (1.7 0.3 micromole per hour per gram fresh weight and 2.2 0.2, respectively) and changed little throughout fruit development. Acid invertase activity decreased during fruit development, (from as high as 40 micromoles per hour per gram fresh weight) in unripe fruit, to undetectable activity in mature, ripened fruits, while SPS activity in the fruit increased (from 7 micromoles per hour per gram fresh weight) to as high as 32 micromoles per hour per gram fresh weight. Genotypes which accumulated different amounts of sucrose had similar acid invertase activity but differed in SPS activity. Our results indicate that both acid invertase and SPS are determinants of sucrose accumulation in melon fruit. However, the decline in acid invertase appears to be a normal function of fruit maturation, and is not the primary factor which determines sucrose accumulation. Rather, the capacity for sucrose synthesis, reflected in the activity of SPS, appears to determine sucrose accumulation, which is an important component of fruit quality.

Hubbard, Natalie L.; Huber, Steven C.; Pharr, D. Mason

1989-01-01

45

Norovirus surrogate survival on spinach during preharvest growth.  

PubMed

Produce can become contaminated with human viral pathogens in the field through soil, feces, or water used for irrigation; through application of manure, biosolids, pesticides, and fertilizers; and through dust, insects, and animals. The objective of this study was to assess the survival and stability of human noroviruses and norovirus surrogates (Murine norovirus [MNV] and Tulane virus [TV]) on foliar surfaces of spinach plants in preharvest growth conditions. Spinach plants were housed in a biocontrol chamber at optimal conditions for up to 7 days and infectivity was determined by plaque assay. Virus inoculation location had the largest impact on virus survival as viruses present on adaxial leaf surfaces had lower decimal reduction time (D values) than viruses present on abaxial leaf surfaces. Under certain conditions, spinach type impacted virus survival, with greater D values observed from survival on semi-savoy spinach leaves. Additional UVA and UVB exposure to mimic sunlight affected virus survival on adaxial surfaces for both semi-savoy and smooth spinach plants for both viruses. Human GII norovirus inoculated onto semi-savoy spinach had an average D value that was not statistically significant from MNV and TV, suggesting that these surrogates may have similar survival on spinach leaves compared with human noroviruses. An understanding of the behavior of enteric viruses on spinach leaves can be used to enhance growers' guidelines and for risk assessment with certain growing conditions. PMID:23506365

Hirneisen, Kirsten A; Kniel, Kalmia E

2013-04-01

46

Characterization of technetium species induced in spinach  

SciTech Connect

Plants have the ability to accumulate the long-lived fission product {sup 99}Tc. In this work, an attempt was made to separate and characterize technetium species induced by spinach plants (Spinacia oleracea L.) grown on a TcO{sub 4}{sup {minus}} containing nutrient solution. Combination of data obtained with selective extraction and chromatography gave us insight into Tc speciation in spinach plants. The following classes of Tc species in spinach leaf homogenate were found after an incubation period of 11 d: TcO{sub 4}{sup {minus}} (ca. 7%), Tc{sup V}-cysteine (ca. 25%), Tc bound to insoluble cell-wall polysaccharides (ca. 17%), Tc bound to proteins (ca. 26%), and hydrophilic non-protein Tc species (ca. 25%). These results may yield a new insight into the metabolic pathways of Tc in plants.

Harms, A.V.; Krijger, G.C.; Elteren, J.T. van; Goeij, J.J.M. de

1999-08-01

47

Subcellular volumes and metabolite concentrations in spinach leaves  

Microsoft Academic Search

Cellular and subcellular volumes in mature leaves of spinach (Spinacia oleracea L. US Hybrid 424) were determined stereologically from light and electron micrographs. Forty-nine-day-old leaves of spinach\\u000a with a total leaf volume of 1177 ?L per mg chlorophyll (Chl) were found to be composed of 3% epidermis, 58% mesophyll, 1%\\u000a vascular tissue, 5% apoplasm and 32% gas space. In the

Heike Winter; David G. Robinson; Hans Walter Heldt

1994-01-01

48

Sucrose phosphate phosphatase in the green alga Klebsormidium flaccidum (Streptophyta) lacks an extensive C-terminal domain and differs from that of land plants.  

PubMed

Previously, it was reported that like land plants, the green alga Klebsormidium flaccidum (Streptophyta) accumulates sucrose during cold acclimation (Nagao et al. Plant Cell Environ 31:872-885, 2008), suggesting that synthesis of sucrose could enhance the freezing tolerance of this alga. Because sucrose phosphate phosphatase (SPP; EC 3.1.3.24) is a key enzyme in the sucrose synthesis pathway in plants, we analyzed the SPP gene in K. flaccidum (KfSPP, GenBank accession number AB669024) to clarify its role in sucrose accumulation. As determined from its deduced amino acid sequence, KfSPP contains the N-terminal domain that is characteristic of the L-2-haloacid-dehalogenase family of phosphatases/hydrolases (the HAD phosphatase domain). However, it lacks the extensive C-terminal domain found in SPPs of land plants. Database searches revealed that the SPPs in cyanobacteria also lack the C-terminal domain. In addition, the green alga Coccomyxa (Chlorophyta) and K. flaccidum, which are closely related to land plants, have cyanobacterial-type SPPs, while Chlorella (Chlorophyta) has a land plant-type SPP. These results demonstrate that even K. flaccidum (Streptophyta), as a recent ancestor of land plants, has the cyanobacterial-type SPP lacking the C-terminal domain. Because SPP and sucrose phosphate synthase (SPS) catalyze sequential reactions in sucrose synthesis in green plant cells and the lack of the C-terminal domain in KfSPP is predicted to decrease its activity, the interaction between decreased KfSPP activity and SPS activity may alter sucrose synthesis during cold acclimation in K. flaccidum. PMID:22095241

Nagao, Manabu; Uemura, Matsuo

2011-11-18

49

LEAFMINER RESISTANCE IN SPINACH  

Technology Transfer Automated Retrieval System (TEKTRAN)

Leafminer (Liriomyza spp.) is a major insect pest of many important vegetable crops including spinach (Spinacia oleracea). Chemical control is not long lasting, and it is well documented that leafminers can develop a high degree of resistance to insecticides. Resistant varieties remain the most econ...

50

International collaborative study of the endogenous reference gene, sucrose phosphate synthase (SPS), used for qualitative and quantitative analysis of genetically modified rice.  

PubMed

One rice ( Oryza sativa ) gene, sucrose phosphate synthase (SPS), has been proven to be a suitable endogenous reference gene for genetically modified (GM) rice detection in a previous study. Herein are the reported results of an international collaborative ring trial for validation of the SPS gene as an endogenous reference gene and its optimized qualitative and quantitative polymerase chain reaction (PCR) systems. A total of 12 genetically modified organism (GMO) detection laboratories from seven countries participated in the ring trial and returned their results. The validated results confirmed the species specificity of the method through testing 10 plant genomic DNAs, low heterogeneity, and a stable single-copy number of the rice SPS gene among 7 indica varieties and 5 japonica varieties. The SPS qualitative PCR assay was validated with a limit of detection (LOD) of 0.1%, which corresponded to about 230 copies of haploid rice genomic DNA, while the limit of quantification (LOQ) for the quantitative PCR system was about 23 copies of haploid rice genomic DNA, with acceptable PCR efficiency and linearity. Furthermore, the bias between the test and true values of eight blind samples ranged from 5.22 to 26.53%. Thus, we believe that the SPS gene is suitable for use as an endogenous reference gene for the identification and quantification of GM rice and its derivates. PMID:19326953

Jiang, Lingxi; Yang, Litao; Zhang, Haibo; Guo, Jinchao; Mazzara, Marco; Van den Eede, Guy; Zhang, Dabing

2009-05-13

51

FDA and Fresh Spinach Safety.  

National Technical Information Service (NTIS)

In September 2006, the United States suffered a major outbreak of E. coli O157:H7, causing hundreds of reported injuries and several deaths and resulting in a spinach recall. The outbreak ultimately was traced to packaged fresh spinach. This was not the f...

2008-01-01

52

Choline Synthesis in Spinach in Relation to Salt Stress.  

PubMed Central

Choline metabolism was examined in spinach (Spinacia oleracea L.) plants growing under nonsaline and saline conditions. In spinach, choline is required for phosphatidylcholine synthesis and as a precursor for the compatible osmolyte glycine betaine (betaine). When control (nonsalinized) leaf discs were incubated for up to 2 h with [1,2-14C]ethanolamine, label appeared in the N-methylated derivatives of phosphoethanolamine including phosphomono-, phosphodi-, and phosphotri- (i.e. phosphocholine) methyl-ethanolamine, as well as in choline and betaine, whereas no radioactivity could be detected in the mono- and dimethylated derivatives of the free base ethanolamine. Leaf discs from salinized plants showed the same pattern of labeling, although the proportion of label that accumulated in betaine was almost 3-fold higher in the salinized leaf discs. Enzymes involved in choline metabolism were assayed in crude leaf extracts of plants. The activites of ethanolamine kinase and of the three S-adenosylmethionine:phospho-base N-methyltransferase enzymes responsible for N-methylating phosphoethanolamine to phosphocholine were all higher in extracts of plants salinized step-wise to 100, 200, or 300 mM NaCI compared with controls. In contrast, choline kinase, phosphocholine phosphatase, and cytidine 5[prime]-triphosphate: phosphocholine cytidylyltransferase activities showed little variation with salt stress. Thus, the increased diversion of choline to betaine in salt-stressed spinach appears to be mediated by the increased activity of several key enzymes involved in choline biosynthesis.

Summers, P. S.; Weretilnyk, E. A.

1993-01-01

53

Photoreduction of Sulfur Dioxide by Spinach Leaves and Isolated Spinach Chloroplasts  

PubMed Central

Labeled sulfur dioxide was found to be extensively absorbed by spinach (Spinacea oleracea L.) leaves. Labeled sulfides detected in leaf blades following fumigations with sulfur dioxide in light indicated that photoreduction of sulfur dioxide had occurred. Measurable proportions of this labeled sulfur was localized within the chloroplast fraction. Suspensions of isolated chloroplasts supplied with labeled sulfur dioxide contained labeled sulfides following a 30-minute illumination period in water-cooled reaction vessels. With reference to recent studies of the chloroplast sulfur reduction pathway, probable points of entry for sulfur dioxide and the subsequent release of hydrogen sulfide are discussed.

Silvius, John E.; Baer, Charles H.; Dodrill, Sherman; Patrick, Homer

1976-01-01

54

Light Modulation and Localization of Sucrose Phosphate Synthase Activity between Mesophyll Cells and Bundle Sheath Cells in C4 Species 1  

PubMed Central

Experiments were conducted with several Panicum species (representing the different C4 subtypes) to examine the light modulation of sucrose phosphate synthase (SPS) activity and the effect of illumination on the distribution of SPS activity between mesophyll cells (MC) and bundle sheath cells (BSC). Activity of SPS in the light decreased in the order: C4 > C3-C4 intermediate > C3. In illuminated leaves, SPS activities were similar among the three C4 subtypes, but SPS activity was higher for NAD-malic enzyme (NAD-ME) species with centripetal chloroplasts in BSC (NAD-ME(P) species) than for NAD-ME species with centrifugal chloroplasts in BSC (NAD-ME(F) species). Transfer of plants into darkness for 30 minutes resulted in decreased SPS activity for all species tested except Panicum bisulcatum (C3 species) and Panicum virgatum (NAD-ME(P) species) which showed little or no change. All C4 subtypes had some SPS activity both in MC and BSC. In the light, SPS activity was mainly in the MC for NADP-ME, NAD-ME(F) and phosphoenolpyruvate carboxykinase species, while it was mainly in the BSC for NAD-ME(P) species. In the dark, for all C4 subtypes, SPS activity in the MC was decreased to a greater extent than that in the BSC. It is intriguing that NAD-ME(F) and NAD-ME(P) species differed in the activity and distribution of SPS activity between MC and BSC, although they are otherwise identical in the photosynthetic carbon assimilation pathway. Diurnal changes in SPS activity in the MC and BSC were also examined in maize leaves. SPS activity in the MC in maize leaves was high and relatively constant throughout the middle of the light period, dropped rapidly after sunset and increased again prior to the light period. On the other hand, SPS activity in the BSC was lower and changed more coincidently with light intensity than that in the MC. The results suggested that light activation of SPS activity located in the BSC may require higher irradiance for saturation than the SPS in the MC. We conclude that SPS may function in both MC and BSC for sucrose synthesis in the light, particularly at high light intensity, while in the dark, the major function may be in the BSC during starch degradation.

Ohsugi, Ryu; Huber, Steven C.

1987-01-01

55

Phenylalanine Hydroxylase from Spinach Leaves.  

National Technical Information Service (NTIS)

Spinach leaves contain an enzyme system which catalyses the hydroxylation of L-beta-phenylalanine to tyrosine. The crude active extract has been partially purified by fractional precipitation with acetone, adsorption on DEAE-cellulose, and with calcium ph...

P. M. Nair L. C. Vining

1964-01-01

56

Betaine aldehyde dehydrogenase isozymes of spinach  

SciTech Connect

Betaine is synthesized in spinach chloroplasts via the pathway Choline ..-->.. Betaine Aldehyde ..-->.. Betaine; the second step is catalyzed by betaine aldehyde dehydrogenase (BADH). The subcellular distribution of BADH was determined in leaf protoplast lysates; BADH isozymes were separated by 6-9% native PAGE. The chloroplast stromal fraction contains a single BADH isozyme (number1) that accounts for > 80% of the total protoplast activity; the extrachloroplastic fraction has a minor isozyme (number2) which migrates more slowly than number1. Both isozymes appear specific for betaine aldehyde, are more active with NAD than NADP, and show a ca. 3-fold activity increase in salinized leaves. The phenotype of a natural variant of isozyme number1 suggests that the enzyme is a dimer.

Hanson, A.D.; Weretilnyk, E.A.; Weigel, P.

1986-04-01

57

Cinnamic Acid Hydroxylase in Spinach.  

National Technical Information Service (NTIS)

An acetone precipitate from an extract of spinach leaves catalysed the hydroxylation of trans-cinnamic acid to p-coumaric acid. The enzyme was unstable and could not be purified. Crude preparations had a pH optimum of 4.6 and showed an absolute requiremen...

P. M. Nair L. C. Vining

1964-01-01

58

Differential Expression of Sucrose-Phosphate Synthase Isoenzymes in Tobacco Reflects Their Functional Specialization during Dark-Governed Starch Mobilization in Source Leaves  

PubMed Central

Sucrose (Suc)-phosphate synthase (SPS) plays a crucial role in the synthesis of Suc in photosynthetic and nonphotosynthetic tissues. Several isoforms of SPS exist in dicotyledonous plants that can be grouped into the different families A, B, and C. To explore whether functional differences between the SPS gene families might exist, we characterized a representative for each family from tobacco (Nicotiana tabacum). RNA-blot analysis revealed a distinct expression pattern for each of the three SPS genes. While the A-family member (NtSPSA) was found to be expressed in all tissues examined, expression of the B isoform (NtSPSB) was mainly confined to the reproductive organs and NtSPSC mRNA was exclusively detected in mature source leaves. We used RNA interference to assess the in planta function of NtSPSA and C. While silencing of NtSPSA had no detectable influence on leaf carbohydrate metabolism, reduction of NtSPSC led to an increase in leaf starch content by a factor of 3 to 8. Further analysis revealed that starch accumulation in NtSPSC-silenced plants was not due to an increased partitioning of carbon into starch, but rather showed that starch mobilization was impaired. The transgenic plants were unable to efficiently mobilize their transitory leaf starch during a prolonged period of darkness and accumulated maltose as a major intermediate of starch breakdown. NtSPSC mRNA level increased appreciably during the dark period while transcript levels of the other isoforms showed no diurnal changes. Together, these results suggest that NtSPSC is specifically involved in the synthesis of Suc during starch mobilization in the dark. The roles of the other SPS isoforms are discussed.

Chen, Shuai; Hajirezaei, Mohammad; Bornke, Frederik

2005-01-01

59

Functional metagenomics of Escherichia coli O157:H7 interactions with spinach indigenous microorganisms during biofilm formation  

Technology Transfer Automated Retrieval System (TEKTRAN)

The increase in foodborne outbreaks worldwide attributed to fresh fruit and vegetables suggests that produce may serve as an ecological niche for enteric pathogens. Here we examined the interaction of E. coli O157:H7 (EcO157) with spinach leaf microflora during co-colonization and establishment of a...

60

Comparison of Survival of Campylobacter jejuni in the Phyllosphere with That in the Rhizosphere of Spinach and Radish Plants  

PubMed Central

Campylobacter jejuni has been isolated previously from market produce and has caused gastroenteritis outbreaks linked to produce. We have tested the ability of this human pathogen to utilize organic compounds that are present in leaf and root exudates and to survive in the plant environment under various conditions. Carbon utilization profiles revealed that C. jejuni can utilize many organic acids and amino acids available on leaves and roots. Despite the presence of suitable substrates in the phyllosphere and the rhizosphere, C. jejuni was unable to grow on lettuce and spinach leaves and on spinach and radish roots of plants incubated at 33C, a temperature that is conducive to its growth in vitro. However, C. jejuni was cultured from radish roots and from the spinach rhizosphere for at least 23 and 28 days, respectively, at 10C. This enteric pathogen also persisted in the rhizosphere of spinach for prolonged periods of time at 16C, a temperature at which many cool-season crops are grown. The decline rate constants of C. jejuni populations in the spinach and radish rhizosphere were 10- and 6-fold lower, respectively, than on healthy spinach leaves at 10C. The enhanced survival of C. jejuni in soil and in the rhizosphere may be a significant factor in its contamination cycle in the environment and may be associated with the sporadic C. jejuni incidence and campylobacteriosis outbreaks linked to produce.

Brandl, Maria T.; Haxo, Aileen F.; Bates, Anna H.; Mandrell, Robert E.

2004-01-01

61

Novel effects of methyl viologen on photosystem II function in spinach leaves  

Microsoft Academic Search

Methyl viologen (MV) is a well-known electron mediator that works on the acceptor side of photosystem I. We investigated the\\u000a little-known, MV-induced inhibition of linear electron flow through photosystem II (PS II) in spinach-leaf discs. Even a low\\u000a [MV] decreased the (1) average, light-adapted photochemical efficiency of PS II traps, (2) oxidation state of the primary\\u000a quinone acceptor QA in

Da-Yong Fan; Husen Jia; James Barber; Wah Soon Chow

2009-01-01

62

Role of ascorbate in detoxifying ozone in the apoplast of spinach (Spinacia oleracea L. ) leaves  

Microsoft Academic Search

Both reduced and oxidized ascorbate (AA and DHA) are present in the aqueous phase of the extracellular space, the apoplast, of spinach (Spinacia oleracea L.) leaves. Fumigation with 0.3 [mu]L L[sup [minus]1] of ozone resulted in ozone uptake by the leaves close to 0.9 pmol cm[sup [minus]2] of leaf surface area s[sup [minus]1]. Apoplastic AA was slowly oxidized by ozone.

Michael W. F. Luwe; Umeo Takahama; Ulrich Heber

1993-01-01

63

CHLOROPLAST DIVISION IN SPINACH LEAVES EXAMINED BY SCANNING ELECTRON MICROSCOPY AND FREEZE-ETCHING  

Microsoft Academic Search

SUMMARY Spinach leaf disks were cultured for 5 days in low-intensity green light and then were trans- ferred to high-intensity white light. Harvests over the next 16 h established that cell area increased by about 80% and chloroplast number per cell increased by about 65 %, while the percentage of dumbbell-shaped chloroplasts per cell decreased by 65 %. Freeze-etch replicas

N. CHALY; J. V. POSSINGHAM; W. W. THOMSON

64

Analysis of energy utilization in spinach processing  

SciTech Connect

The equipment and methods used to monitor the electrical and thermal energy consumed in various unit operations in a spinach processing plant are described and the results of a processing plant energy audit are presented. It is concluded that it requires 6.5 MJ of natural gas and fuel oil and 0.072 MJ of electric power to process one kg of new spinach; the energy intensive operations in spinach processing are associated with exhaust boxes, blanchers, and retorts; uniform product flow through the canning line is essential to energy conservation; and design improvements are needed for the blancher, exhaust box, and retort. (LCL)

Chhinnan, M.S. (Univ. of Georgia Experiment Station, Experiment); Singh, R.P.; Pedersen, L.D.; Carroad, P.A.; Rose, W.W.; Jacob, N.L.

1980-03-01

65

Glutamine Synthetase in Spinach Leaves 1  

PubMed Central

By polyacrylamide gel electrophoresis, DEAE Sephacel, and hydroxyapatite chromatography, one form of glutamine synthetase has been identified in spinach (Spinacia oleracea L. cv. Monstrueux de Viroflay) leaves. It is localized only inside the chloroplast. The enzyme was purified to homogeneity and specific antibodies against the protein were raised by immunization of rabbits. The intracellular localization of glutamine synthetase in spinach leaves was studied by indirect immunofluorescence microscopy on thin-sectioned spinach leaves. It has been demonstrated that the enzyme is specifically associated with the chloroplasts of parenchymatous cells. Images

Hirel, Bertrand; Perrot-Rechenmann, Catherine; Suzuki, Akira; Vidal, Jean; Gadal, Pierre

1982-01-01

66

Choline oxidation by intact chloroplasts isolated directly from spinach leaves  

SciTech Connect

Illuminated chloroplasts derived from spinach leaf protoplasts synthesize betaine from choline via the intermediate betaine aldehyde (BAL) (PNAS 82:3678). Photosynthetically active chloroplasts isolated directly from spinach leaves oxidized (/sup 14/C)choline in the light at rates 10 times higher (25-80 nmol/mg chl b) than protoplast-derived chloroplasts. Up to 20% of the (/sup 14/C)choline supplied during a 30 min incubation was oxidized in the light; the main product was (/sup 14/C)BAL. Rates of (/sup 14/C)choline oxidation in darkness were only 5-30% of rates in light. Light-dependent (/sup 14/C)choline oxidation was abolished by DCMU and 5 mM DTT. Pre-illumination of the chloroplasts did not promote (/sup 14/C)choline oxidation in darkness. The uncouplers nigericin and CCCP at concentrations which eliminated CO/sub 2/-dependent O/sub 2/ evolution did not affect (/sup 14/C)choline oxidation in the light. They hypothesize that (/sup 14/C)choline oxidation is not dependent upon light activation of an enzymatic system or upon the electrochemical proton gradient but requires an oxidant generated in the light.

Weigel, P.; Hanson, A.D.

1986-04-01

67

Transport of inorganic pyrophosphate across the spinach chloroplast envelope.  

PubMed Central

Spinach-leaf chloroplasts take up PPi at a rate of 1.9 mumol/h per mg of chlorophyll (Chl) in the dark and 1.6 mumol/h per mg of Chl in the light. The Km for PPi transport is 32 microM in the dark and 6 microM in the light. Uptake is inhibited by pyridoxal phosphate, 4,4'-di-isothiocyanatostilbene-2,2'-disulphonic acid and imidodiphosphate, but not by NaF or EDTA. PPi does not appear to cross the chloroplast envelope in exchange for Pi, suggesting that it is not transported by the phosphate translocator. Exchange of PPi and adenine nucleotides across the chloroplast envelope is very slow and PPi does not competitively inhibit ATP uptake, suggesting that little, if any, PPi is transported by the adenine-nucleotide translocator. These results are consistent with the presence of a specific, high-affinity PPi translocator in the spinach chloroplast envelope. It is proposed that in vivo PPi is taken up into the chloroplast from the cytosol to replenish the Pi pool in the stroma.

Lunn, J E; Douce, R

1993-01-01

68

Tuber-specific expression of a yeast invertase and a bacterial glucokinase in potato leads to an activation of sucrose phosphate synthase and the creation of a sucrose futile cycle.  

PubMed

Fluxes were investigated in growing tubers from wild-type potato (Solanum tuberosum L. cv.Desiree) and from transformants expressing a yeast invertase in the cytosol under the control of the tuber-specific patatin promoter either alone (EC 3.2.1.26;U-IN2-30) or in combination with a Zymomonas mobilis glucokinase (EC 2.7.1.2; GK3-38) by supplying radiolabelled [14C]sucrose, [14C]glucose or [14C]fructose to tuber discs for a 90-min pulse and subsequent chase incubations of 4 and 12 h, and by supplying [14C]fructose for 2 h and 4 h to intact tubers attached to the mother plant. Contrary to the expectation that this novel route for sucrose degradation would promote starch synthesis,the starch content decreased in the transgenic lines.Labelling kinetics did not reveal whether this was due to changes in the fluxes into or out of starch. However,they demonstrated that glycolysis is enhanced in the transgenic lines in comparison to the wild type. There was also a significant stimulation of sucrose synthesis,leading to a rapid cycle of sucrose degradation and resynthesis. The labelling pattern indicated that sucrose phosphate synthase (SPS; EC 2.4.1.14) was responsible for the enhanced recycling of label into sucrose. In agreement, there was a 4-fold and 6-fold increase in the activation status of SPS in U-IN2-30 and GK3-38,respectively, and experiments with protein phosphatase inhibitors indicated that this activation involves enhanced dephosphorylation of SPS. It is proposed that this activation of SPS is promoted by the elevated glucose 6-phosphate levels in the transgenic tubers.These results indicate the pitfalls of metabolic engineering without a full appreciation of the metabolic system and regulatory circuits present in the tissue under investigation. PMID:19402252

Trethewey, R N; Riesmeier, J W; Willmitzer, L; Stitt, M; Geigenberger, P

1999-04-01

69

Diversity of the spinach (Spinacia oleracea) spermosphere and phyllosphere bacterial communities.  

PubMed

The bacterial diversity of seeds, transmission of bacteria from seed to phyllosphere, and fate of seed-transmitted bacteria on mature plants are poorly characterized. Understanding the dynamics of microbial communities is important for finding bio-control or mitigation strategies for human and plant pathogens. Bacterial populations colonizing spermosphere and phyllosphere of spinach (Spinacia oleracea) seedlings and plants were characterized using pyrosequencing of 16S rRNA gene amplicons. Spinach seed microbiota was composed of three bacterial phyla: Proteobacteria, Firmicutes and Actinobacteria, belonging to >250 different operational taxonomic units (OTUs). Seed and cotyledon bacterial communities were similar in richness and diversity. Richness of 3-4 leaf-stage of development plants increased markedly to >850 OTUs classified within 11 phyla. Although some bacterial OTUs were detected on seeds, cotyledons and plants, the breadth of new sequences indicates the importance of multiple sources outside the seed in shaping phyllosphere community. Most classified sequences were from previously undescribed taxa, highlighting the benefits of pyrosequencing in describing seed diversity and phyllosphere bacterial communities. Bacterial community richness increased from 250 different OTUs for spinach seeds and cotyledons, to 800 OTUs for seedlings. To our knowledge this is the first comprehensive characterization of the spinach microbiome, complementing previous culture-based and clone library studies. PMID:23859062

Lopez-Velasco, Gabriela; Carder, Phyllis A; Welbaum, Gregory E; Ponder, Monica A

2013-08-02

70

Spinach Thylakoid Polyphenol Oxidase 1  

PubMed Central

Polyphenol oxidase activity (E.C. 1.14.18.1) has been found in two enzyme species isolated from thylakoid membranes of spinach chloroplasts. The proteins were released from the membrane by sonication and purified >900-fold by ammonium sulfate precipitation, gel filtration, and ion-exchange chromatography. The enzymes appear to be the tetramer and monomer of a subunit with a molecular weight of 42,500 as determined by lithium dodecyl sulfate gel electrophoresis. The higher molecular weight enzyme is the predominant form in freshly isolated preparations but on aging or further purification, the amount of lower molecular weight enzyme increases at the expense of the higher. Sonication releases polyphenol oxidase from the membrane largely in the latent state. C18 fatty acids, especially linolenic acid, are potent activators of the enzymic activity. In the absence of added fatty acids, the isolated enzyme spontaneously, but slowly, activates with time. Purified polyphenol oxidase utilizes o-diphenols as substrates and shows no detectable levels of monophenol or p-diphenol oxidase activities. The Km values for 3,4-dihydroxyphenylalanine and O2 are 6.5 and 0.065 millimolar, respectively. Suitable substrates include chlorogenic acid, catechol, caffeic acid, pyrogallol, and dopamine; however, the enzyme is substrate-inhibited by the last four at concentrations near their Km A large seasonal variation in polyphenol oxidase activity may result from a decrease in enzyme content rather than inhibition of the enzyme present. Images

Golbeck, John H.; Cammarata, Kirk V.

1981-01-01

71

Comparison of two possible routes of pathogen contamination of spinach leaves in a hydroponic cultivation system.  

PubMed

The route of pathogen contamination (from roots versus from leaves) of spinach leaves was investigated with a hydroponic cultivation system. Three major bacterial pathogens, Escherichia coli O157:H7, Salmonella, and Listeria monocytogenes, were inoculated into the hydroponic solution, in which the spinach was grown to give concentrations of 10? and 10 CFU/ml. In parallel, the pathogens were inoculated onto the growing leaf surface by pipetting, to give concentrations of 10? and 10 CFU per leaf. Although contamination was observed at a high rate through the root system by the higher inoculum (10? CFU) for all the pathogens tested, the contamination was rare when the lower inoculum (10 CFU) was applied. In contrast, contamination through the leaf occurred at a very low rate, even when the inoculum level was high. For all the pathogens tested in the present study, the probability of contamination was promoted through the roots and with higher inoculum levels. The probability of contamination was analyzed with logistic regression. The logistic regression model showed that the odds ratio of contamination from the roots versus from the leaves was 6.93, which suggested that the risk of contamination from the roots was 6.93 times higher than the risk of contamination from the leaves. In addition, the risk of contamination by L. monocytogenes was about 0.3 times that of Salmonella enterica subsp. enterica serovars Typhimurium and Enteritidis and E. coli O157:H7. The results of the present study indicate that the principal route of pathogen contamination of growing spinach leaves in a hydroponic system is from the plant's roots, rather than from leaf contamination itself. PMID:21902924

Koseki, Shigenobu; Mizuno, Yasuko; Yamamoto, Kazutaka

2011-09-01

72

Relative Efficacy of Sodium Hypochlorite Wash Versus Irradiation to Inactivate Escherichia coli O157:H7 Internalized in Leaves of Romaine Lettuce and Baby Spinach  

Technology Transfer Automated Retrieval System (TEKTRAN)

Pathogenic bacteria which are internalized in leaf tissues are protected from the antimicrobial effects of surface treatments. Ionizing radiation is known to penetrate foods, but the efficacy of the process against internalized bacteria is unknown. Leaves of romaine lettuce and baby spinach were cut...

73

The present position of spinach breeding  

Microsoft Academic Search

The author gives a review of the present position of spinach breeding. In succession the following sections are treated: Historical data, secondary sex characters, biology of the flower, shortening the time required for a generation, breeding methods, inheritance of some characters, the testing and selection methods and the breeding objectives.

J. Sneep

1958-01-01

74

Investigations on heat resistance of spinach leaves  

Microsoft Academic Search

Exposure of spinach plants to high temperature (35 C) increased the heat resistance of the leaves by about 3 C. This hardening process occurred within 4 to 6 h, whereas dehardening at 20\\/15 C required 1 to 2 days. At 5 C dehardening did not take place. Hardening and dehardening occurred in both the dark and the light. The hardiness

Kurt A. Santarius; Mechthild Mfiller

1979-01-01

75

The inhibitor protein of phosphorylated nitrate reductase from spinach ( Spinacia oleracea) leaves is a 14-3-3 protein  

Microsoft Academic Search

The inhibitor protein (IP) that inactivates spinach leaf NADH:nitrate reductase (NR) has been identified for the first time as a member of the eukaryotic 14-3-3 protein family based on three lines of evidence. First, the sequence of an eight amino acid tryptic peptide, obtained from immunopurified IP, matched that of a highly conserved region of the 14-3-3 proteins. Second, an

Markus Bachmann; Joan L. Huber; Pao-Chi Liao; Douglas A. Gage; Steven C. Huber

1996-01-01

76

Functional metagenomics of Escherichia coli O157:H7 interactions with spinach indigenous microorganisms during biofilm formation.  

PubMed

The increase in foodborne outbreaks worldwide attributed to fresh fruit and vegetables suggests that produce may serve as an ecological niche for enteric pathogens. Here we examined the interaction of E. coli O157:H7 (EcO157) with spinach leaf indigenous microorganisms during co-colonization and establishment of a mixed biofilm on a stainless steel surface. Stainless steel surface was selected to mimic the surface of produce-processing equipment, where retention of foodborne pathogens such as EcO157 could serve as a potential source for transmission. We observed a positive effect of spinach-associated microbes on the initial attachment of EcO157, but an antagonistic effect on the EcO157 population at the later stage of biofilm formation. Metagenomic analyses of the biofilm community with the GeoChip revealed an extremely diverse community (gene richness, 23409; Shannon-Weiner index H, 9.55). Presence of EcO157 in the mixed biofilm resulted in a significant decrease in the community ?-diversity (t test, P<0.05), indicating a putative competition between the pathogen and indigenous spinach microbes. The decrease in the ?-diversity of the EcO157-inoculated biofilm at 48 h (ANOVA, P<0.05) suggested a convergent shift in functional composition in response to EcO157 invasion. The success of EcO157 in the mixed biofilm is likely associated with its metabolic potential in utilizing spinach nutrients: the generation time of EcO157 in spinach lysates at 28C is ~ 38 min, which is comparable to that in rich broth. The significant decrease in the abundance of many genes involved in carbon, nitrogen, and phosphorus cycling in the EcO157-inoculated biofilms (t test, P<0.05) further support our conclusion that competition for essential macronutrients is likely the primary interaction between the EcO157 and indigenous spinach-biofilm species. PMID:22957052

Carter, Michelle Q; Xue, Kai; Brandl, Maria T; Liu, Feifei; Wu, Liyou; Louie, Jacqueline W; Mandrell, Robert E; Zhou, Jizhong

2012-09-05

77

Toxicity effects of olive-mill wastewater on growth, photosynthesis and pollen morphology of spinach plants.  

PubMed

Olive mill-wastewater (OMW), a by-product of the olive oil extraction process, represents a significant environmental problem in Mediterranean areas. We studied the impact of OMW dilutions (1:10 and 1:20) on growth, photosynthesis, proline and sugar accumulation as well as on pollen morphology of spinach (Spinacia oleracea L.) plants, to evaluate the application of OMW dilutions as pretreatment technique, prior to land disposal. Biomass, height, total chlorophyll and leaf area of spinach declined progressively with decreasing OMW dilution. Since fatty acids and phenolic compounds (present in the OMW) are considered precursors in the polymerization of sporopollenin, we suggest that under OMW treatment spinach plants seem to 'direct' the excess of these substances in the production and formation of increased pollen grains. Proline did not accumulate under OMW stress, but decreased possible due to transport to pollens in response to increased demand to over-production of pollens. Both OMW dilutions resulted in a decreased efficiency of PSII functioning and an increased excitation pressure (1-q(p)). It is concluded that, higher than 1:20 OMW dilutions should be used, and/or additional treatment should be applied before use of the OMW in the environment. PMID:22455663

Asfi, Maria; Ouzounidou, Georgia; Panajiotidis, Sampson; Therios, Ioannis; Moustakas, Michael

2012-03-26

78

Acid-base-modulation of nitrate reductase in leaf tissues  

Microsoft Academic Search

The effect of acid or base-loading of spinach (Spinacia oleracea L.) leaf discs on the activation status of nitrate reductase (NR) in the dark and in the light was investigated. Activity of NR (NRA), measured in crude extracts of leaf discs with removed lower epidermis, which had been floating on Mes-buffer [2-(N-morpholino)ethane sulfonic acid] pH 5.2 in the dark, was

Werner M. Kaiser; Elke Brendle-Behnisch

1995-01-01

79

Enzymes of Choline Synthesis in Spinach (Response of Phospho-Base N-Methyltransferase Activities to Light and Salinity).  

PubMed Central

In spinach (Spinacia oleracea L.), choline is synthesized by the sequential N-methylation of phosphoethanolamine -> phosphomono- -> phosphodi- -> phosphotrimethylethanolamine (i.e. phosphocholine) followed by hydrolysis to release choline. Differential centrifugation of spinach leaf extracts shows that enzymes catalyzing the three N-methylations are cytosolic. These enzymes were assayed in leaf extracts prepared from plants growing under various light/dark periods. Under a diurnal, 8-h light/16-h dark photoperiod, the activity of the enzyme catalyzing the N-methylation of phosphoethanolamine is highest at the end of the light period and lowest following the dark period. Prolonged dark periods (exceeding 16 h) lead to a further reduction in the activity of this enzyme, although activity is restored when plants are reexposed to light. In contrast, the activity of the enzyme(s) catalyzing the N-methylations of phosphomono- and phosphodimethylethanolamine does not undergo comparable changes in response to light/dark treatments. Salt shock of plants with 200 mM NaCl results in a 2-fold increase in all three N-methylation activities relative to nonsalinized controls but only in plants exposed to light. Thus, light is required for the salt-responsive up-regulation of choline synthesis in spinach.

Weretilnyk, E. A.; Smith, D. D.; Wilch, G. A.; Summers, P. S.

1995-01-01

80

Pathway for the Synthesis of Triacylglycerols from Monogalactosyldiacylglycerols in Ozone-Fumigated Spinach Leaves  

PubMed Central

When the upper leaf surface of spinach (Spinacia oleracea L.) plants was treated with [1-14C]acetate and grown for 2 days, 14C was effectively incorporated into acyl moieties of leaf lipids in ratios approximately their composition by mass. Fumigation of the plants with ozone (0.5 microliter per liter) caused a redistribution of 14C among lipid classes, i.e. a marked increase of 14C content in triacylglycerol (TG) and 1,2-diacylglycerol (1,2-DG) and a decrease of label in monogalactosyldiacylglycerol (MGDG) without affecting 14C distribution in leaf fatty acids. Label in both TG and 1,2-DG was found predominantly in their polyene molecular species. Since MGDG consists of similar polyene molecular species, the results indicate the synthesis of TG from MGDG via 1,2-DG. Label was also accumulated in tri- and tetragalactosyldiacylglycerol, products of galactolipid:galactolipid galactosyltransferase (GGGT). Moreover, there was a close relation between increases in the amounts of TG and the oligogalactolipids in ozonetreated leaves. These results indicate that MGDG was converted to 1,2-DG by GGGT and then to TG. In intact chloroplasts isolated from ozone-treated leaves, there was an enhanced production of free fatty acid (FFA), which was diminished by the addition of coenzyme A (CoA) and ATP, indicating that ozone stimulated the hydrolysis of MGDG to liberate FFA, which was in turn converted to acyl-CoA. The final step of TG synthesis, acylation of 1,2-DG with acyl-CoA, was confirmed by feeding with [1-14C]linolenic acid in leaf discs excised from ozone-fumigated leaves; 14C was effectively incorporated into TG but not into 1,2-DG. These results demonstrate the synthesis of TG from 1,2-DG and FFA which were liberated from MGDG in ozone-fumigated spinach leaves. Images Figure 3

Sakaki, Takeshi; Kondo, Noriaki; Yamada, Mitsuhiro

1990-01-01

81

A Model to Predict Microbial Contamination of Blanched Spinach  

Microsoft Academic Search

To predict the microbial concentration of blanched spinach a mathematical model was set up which takes microbial heat resistance into account. Two versions describe microbial counts of vegetative cells and of endospores in blanched spinach as a function of operating conditions during batch and continuous blanching. The predictive model was verified in several batch blanching experiments. Although based on simplified

E. Mayer-Miebach; B. Zanoni; W. E. L. Spiess

1997-01-01

82

Short-term and long-term effects of low total pressure on gas exchange rates of spinach  

NASA Astrophysics Data System (ADS)

In this study, spinach plants were grown under atmospheric and low pressure conditions with constant O2 and CO2 partial pressures, and the effects of low total pressure on gas exchange rates were investigated. CO2 assimilation and transpiration rates of spinach grown under atmospheric pressure increased after short-term exposure to low total pressure due to the enhancement of leaf conductance. However, gas exchange rates of plants grown at 25 kPa total pressure were not greater than those grown at atmospheric pressure. Stomatal pore length and width were significantly smaller in leaves grown at low total pressure. This result suggested that gas exchange rates of plants grown under low total pressure were not stimulated even with the enhancement of gas diffusion because the stomatal size and stomatal aperture decreased.

Iwabuchi, K.; Kurata, K.

83

Effect of route of introduction and host cultivar on the colonization, internalization, and movement of the human pathogen Escherichia coli O157:H7 in spinach.  

PubMed

Human pathogens can contaminate leafy produce in the field by various routes. We hypothesized that interactions between Escherichia coli O157:H7 and spinach are influenced by the route of introduction and the leaf microenvironment. E. coli O157:H7 labeled with green fluorescent protein was dropped onto spinach leaf surfaces, simulating bacteria-laden raindrops or sprinkler irrigation, and survived on the phylloplane for at least 14 days, with increasing titers and areas of colonization over time. The same strains placed into the rhizosphere by soil infiltration remained detectable on very few plants and in low numbers (10(2) to 10(6) CFU/g fresh tissue) that decreased over time. Stem puncture inoculations, simulating natural wounding, rarely resulted in colonization or multiplication. Bacteria forced into the leaf interior survived for at least 14 days in intercellular spaces but did not translocate or multiply. Three spinach cultivars with different leaf surface morphologies were compared for colonization by E. coli O157:H7 introduced by leaf drop or soil drench. After 2 weeks, cv. Bordeaux hosted very few bacteria. More bacteria were seen on cv. Space and were dispersed over an area of up to 0.3 mm2. The highest bacterial numbers were observed on cv. Tyee but were dispersed only up to 0.15 mm2, suggesting that cv. Tyee may provide protected niches or more nutrients or may promote stronger bacterial adherence. These findings suggest that the spinach phylloplane is a supportive niche for E. coli O157:H7, but no conclusive evidence was found for natural entry into the plant interior. The results are relevant for interventions aimed at minimizing produce contamination by human pathogens. PMID:19681281

Mitra, R; Cuesta-Alonso, E; Wayadande, A; Talley, J; Gilliland, S; Fletcher, J

2009-07-01

84

cDNA sequence and heterologous expression of monomeric spinach pullulanase: multiple isomeric forms arise from the same polypeptide.  

PubMed Central

The spinach pullulanase gene was cloned and sequenced using peptide sequences of the purified enzyme as a starting point and employing PCR techniques and cDNA library screening. Its open reading frame codes for a protein of 964 amino acids which represents a precursor of the pullulanase. The N-terminal transit peptide consists of 65 amino acids, and the mature protein, comprising 899 amino acids, has a calculated molecular mass of 99kDa. Pullulanase is a member of the alpha-amylase family. In addition to a characteristic catalytic (beta/alpha)8-barrel domain, it contains a domain, F, that is specific for branching and debranching enzymes. Pullulanase cDNA was expressed in Escherichia coli, and the purified protein was compared with the enzyme from spinach leaves. Identity of the two proteins was confirmed in terms of catalytic properties, N-terminal amino acid sequences and molecular masses. The pullulanase produced by E. coli showed the same microheterogeneity as the spinach leaf enzyme: it could be resolved into two substrate-induced forms by electrophoresis in amylopectin-containing polyacrylamide gels, and, in the absence of substrate, into several free forms (charge isomers) by isoelectric focusing or chromatofocusing. Rechromatofocusing of single free forms resulted in the originally observed pattern of molecular forms. However, heterogeneity of the protein disappeared on isoelectric focusing under completely denaturing conditions when only one protein band was observed. Post-translational modifications such as glycosylation and phosphorylation could be excluded as potential explanations for the protein heterogeneity. Therefore the microheterogeneity of spinach leaf pullulanase results from neither genetic variation nor post-translational modifications, but is a property of the single unmodified gene product. The different interconvertible forms of the pullulanase represent protein populations of different tertiary structure of the same polypeptide.

Renz, A; Schikora, S; Schmid, R; Kossmann, J; Beck, E

1998-01-01

85

INVITRO AND INVIVO STUDIES ON THE ANTIOXIDATIVE ACTIVITIES, MEMBRANE STABILIZATION AND CYTOTOXICITY OF WATER SPINACH (Ipomoea aquatica Forsk) FROM IBAJI PONDS, NIGERIA  

Microsoft Academic Search

In this study, possible antioxidant activities membrane stabilizing potential and cytotoxicity of ethanol extract from water spinach (Ipomoea aquatical Forsk) leaf and stem were examined. 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical, nitric oxide radical, invivo antioxidant enzyme activity assay were carried out to evaluate the antioxidant potential of the extract. The antioxidant activity of the methanol extract increased in a concentration dependent manner.

OMALE JAMES; OKAFOR POLYCARP NNACHETA; HASSAN SANUSI WARA; UMAR RABIU ALIYU

86

A dual radiotracer speciation technique with emphasis on probing of artefacts: a case study for technetium and spinach ( Spinacia oleracea L.)  

Microsoft Academic Search

Speciation is required for obtaining information on chemical reactivity, toxicity and bioavailability of an element. In this work, a novel analytical speciation methodology, using a dual radiotracer technique is described. The approach is illustrated with the speciation of 99Tc, a pure ??-emitter, in spinach plants. The actual leaf concentration of two technetium species, i.e. 99TcO?4 and 99TcX (plant-formed Tc species),

A. V Harms; J. T van Elteren; H. Th Wolterbeek; J. J. M de Goeij

1999-01-01

87

End-Product Control of Carbon Metabolism in Culture-Grown Sugar Beet Plants (Molecular and Physiological Evidence on Accelerated Leaf Development and Enhanced Gene Expression).  

PubMed Central

Sugar beet (Beta vulgaris L.) seedlings were grown on media containing 90 to 300 mM sucrose or glucose. Compared to controls, sugar-grown plants had higher growth rate, photosynthesis, and leaf sugar levels. The steady-state level of transcripts increased significantly for the small subunit of ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) (rbcS) and the cytosolic fructose-1,6-bisphosphatase and moderately for the Rubisco large subunit (rbcL). The transcript level of sucrose phosphate synthase remained unchanged. Fructose-1,6-bisphosphatase and Rubisco activities did not change in the presence of sugars, but that of sucrose phosphate synthase increased (44 and 90% under selective and nonselective assay conditions, respectively). Accelerated leaf development was indicated by (a) autoradiograms of leaves that showed that sucrose loading occurred earlier, (b) export capacity that also occurred earlier but, after about 2 weeks, differences were not detectable, and (c) sucrose synthase activity that declined significantly. Several conclusions emerged: (a) response was nonosmotic and gene and sugar specific, (b) sugars caused accelerated leaf development and sink-to-source transition, (c) enhanced gene expression was due to advanced leaf development, and (d) whereas Rubisco and cytosolic fructose-1,6-bisphosphatase genes were sugar repressed in mature leaves of greenhouse-grown plants, they were unaffected in mature, culture-grown leaves. To our knowledge, these data provide the first evidence in higher plants that, depending on the physiological/developmental context of leaves, sugars lead to differential regulation of the same gene.

Kovtun, Y.; Daie, J.

1995-01-01

88

Response of spinach and komatsuna to biogas effluent made from source-separated kitchen garbage.  

PubMed

Recycling of kitchen garbage is an urgent task for reducing public spending and environmental burdens by incineration and/or landfill. There is an interesting regional effort in Ogawa, Saitama prefecture, Japan, in which source-separated kitchen garbage is anaerobically fermented with a biogas plant and the resultant effluent is used as a quick-release organic fertilizer by surrounding farmers. However, scientific assessments of fertilizer values and risks in the use of the effluent were lacking. Thus, a field experiment was conducted from 2003 to 2004 in Tohoku National Agricultural Research Center to grow spinach (Spinacia oleracea L.) and komatsuna (Brassica rapa var. perviridis L. H. Bailey) for evaluating the fertilizer value of the kitchen garbage effluent (KGE), nitrate, coliform group (CG), Escherichia coli, fecal streptococci (FS), and Vibrio parahaemolyticus concentrations of KGE and in the soil and the plant leaves. A cattle manure effluent (CME) and chemical fertilizers (NPK) were used as controls. Total nitrogen (N) and ammonium N concentrations of the KGE were 1.47 and 1.46 g kg(-1), respectively. The bacteria tested were detected in both biogas effluents in the order of 2 to 3 log CFU g(-1), but there was little evidence that the biogas effluents increased these bacteria in the soil and the plant leaves. At the rate of 22 g N m(-2), yield, total N uptake, apparent N recovery rate, and leaf nitrate ion concentration at harvest of spinach and komatsuna in the KGE plot were mostly comparable to those in the NPK and CME plots. We conclude that the KGE is a quick-release N fertilizer comparable to chemical fertilizers and does not cause contamination of CG, E. coli, FS, or V. parahaemolyticus in the soil and spinach and komatsuna leaves. PMID:16973635

Furukawa, Yuichiro; Hasegawa, Hiroshi

2006-09-13

89

Internalization of Escherichia coli O157:H7 following biological and mechanical disruption of growing spinach plants.  

PubMed

The internalization and persistence of a bioluminescent Escherichia coli O157:H7 Ph1 was investigated in growing spinach plants that had been either biologically or mechanically damaged. In control (undamaged) plants cultivated in soil microcosms inoculated with E. coli O157:H7 Phl, the bacterium was recovered from surface-sterilized root tissue but not from leaves. Mechanical disruption of the seminal root and root hairs of the plants did not result in the internalization of the pathogen into the aerial leaf tissue. When imprints of the root tissue were made on plates of tryptic soy agar plus ampicillin, no colonies of E. coli O157:H7 were observed around damaged tissue. The roots of growing plants were exposed to the northern root-knot nematode, Meloidogyne hapla, in the presence of E. coli O157:H7. Although this treatment caused knot formation on the roots, it did not enhance the internalization of the bacterium into the plant vascular system. Coinoculation of intact leaves with E. coli O157:H7 and the phytopathogen Pseudomonas syringae DC3000 resulted in localized necrosis, but the persistence of the human pathogen was not affected. The mechanical disruption of roots does not result in the internalization of E. coli O157:H7 into the aerial tissue of spinach, and there does not appear to be any effect of P. syringae in terms of enhancing the persistence of E. coli O157:H7 in spinach leaves. PMID:16355819

Hora, Rajneesh; Warriner, Keith; Shelp, Barry J; Griffiths, Mansel W

2005-12-01

90

Chloroplast Growth and Replication in Germinating Spinach Cotyledons following Massive gamma-Irradiation of the Seed.  

PubMed

Spinach seeds (Spinacia oleracea L.) given massive doses of gamma-irradiation (500 krad) germinate and form a seedling with two green cotyledons and a radicle, but develop no further. Irradiated cotyledons show no increase in cell number or total DNA over a 7-day period in the light, while in control cotyledons there is a small increase in cell number and large increases in total DNA and chloroplast number. The chloroplasts of irradiated cotyledons are delayed in their division, become greatly enlarged and contain large amounts of starch. The whole population of chloroplasts subsequently undergoes a wave of division. The daughter chloroplasts show normal thylakoid development, but have some abnormal structural features caused by the radiation stress. Information on the effect of X-irradiation, ultraviolet irradiation, and 5-fluorodeoxyuridine on chloroplast replication and on chloroplast and nuclear DNA synthesis was obtained from cultured spinach leaf discs. It appears that chloroplast replication is more resistant to ionizing radiation than cell division and can proceed in the absence of nuclear DNA synthesis and greatly reduced chloroplast DNA synthesis. PMID:16659421

Rose, R; Possingham, J

1976-01-01

91

Publix Recalls Spinach Dip Due To Possible Health Risk  

NASA Website

Publix Super Markets is issuing a voluntary recall for spinach dip because it may be adulterated with Listeria monocytogenes. The problem was discovered as a result of routine microbial testing conducted by Publix.

92

Ammonia Accumulation and Inhibition of Photosynthesis in Methionine Sulfoximine Treated Spinach  

PubMed Central

Ammonia accumulation and photosynthetic rate inhibition took place when spinach leaf tissue was supplied with methionine sulfoximine (MSO), an inhibitor of glutamine synthetase. This effect was observed in the absence of significant inorganic nitrogen reduction or an exogenous source of ammonia. Both the time lag prior to the initial photosynthetic rate decrease and the rate of that decrease depend on the O2 and MSO concentrations supplied to the leaf tissue. However, the total rate of ammonia accumulation was similar at both 20% and 2.2% O2. The decline in photosynthetic rate was not caused by stomatal closure but may be a result of ammonia toxicity. The data point out the importance of glutamine synthetase in preventing the poisoning of leaf metabolism by ammonia generated internally through processes not involved in net nitrogen assimilation. The rapidity of the action of MSO in suppressing photosynthesis was unexpected and should not be overlooked in interpreting data from other experiments involving that inhibitor. MSO shows promise as a tool for investigating C-N flow, particularly during photorespiration.

Platt, Steven G.; Anthon, Gordon E.

1981-01-01

93

R.egulation of Maize leaf Nitrate Reductase Activity Involves Both Gene Expression and Protein Phosphorylation  

Microsoft Academic Search

ginning of the photoperiod in mature green maize (rea mays l.) leaves as a result of increased enzyme protein level and protein dephosphorylation. In vitro experiments suggested that phos- phorylation of maize leaf NR affected sensitivity to Mgz* inhibition, as shown previously in spinach. When excised leaves were fed 32P-labeled inorganic phosphate, NR was phosphorylated on seryl residues in both

Margaret G. Redinbaugh; Steven C. Huber; Wilbur H. Campbell

94

Biosynthesis of sucrose and mannitol as a function of leaf age in celery (Apium graveolens L. )  

SciTech Connect

In celery (Apium graveolens L.), the two major translocated carbohydrates are sucrose and the acyclic polyol mannitol. Their metabolism, however, is different and their specific functions are uncertain. To compare their roles in carbon partitioning and sink-source transitions, developmental changes in /sup 14/CO/sub 2/ labeling, pool sizes, and key enzyme activities in leaf tissues were examined. The proportion of label in mannitol increased dramatically with leaf maturation whereas that in sucrose remained fairly constant. Mannitol content, however, was high in all leaves and sucrose content increased as leaves developed. Activities of mannose-6-P reductase, cytoplasmic and chloroplastic fructose-1,6-bis-phosphatases, sucrose phosphate synthase, and sucrose synthase increased with leaf maturation and decreased as leaves senesced. Ribulose bisphosphate carboxylase and nonreversible glyceraldehyde-3-P dehydrogenase activities rose as leaves developed but did not decrease. Thus, sucrose is produced in all photosynthetically active leaves whereas mannitol is synthesized primarily in mature leaves and stored in all leaves. Onset of sucrose export in celery may result from sucrose accumulation in expanding leaves, but mannitol export is clearly unrelated to mannitol concentration. Mannitol export, however, appears to coincide with increased mannitol biosynthesis. Although mannitol and sucrose arise from a common precursor in celery, subsequent metabolism and transport must be regulated separately.

Davis, J.M.; Fellman, J.K.; Loescher, W.H.

1988-01-01

95

Novel antifungal peptides from Ceylon spinach seeds.  

PubMed

Two novel antifungal peptides, designated alpha- and beta-basrubrins, respectively, were isolated from seeds of the Ceylon spinach Basella rubra. The purification procedure involved saline extraction, (NH(4))(2)SO(4) precipitation, ion exchange chromatography on DEAE-cellulose, affinity chromatography on Affi-gel blue gel, ion exchange chromatography on CM-cellulose and FPLC-gel filtration on Superdex peptide column. alpha- and beta-basrubrins exhibited a molecular weight of 4.3 and 5 kDa, respectively. They inhibited translation in a rabbit reticulocyte system with an IC(50) value of 400 and 100 nM, respectively. alpha- and beta-basrubrin inhibited HIV-1 reverse transcriptase by (79.4 +/- 7.8)% and (54.6 +/- 3.6)%, respectively, at a concentration of 400 microM, and (10.56 +/- 0.92)% and (2.12 +/- 0.81)%, respectively, at a concentration of 40 microM. Both alpha- and beta-basrubrins exerted potent antifungal activity toward Botrytis cinerea, Mycosphaerella arachidicola, and Fusarium oxysporum. PMID:11688973

Wang, H; Ng, T B

2001-11-01

96

USE OF CATALASE FROM SPINACH FOR TESTING AT MOLECULAR LEVEL THE TOXICITY OF SOME IONIC LIQUIDS  

Microsoft Academic Search

SUMMARY The present work tries to evaluate catalase from spinach in order to introduce it into an ecotoxicological test battery. Previous to the determination of the influence of some ionic liquids on spinach catalase activity, the optimization of assay enzyme was performed. Optimum pH for spinach leaves catalase is between 7.5-8. Spinach catalase seems to not be inhibited by its

Ana-Maria Lacr; Laura Pope; Vasile Ostafe

97

Seasonal Changes in Tissue Nitrate Levels in Fall-Planted Spinach (Spinacia oleracea)  

Microsoft Academic Search

Excessive levels of nitrates in spinach (Spinacia oleracea) and other green vegetables pose a potential health risk. This study measured the changes in fresh matter nitrate concentrations in four spinach cultivars in the fall of 2005. Spinach grown in research plots in Saskatoon, SK were sampled from mid-September through to freeze up in mid-November. Nitrate concentrations varied between cultivars and

Adithya Ramachandran; William Hrycan; Jackie Bantle; Doug Waterer

98

Leaf Margins  

NSDL National Science Digital Library

This illustrated guide is designed to help students recognize and learn the difference between entire and toothed leaf margins. The single Web page can be easily printed for use at field sites. Both leaf margin illustrations identify the leaf blade and the petiole.

99

Flow Cytometry of Spinach Chloroplasts 1  

PubMed Central

Intact spinach (Spinacia oleracea) chloroplasts, thylakoid membranes, and inside-out or right-side-out thylakoid vesicles have been characterized by flow cytometry with respect to forward angle light scatter, right angle light scatter, and chlorophyll fluorescence. Analysis of intact chloroplasts with respect to forward light scatter and the chlorophyll fluorescence parameter revealed the presence of truly intact and disrupted chloroplasts. The forward light scatter parameter, normally considered to reflect object size, was instead found to reflect the particle density. One essential advantage of flow cytometry is that additional parameters such as Ricinus communis agglutinin (linked to fluorescein isothiocyanate) fluorescence can be determined through logical conditions placed on bit-maps, amounting to an analytical purification procedure. In the present case, chloroplast subpopulations with fully preserved envelopes, thylakoid membrane, and inside-out or right-side-out thylakoid membranes vesicles can be distinguished. Flow cytometry is also a useful tool to address the question of availability of glycosyl moities on the membrane surfaces if one keeps in mind that organelle-to-organelle interactions could be partially mediated through a recognition process. A high specific binding of R. communis agglutinin and peanut lectin to the chloroplast envelope was detected. This showed that galactose residues were exposed and accessible to specific lectins on the chloroplast surface. No exposed glucose, fucose, or mannose residues could be detected by the appropriate lectins. Ricin binding to the intact chloroplasts caused a strong aggregation. Disruption of these aggregates by resuspension or during passage in the flow cytometer induced partial breakage of the chloroplasts. Only minor binding of R. communis agglutinin and peanut lectin to the purified thylakoid membranes was detected; the binding was found to be low for both inside-out and right-side-out vesicles of the thylakoid membranes. Images Figure 1 Figure 1 Figure 1

Schroder, Wolfgang P.; Petit, Patrice X.

1992-01-01

100

Role of ascorbate in detoxifying ozone in the apoplast of spinach (Spinacia oleracea L. ) leaves  

SciTech Connect

Both reduced and oxidized ascorbate (AA and DHA) are present in the aqueous phase of the extracellular space, the apoplast, of spinach (Spinacia oleracea L.) leaves. Fumigation with 0.3 [mu]L L[sup [minus]1] of ozone resulted in ozone uptake by the leaves close to 0.9 pmol cm[sup [minus]2] of leaf surface area s[sup [minus]1]. Apoplastic AA was slowly oxidized by ozone. The initial decrease of apoplastic AA was <0.1 pmol cm[sup [minus]2] s[sup [minus]1]. The apoplastic ratio of AA to (AA + DHA) decreased within 6 h of fumigation from 0.9 to 0.1. Initially, the concentration of (AA + DHA) did not change in the apoplast, but when fumigation was continued, DHA increased and AA remained at a very low constant level. After fumigation was discontinued, DHA decreased very slowly in the apoplast, reaching control level after 70 h. Insufficient AA reached the apoplast from the cytosol to detoxify ozone in the apoplast when the ozone flux into the leaves was 0.9 pmol cm[sup [minus]2] s[sup [minus]1]. The transport of DHA back into the cytosol was slower than AA transport into the apoplast. No dehydroascorbate reductase activity could be detected in the apoplast of spinach leaves. In contrast to its extracellular redox state, the intracellular redox state of AA did not change appreciably during a 24-h fumigation period. However, intracellular glutathione became slowly oxidized. At the beginning of fumigation, 90% of the total glutathione was reduced. Only 10% was reduced after 24-h exposure of the leaves to 0.3 [mu]L L[sup [minus]1] of ozone. Necrotic leaf damage started to become visible when fumigation was extended beyond a 24-h period. A close correlation between the extent of damage, on the one hand, and the AA content and the ascorbate redox state of whole leaves, on the other, was observed after 48 h of fumigation. Only the youngest leaves that contained high ascorbate concentrations did not exhibit necrotic leaf damage after 48 h. 30 refs., 6 figs., 1 tab.

Luwe, M.W.F.; Takahama, Umeo; Heber, U. (Univ. of Wuerzburg (Germany))

1993-03-01

101

Spinach Thioredoxin m Inhibits DNA Synthesis in Fertilized Xenopus Eggs  

Microsoft Academic Search

A role for thioredoxin in metazoan DNA synthesis has been assessed by injecting rapidly dividing Xenopus eggs with purified heterologous thioredoxins, which might act as inhibitors if they were to replace resident thioredoxins in some but not all reaction steps. Of 10 tested proteins, spinach chloroplast thioredoxin m is the most potent inhibitor. Eggs cleave and produce cells lacking nuclei.

H. Hartman; M. Wu; B. B. Buchanan; J. C. Gerhart

1993-01-01

102

Survival of pathogenic Escherichia coli on basil, lettuce, and spinach  

Technology Transfer Automated Retrieval System (TEKTRAN)

The contamination of lettuce, spinach and basil with pathogenic E. coli has caused numerous illnesses over the past decade. E. coli O157:H7, E. coli O104:H4 and avian pathogenic E. coli (APECstx- and APECstx+) were inoculated on basil plants and in promix soiless substrate using drip and overhead ir...

103

Changes in microbial populations on fresh cut spinach  

Microsoft Academic Search

The microbial populations found on fresh-cut spinach leaves that were stored in gas permeable bags at 10 C for 12 days were examined and identified. The microorganisms consisted of mesophilic aerobic bacteria, psychrotrophic bacteria, Pseudomonadaceae, Enterobacteriaceae, Micrococcaceae, lactic acid bacteria and yeasts. Populations of mesophiles, psychrotrophs, Pseudomonadaceae and Enterobacteriaceae increased sharply during the storage period. The initial populations were 107,

I. Babic; S. Roy; A. E. Watada; W. P. Wergin

1996-01-01

104

Heterogeneous photosystem 2 activity in isolated spinach chloroplasts  

Microsoft Academic Search

A study was made of the fluorescence induction curves from gently-broken spinach chloroplasts inhibited with DCMU. It was found that there were four kinetically different phases associated with such curves of which only the fastest did not appear to follow exponential kinetics. A comparison of the effects of various concentrations of DCMU on the rate of oxygen evolution and on

John Sinclair; Sandra M. Spence

1990-01-01

105

Sulfur dioxide inhibition of photosynthesis in isolated spinach chloroplasts  

Microsoft Academic Search

Photosynthetic oxygen evolution by isolated spinach (Spinacia oleracea L.) chloroplasts approached complete inhibition in the presence of a 5 mM concentration of sulfur dioxide. A similar inhibition was observed in the presence of equimolar concentrations of bisulfite ions, suggesting a parallel mode of action. In contrast, an equimolar concentration of sulfite ions was markedly less inhibitory and sulfate ions caused

J. E. Silvius; M. Ingle; C. H. Baer

1975-01-01

106

Freezing Injury and Resistance in Spinach Chloroplast Grana 12  

PubMed Central

Spinach grana appear to be injured by the same mechanism and by the same degree of dehydration and volume reduction that injures animal cells. Winter-hardened or artificially protected grana avoid injury by permitting a reversible influx of solute which forestalls excessive dehydration and shrinkage.

Williams, Robert J.; Meryman, H. T.

1970-01-01

107

First report of Tobacco rattle virus in spinach in California.  

Technology Transfer Automated Retrieval System (TEKTRAN)

In 2009 in coastal California (Santa Barbara County), commercially grown spinach (Spinacia oleracea) in two nearby fields exhibited symptoms of a previously unrecognized virus-like disease. Symptoms consisted of general chlorosis and bright yellow blotches and spots. Necrotic spots were also associa...

108

Isolation and Characterization of Phosphatidyl Choline from Spinach Leaves.  

ERIC Educational Resources Information Center

|This inexpensive but informative experiment for undergraduate biochemistry students involves isolating phosphatidyl choline from spinach leaves. Emphasis is on introducing students to techniques of lipid extraction, separation of lipids, identification using thin layer chromatography, and identification of fatty acids. Three periods of three

Devor, Kenneth A.

1979-01-01

109

Expression and purification of spinach nitrite reductase in E. coli  

SciTech Connect

The study of structure-function relationships in nitrite reductase (NiR) by site-directed mutagenesis requires an expression system from which suitable quantities of active enzyme can be purified. Spinach NiR cDNA was cloned into pUC18 and expressed in E.coli JM109 as a beta-galactosidase fusion protein. The IPTG-induced fusion protein contains five additional amino acids at the N-terminus. The expressed NiR in aerobic cultures was mostly insoluble and inactive indicating the presence of inclusion bodies. By altering growth conditions, active NiR could represent 0.5-1.0% of the total E.coli protein, Effects of the addition of delta-aminolevulinic acid, a heme precursor, and anaerobic growth were also examined. Spinach NiR was purified approximately 200 fold to homogeneity. When subjected to electrophoresis on SDS polyacrylamide gels, the NiR migrated as a single band with similar mobility to pure spinach enzyme. The expressed enzyme also reacted with rabbit anti-spinach NiR antibody as visualized by Western blot analysis. The absorption spectrum of the E.coli-expressed enzyme was identical to spinach enzyme with a Soret and alpha band a 386 and 573 nm, respectively, and an A{sub 278}/A{sub 386} = 1.9. The addition of nitrite produced the characteristic shifts in the spectrum. The E. coli-expressed NiR catalyzed the methylviologen-dependent reduction of nitrite. The specific activity was 100 U/mg. The K{sub m} determined for nitrite was 0.3 mM which is in agreement with values reported for the enzyme. These results indicate that the E.coli-expressed NiR is fully comparable to spinach NiR in purity, catalytic activity and physical state. Site-directed mutants have been made using PCR to examine structure-function relationships in this enzyme.

Bellissimo, D.; Privalle, L. (Ciba-Giegy Corp., Research Triangle Park, NC (United States))

1991-03-11

110

Leaf Identification  

NSDL National Science Digital Library

This straightforward tutorial on leaf identification comes from the Department of Horticulture at Penn State University. Simple diagrams, helpful photos, and clear explanations make short work of learning the basics of leaf identification. The website even includes a section on why anyone should bother learning this skill (i.e. it's not just for dedicated horticulturists and botanists). The tutorial covers leaf structure, blade shape, margins, venation, and so on. The self-testing component appears to be unavailable at this time, but this site as a whole is definitely worth a look.

111

Sizes of Mn-binding sites in spinach thylakoids  

SciTech Connect

The sizes of the Mn-binding sites in spinach thylakoids were estimated by target size analysis, assaying the membrane-bound Mn that was resistant to EDTA washing after radiation inactivation. The inactivation curve showed well the inactivation of two independent Mn-binding sites of different sizes: about two-thirds of the Mn coordinated to a binding site of 65 kDa, and the rest bound to a much smaller site of only about 3 kDa. In the large site, there was about 1 g atom of Mn/110 mol of chlorophyll in spinach thylakoids, which was constant in normally grown plants, although the Mn level in the small site depended on culture conditions. Thylakoids that had been incubated with hydroxylamine or in 0.8 M Tris lost Mn exclusively from the large binding site.

Takahashi, M.; Asada, K.

1986-12-25

112

Photosynthate partitioning during flowering in relation to senescence of spinach  

SciTech Connect

Male spinach plants are frequently cited as a counter-example to the nutrient drain hypothesis. Photosynthate partitioning in both male and female plants was examined. Leaves just below the inflorescences in plants at various stages of flowering were labelled with {sup 14}CO{sub 2} and the photosynthate allowed to partition for three hours. The leaves, flowers and stems of the inflorescence, and the other above ground vegetative tissue were harvested. These parts were combusted in a sample oxidizer for the collection of the {sup 14}CO{sub 2}. Allocation to the male and female flowers at very early stages are similar. As the flowers develop further, male flowers receive more photosynthate than do female flowers in early fruit production. Thus it is possible that nutrient drain to the flowers in male spinach plants is sufficient to account for senescence.

Sklensky, D.; Davies, P.J. (Cornell Univ., Ithaca, NY (USA))

1990-05-01

113

Characterization of starch breakdown in the intact spinach chloroplast  

Microsoft Academic Search

Starch degradation with a rate of 1 to 2 microgram-atom carbon per milligram chlorophyll per hour was monitored in the isolated intact spinach (Spinacia oleracea) chloroplast which had been preloaded with ¹⁴C-starch photosynthetically from ¹⁴CO. Starch breakdown was dependent upon inorganic phosphate and the ¹⁴C-labeled intermediates formed were principally those of the Embden-Meyerhof pathway from glucose phosphate to glycerate 3-phosphate.

D. G. Peavey; M. Steup; M. Gibbs

1977-01-01

114

Suppression of Fusarium wilt of spinach with compost amendments  

Microsoft Academic Search

The effect of different organic composts on the suppression of wilt disease of spinach caused by Fusarium oxysporum f. sp. spinaciae was evaluated in a continuous cropping system in both containers and in microplot field trials. Test soils infested with\\u000a the pathogen were amended with wheatbran, wheatbran and sawdust, coffee grounds, chicken manure, or mixture of different composts\\u000a with and

Gina M. Edurise Escuadra; Yoshimiki Amemiya

2008-01-01

115

Studies of GA sub 53 oxidase from spinach  

SciTech Connect

GA{sub 53} oxidase was purified 1,750-fold with 1% recovery of activity from spinach after exposure to 8 long days. This preparation was injected into balb/c mice and hybridomas from spleen cells were produced. Upon preliminary screening by immunoprecipitation of enzyme activity, three positive cell lines were selected. These are being cloned to select a true monoclonal antibody cell line. This antibody will be used to study the light/dark regulation of this enzyme.

Wilson, T.; Zeevaart, J.A.D. (Michigan State Univ., East Lansing (USA))

1990-05-01

116

Microbiological Quality of Bagged Cut Spinach and Lettuce Mixes?  

PubMed Central

Analysis of 100 bagged lettuce and spinach samples showed mean total bacterial counts of 7.0 log10 CFU/g and a broad range of <4 to 8.3 log10 CFU/g. Most probable numbers (MPN) of ?11,000 /g coliforms were found in 55 samples, and generic Escherichia coli bacteria were detected in 16 samples, but no E. coli count exceeded 10 MPN/g.

Valentin-Bon, Iris; Jacobson, Andrew; Monday, Steven R.; Feng, Peter C. H.

2008-01-01

117

Leaf Development  

PubMed Central

The shoot system is the basic unit of development of seed plants and is composed of a leaf, a stem, and a lateral bud that differentiates into a lateral shoot. The most specialized organ in angiosperms, the flower, can be considered to be part of the same shoot system since floral organs, such as the sepal, petal, stamen, and carpel, are all modified leaves. Scales, bracts, and certain kinds of needle are also derived from leaves. Thus, an understanding of leaf development is critical to an understanding of shoot development. Moreover, leaves play important roles in photosynthesis, respiration and photoperception. Thus, a full understanding of leaves is directly related to a full understanding of seed plants. The details of leaf development remain unclear. The difficulties encountered in studies of leaf development, in particular in dicotyledonous plants such as Arabidopsis thaliana (L.) Henyn., are derived from the complex process of leaf development, during which the division and elongation of cells occur at the same time and in the same region of the leaf primordium (Maksymowych, 1963; Poethig and Sussex, 1985). Thus, we cannot divide the entire process into unit processes in accordance with the tenets of classical anatomy. Genetic approaches in Arabidopsis, a model plant (Meyerowitz and Pruitt, 1985), have provided a powerful tool for studies of mechanisms of leaf development in dicotyledonous plants, and various aspects of the mechanisms that control leaf development have been revealed in recent developmental and molecular genetic studies of Arabidopsis (for reviews, see Tsukaya, 1995 and 1998; Van Lijsebettens and Clarke, 1998; Sinha, 1999; Van Volkenburgh, 1999; Tsukaya, 2000; Byrne et al., 2001; Dengler and Kang, 2001; Dengler and Tsukaya, 2001; Tsukaya, 2001). In this review, we shall examine the information that is currently available about various mechanisms of leaf development in Arabidopsis. Vascular patterning is also an important factor in the determination of leaf shape, and this topic is reviewed in this resource by Turner (see also Dengler and Kang, 2001). The interested reader is also referred to work on the basic characterization of the vascular patterning in foliage leaves of Arabidopsis has been carried out by Candela et al. (1999) and Semiarti et al. (2001). For terminology, see Fig. 1.

Tsukaya, Hirokazu

2002-01-01

118

Leaf development.  

PubMed

Leaves are the most important organs for plants. Without leaves, plants cannot capture light energy or synthesize organic compounds via photosynthesis. Without leaves, plants would be unable perceive diverse environmental conditions, particularly those relating to light quality/quantity. Without leaves, plants would not be able to flower because all floral organs are modified leaves. Arabidopsis thaliana is a good model system for analyzing mechanisms of eudicotyledonous, simple-leaf development. The first section of this review provides a brief history of studies on development in Arabidopsis leaves. This history largely coincides with a general history of advancement in understanding of the genetic mechanisms operating during simple-leaf development in angiosperms. In the second section, I outline events in Arabidopsis leaf development, with emphasis on genetic controls. Current knowledge of six important components in these developmental events is summarized in detail, followed by concluding remarks and perspectives. PMID:23864837

Tsukaya, Hirokazu

2013-06-07

119

Behavior of Escherichia coli O157:H7 on damaged leaves of spinach, lettuce, cilantro, and parsley stored at abusive temperatures.  

PubMed

Recent foodborne illness outbreaks associated with the consumption of leafy green produce indicates a need for additional information on the behavior of pathogenic bacteria on these products. Previous research indicates that pathogen growth and survival is enhanced by leaf damage. The objective of this study was to compare the behavior of Escherichia coli O157:H7 on damaged leaves of baby Romaine lettuce, spinach, cilantro, and parsley stored at three abusive temperatures (8, 12, and 15 degrees C). The damaged portions of leaves were inoculated with approximately 10(5) CFU E. coli O157:H7 per leaf. The pathogen grew on damaged spinach leaves held for 3 days at 8 and 12 degrees C (P < 0.05), with the population increasing by 1.18 and 2.08 log CFU per leaf, respectively. E. coli O157:H7 did not grow on damaged Romaine leaves at 8 or 12 degrees C, but growth was observed after 8 h of storage at 15 degrees C, with an increase of less than 1.0 log. Growth of E. coli O157:H7 on Romaine lettuce held at 8 or 12 degrees C was enhanced when inocula were suspended in 0.05% ascorbic acid, indicating the possibility of inhibition by oxidation reactions associated with tissue damage. Damaged cilantro and Italian parsley leaves held at 8 degrees C for 4 days did not support the growth of E. coli O157:H7. Behavior of the pathogen in leaf extracts differed from behavior on the damaged tissue. This study provides evidence that the damaged portion of a leafy green is a distinct growth niche that elicits different microbial responses in the various types of leafy greens. PMID:20132665

Khalil, Rowaida K; Frank, Joseph F

2010-02-01

120

Spinach downy mildew: overview of races and the development of molecular markers linked to major resistance genes.  

Technology Transfer Automated Retrieval System (TEKTRAN)

Spinach (Spinacia aleracea) has become an increasingly popular leafy vegetable crop, particularly in the United States. Recent trends have shown a substantial increase in per capita fresh market spinach consumption with a corresponding increase in production. As a result, spinach production practic...

121

Biofilm formation Escherichia coli O157:H7 and Salmonella on spinach harvester blades  

Technology Transfer Automated Retrieval System (TEKTRAN)

Outbreaks associated with leafy greens have focused attention on the transfer of human pathogens to leafy greens during mechanical harvesting. Harvesting of baby spinach presents an opportunity for contaminated blades to transfer bacterial foodborne pathogens to recently harvested spinach. Biofilm f...

122

A real-time PCR assay for detection and quantification of verticillium dahliae in spinach seed  

Technology Transfer Automated Retrieval System (TEKTRAN)

Verticillium dahliae is a soilborne fungus that causes Verticillium wilt on multiple crops in central coastal California. Although spinach crops grown in this region for fresh and processing commercial production do not display Verticillium wilt symptoms, spinach seed produced in the U.S. or Europe ...

123

The antioxidant activity of aqueous spinach extract: chemical identification of active fractions  

Microsoft Academic Search

In previous studies we have elucidated the presence of powerful, natural antioxidants (NAO) in water extracts of spinach leaves and demonstrated their biological activity in both in vitro and in vivo systems. In the present study, the chemical identity of several of these antioxidant components is presented. Spinach leaves were extracted with water and the 20,000 g supernatant which contained

Margalit Bergman; Lucy Varshavsky; Hugo E. Gottlieb; Shlomo Grossman

2001-01-01

124

A comparative flash-photolysis study of electron transfer from pea and spinach plastocyanins to spinach Photosystem 1. A reaction involving a rate-limiting conformational change  

Microsoft Academic Search

Two mutants of plastocyanin have been constructed by site-directed mutagenesis in spinach and pea to elucidate the binding and electron transfer properties between plastocyanin and spinach Photosystem 1. The conserved, surface-exposed Tyr-83 has been replaced by phenylalanine and leucine in plastocyanin from both species and the proteins have been expressed in Escherichia coli. The reaction mechanism of electron transfer from

Kalle Sigfridsson; Shiping He; Sandeep Modi; Derek S. Bendall; John Gray; rjan Hansson

1996-01-01

125

Survival of Pathogenic Escherichia Coli on Basil, Lettuce, and Spinach.  

PubMed

The contamination of lettuce, spinach and basil with pathogenic E.coli has caused numerous illnesses over the past decade. E.coli O157:H7, E.coli O104:H4 and avian pathogenic E.coli (APECstx- and APECstx+) were inoculated on basil plants and in promix substrate using drip and overhead irrigation. When overhead inoculated with 7 log CFU/ml of each strain, E.coli populations were significantly (P=0.03) higher on overhead-irrigated plants than on drip-irrigated plants. APECstx-, E.coli O104:H4 and APECstx+ populations were recovered on plants at 3.6, 2.3 and 3.1 log CFU/g at 10 dpi (days post-inoculation), respectively. E.coli O157:H7 was not detected on basil after 4 dpi. The persistence of E.coli O157:H7 and APECstx- were similar when co-inoculated on lettuce and spinach plants. On spinach and lettuce, E.coli O157:H7 and APEC populations declined from 5.7 to 6.1 log CFU/g and 4.5 log CFU/g, to undetectable at 3 dpi and 0.6-1.6 log CFU/g at 7 dpi, respectively. The detection of low populations of APEC and E. coli O104:H4 strains 10 dpi indicates these strains may be more adapted to environmental conditions than E.coli O157:H7. This is the first reported study of E. coli O104:H4 on a produce commodity. PMID:23280331

Markland, S M; Shortlidge, K L; Hoover, D G; Yaron, S; Patel, J; Singh, A; Sharma, M; Kniel, K E

2012-12-28

126

Pathway for the synthesis of triacylglycerols from monogalactosyldiacylglycerols in ozone-fumigated spinach leaves. [Spinacia oleracea L  

SciTech Connect

When the upper leaf surface of spinach (Spinacia oleracea L.) plants was treated with (1-{sup 14}C)acetate and grown for 2 days, {sup 14}C was effectively incorporated into acyl moieties of leaf lipids in ratios approximately their composition by mass. Fumigation of the plants with ozone (0.5 microliter per liter) caused a redistribution of {sup 14}C among lipid classes, i.e. a marked increase of {sup 14}C content in triacylglycerol (TG) and 1,2-diacylglycerol (1,2-DG) and a decrease of label in monogalactosyldiacylglycerol (MGDG) without affecting {sup 14}C distribution in leaf fatty acids. Label in both TG and 1,2-DG was found predominantly in their polyene molecular species. Since MGDG consists of similar polyene molecular species, the results indicate the synthesis of TG from MGDG via 1,2-DG. Label was also accumulated in tri- and tetragalactosyldiacylglycerol, products of galactolipid:galactolipid galactosyltransferase (GGGT). Moreover, there was a close relation between increases in the amounts of TG and the oligogalactolipids in ozone-treated leaves. These results indicate that MGDG was converted to 1,2-DG by GGGT and then to TG. In intact chloroplasts isolated from ozone-treated leaves, there was an enhanced production of free fatty acid (FFA), which was diminished by the addition of coenzyme A (CoA) and ATP, indicating that ozone stimulated the hydrolysis of MGDG to liberate FFA, which was in turn converted to acyl-CoA. The final step of TG synthesis, acylation of 1,2-DG with acyl-CoA, was confirmed by feeding with (1-{sup 14}C)linolenic acid in leaf discs excised from ozone-fumigated leaves; {sup 14}C was effectively incorporated into TG but not into 1,2-DG.

Sakaki, Takeshi; Kondo, Noriaki; Yamada, Mitsuhiro (National Institute for Environmental Studies, Ibaraki (Japan) Univ. of Tokyo (Japan))

1990-10-01

127

Correlating Arsenic-Induced Morphological Change in Spinach Leaves With Leaf Spectral Characteristics  

Technology Transfer Automated Retrieval System (TEKTRAN)

Arsenic (As) is a widely spread soil contaminant which can be accumulated into plant parts. The presence of As in edible portions of plants allows for potentially dangerous ingestion by humans and animals. The ability to detect As in plants is an important tool to minimize such risks. Remote sens...

128

Effect of photoperiod on gibberellin biosynthetic enzymes in spinach  

SciTech Connect

The photoperiodic control of stem elongation in spinach, a long day (LD) rosette plant, is mediated by gibberellins (GAs). The early 13-hydroxylated GA biosynthetic pathway from GA/sub 12/ to GA/sub 20/ operates in spinach: GA/sub 12/ ..-->.. GA/sub 53/ ..-->.. GA/sub 44/ ..-->.. GA/sub 19/ ..-->.. GA/sub 20/. Two enzymes of this pathway, those converting GA/sub 53/ to GA/sub 44/ (GA/sub 53/ oxidase) and GA/sub 19/ to GA/sub 20/ (GA/sub 19/ oxidase), are regulated by light. The enzyme converting GA/sub 44/ to GA/sub 19/ (GA/sub 44/ oxidase) is not light-regulated. In the light GA/sub 53/ and GA/sub 18/ oxidase activities are increased, therefore causing the GA biosynthetic pathway to be turned on. This leads to the production of an active GA in LD, which causes an increase in stem elongation. Two the enzymes, GA/sub 44/ and GA/sub 53/ oxidases, can be separated from one another by anion exchange HPLC. Estimates of the molecular weights of these two enzymes based on gel filtration HPLC will be reported.

Gilmour, S.J.; Bleecker, A.B.; Zeevaart, J.A.D.

1986-04-01

129

Choline oxidation by intact spinach chloroplasts. [Spinacia oleracea L  

SciTech Connect

Plants synthesize betaine by a two-step oxidation of choline (choline ..-->.. betaine aldehyde ..-->.. betaine). Protoplast-derived chloroplasts of spinach (Spinacia oleracea L.) carry out both reactions, more rapidly in light than in darkness. We investigated the light-stimulated oxidation of choline, using spinach chloroplasts isolated directly from leaves. The rates of choline oxidation obtained (dark and light rates: 10-50 and 100-300 nanomoles per hour per milligram chlorophyll, respectively) were approximately 20-fold higher than for protoplast-derived chloroplasts. Betaine aldehyde was the main product. Choline oxidation in darkness and light was suppressed by hypoxia. Neither uncouplers not the Calvin cycle inhibitor glyceraldehyde greatly affected choline oxidation in the light, and maximal choline oxidation was attained far below light saturation of CO/sub 2/ fixation. The light stimulation of choline oxidation was abolished by the PSII inhibitors DCMU and dibromothymoquinone, and was partially restored by adding reduced diaminodurene, an electron donor to PSI. Both methyl viologen and phenazine methosulfate prevented choline oxidation. Adding dihydroxyacetone phosphate, which can generate NADPH in organello, doubled the dark rate of choline oxidation. These results indicate that choline oxidation in chloroplasts requires oxygen, and reducing power generated from PSI. Enzymic reactions consistent with these requirements are discussed.

Weigel, P.; Lerma, C.; Hanson, A.D.

1988-01-01

130

Insect molting hormone and sterol biosynthesis in spinach  

SciTech Connect

Insect molting hormones, which are produced by plants and are effective molecules in the control of insect crop pests, are biosynthesized in developing spinach leaves (Spinacia oleracea L.). The major sterols biosynthesized by spinach are avenasterol (24{alpha}-ethyl-5{alpha}-cholesta-7,24(28)-dien-3{beta}-ol), spinasterol (24{alpha}-ethyl-5{alpha}-cholesta-7,22-dien-3{beta}-ol), and 22-dihydrospinasterol (24{alpha}-ethyl-5{alpha}-cholest-7-en-3{beta}-ol). The major ecdysteroids biosynthesized are ecdysterone (2{beta},3{beta},14{alpha},20R,22R,25-hexahydroxy-5{beta}-cholest-7-en-6-one) and polypodine B (2{beta},3{beta},5{beta},14{alpha},20R,22R,25-heptahycroxycholest-7-en-6-one) and polypodine B (2{beta},3{beta},5{beta},14{alpha},20R,22R,25-heptahydroxycholest-7-en-6-one). When labeled 2-{sup 14}C-mevalonic acid was incorporated into young leaves isolated squalene, sterols and ecdysteroids contained the label. During a short (16 h) incorporation period in intact young leaves of 100 day old plants, the avenasterol has the highest specific activity in counts per minute per {mu}g of sterol followed by 22-dihydrospinasterol which is more highly labeled than spinasterol. The ecdysteroids synthesized, on an entire plant basis, account for 20% of the total steroid (sterol and ecdysteroid) isolated from the plant.

Grebenok, R.J.; Adler, J.H. (Michigan Technological Univ., Houghton (USA))

1990-05-01

131

Effect of ?-irradiation on the thermomechanical and morphological properties of chitosan obtained from prawn shell: Evaluation of potential for irradiated chitosan as plant growth stimulator for Malabar spinach  

NASA Astrophysics Data System (ADS)

In the present study we have synthesized chitosan from waste prawn shell via ?-irradiation of chitin and subsequent alkaline treatment. The detailed experimental studies demonstrated that nonirradiated chitin deacetylated by 40% NaOH solution showed 72% degree of deacetylation (DD), however 50 kGy irradiated chitin, deacetylated by 20% NaOH demonstrated 81.5% DD. Chitosan in solid state as obtained from ?-irradiation of chitin was further irradiated by different doses (2-100 kGy) of gamma irradiation and the effects of irradiation on the molecular weight, thermo-mechanical by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA), and antimicrobial properties were evaluated with respect to nonirradiated chitosan sample. Gamma irradiation of chitosan with a dose of 100 kGy caused a decrease in average molecular weight from 1.9105 to 6.5104 Da and thus increased its solubility in water. Nonirradiated and ?-irradiated chitosan at concentration 1% (w/w) in water were prepared and used to evaluate of its potentiality for growth stimulation of Malabar spinach. The chitosan solution was sprayed on the specimen plants and neighboring soil where germinations were taken place and various plant growth parameters such as plant height, number of leaves, leaf areas, dry and wet weight of the plants and roots were investigated. The details study revealed that application of 30 kGy irradiated chitosan yielded 60% higher growth of the Malabar spinach than that obtained from nonirradiated chitosan. The data are consistent with preliminary results from field experiments and unambiguously confirms that a minor amount of chitosan has a profound effect on the growth and development of Malabar spinach.

Rahman, Mohammed Mizanur; Kabir, Shahriar; Rashid, Taslim Ur; Nesa, Bodrun; Nasrin, Romana; Haque, Papia; Khan, Mubarak A.

2013-01-01

132

Purification and characterization of ribulose-5-phosphate kinase from spinach  

SciTech Connect

An efficient purification procedure utilizing affinity chromatography is described for spinach ribulose-5-phosphate kinase, a light-regulated chloroplastic enzyme. Gel filtration and polyacrylamide gel electrophoresis of the purified enzyme reveal a dimeric structure of 44,000 Mr subunits. Chemical crosslinking with dimethyl suberimidate confirms the presence of two subunits per molecule of native kinase, which are shown to be identical by partial NH2-terminal sequencing. Based on sulfhydryl titrations and on amino acid analyses, each subunit contains four to five cysteinyl residues. The observed slow loss of activity during spontaneous oxidation in air-saturated buffer correlates with the intramolecular oxidation of two sulfhydryl groups, presumably those involved in thioredoxin-mediated regulation.

Porter, M.A.; Milanez, S.; Stringer, C.D.; Hartman, F.C.

1986-02-15

133

Enzymatic Evidence for a Complete Oxidative Pentose Phosphate Pathway in Chloroplasts and an Incomplete Pathway in the Cytosol of Spinach Leaves.  

PubMed Central

The intracellular localization of transaldolase, transketolase, ribose-5-phosphate isomerase, and ribulose-5-phosphate epimerase was reexamined in spinach (Spinacia oleracea L.) leaves. We found highly predominant if not exclusive localization of these enzyme activities in chloroplasts isolated by isopyknic centrifugation in sucrose gradients. Glucose-6-phosphate dehydrogenase, 6-phosphogluconate dehydrogenase, glucose phosphate isomerase, and triose phosphate isomerase activity was present in the chloroplast fraction but showed additional activity in the cytosol (supernatant) fraction attributable to the cytosol-specific isoforms known to exist for these enzymes. Anion-exchange chromatography of proteins of crude extracts on diethylaminoethyl-Fractogel revealed only a single enzyme each for transaldolase, transketolase, ribose-5-phosphate isomerase, and ribulose-5-phosphate epimerase. The data indicate that chloroplasts of spinach leaf cells possess the complete complement of enzymes of the oxidative pentose phosphate path-way (OPPP), whereas the cytosol contains only the first two reactions, contrary to the widely held view that plants generally possess a cytosolic OPPP capable of cyclic function. The chloroplast enzymes transketolase, ribose-5-phosphate isomerase, and ribulose-5-phosphate epimerase appear to be amphibolic for the Calvin cycle and OPPP.

Schnarrenberger, C.; Flechner, A.; Martin, W.

1995-01-01

134

Phytotoxicity of multi-walled carbon nanotubes on red spinach (Amaranthus tricolor L) and the role of ascorbic acid as an antioxidant.  

PubMed

Carbon nanotubes (CNTs) are a novel nanomaterial with wide potential applications; however the adverse effects of CNTs following environmental exposure have recently received significant attention. Herein, we explore the systemic toxicity and potential influence of 0-1000 mg L(-1) the multi-walled CNTs on red spinach. The multi-walled CNTs exposed plants exhibited growth inhibition and cell death after 15 days of hydroponic culture. The multi-walled CNTs had adverse effects on root and leaf morphology, as observed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Raman spectroscopy detected the multi-walled CNTs in leaves. Biomarkers of nanoparticle toxicity, reactive oxygen species (ROS), and cell damage in the red spinach were greatly increased 15 days post-exposure to the multi-walled CNTs. These effects were reversed when the multi-walled CNTs were supplemented with ascorbic acid (AsA), suggesting a role of ROS in the multi-walled CNT-induced toxicity and that the primary mechanism of the multi-walled CNTs' toxicity is oxidative stress. PMID:23146354

Begum, Parvin; Fugetsu, Bunshi

2012-10-22

135

Solar energy from spinach and toothpaste: fabrication of a solar cell in schools  

NASA Astrophysics Data System (ADS)

We will show how pupils can make a solar cell with spinach, toothpaste and a few other items found in any school laboratory. This device is called a Graetzel cell, and could trigger off a revolution in photovoltaic technology.

Siemsen, F.; Bunk, A.; Fischer, K.; Korneck, F.; Engel, H.; Roux, D.

1998-01-01

136

Antioxidant capacity and phenolic content of spinach as affected by genetics and maturation.  

PubMed

Spinach leaves harvested at three maturity stages from eight commercial cultivars (CC) and eight advanced breeding lines (ABL) were evaluated for oxygen radical absorbing capacity (ORAC), total phenolics, and flavonoid composition and content. ABL had higher levels of total phenolics, total flavonoids, and ORAC than CC. Midmaturity spinach leaves had higher levels of total phenolics, total flavonoids, and antioxidant capacity than immature and mature leaves. The contents of individual flavonoids varied in response to maturation, with the predominant glucuronated flavones decreasing and patuletin and spinacetin derivatives increasing. Both total phenolics and total flavonoids correlated well with ORAC (r(xy)() = 0.78 and 0.81, respectively) demonstrating that flavonoids were major contributors to antioxidant capacity. Our results indicate that spinach genotypes should be harvested at the midmaturity stage for consumers to benefit from elevated levels of health promoting flavonoids present in the leaves. Additionally, plant breeders can select for increased phenolic content to increase antioxidant capacity of spinach genotypes. PMID:16248562

Pandjaitan, N; Howard, L R; Morelock, T; Gil, M I

2005-11-01

137

The effect of cerium (III) on the chlorophyll formation in spinach  

Microsoft Academic Search

The effect of Ce3+ on the chlorophyll (chl) of spinach was studied in pot culture experiments. The results showed that Ce3+ could obviously stimulate the growth of spinach and increase its chlorophyll contents and photosynthetic rate. It could also\\u000a improve the PSII formation and enhance its electron transport rate of PSII as well. By inductively coupled plasma-mass spectroscopy\\u000a and atom

Fashui Hong; Ling Wang; Xiangxuan Meng; Zheng Wei; Guiwen Zhao

2002-01-01

138

Restrictions to Carbon Dioxide Conductance and Photosynthesis in Spinach Leaves Recovering from Salt Stress  

Microsoft Academic Search

Salt accumulation in spinach (Spinacia oleracea L.) leaves first inhibits photosynthesis by decreasing stomatal and mesophyll conductances to CO2 diffusion and then impairs ribulose- 1,5-bisphosphate carboxylase\\/oxygenase (S. Delfine, A. Alvino, M. Zacchini, F. Loreto (1998) Aust J Plant Physiol 25: 395-402). We measured gas exchange and fluorescence in spinach recovering from salt accumulation. When a 21-d salt accumulation was re-

Sebastiano Delfine; Arturo Alvino; Maria Concetta Villani; Francesco Loreto

1999-01-01

139

Nitrite Reduction in Reconstituted and Whole Spinach Chloroplasts during Carbon Dioxide Reduction 1  

PubMed Central

Nitrite reduction in either whole, isolated spinach chloroplasts (Spinacia oleracea L.) or in reconstituted spinach chloroplasts is stimulated by a short period of photosynthetic CO2 fixation in the light prior to nitrite addition. With reconstituted chloroplasts, a similar stimulation can be obtained in nitrite reduction without CO2 fixation by the addition of dihydroxyacetone phosphate or fructose 6-phosphate. Specific intermediate metabolites of the photosynthetic carbon reduction cycle may have a regulatory role in nitrite reduction in chloroplasts in the light.

Plaut, Zvi; Lendzian, Klaus; Bassham, James A.

1977-01-01

140

Tandem mass spectrometric identification of spinach Photosystem II light-harvesting components  

Microsoft Academic Search

Light-harvesting proteins harness light energy for photosynthesis. Sequences of the Photosystem II (PS II) light harvesting proteins, Lhcb1-6, have been deduced from many plants. However, limited information is available for spinach Lhcb sequences, although a spinach PS II preparation (BBY) is commonly used as a model for plant photosynthetic oxygen evolution (DA Berthold, GT Babcock and CF Yocum (1981) FEBS

Anthony J. A. Ouellette; Bridgette A. Barry

2002-01-01

141

Tandem mass spectrometric identification of spinach Photosystem II light-harvesting components  

Microsoft Academic Search

Light-harvesting proteins harness light energy for photosynthesis. Sequences of the Photosystem II (PS II) light harvesting\\u000a proteins, Lhcb16, have been deduced from many plants. However, limited information is available for spinach Lhcb sequences,\\u000a although a spinach PS II preparation (BBY) is commonly used as a model for plant photosynthetic oxygen evolution [DA Berthold,\\u000a GT Babcock and CF Yocum (1981) FEBS

Anthony J. A. Ouellette; Bridgette A. Barry

2002-01-01

142

Antioxidant capacity and phenolic content of spinach as affected by genetics and growing season.  

PubMed

Total phenolic content and antioxidant capacity of 11 commercial cultivars and 15 advanced breeding lines of spinach were determined over two growing seasons known to vary in biotic and abiotic stresses. Flavonoid composition and content of fall-grown commercial cultivars and advanced breeding lines were also determined. Over-winter spinach, which was planted in late fall and harvested in the spring, had much higher levels of total phenolics and antioxidant capacity than spinach planted in early fall and harvested in late fall, indicating that growing conditions, as well as biotic and abiotic stresses, influenced phenolic metabolism. Genotype also appeared to play an important role in affecting phenolic metabolism and antioxidant capacity in spinach. Advanced breeding lines of spinach, which show increased disease resistance, had higher levels of total phenolics, individual and total flavonoids, and antioxidant capacity than commercial cultivars. Our results indicate that plant breeders can select for increased phenolic content to increase antioxidant capacity in spinach cultivars, or the crops can be grown in different seasons or under certain stress conditions to elevate levels of antioxidants. PMID:12358455

Howard, L R; Pandjaitan, N; Morelock, T; Gil, M I

2002-10-01

143

Sequences within the Spinach curly top virus virion sense promoter are necessary for vascular-specific expression of virion sense genes.  

PubMed

Sequences necessary for activity of the Spinach curly top virus virion sense promoter have been identified within an 84 bp region upstream of two transcription start sites located at nt 252 and 292. RNAs initiating at these sites are expressed at equivalent levels in SCTV-infected Arabidopsis and from promoter-reporter constructs. The promoter is capable of directing expression of all three virion sense genes, although not to the same degree. While CP and V3 expression are similar, expression of V2 is elevated. The promoter is active in transient leaf infusion assays in the absence of C2. In Nicotiana benthamiana plants the promoter is active in vascular tissue and under no conditions did we detect promoter activity in the mesophyll. This is in contrast to begomoviruses where the virion sense promoter is dependent on AL2, a positional homolog of C2, and the promoter is functional in both vascular and mesophyll tissue. PMID:22727833

Rao, Kavitha; Sunter, Garry

2012-06-22

144

Molecular cloning and photoperiod-regulated expression of gibberellin 20-oxidase from the long-day plant spinach  

Microsoft Academic Search

~ Spinach (Spinacia oleracea L.) is a long-day (LD) rosette plant in which stem growth under LD conditions is mediated by gibberellins (CAs). Major control points in spinach are the later steps of sequen- tia1 oxidation and elimination of C-20 of C,,-GAs. Degenerate oligonucleotide primers were used to obtain a polymerase chain reaction product from spinach genomic DNA that has

Keqiang Wu; Li Li; Douglas A. Gage; Jan A. D. Zeevaart

1996-01-01

145

Perchlorate uptake in spinach as related to perchlorate, nitrate, and chloride concentrations in irrigation water.  

PubMed

Several studies have reported on the detection of perchlorate (ClO(4)(-)) in edible leafy vegetables irrigated with Colorado River water. However, there is no information on spinach as related to ClO(4)(-) in irrigation water nor on the effect of other anions on ClO(4)(-) uptake. A greenhouse ClO(4)(-) uptake experiment using spinach was conducted to investigate the impact of presence of chloride (Cl(-)) and nitrate (NO(3)(-)) on ClO(4)(-) uptake under controlled conditions. We examined three concentrations of ClO(4)(-), 40, 220, and 400 nmol(c)/L (nanomoles of charge per liter of solution), three concentrations of Cl(-), 2.5, 13.75, and 25 mmol(c)/L, and NO(3)(-) at 2, 11, and 20 mmol(c)/L. The results revealed that ClO(4)(-) was taken up the most when NO(3)(-) and Cl(-) were lowest in concentration in irrigation water. More ClO(4)(-) was detected in spinach leaves than that in the root tissue. Relative to lettuces, spinach accumulated more ClO(4)(-) in the plant tissue. Perchlorate was accumulated in spinach leaves more than reported for outer leaves of lettuce at 40 nmol(c)/L of ClO(4)(-) in irrigation water. The results also provided evidence that spinach selectively took up ClO(4)(-) relative to Cl(-). We developed a predictive model to describe the ClO(4)(-) concentration in spinach as related to the Cl(-), NO(3)(-), and ClO(4)(-) concentration in irrigation water. PMID:21939238

Ha, Wonsook; Suarez, Donald L; Lesch, Scott M

2011-10-11

146

Inactivation of Escherichia coli O157:H7 attached to spinach harvester blade using bacteriophage.  

PubMed

Outbreaks associated with leafy greens have focused attention on the transfer of human pathogens to these commodities during harvest with commercial equipment. Attachment of Escherichia coli O157:H7 on new or rusty spinach harvester blades immersed in spinach extract or 10% tryptic soy broth (TSB) was investigated. Bacteriophages specific for E. coli O157:H7 were evaluated to kill cells attached to blade. A cocktail of five nalidixic acid-resistant E. coli O157:H7 isolates was transferred to 25 mL of spinach extract or 10% TSB. A piece of sterilized spinach harvester blade (21") was placed in above spinach extract or 10% TSB and incubated at room (22 C) or dynamic (30 C day, 20 C night) temperatures. E. coli O157:H7 populations attached to blade during incubation in spinach extract or 10% TSB were determined. When inoculated at 1 log CFU/mL, E. coli O157:H7 attachment to blades after 24 and 48 h incubation at dynamic temperature (6.09 and 6.37 log CFU/mL) was significantly higher than when incubated at 22 C (4.84 and 5.68 log CFU/mL), respectively. After 48 h incubation, two blades were sprayed on each side with a cocktail of E. coli O157-specific bacteriophages before scraping the blade, and subsequent plating on Sorbitol MacConkey media-nalidixic acid. Application of bacteriophages reduced E. coli O157:H7 populations by 4.5 log CFU on blades after 2 h of phage treatment. Our study demonstrates that E. coli O157:H7 can attach to and proliferate on spinach harvester blades under static and dynamic temperature conditions, and bacteriophages are able to reduce E. coli O157:H7 populations adhered to blades. PMID:21453119

Patel, Jitendra; Sharma, Manan; Millner, Patricia; Calaway, Todd; Singh, Manpreet

2011-04-01

147

Effect of home processing on total and extractable calcium and zinc content of spinach ( Spinach oleracia ) and amaranth ( Amaranthus tricolor ) leaves  

Microsoft Academic Search

Spinach (Spinacia oleracia) and amaranth (Amaranthus tricolor) leaves were stored in polyethylene bags and without packing for 24 and 48 hours in a refrigerator at 5 and 30 C in polyethylene bags. The fresh leaves were also dried (oven and sun); blanched (5, 10 and 15 min) and cooked in an open pan and a pressure cooker. The processed leaves

Shashi Kala Yadav; Salil Sehgal

1995-01-01

148

Influence of variations in soil copper on the yield and nutrition of spinach grown in microplots on two organic soils  

SciTech Connect

Spinach (Spinacia oleracea L. cv. Symphony) was grown in spring 1982 in field microplots of an organic soil (site I-mucky peat) containing 81 to 1063 ..mu..g Cu.g/sup -1/ soil, and cv. America of the same crop taken in summer 1982 on a peaty organic soil (site II) varying in Cu content from 13 to 1659 ..mu..g.g/sup -1/. The variations in soil Cu were mainly due to three rates of Cu applications in 1978 at site II and in 1979 at site I. At site I, the diversity in soil-Cu had no effect on yield or foliar-Cu levels in the crop. At site II soil-Cu was positively correlated with yield and foliar Cu; and negatively with leaf Fe due to a dilution effect. Neither soil Cu nor foliar Cu had any significant effect on Mo in leaves at both sites, except that the increase in yield due to the highest level of Cu at site II was accompanied by an increased plant uptake of Mo. Also, foliar Cu was positively correlated with P, Mg and Mn levels in leaves at site I; and foliar Ca, Mg and Mn at site II. Residual soil Cu up to 1063 ..mu..g.g/sup -1/ in a mucky peat and 1659 ..mu..g./sup -1/ in a peat showed no signs of causing phytotoxocity or significant nutritional imbalance. 19 references, 4 tables.

Mathur, S.P.; Belanger, A.; Sanderson, R.B.; Valk, M.; Knibbe, E.N.

1984-01-01

149

Purification of gibberellin sub 53 -oxidase from spinach  

SciTech Connect

Spinach is a long-day rosette plants, in which stem growth is mediated by gibberellins. It has been shown that two enzymatic steps, GA{sub 53}-oxidase and GA{sub 19}-oxidase, are controlled by light. To develop an understanding into this light regulation, purification of GA{sub 53}-oxidase has been undertaken. The original assay relied on the HPLC separation of the product and substrate, but was considered too slow for the development of a purification scheme. A TLC system was developed which in conjunction with improvements to the assay conditions was sensitive and gave rapid results. The partial purification of the GA{sub 53}-oxidase is achieved by a high speed centrifugation, 40-55% ammonium sulfate precipitation, an hydroxyapatite column, Sephadex G-100 column and an anion exchange FPLC column, Mono Q HR10/10, yielding 1000-fold purification and 15% recovery. Monoclonal antibodies to the protein will be raised and used to further characterize the enzyme.

Wilson, T.M.; Zeevaart, J.A.D. (Michigan State Univ., East Lansing (USA))

1989-04-01

150

Spinach pyruvate kinase isoforms: partial purification and regulatory properties  

SciTech Connect

Pyruvate kinase from spinach (Spinacea oleracea L.) leaves consists of two isoforms, separable by blue agarose chromatography. Both isoforms share similar pH profiles and substrate and alternate nucleotide K/sub m/ values. In addition, both isoforms are inhibited by oxalate and ATP and activated by AMP. The isoforms differ in their response to three key metabolites; citrate, aspartate, and glutamate. The first isoform is similar to previously reported plant pyruvate kinases in its sensitivity to citrate inhibition. The K/sub i/ for this inhibition is 1.2 millimolar citrate. The second isoform is not affected by citrate but is regulated by aspartate and glutamate. Aspartate is an activator with a K/sub a/ of 0.05 millimolar, and glutamate is an inhibitor with a K/sub i/ of 0.68 millimolar. A pyruvate kinase with these properties has not been previously reported. Based on these considerations, the authors suggest that the activity of the first isoform is regulated by respiratory metabolism. The second isoform, in contrast, may be regulated by the demand for carbon skeletons for use in ammonia assimilation.

Baysdorfer, C.; Bassham, J.A.

1984-02-01

151

Phosphoglycolate phosphatase of spinach acts as a phosphoenzyme  

SciTech Connect

When /sup 32/P-glycolate and phosphoglycolate phosphatase from spinach are mixed, /sup 32/P is incorporated into acid precipitated protein. Properties that relate this phosphorylation to the enzyme are: The K/sub m/ value for P-glycolate is similar for protein phosphorylation and substrate hydrolysis; the /sup 32/P appearing in the phosphoenzyme is diluted by unlabeled P-glycolate or the alternative substrate, ethyl-P; the activator Cl/sup -/ enhances the effectiveness of ethyl-P as a substrate and as an inhibitor of the formation of /sup 32/P-enzyme; and /sup 32/P is lost from the enzyme when /sup 32/P-glycolate is consumed. The acid denatured phosphorylated protein is a molecule of 34,000 Da, which is half of the molecular weight of the native protein and is similar in size to the labeled band that is seen on SDS-polyacrylamide gels. The enzyme-bound phosphoryl group appears to be an acyl-phosphate from its pH stability, being quite stable at pH 1, less stable at pH 5, and very unstable above pH 5. The bond is readily hydrolyzed in acid molybdate and it is sensitive to cleavage by hydroxylamine at pH 6.8. The demonstration of enzyme phosphorylation by /sup 32/P-glycolate resolves the dilemma presented by initial rate studies in which alternative substrates appeared to have different mechanisms.

Rose, Z.B.; Seal, S.N.

1987-05-01

152

RNA-Binding Characteristics of a Ribonucleoprotein from Spinach Chloroplast.  

PubMed Central

A chloroplast (nuclear-encoded) RNA-binding protein (28RNP) was previously purified from spinach (Spinacia oleracea). This 28RNP was found to be the major RNA-binding protein co-purified during the isolation scheme of 3[prime] end RNA-processing activity of several chloroplastic genes. To learn more about the possible involvement of 28RNP in the 3[prime] end RNA-processing event, we investigated the RNA-binding properties and the location of the protein in the chloroplast. We found that recombinant Escherichia coliexpressed 28RNP binds with apparently the same affinity to every chloroplastic 3[prime] end RNA that was analyzed, as well as to RNAs derived from the 5[prime] end or the coding region of some chloroplastic genes. Differences in the RNA-binding affinities for some chloroplastic 3[prime] end RNAs were observed when the recombinant 28RNP was compared with the "native" 28RNP in the chloroplast-soluble protein extract. In addition, we found that the 28RNP is not associated with either thylakoid-bound or soluble polysomes in which a great portion of the chloroplast rRNA and mRNA are localized. These results suggest that the native 28RNP binds specifically to certain RNA molecules in the chloroplast in which other components (possibly proteins) and/or posttranslational modifications are involved in determining RNA-binding specificity of the 28RNP.

Lisitsky, I.; Liveanu, V.; Schuster, G.

1995-01-01

153

Uptake of l-Ascorbate by Intact Spinach Chloroplasts  

PubMed Central

Uptake of l-[1-14C]ascorbate by intact ascorbate-free spinach (Spinacia oleracea L. cv Vitalr) chloroplasts has been investigated using the technique of silicone oil filtering. Rates greater than 100 micromoles per milligram chlorophyll per hour (external concentration, 10 millimolar) of ascorbate transport were observed. Ascorbate uptake into the sorbitol-impermeable space (stroma) followed the Michaelis-Menten-type characteristic for substrate saturation. A Km of 18 to 40 millimolar was determined. Transport of ascorbate across the chloroplast envelope resulted in an equilibrium of the ascorbate concentrations between stroma and medium. A pH optimum of 7.0 to 7.5 and the lack of alkalization of the medium upon ascorbate uptake suggest that only the monovalent ascorbate anion is able to cross the chloroplast envelope. The activation energy of ascorbate uptake was determined to be 65.8 kilojoules (16 kilocalories) per mole (8 to 20C). Interference of ascorbate transport with substrates of the phosphate or dicarboxylate translocator could not be detected, but didehydroascorbate was a competitive inhibitor. Preloading of chloroplasts with didehydroascorbate resulted in an increase of Vmax but did not change the Km for ascorbate. Millimolar concentrations of the sulfhydryl reagent p-chloromercuriphenyl sulfonate inhibited ascorbate uptake. The data are interpreted in terms of ascorbate uptake into chloroplasts by the mechanism of facilitated diffusion mediated by a specific translocator.

Beck, Erwin; Burkert, Anette; Hofmann, Margit

1983-01-01

154

Purification and Properties of Glutamine Synthetase from Spinach Leaves  

PubMed Central

The chloroplastic glutamine synthetase of spinach leaves has been purified to homogeneity using affinity chromatography. This involves a tandem `reactive blue A-agarose' and `reactive red-A-agarose' as the final step in the procedure. This procedure results in a yield of 18 milligrams of pure glutamine synthetase per kilogram of starting material. The purity of our enzyme has been demonstrated on both one- and two-dimensional polyacrylamide gels. Purified glutamine synthetase has a molecular weight of 360,000 daltons and consists of eight 44,000 dalton subunits. The Km is 6.7 millimolar for glutamate, 1.8 millimolar for ATP (synthetase assay), and 37.6 millimolar for glutamine (transferase assay). The isoelectric point is 6.5 and the pH optima are 7.3 in the synthetase assay and 6.4 in the transferase assay. The irreversible, competitive inhibitors methionine sulfoxamine and phosphinothricin have Ki values of 0.1 millimolar and 6.1 micromolar, respectively. Amino acid analysis has been carried out and the results compared with published analyses for other isoforms of glutamine synthetase. Images Fig. 1

Ericson, Mary C.

1985-01-01

155

Purification and properties of glutamine synthetase from spinach leaves.  

PubMed

The chloroplastic glutamine synthetase of spinach leaves has been purified to homogeneity using affinity chromatography. This involves a tandem ;reactive blue A-agarose' and ;reactive red-A-agarose' as the final step in the procedure. This procedure results in a yield of 18 milligrams of pure glutamine synthetase per kilogram of starting material. The purity of our enzyme has been demonstrated on both one- and two-dimensional polyacrylamide gels.Purified glutamine synthetase has a molecular weight of 360,000 daltons and consists of eight 44,000 dalton subunits. The K(m) is 6.7 millimolar for glutamate, 1.8 millimolar for ATP (synthetase assay), and 37.6 millimolar for glutamine (transferase assay). The isoelectric point is 6.5 and the pH optima are 7.3 in the synthetase assay and 6.4 in the transferase assay. The irreversible, competitive inhibitors methionine sulfoxamine and phosphinothricin have K(i) values of 0.1 millimolar and 6.1 micromolar, respectively. Amino acid analysis has been carried out and the results compared with published analyses for other isoforms of glutamine synthetase. PMID:16664546

Ericson, M C

1985-12-01

156

Effects of conventional and organic fertilization on spinach ( Spinacea oleracea L.) growth, yield, vitamin C and nitrate concentration during two successive seasons  

Microsoft Academic Search

Current experiment was laid out in order to compare different kinds of organic manure and chemical fertilizer application in growing spinach under the open-field conditions in two successive seasons. Matador type spinach (Spinacea oleracea L.) was cultivated organically and conventionally and spinach growth, yield, vitamin C and nitrate concentrations were checked throughout two successive seasons (autumn and winter). Commercial chemical

Sedat Citak; Sahriye Sonmez

2010-01-01

157

Spinach or carrots can supply significant amounts of vitamin A as assessed by feeding with intrinsically deuterated vegetables1-4  

Microsoft Academic Search

Background: The vitamin A value of spinach and carrots needs to be measured directly. Objective: The objective was to determine the vitamin A value of intrinsically labeled dietary spinach and carrots in humans. Design: Spinach and carrots were intrinsically labeled by growing these plants in 25 atom% 2H2O nutrient solution. Growth in this medium yielded a range of trans -carotene

Guangwen Tang; Jian Qin; Gregory G Dolnikowski; Robert M Russell; Michael A Grusak

158

Effect of increasing offer level of water spinach (Ipomoea aquatica) on intake, growth and digestibility coefficients of rabbits  

Microsoft Academic Search

Twelve New Zealand White rabbits with an initial live weight of 897 95.2 g were allocated to a randomized block design to study the effect of different levels of water spinach (Ipomoea aquatica) (8, 10, 12, 14, 16 and 18% of live weight in DM). The water spinach was taken from the first and second harvests of plants established

Pok Samkol; T R Preston; J Ly

159

Ultrasound enhanced sanitizer efficacy in reduction of Escherichia coli O157:H7 population on spinach leaves  

Technology Transfer Automated Retrieval System (TEKTRAN)

The use of ultrasound to enhance the efficacy of selected sanitizers in reduction of Escherichia coli O157:H7 populations on spinach was investigated. Spot-inoculated spinach samples were treated with water, chlorine, acidified sodium chlorite (ASC), peroxyacetic acid (POAA), and acidic electrolyzed...

160

An Improved Method for the Extraction and Thin-Layer Chromatography of Chlorophyll A and B from Spinach  

ERIC Educational Resources Information Center

|A simple and fast method, which resolves chlorophyll a and b from spinach leaves on analytical plates while minimizing the appearance of chlorophyll degradation products is shown. An improved mobile phase for the Thin-layer chromatographic analysis of spinach extract that allows for the complete resolution of the common plant pigments found in

Quach, Hao T.; Steeper, Robert L.; Griffin, William G.

2004-01-01

161

An Improved Method for the Extraction and Thin-Layer Chromatography of Chlorophyll A and B from Spinach  

ERIC Educational Resources Information Center

A simple and fast method, which resolves chlorophyll a and b from spinach leaves on analytical plates while minimizing the appearance of chlorophyll degradation products is shown. An improved mobile phase for the Thin-layer chromatographic analysis of spinach extract that allows for the complete resolution of the common plant pigments found in

Quach, Hao T.; Steeper, Robert L.; Griffin, William G.

2004-01-01

162

Chloroplast and cytosolic triosephosphate isomerases from spinach: purification, microsequencing and cDNA cloning of the chloroplast enzyme  

Microsoft Academic Search

Chloroplast and cytosolic triosephosphate isomerases from spinach were separated and purified to homogeneity. Both enzymes were partially sequenced by Edman degradation. Using degenerate primers designed against the amino acid sequences, a homologous probe for the chloroplast enzyme was amplified and used to isolate several full-size cDNA clones. Chloroplast triosephosphate isomerase is encoded by a single gene in spinach. Analysis of

Katrin Henze; Claus Schnarrenberger; Josef Kellermann; William Martin

1994-01-01

163

Development and evaluation of an enriched natural antioxidant preparation obtained from aqueous spinach ( Spinacia oleracea) extracts by an adsorption procedure  

Microsoft Academic Search

Spinach (Spinacia oleracea) leaves contain antioxidant flavonoids, in particular spinacetin and patuletin. An adsorption procedure for the recovery of these flavonoids from a crude spinach extract was developed and evaluated. Four different resin and charcoal adsorbents, chosen for their high affinity for polyphenolic compounds, were tested in an open batch system. All proved to be very efficient in adsorbing polyphenols.

Elke Aehle; Sophie Raynaud-Le Grandic; Robert Ralainirina; Sylvie Baltora-Rosset; Franois Mesnard; Christophe Prouillet; Jean-Claude Mazire; Marc-Andr Fliniaux

2004-01-01

164

Expression of the rpl23, rpl2 and rps19 genes in spinach chloroplasts.  

PubMed Central

The expression of the spinach rpl23, rpl2 and rps19 chloroplast genes has been studied. The rpl23 gene identified in tobacco and Marchantia, is split into two overlapping reading frames in spinach. S1 mapping has shown that initiation sites could occur upstream of each reading frames. A large transcription unit is also present covering the rpl2 and rps19 genes. The rps19 and rpl2 gene products are identified by NH2-terminal amino acid sequences. They correspond to spinach chloroplast ribosomal proteins CS-S23 and CS-L4, respectively. No product of the rpl23 gene was detected in the chloroplast 50S ribosomal subunit. This strongly suggest that a corresponding gene has been transfered into the nucleus. Images

Thomas, F; Massenet, O; Dorne, A M; Briat, J F; Mache, R

1988-01-01

165

Postharvest handling conditions affect internalization of Salmonella in baby spinach during washing.  

PubMed

Internalization of foodborne pathogens in fruits and vegetables is an increasing safety concern. The aim of this research was to assess the potential for internalization of an enteric pathogen (Salmonella enterica serotype Typhimurium) in a leafy vegetable (baby spinach) during washing as influenced by three postharvest handling conditions: (i) illumination, (ii) negative temperature differential, and (iii) relative humidity (RH). To compare these potential postharvest handling conditions, leaves were exposed to different levels of illumination (0, 1,000, and 2,000 lx), temperature differential (5, 11, 14, 20, and 26C), and RH (99, 85, and 74%) for a short time before or during washing. Washing of baby spinach was carried out in water containing green fluorescent protein-tagged Salmonella Typhimurium (6.5 log CFU/ml) at 5C for 2 min, followed by surface disinfection with chlorine (10,000 ?g/ml) for 1 min, two rinses in water for 10 s, and spin drying for 15 s. Internalization was assessed by enumerating the pathogen on Salmonella-Shigella agar and by confocal laser scanning microscopy. Illumination of spinach leaves before and during washing and a negative temperature differential during washing did not significantly (P > 0.05) increase the number of internalized bacteria. However, exposure of leaves to low-RH conditions before washing, which reduced the tissue water content, decreased internalization of Salmonella compared with internalization in baby spinach exposed to high RH (P ? 0.05). Green fluorescent protein-tagged Salmonella Typhimurium was visualized by confocal laser scanning microscopy at a depth of up to 30 m m beneath the surface of spinach leaves after exposure to a high inoculum level (8 log CFU/ml) for an extended time (2 h). Results show that internalization of Salmonella into baby spinach leaves can occur but can be minimized under specific postharvest handling conditions such as low RH. PMID:23834788

Gmez-Lpez, Vicente M; Marn, Alicia; Allende, Ana; Beuchat, Larry R; Gil, Mara I

2013-07-01

166

Nutritional Composition of Water Spinach (Ipomoea aquatica Forsk.) Leaves  

NASA Astrophysics Data System (ADS)

Analyses of the nutritional composition of water spinach (Ipomoea aquatica) Forsk leaves were carried out using standard methods of food analysis. The proximate composition as well as mineral elements were determined. The leaves were found on dry weight basis to have high moisture (72.830.29%), ash (10.830.80%), crude lipid (11.000.50%), crude fibre (17.670.35%) and available carbohydrate (54.200.68%), but low in crude protein content (6.300.27%). The leaves also have energy value (300.945.31 kcal/100 g) that is within the range reported in some Nigerian leafy vegetables. The mineral element contents were high with remarkable concentration of K (5,458.33954.70 mg/100 g) and Fe (210.302.47 mg/100 g). Also the leaves content moderate concentrations of Na (135.002.50 mg/100 g), calcium (416.705.77 mg/100 g), Magnesium (301.6412.69 mg/100 g) and P (109.290.55 mg/100 g), with low Cu (0.360.01 mg/100 g), Mn (2.140.22 mg/100 g) and Zn (2.470.27 mg/100 g) contents. Comparing the mineral content with recommended dietary allowance, it was showed that the plant leaves is good sources of K, Mn and Fe for all categories of people, while Mg is adequate enough for adult female and children. From the result, Ipomoea aquatica Forsk leaves could be used for nutritional purposes, due to the amount and diversity of nutrients it contains.

Umar, K. J.; Hassan, L. G.; Dangoggo, S. M.; Ladan, M. J.

167

Regulation of spinach chloroplast acetyl-CoA carboxylase.  

PubMed

We have investigated several factors which influence acetyl-CoA carboxylase (ACCase) activity in lysed spinach chloroplasts. (1) When assayed after rapid lysis of light-incubated chloroplasts, ACCase activity was 2-fold higher than activity from dark-incubated chloroplasts. Within 5 min after lysis, activity from dark-incubated chloroplasts increased, suggesting a transient inactivation or inhibition of ACCase in the dark. (2) When lysed chloroplast suspensions were incubated with 30 to 100 microM acetyl-CoA before starting assays, activity was 4-fold higher than if suspensions were not preincubated with acetyl-CoA. CoA, malonyl-CoA, propionyl-CoA, and butyryl-CoA also activated ACCase. Full acetyl-CoA activation required MgATP and was essentially complete after 8 min. ACCase activity decreased upon removal of acetyl-CoA by gel filtration and was partially restored by readdition of acetyl-CoA. Thus, ACCase activation by acetyl-CoA was reversible. (3) Dithiothreitol and thioredoxin stimulated ACCase activity, but only in preparations where ACCase activity was low. (4) ACCase was assayed in concentrations of ATP, ADP, NADPH, NADP+, Mg2+, and CO2/HCO-3, which are estimated to occur in the stroma of chloroplasts under illumination or darkness. ACCase activity from lysed chloroplast suspensions was 10-fold higher when illuminated conditions were used. However, this activity was still 5-fold to 10-fold lower than the rates required to sustain known in vivo rates of fatty acid synthesis and in vitro rates achieved under optimum assay conditions with saturating substrates. PMID:9808758

Hunter, S C; Ohlrogge, J B

1998-11-15

168

Hydrogen Peroxide Synthesis in Isolated Spinach Chloroplast Lamellae 1  

PubMed Central

Light-dependent O2 reduction concomitant with O2 evolution, ATP formation, and NADP reduction were determined in isolated spinach (Spinacia oleracea L. var. America) chloroplast lamellae fortified with NADP and ferredoxin. These reactions were investigated in the presence or absence of catalase, providing a tool to estimate the reduction of O2 to H2O2 (Mehler reaction) concomitant with NADP reduction. In the presence of 250 micromolar O2, O2 photoreduction, simultaneous with NADP photoreduction, was dependent upon light intensity, ferredoxin, Mn2+, NADP, and the extent of coupling of phosphorylation to electron flow. In the presence of an uncoupling concentration of NH4+, saturating light intensity (>500 watts/square meter), saturating ferredoxin (10 micromolarity) rate-limiting to saturating NADP (0.2-0.9 millimolarity), and Mn2+ (50-1000 micromolarity), the maxium rates of O2 reduction were 13-25 micromoles/milligram chlorophyll per hour, while concomitant rates of O2 evolution and NADP reduction were 69 to 96 and 134 to 192 micromoles/milligram chlorophyll per hour, respectively. Catalase did not affect the rate of NADPH or ATP formation but decreased the NADPH:O2 ratios from 2.3-2.8 to 1.9-2.1 in the presence of rate-limiting as well as saturating concentrations of NADP. Photosynthetic electron flow at a rate of 31 micromoles O2 evolved/milligram chlorophyll per hour was coupled to the synthesis of 91 micromoles ATP/milligram chlorophyll per hour, while the concomitant rate of O2 reduction was 0.6 micromoles/milligram chlorophyll per hour and was calculated to be associated with an apparent ATP formation of only 2 micromoles/milligram chlorophyll per hour. Thus, electron flow from H2O to O2 did not result in ATP formation significantly above that produced during NADP reduction.

Robinson, J. Michael; Gibbs, Martin

1982-01-01

169

Effect of nano-TiO 2 on photochemical reaction of chloroplasts of spinach  

Microsoft Academic Search

The effects of nano-TiO2 (rutile) on the photochemical reaction of chloroplasts of spinach were studied. The results showed that when spinach was\\u000a treated with 0.25% nano-TiO2, the Hill reaction, such as the reduction rate of FeCy, and the rate of evolution oxygen of chloroplasts was accelerated\\u000a and noncyclic photophosphorylation (nc-PSP) activity of chloroplasts was higher than cyclic photophosphorylation (c-PSP) activity,

Fashui Hong; Juan Zhou; Chao Liu; Fan Yang; Cheng Wu; Lei Zheng; Ping Yang

2005-01-01

170

Isolation of a cDNA clone for spinach lipid transfer protein and evidence that the protein is synthesized by the secretory pathway  

SciTech Connect

A cDNA clone encoding a nonspecific lipid transfer protein from spinach (Spinacia oleracea) was isolated by probing a library with synthetic oligonucleotides based on the amino acid sequence of the protein. Determination of the DNA sequence indicated a 354-nucleotide open reading frame which encodes a 118-amino acid residue polypeptide. The first 26 amino acids of the open reading frame, which are not present in the mature protein, have all the characteristics of a signal sequence which is normally associated with the synthesis of membrane proteins or secreted proteins. In vitro transcription of the cDNA and translation in the presence of canine pancreatic microsomes or microsomes from cultured maize endosperm cells indicated that proteolytic processing of the preprotein to the mature form was associated with cotranslational insertion into the microsomal membranes. Because there is no known mechanism by which the polypeptide could be transferred from the microsomal membranes to the cytoplasm, the proposed role of this protein in catalyzing lipid transfer between intracellular membranes is in doubt. Although the lipid transfer protein is one of the most abundant proteins in leaf cells, the results of genomic Southern analysis were consistent with the presence of only one gene. Analysis of the level of mRNA by Northern blotting indicated that the transcript was several-fold more abundant than an actin transcript in leaf and petiole tissue, but was present in roots at less than 1% of the level in petioles.

Bernhard, W.R.; Thoma, S.; Botella, J.; Somerville, C.R. (Michigan State Univ., East Lansing (United States))

1991-01-01

171

Mapping leaf surface landscapes.  

PubMed Central

Leaf surfaces provide the ecologically relevant landscapes to those organisms that encounter or colonize the leaf surface. Leaf surface topography directly affects microhabitat availability for colonizing microbes, microhabitat quality and acceptability for insects, and the efficacy of agricultural spray applications. Prior detailed mechanistic studies that examined particular fungi-plant and pollinator-plant interactions have demonstrated the importance of plant surface topography or roughness in determining the outcome of the interactions. Until now, however, it has not been possible to measure accurately the topography--i.e., the three-dimensional structure--of such leaf surfaces or to record precise changes in patterns of leaf surface elevation over time. Using contact mode atomic force microscopy, we measured three-dimensional coordinates of upper leaf surfaces of Vaccinium macrocarpon (cranberry), a perennial plant, on leaves of two age classes. We then produced topographic maps of these leaf surfaces, which revealed striking differences between age classes of leaves: old leaves have much rougher surfaces than those of young leaves. Atomic force microscope measurements were analyzed by lag (1) autocorrelation estimates of leaf surfaces by age class. We suggest that the changes in topography result from removal of epicuticular lipids and that the changes in leaf surface topography influence phylloplane ecology. Visualizing and mapping leaf surfaces permit detailed investigations into leaf surface-mediated phenomena, improving our understanding of phylloplane interactions. Images Fig. 1

Mechaber, W L; Marshall, D B; Mechaber, R A; Jobe, R T; Chew, F S

1996-01-01

172

Persistence of enterohemorrhagic and non-pathogenic E. coli on spinach leaves and in rhizosphere  

Technology Transfer Automated Retrieval System (TEKTRAN)

Introduction: Outbreaks associated with leafy greens have focused attention on the persistence of Escherichia coli O157:H7 on produce. Ecological interactions of E. coli O157:H7 and spinach require detailed characterization. Purpose: Survival of E. coli O157:H7 and non-pathogenic E. coli was evalua...

173

Expression of Spinach Ascorbate Peroxidase Isoenzymes in Response to Oxidative Stresses1  

Microsoft Academic Search

We studied the response of each ascorbate peroxidase (APX) isoenzyme in spinach leaves under stress conditions imposed by high light intensity, drought, salinity, and applications of methyl viologen and abscisic acid. The steady-state transcript level of cytosolic APX remarkably increased in response to high-light stress and methyl viologen treatment, but not in response to the other stress treatments. The transcript

Kazuya Yoshimura; Yukinori Yabuta; Takahiro Ishikawa; Shigeru Shigeoka

2000-01-01

174

Microdissection and painting of the Y chromosome in spinach (Spinacia oleracea).  

PubMed

Spinach has long been used as a model for genetic and physiological studies of sex determination and expression. Although trisomic analysis from a cross between diploid and triploid plants identified the XY chromosome as the largest chromosome, no direct evidence has been provided to support this at the molecular level. In this study, the largest chromosomes of spinach from mitotic metaphase spreads were microdissected using glass needles. Degenerate oligonucleotide primed polymerase chain reaction was used to amplify the dissected chromosomes. The amplified products from the Y chromosome were identified using the male-specific marker T11A. For the first time, the largest spinach chromosome was confirmed to be a sex chromosome at the molecular level. PCR products from the isolated chromosomes were used in an in situ probe mixture for painting the Y chromosome. The fluorescence signals were mainly distributed on all chromosomes and four pair of weaker punctate fluorescence signal sites were observed on the terminal region of two pair of autosomes. These findings provide a foundation for the study of sex chromosome evolution in spinach. PMID:23381038

Deng, Chuan-Liang; Qin, Rui-Yun; Cao, Ying; Gao, Jun; Li, Shu-Fen; Gao, Wu-Jun; Lu, Long-Dou

2013-02-05

175

Secondary fluorescence kinetics of spinach leaves in relation to the onset of photosynthetic carbon assimilation  

Microsoft Academic Search

When spinach leaves are re-illuminated, after dark periods of 90 s or less, an initial fluorescence peak is observed which rapidly gives way to a much lower terminal value. After 2 min or more in the dark, however, there is a secondary rise, at about 5070 s, which then gives way, more slowly, to approximately the same low terminal value

D. A. Walker

1981-01-01

176

Perchlorate uptake in spinach as related to perchlorate, nitrate and chloride concentrations in irrigation water  

Technology Transfer Automated Retrieval System (TEKTRAN)

Several studies have reported on the detection of perchlorate in edible leafy vegetables irrigated with Colorado River water. However, there is no information on spinach as related to perchlorate in irrigation water nor on the effect of other anions on perchlorate uptake. A greenhouse perchlorate up...

177

Survival of Salmonella on spinach leaves treated with contaminated irrigation water  

Technology Transfer Automated Retrieval System (TEKTRAN)

Introduction: Salmonella outbreaks have been associated with the consumption of fresh produce. The produce may be contaminated with Salmonella during on-farm contact with contaminated water. Transmission of Salmonella from contaminated irrigation water to spinach plants in growth chamber settings ...

178

GROWTH RESPONSE IN SPINACH TO SEQUENTIAL AND SIMULTANEOUS EXPOSURE TO NO2 AND SO2  

EPA Science Inventory

Spinach (Spinacia oleracea) was exposed intermittently to NO2 and SO2 (2 hours/week; 0.8 or 1.5ppm) in a simultaneous or sequential fashion over the 42-day growth period. Nighttime simultaneous exposure to NO2 and SO2 reduced growth and altered assimilate partitioning to the root...

179

Isolation of cDNA clones coding for spinach nitrite reductase: Complete sequence and nitrate induction  

Microsoft Academic Search

The main nitrogen source for most higher plants is soil nitrate. Prior to its incorporation into amino acids, plants reduce nitrate to ammonia in two enzymatic steps. Nitrate is reduced by nitrate reductase to nitrite, which is further reduced to ammonia by nitrite reductase. In this paper, the complete primary sequence of the precursor protein for spinach nitrite reductase has

Eduard Back; William Burkhart; Mary Moyer; Laura Privalle; Steven Rothstein

1988-01-01

180

Polycations Globally Enhance Binding of 14-3-3 omega to Target Proteins in Spinach Leaves  

Technology Transfer Automated Retrieval System (TEKTRAN)

The binding of 14-3-3' to phosphorylated NR (pNR) is stimulated by cations such as Mg2+ or spermine, and decreased by 5'-AMP. In order to determine whether binding to other cellular proteins is affected similarly, Far-Western overlays of extracts prepared from light- or dark-treated spinach (Spinac...

181

Characterization of a prokaryotic topoisomerase I activity in chloroplast extracts from spinach  

Microsoft Academic Search

A topoisomerase I activity has been partially purified from crude extracts of spinach chloroplasts. This activity relaxes the supercoiled covalently closed circular DNA of pBR322. The enzyme requires Mg , but not ATP, and has an apparent molecular weight of about 115,000. It catalyzes a unit change in the linkage number of supercoiled DNA but cannot relax positive supercoiled DNA.

Janusz Siedlecki; Wolfgang Zimmermann; Arthur Weissbach

1983-01-01

182

Adherence of curli producing Shiga-toxigenic Escherichia coli to baby spinach leaves  

Technology Transfer Automated Retrieval System (TEKTRAN)

Cellular appendages, such as curli fibers have been suggested to be involved in STEC persistence in fresh produce as these curli are critical in biofilm formation and adherence to animal cells. We determined the role of curli in attachment of STEC on spinach leaves. The curli expression by wild-ty...

183

Persistence of enterohemorrhagic and non-pathogenic E. coli on spinach leaves and in rhizosphere soil  

Technology Transfer Automated Retrieval System (TEKTRAN)

Foodborne illness outbreaks associated with leafy greens have raised concerns about the persistence of Escherichia coli O157:H7 on fresh produce and in the cropping environment. The set of characteristics that enable the enteric bacterium E. coli O157:H7 to survive on undamaged spinach leaves, roots...

184

Proteomic, pigment composition, and organization of thylakoid membranes in iron-deficient spinach leaves  

Microsoft Academic Search

The changes induced in the photosynthetic apparatus of spinach (Spinacia oleracea L.) seedlings exposed to iron deficiency shortly after germination were charac- terized with two proteomic approaches coupled with chlorophyll and xanthophyll analysis and in vivo measurements of photosynthesis. During the first 10 d of iron deficiency the concentrations of chlorophyll b and violaxanthin were greatly reduced, but all xanthophylls

Anna Maria Timperio; Gian Maria D'Amici; Csengele Barta; Francesco Loreto; Lello Zolla

2010-01-01

185

Atomic-force microscopy imaging of plasma membranes purified from spinach leaves  

Microsoft Academic Search

Summary Plasma membranes purified from spinach leaves by aqueous two-phase partitioning were examined by atomic-force microscopy (AFM) in phosphate buffer, and details on their structure were reported at nanometric scale. Examination of the fresh membrane preparation deposited on mica revealed a complex organization of the surface. It appeared composed of a first layer of material, about 8 nm in thickness,

M. Crvecoeur; E. Lesniewska; V. Vi; J. P. Goudonnet; H. Greppin; C. Le Grimellec

2000-01-01

186

Food Recalls and Food Safety Perceptions: The September 2006 Spinach Recall Case  

Microsoft Academic Search

This paper examines public perceptions on food safety particularly relating to spinach, which was subject of countrywide recall in 2006. Results indicate that food safety perceptions may be driven by public trust\\/confidence in institutions whose activities may be directly or indirectly related to food safety. The results further suggest that food safety perceptions may also be related to the type

Benjamin M. Onyango; Dragan Miljkovic; William K. Hallman; William E. Nganje; Sarah C. Condry; Cara L. Cuite

2007-01-01

187

Light saturation response of inactive photosystem II reaction centers in spinach  

Microsoft Academic Search

The effective absorption cross section of inactive photosystem II (PS II) centers, which is the product of the effective antenna size and the quantum yield for photochemistry, was investigated by comparing the light saturation curves of inactive PS II and active reaction centers in intact chloroplasts and thylakoid membranes of spinach (Spinacia oleracea). Inactive PS II centers are defined as

Roger A. Chylla; John Whitmarsh

1990-01-01

188

Recycling of Chicken and Duck Litter Ash as a Nutrient Source for Japanese Mustard Spinach  

Microsoft Academic Search

Recycling combusted poultry litter ash as a soil amendment would potentially ameliorate problems normally associated with poultry waste management. We evaluated the effect of chicken litter ash (CLA) and duck litter ash (DLA) as nutrient sources for Japanese mustard spinach (Brassica rapa L. var. perviridis) grown on a sand dune soil. Chicken and duck litter were ashed at five temperatures:

Faridullah; Muhammad Irshad; Sadahiro Yamamoto; A. Egrinya Eneji; Tomoji Uchiyama; Toshimasa Honna

2009-01-01

189

Time-resolved spectroscopy of the blue fluorescence of spinach leaves  

Microsoft Academic Search

When excited by ultraviolet radiation, leaves of a great number of species of higher plants exhibit emission of blue fluorescence, comparable in intensity to the red emission of chlorophyll. The fluorescence decay of the blue emission of spinach leaves recorded by single photon counting techniques is decomposed into exponential components and it is shown that at least three different components

Yves Goulas; Ismael Moya; Guido Schmuck

1990-01-01

190

Structure and Stability of the Spinach Aquaporin SoPIP2;1 in Detergent Micelles and Lipid Membranes  

PubMed Central

Background SoPIP2;1 constitutes one of the major integral proteins in spinach leaf plasma membranes and belongs to the aquaporin family. SoPIP2;1 is a highly permeable and selective water channel that has been successfully overexpressed and purified with high yields. In order to optimize reconstitution of the purified protein into biomimetic systems, we have here for the first time characterized the structural stability of SoPIP2;1. Methodology/Principal Finding We have characterized the protein structural stability after purification and after reconstitution into detergent micelles and proteoliposomes using circular dichroism and fluorescence spectroscopy techniques. The structure of SoPIP2;1 was analyzed either with the protein solubilized with octyl-?-D-glucopyranoside (OG) or reconstituted into lipid membranes formed by E. coli lipids, diphytanoylphosphatidylcholine (DPhPC), or reconstituted into lipid membranes formed from mixtures of 1-palmitoyl-2-oleoyl-phosphatidylcholine (POPE), 1-palmitoyl-2oleoyl-phosphatidylethanolamine (POPE), 1-palmitoyl-2-oleoyl-phosphatidylserine (POPS), and ergosterol. Generally, SoPIP2;1 secondary structure was found to be predominantly ?-helical in accordance with crystallographic data. The protein has a high thermal structural stability in detergent solutions, with an irreversible thermal unfolding occurring at a melting temperature of 58C. Incorporation of the protein into lipid membranes increases the structural stability as evidenced by an increased melting temperature of up to 70C. Conclusion/Significance The results of this study provide insights into SoPIP2;1 stability in various host membranes and suggest suitable choices of detergent and lipid composition for reconstitution of SoPIP2;1 into biomimetic membranes for biotechnological applications.

Plasencia, Ines; Survery, Sabeen; Ibragimova, Sania; Hansen, Jesper S.; Kjellbom, Per; Helix-Nielsen, Claus; Johanson, Urban; Mouritsen, Ole G.

2011-01-01

191

Leaf Pack Network  

NSDL National Science Digital Library

The Leaf Pack Network (LPN) is a network of teachers and students investigating their local stream ecosystems by participating in the leaf pack experiment, which involves creating an artificial leaf pack (dry leaves in a mesh bag), immersing it in a stream for 3-4 weeks, and examining it for signs of aquatic insects as indicators of stream health. Participating classrooms share their data through the internet. This activity highlights the connection between streamside forests and the ecology of rivers and streams.

192

Photoinhibition of photosystem I is accelerated by dimethyldithiocarbamate, an inhibitor of superoxide dismutase, during light-chilling of spinach leaves  

Microsoft Academic Search

In vivo photoinhibition of photosystem I (PS I) was investigated at chilling temperature using the leaves of the chilling-resistant spinach plant treated with an inhibitor of superoxide dismutase, diethyldithiocarbamate (DDC). When spinach leaves were treated with DDC during chilling at 4 C for 12 h with a light intensity of 120 ?molm?2s?1, the activity of PS I and the content

Hong Jin Hwang; Jin-Hong Kim; Young-Jae Eu; Byoung Yong Moon; Sung Ho Cho; Choon-Hwan Lee

2004-01-01

193

Molecular characterization of transketolase (EC 2.2.1.1) active in the Calvin cycle of spinach chloroplasts  

Microsoft Academic Search

A cDNA encoding the Calvin cycle enzyme transketolase (TKL; EC 2.2.1.1) was isolated from Sorghum bicolor via subtractive differential hybridization, and used to isolate several full-length cDNA clones for this enzyme from spinach. Functional identity of the encoded mature subunit was shown by an 8.6-fold increase of TKL activity upon induction of Escherichia coli cells that overexpress the spinach TKL

Anke Flechner; Uta Dressen; Peter Westhoff; Katrin Henze; Claus Schnarrenberger; William Martin

1996-01-01

194

Spinach and tomato consumption increases lymphocyte DNA resistance to oxidative stress but this is not related to cell carotenoid concentrations  

Microsoft Academic Search

Summary\\u000a Background The increased consumption of fruit and vegetables has been linked to protection against different chronic diseases, but the\\u000a dietary constituents responsible for this association have not been clearly identified. Aim of the study We evaluated the effect of spinach and spinach+tomato puree consumption on cell DNA resistance to an oxidative stress. Methods To this aim, in a dietary

Marisa Porrini; Patrizia Riso; Giovannangelo Oriani

2002-01-01

195

d Ribose5Phosphate Isomerase from Spinach: Heterologous Overexpression, Purification, Characterization, and Site-Directed Mutagenesis of the Recombinant Enzyme  

Microsoft Academic Search

A cDNA encoding spinach chloroplastic ribose-5-phosphate isomerase (RPI) was cloned and overexpressed in Escherichia coli, and a purification scheme for the recombinant enzyme was developed. The purified recombinant RPI is a homodimer of 25-kDa subunits and shows kinetic properties similar to those of the homodimeric enzyme isolated from spinach leaves (A. C. Rutner, 1970, Biochemistry 9, 178184). Phosphate, used as

Che-Hun Jung; Fred C. Hartman; Tse-Yuan S. Lu; Frank W. Larimer

2000-01-01

196

Microbial and quality changes in minimally processed baby spinach leaves stored under super atmospheric oxygen and modified atmosphere conditions  

Microsoft Academic Search

The effect of super atmospheric O2 and modified atmosphere packaging (MAP) on plant metabolism, organoleptic quality and microbial growth of minimally processed baby spinach was studied. Packaging film O2 transmission rates and initial levels of super atmospheric O2 in the packages significantly affected the changes of in-package atmospheres during storage, and consequently quality of baby spinach leaves. In general, a

Ana Allende; Yaguang Luo; James L McEvoy; Francisco Arts; Chien Y Wang

2004-01-01

197

Effects of mercury on visible\\/near-infrared reflectance spectra of mustard spinach plants ( Brassica rapa P.)  

Microsoft Academic Search

Mustard spinach plants were grown in mercury-spiked and contaminated soils collected in the field under controlled laboratory conditions over a full growth cycle to test if vegetation grown in these soils has discernible characteristics in visible\\/near-infrared (VNIR) spectra. Foliar Hg concentrations (0.1743.993ppm) of the Mustard spinach plants were positively correlated with Hg concentration of soils and varied throughout the growing

Sarah C. Dunagan; Martha S. Gilmore; Johan C. Varekamp

2007-01-01

198

Effect of nano-TiO 2 on strength of naturally aged seeds and growth of spinach  

Microsoft Academic Search

The effects of nano-TiO2 (rutile) and non-nano-TiO2 on the germination and growth of naturally aged spinach seeds were studied by measuring the germination rate and the germination\\u000a and vigor indexes of aged spinach seeds. An increase of these factors was observed at 0.254 nano-TiO2 treatment. During the growth stage, the plant dry weight was increased, as was the chlorophyll formation,

Lei Zheng; Fashui Hong; Shipeng Lu; Chao Liu

2005-01-01

199

Leaf cutter ants  

NSDL National Science Digital Library

There is much diversity between ants. Leaf cutter ants use their mandibles to cut leaf fragments and take them back to their home. They don't eat the leaves, but instead use them to grow fungus on. They then eat the fungus.

N/A N/A (None;)

2007-12-15

200

Gamma irradiation dose: Effects on spinach baby-leaf ascorbic acid, carotenoids, folate, alpha-tocopherol, and phylloquinone concentrations  

Technology Transfer Automated Retrieval System (TEKTRAN)

Ionizing radiation of fruits and vegetables, in the form of gamma rays or electron beams, is effective in overcoming quarantine barriers in trade, decontamination, disinfestation and prolonging shelf life, but a void of information persists on ionizing radiation effects of vitamin profiles in indivi...

201

Inactivation of Escherichia coli O157:H7, Listeria monocytogenes, Salmonella enterica and Shigella flexneri on spinach leaves by X-ray  

Microsoft Academic Search

Several recent foodborne disease outbreaks associated with leafy green vegetables, including spinach, have been reported. X-ray is a non-thermal technology that has shown promise for reducing pathogenic and spoilage bacteria on spinach leaves. Inactivation of inoculated Escherichia coli O157:H7, Listeria monocytogenes, Salmonella enterica and Shigella flexneri on spinach leaves using X-ray at different doses (0.1, 0.2, 0.3, 0.5, 0.75, 1.0,

Barakat S. M. Mahmoud; Gary Bachman; Richard H. Linton

2010-01-01

202

Fat Metabolism in Higher Plants: LXII. Stearl-acyl Carrier Protein Desaturase from Spinach Chloroplasts.  

PubMed

Stearyl-acyl carrier protein desaturase (EC 1.14.99.6), present in the stroma fraction of spinach (Spinacia oleracea) chloroplasts, rapidly desaturated enzymatically prepared stearyl-acyl carrier protein to oleic acid. No other substrates were desaturated. In addition to stearyl-acyl carrier protein, reduced ferredoxin was an essential component of the system. The electron donor systems were either ascorbate, dichlorophenolindophenol, photosystem I and light, or NADPH and ferredoxin-NADP reductase. The desaturase was more active in extracts prepared from chloroplasts obtained from immature spinach leaves than from mature leaves. Stearyl-acyl carrier protein desaturase also occurs in soluble extracts of avocado (Persea americana Mill.) mesocarp and of developing safflower (Carthamus tinctorius) seeds. PMID:16658913

Jacobson, B S; Jaworski, J G; Stumpf, P K

1974-10-01

203

Increasing total and biologically active chromium in wheat grain and spinach by spraying with chromium salts  

SciTech Connect

Recently, chromium has been shown to be necessary for glucose metabolism in man. But most plant species greatly restrict the uptake of Cr. This study was conducted to determine if both total and biologically active Cr could be increased in wheat grain or spinach by spraying the plants with either Cr/sub 2/(SO/sub 4/)/sub 3/ or Cr-EDTA. Concentrations of Cr in wheat grain were about doubled in a greenhouse experiment by spraying with either Cr source. Biologically active Cr (estimated by extraction with ethanol or NH/sub 4/OH) was increased from about 40 to greater than 50% of total Cr when wheat was sprayed with Cr salts. Total Cr in spinach leaves was increased by as much as 10-fold by spraying, with the sulfate source being more effective than the EDTA.

Vicini, F.A.; Ellis, B.G.

1981-06-01

204

Impact of coal mine dump contaminated soils on elemental uptake by Spinacia oleracea (spinach)  

SciTech Connect

The elemental uptake and the growth response of Spinacia oleracea (spinach) to the soil contaminated with the South African bituminous coal mine dump soil, viz. 0%, 5%, 15%, and 25% w/w, was investigated. The contaminated soils were analyzed for pH, cation exchange capacity (CEC), soil organic matter (SOM), and concentrations of selected heavy metals. The pH, SOM, and CEC decreased with an increase in contamination indicating the acidic nature of coal mine soil and the raise in the soil binding sites. The distribution of Fe, Mn, Ni, Cd, and Pb in the roots and leaves of the plants was determined in two stages of plant growth. Spinach showed high accumulation of Fe and increased levels of Ni and Cd with an increase in contamination. No plant growth was recorded with 25% contamination.

Chunilall, V.; Kindness, A.; Jonnalagadda, S.B. [University of KwaZulu Natal, Durban (South Africa)

2006-07-01

205

Inhibitory effect of aqueous spinach extract on degranulation of RBL-2H3 cells.  

PubMed

The inhibitory effect of an aqueous extract from spinach on degranulation of RBL-2H3 cells is herein reported. The extract significantly suppressed antigen-induced degranulation in a dose-dependent manner without affecting cell viability. Active substances in the extract were heat-stable and trypsin-resistant with molecular weights ranging from 500 Da to 14 kDa. The extract inhibited elevation of the intracellular Ca(2+) concentration caused by stimulation by antigen, while not suppressing degranulation induced by a calcium ionophore A23187. Immunoblot analysis revealed that the inhibitory effect results from downregulation of phosphorylation of both Syk kinase and phosphatidylinositol 3-kinase in the signalling pathways involved in degranulation caused by the antigen-antibody interaction. Taken together, these findings suggest that aqueous spinach extract has an anti-allergic activity that controls degranulation. PMID:23122065

Ishida, Momoko; Nishi, Kosuke; Watanabe, Hisashi; Sugahara, Takuya

2012-09-08

206

Structure Prediction of Dihydroflavonol 4- Reductase and Anthocyanidin Synthase from Spinach  

PubMed Central

Spinach is an important dietary vegetable associated with beneficial health effects. Flavonoids have various biological activities such as antioxidant, antibacterial, and anticancer effect Flavonoid including anthocyanin provides brilliant and colored pigments in different plant tissues. Anthocyanidin synthase and dihydroflavonol 4-reductase are responsible for anthocyanin biosynthesis. They contributed in plant protection against UV-B radiation, microbial and herbivore pathogens. A 3D structures of anthocyanidin synthase and dihydroflavonol 4-reductase from spinach are constructed in this study through homology modeling. The homology modeling is done by using the MODELLER 9v7 software. The energy of models was minimized by applying molecular mechanics method. The root mean square deviation (RMSD) for C atoms between the template and the homology-modeled structures was estimated by CE program. The final models were assessed by PROCHECK and WHATCHECK which showed that the final refined models are reliable.

Sahay, Archna; Shakya, Madhvi

2010-01-01

207

Cadmium Phytotoxicity in Spinach with or without Spent Wash in a Vertisol  

Microsoft Academic Search

The phytotoxicity due to cadmium (Cd) and its likely contamination of the food chainresulting from its addition from low to very high levels to a swell?shrink clayey soil (Haplustert) in spinach (Spinacia oleracea L.)was studied in a pot culture experiment. Twelve levels of Cd (0, 2, 4, 8, 10, 20, 40, 60, 80, 120, 160, 200mgkg soil) were applied singly

Tapan Adhikari; A. K. Biswas; J. K. Saha; Ajay

2005-01-01

208

Expression of an active spinach acyl carrier protein-I\\/protein-A gene fusion  

Microsoft Academic Search

A synthetic gene encoding spinach acyl carrier protein I (ACP-I) was fused to a gene encoding the Fc-binding portion of staphylococcal protein A. This gene fusion, under the control of the ?PR promoter, was expressed at high levels in Escherichia coli producing a 42 kDa fusion protein. This fusion protein was phosphopantethenylated in E. coli. In vitro the ACP portion

Phillip D. Beremand; DonitaDoyle Elmore; Katarzyna Dziewanowska; Daniel J. Guerra

1989-01-01

209

In-vitro degradation of starch granules isolated from spinach chloroplasts  

Microsoft Academic Search

The initial reactions of transitory starch degradation in Spinacia oleracea L. were investigated using an in-vitro system composed of native chloroplast starch granules, purified chloroplast and non-chloroplast forms of phosphorylase (EC 2.4.1.1) from spinach leaves, and a-amylase (EC 3.2.1.1) isolated from Bacillus subtilis. Starch degradation was followed by measuring the release of soluble glucans, by determining phosphorylase activity, and by

Martin Steup; Horst Robenek; Michael Melkonian

1983-01-01

210

Developmental regulation of the PsbS gene expression in spinach seedlings: the role of phytochrome  

Microsoft Academic Search

The PsbS gene product (PSII-S) which is an integral subunit of photosystem II has recently been reported to be a new type of pigment-binding protein [11]. The chlorophylls of the PSII-S protein exhibit weak excitonic coupling and this protein is stable also in the absence of pigments. Here we investigated the expression of the PsbS gene in etiolated spinach seedlings

Iwona Adamska; Christiane Funk; Gernot Renger; Bertil Andersson

1996-01-01

211

Protective systems against active oxygen species in spinach: response to cold acclimation in excess light  

Microsoft Academic Search

Spinach (Spinacia oleracea L.) plants were acclimated to 1 C or maintained at 18 C under the same light regime (260300 mol photonsm-2s-1). The cold acclimation led to several metabolic and biochemical changes that apparently include improved protection of the photosynthetic apparatus against active oxygen species. In particular, cold-acclimated leaves exhibited a considerably higher ascorbate content and significantly increased activities

Susanne Schner; G. Heinrich Krause

1990-01-01

212

Localization of genes for coupling factor subunits on the spinach plastid chromosome  

Microsoft Academic Search

1)Messenger RNA obtained from spinach cotyledons directs the synthesis of all five CF1 subunits in vitro in a rabbit reticulocyte translation system. The alpha, beta and epsilon subunit polypeptides were found as translation products from ptRNA and whole-cell poly A--RNA. The gamma and delta subunits were synthesized from whole-cell poly A+-RNA as precursors of substantially greater molecular weight indicating that

P. Westhoff; N. Nelson; H. Bnemann; R. G. Herrmann

1981-01-01

213

Properties and physiological function of a glutathione reductase purified from spinach leaves by affinity chromatography  

Microsoft Academic Search

Glutathione reductase (EC 1.6.4.2) was purified from spinach (Spinacia oleracea L.) leaves by affinity chromatography on ADP-Sepharose. The purified enzyme has a specific activity of 246 enzyme units\\/mg protein and is homogeneous by the criterion of polyacrylamide gel electrophoresis on native and SDS-gels. The enzyme has a molecular weight of 145,000 and consists of two subunits of similar size. The

B. Halliwell; C. H. Foyer

1978-01-01

214

Interactions between food-borne pathogens and protozoa isolated from lettuce and spinach.  

PubMed

The survival of Salmonella enterica was recently shown to increase when the bacteria were sequestered in expelled food vacuoles (vesicles) of Tetrahymena. Because fresh produce is increasingly linked to outbreaks of enteric illness, the present investigation aimed to determine the prevalence of protozoa on spinach and lettuce and to examine their interactions with S. enterica, Escherichia coli O157:H7, and Listeria monocytogenes. Glaucoma sp., Colpoda steinii, and Acanthamoeba palestinensis were cultured from store-bought spinach and lettuce and used in our study. A strain of Tetrahymena pyriformis previously isolated from spinach and a soil-borne Tetrahymena sp. were also used. Washed protozoa were allowed to graze on green fluorescent protein- or red fluorescent protein-labeled enteric pathogens. Significant differences in interactions among the various protist-enteric pathogen combinations were observed. Vesicles were produced by Glaucoma with all of the bacterial strains, although L. monocytogenes resulted in the smallest number per ciliate. Vesicle production was observed also during grazing of Tetrahymena on E. coli O157:H7 and S. enterica but not during grazing on L. monocytogenes, in vitro and on leaves. All vesicles contained intact fluorescing bacteria. In contrast, C. steinii and the amoeba did not produce vesicles from any of the enteric pathogens, nor were pathogens trapped within their cysts. Studies of the fate of E. coli O157:H7 in expelled vesicles revealed that by 4 h after addition of spinach extract, the bacteria multiplied and escaped the vesicles. The presence of protozoa on leafy vegetables and their sequestration of enteric bacteria in vesicles indicate that they may play an important role in the ecology of human pathogens on produce. PMID:18310421

Gourabathini, Poornima; Brandl, Maria T; Redding, Katherine S; Gunderson, John H; Berk, Sharon G

2008-02-29

215

Herbicides affect fluorescence and electron transfer activity of spinach chloroplasts, thylakoid membranes and isolated Photosystem II  

Microsoft Academic Search

In this work, studies on the effects produced by atrazine, terbutryn or diuron onto spinach photosynthetic materials were performed by observing changes in fluorescence emission and in electron transfer activities of the bio-samples in the presence of such herbicides; chloroplasts, thylakoids, Photosystem II-enriched thylakoids (BBYs) and isolated Photosystem II (PSII) were employed. This approach evidenced differences in the herbicidephotosynthetic material

Andrea Ventrella; Lucia Catucci; Angela Agostiano

2010-01-01

216

Biogenesis of photosystem I reaction center during greening of oat, bean and spinach leaves  

Microsoft Academic Search

SummaryThe relative amounts of some chloroplast polypeptides were followed during greening of leaves from three different plant families.\\u000a Oat, bean and spinach were the representatives of the Gramineae, Leguminosae and Chenopodiaceae, respectively. By using specific\\u000a antibodies against subunits of the chloroplast protein complexes, it was found with that method that the protein complexes\\u000a which are not involved in a photobiochemical

Rachel Nechushtai; Nathan Nelson

1985-01-01

217

Biosynthesis of active spinach-chloroplast thioredoxin f in transformed E. coli  

Microsoft Academic Search

The recently cloned gene for spinach chloroplast thioredoxin f was subcloned in a modified pKK233-2 expression vector and used for transformation of Escherichia coli cells containing the Iq plasmid. After induction with IPTG (isopropyl--D-thiogalactoside) the transformed cells produce the chloroplast protein in large amounts as insoluble deposit within the cell. The protein has been solubilized, purified and analysed for activity.

F. Aguilar; B. Brunner; L. Gardet-Salvi; E. Stutz; P. Schfirmann

1992-01-01

218

Effects of Pb 2+ on energy distribution and photochemical activity of spinach chloroplast  

Microsoft Academic Search

Lead (Pb2+) is a well-known highly toxic element. The mechanisms of the Pb2+ toxicity are not well understood for photosynthesis. In this paper, we reported the effect of Pb2+ on light absorption, distribution and conversion of spinach chloroplast by spectroscopy, and photochemical reaction activities. Several effects of Pb2+ were observed: (1) the absorption peak intensity of chloroplast obviously decreased in

Xiao Wu; Fashui Hong; Chao Liu; Mingyu Su; Lei Zheng; Fengqing Gao; Fan Yang

2008-01-01

219

Interactions between Food-Borne Pathogens and Protozoa Isolated from Lettuce and Spinach?  

PubMed Central

The survival of Salmonella enterica was recently shown to increase when the bacteria were sequestered in expelled food vacuoles (vesicles) of Tetrahymena. Because fresh produce is increasingly linked to outbreaks of enteric illness, the present investigation aimed to determine the prevalence of protozoa on spinach and lettuce and to examine their interactions with S. enterica, Escherichia coli O157:H7, and Listeria monocytogenes. Glaucoma sp., Colpoda steinii, and Acanthamoeba palestinensis were cultured from store-bought spinach and lettuce and used in our study. A strain of Tetrahymena pyriformis previously isolated from spinach and a soil-borne Tetrahymena sp. were also used. Washed protozoa were allowed to graze on green fluorescent protein- or red fluorescent protein-labeled enteric pathogens. Significant differences in interactions among the various protist-enteric pathogen combinations were observed. Vesicles were produced by Glaucoma with all of the bacterial strains, although L. monocytogenes resulted in the smallest number per ciliate. Vesicle production was observed also during grazing of Tetrahymena on E. coli O157:H7 and S. enterica but not during grazing on L. monocytogenes, in vitro and on leaves. All vesicles contained intact fluorescing bacteria. In contrast, C. steinii and the amoeba did not produce vesicles from any of the enteric pathogens, nor were pathogens trapped within their cysts. Studies of the fate of E. coli O157:H7 in expelled vesicles revealed that by 4 h after addition of spinach extract, the bacteria multiplied and escaped the vesicles. The presence of protozoa on leafy vegetables and their sequestration of enteric bacteria in vesicles indicate that they may play an important role in the ecology of human pathogens on produce.

Gourabathini, Poornima; Brandl, Maria T.; Redding, Katherine S.; Gunderson, John H.; Berk, Sharon G.

2008-01-01

220

Impact of Coal Mine Dump Contaminated Soils on Elemental Uptake by Spinacia Oleracea (Spinach)  

Microsoft Academic Search

The elemental uptake and the growth response of Spinacia oleracea (spinach) to the soil contaminated with the South African bituminous coal mine dump soil, viz. 0%, 5%, 15%, and 25% w\\/w, was investigated. The contaminated soils were analyzed for pH, cation exchange capacity (CEC), soil organic matter (SOM), and concentrations of selected heavy metals. The pH, SOM, and CEC decreased

VIREN CHUNILALL; ANDREW KINDNESS; SREEKANTH B. JONNALAGADDA

2006-01-01

221

Phenolic Constituents of Celosia cristata L. Susceptible to Spinach Root Rot Pathogen Aphanomyces cochlioides  

Microsoft Academic Search

Aphanomyces cochlioides is a soil-borne phytopatho- genic Peronosporomycete which is responsible for the root rot disease of spinach (Spinacia oleracea L.) and damping-off disease of sugar beet (Beta vulgaris var. rapa Dum.). The presence of the potent zoospore attractant, cochliophilin A (5-hydroxy-6,7-methylene- dioxyflavone, 1), has been confirmed in a range of host plants in the Chenopodiaceae including sugar beet, 1)

Yaolin WEN; Satoshi TAHARA

2006-01-01

222

Uptake, translocation, and transformation of pentachlorophenol in soybean and spinach plants  

SciTech Connect

Soybean plants were grown for 90 days and spinach plants for 64 days in a mixture of sterilized greenhouse soil and sand containing 10 ppm pentachlorophenol. All plant parts and soil samples were extracted and separated into nonpolar and polar fractions. Major nonpolar and polar metabolites were identified by gas-liquid chromatography and mass spectrometry. Nonpolar fractions from both soybean and spinach plants were found to contain pentachlorophenol and its metabolites, 2,3,4,6-tetrachlorophenol, methoxytetrachlorophenol, 2,3,4,6-tetrachloroanisole, and pentachloroanisole. Cleavage of polar metabolites from the soybean plants by acid hydrolysis yielded organic solvent-extractable products. These products were identified as pentachlorophenol, 2,3,4,6-tetrachlorophenol, and methoxytetrachlorophenol. Cleavage of polar materials from spinach plants yielded only pentachlorophenol. The polar metabolites from the soybean plants were also subjected to enzymatic cleavage by beta-glucosidase. The conjugates consisted mostly of O-glucosides of the same metabolites released by acid hydrolysis. Failure of hydrolysis by aryl sulfatase indicated that very little or no sulfates were present. The metabolites found in the plants were not detected in soil samples obtained from pots immediately after the plants were harvested.

Casterline, J.L. Jr.; Barnett, N.M.; Ku, Y.

1985-06-01

223

Conversion of monogalactosyldiacylglycerols to triacylglycerols in ozone-fumigated spinach leaves. [Spinacia oleracea L  

SciTech Connect

Molecular species and fatty acid distribution of triacylglycerol (TG) accumulated in spinach (Spinacia oleracea L.) leaves fumigated with ozone (0.5 microliter per liter) were compared with those of monogalactosyldiacylglyerol (MGDG). Analysis of positional distribution of the fatty acids in MGDG and the accumulated TG by the enzymatic digestion method showed that hexadecatrienoate (16:3) was restricted to sn-2 position of the glycerol backbone in both MGDG and TG, whereas {alpha}-linolenate (18:3) was preferentially located at sn-1 position in MGDG, and sn-1 and/or sn-3 positions in TG, suggesting that 1,2-diacylglycerol moieties of MGDG are the direct precursor of TG in ozone-fumigated leaves. Further analysis of TG molecular species by argentation chromatography and mass spectrometry showed that TG increased with ozone fumigation consisted of approximately an equal molar ratio of sn-1,3-18:3-2-16:3 and sn-1,2,3-18:3. Because the molecular species of MGDG in spinach leaves is composed of a similar molar ratio of sn-1-18:3-2-16:3 and sn-1,2-18:3, we conducted that MGDG was converted to 1,2-diacylglycerol and acylated with 18:3 to TG in ozone-fumigated spinach leaves.

Sakaki, Takeshi; Saito, Kazuki; Kawaguchi, Akihiko; Kondo, Noriaki; Yamada, Mitsuhiro (National Institute for Environmental Studies, Ibaraki (Japan) Keio Univ., Tokyo (Japan) Univ. of Tokyo (Japan))

1990-10-01

224

Effects of cerium on key enzymes of carbon assimilation of spinach under magnesium deficiency.  

PubMed

The mechanism of the fact that cerium improves the photosynthesis of plants under magnesium deficiency is poorly understood. The main aim of the study was to determine the role of cerium in the amelioration of magnesium deficiency effects in CO(2) assimilation of spinach. Spinach plants were cultivated in Hoagland's solution. They were subjected to magnesium deficiency and to cerium chloride administered in the magnesium-present Hoagland's media and magnesium-deficient Hoagland's media. The results showed that the chlorophyll synthesis and oxygen evolution was destroyed, and the activities of Rubisco carboxylasae and Rubisco activase and the expression of Rubisco large subunit (rbcL), Rubisco small subunit (rbcS), and Rubisco activase subunit (rca) were significantly inhibited, then plant growth was inhibited by magnesium deficiency. However, cerium promotes the chlorophyll synthesis, the activities of two key enzymes in CO(2) assimilation, and the expression of rbcL, rbcS, and rca, thus leading to the enhancement of spinach growth under magnesium-deficient conditions. PMID:19274447

Yuguan, Ze; Min, Zhou; Luyang, Luo; Zhe, Ji; Chao, Liu; Sitao, Yin; Yanmei, Duan; Na, Li; Fashui, Hong

2009-03-10

225

The antioxidant activity of aqueous spinach extract: chemical identification of active fractions.  

PubMed

In previous studies we have elucidated the presence of powerful, natural antioxidants (NAO) in water extracts of spinach leaves and demonstrated their biological activity in both in vitro and in vivo systems. In the present study, the chemical identity of several of these antioxidant components is presented. Spinach leaves were extracted with water and the 20,000 g supernatant which contained the antioxidant activity was extracted with a water:acetone (1:9) solution. The 20,000 g supernatant obtained was further purified on reverse phase HPLC using C-8 semi-preparative column. Elution with 0.1% TFA resulted in five hydrophilic peaks. Elution with acetonitrile in TFA resulted in seven additional hydrophobic peaks. All the peaks were detected at 250 nm. All the fractions obtained showed antioxidant activity when tested using three different assays. Based on 1H and 13C NMR spectroscopy four of the hydrophobic fractions were identified as glucuronic acid derivatives of flavonoids and three additional fractions as trans and cis isomers of p-coumaric acid and others as meso-tartarate derivatives of p-coumaric acid. The present study demonstrates for the first time the presence of both flavonoids and p-coumaric acid derivatives as antioxidant components of the aqueous extract of spinach leaves. PMID:11524124

Bergman, M; Varshavsky, L; Gottlieb, H E; Grossman, S

2001-09-01

226

Ligand-triggered conformational perturbations elicit changes at the single cysteinyl residue of spinach calmodulin.  

PubMed

Following application of stoichiometric amounts of Ca2+ or specific partner peptides to spinach calmodulin, dynamic changes in the nanosecond range could be monitored at a strategically anchored fluorescence or spin probe. For these studies the single cysteinyl residue 26 of spinach calmodulin was labelled with a thiol-specific proxyl (i.e. 2,2,5,5-tetramethyl-1-pyrrolidinyl-oxyl) spin probe or with a bimane fluorescence probe. With Ca2+ and a specific ligand (mastoparan) present, fluorescence studies (anisotropy, lifetime) indicated that the rotational motion of the protein complex becomes slower relative to the motion of calmodulin in the absence of the specific ligand. The probe's attachment site 26 appears to reside in a fairly polar microenvironment as reported by a series of proxyl spin probes varying in label length. The rotational correlation time of the shortest spin probe markedly changed upon binding of a specific peptide to a calmodulin region distant from that of the monitoring spin probe. We interpret these observations as indicating that ligand-triggered conformational perturbations are eliciting specific responses at the cysteinyl residue 26 of spinach calmodulin. PMID:2841122

Yuan, S X; Haug, A

1988-07-15

227

Estimating Near-Infrared Leaf Reflectance from Leaf Structural Characteristics  

Microsoft Academic Search

The relationship between near-infrared reflectance at 800 nm (NIRR) from leaves and characteristics of leaf structure known to affect photosynthesis was investigated in 48 species of alpine angiosperms. This wavelength was selected to discriminate the effects of leaf structure vs. chemical or water content on leaf reflectance. A quantitative model was first constructed correlating NIRR with leaf structural characteristics for

Michele R. Slaton; E. Raymond Hunt; William K. Smith

2001-01-01

228

Four-Leaf Clover  

NSDL National Science Digital Library

Scientist-in-training Summer Praetorius has an unusual skillshe is really, really good at spotting four-leaf clovers (Trifolium repens L.). A single gene causes the normally three-leafed clover to produce a fourth, supposedly lucky, leaf. As it turns out, good science depends on both close observationa skill Praetorius uses to spot tiny shelled animals called foraminiferaand a little bit of luck. Ari Daniel Shapiro explains. Also included is a Learn More section that provides background information on the scientists recorded in the podcast, lessons, images, and cool facts.

2009-01-01

229

mRNA decay in spinach chloroplasts: psbA mRNA degradation is initiated by endonucleolytic cleavages within the coding region.  

PubMed Central

The expression of chloroplast genes during leaf development in higher plants is regulated on several levels as transcription, RNA processing and stability, protein stability and turnover. Differential mRNA stability is one major component which contributes to the developmentally controlled accumulation of higher plant chloroplast psbA mRNA, which encodes the D1 protein of photosystem II. To understand the molecular mechanisms of specific mRNA degradation an in vitro mRNA decay system based on lysed chloroplasts from spinach leaves was established. Employing this degradation extract the decay of psbA mRNA was analyzed. Half-life of the psbA mRNA in vitro is dependent on the degradation conditions as the presence of Mg2+, which was found to stabilize the mRNA. Addition of tRNA stabilizes the mRNA and allows the accumulation of distinct degradation intermediates. psbA mRNA derived fragments of the same size were detected in degradation experiments in vitro, in organello and in vivo. 5' ends of the degradation intermediates were identified by primer extension and found to be localized in the 5' part of the coding region. The data indicate a degradation mechanism involving initiation of psbA mRNA decay by specific endonucleolytic cleavage and subsequent exonucleolytic degradation of the fragments. Possible models for cleavage site recognition are discussed. Images

Klaff, P

1995-01-01

230

Do Leaf Breakdown Rates Actually Measure Leaf Disappearance from Streams?  

Microsoft Academic Search

Abstract Wemeasured leaf input, leaf breakdown, and benthic leaf standing stock in Hugh White Creek, a second-order, Appalachian Mountain stream in North Carolina, U. S. A. Leaf input and leaf breakdown data were used in a ,computer ,model to predict standing stocks. Predicted standing stocks were then compared,with measured,values. Once the model was modified to include leaves in four breakdown,rate

J. R. Webster; E. F. Benfield; J. J. Hutchens; J. L. Tank; S. W. Golladay; J. C. Adams

2001-01-01

231

The wetting of leaf surfaces  

Microsoft Academic Search

Recent advances in the area of the wetting of leaf areas are reviewed with particular emphasis on their relation to agrochemical application. Areas reviewed include leaf wax composition, leaf wetting and superhydrophobicity, agrochemical deposit formation and spray retention. It is thought that most progress has been made in the area of leaf wetting through the work on lotus leaves. In

Philip Taylor

2011-01-01

232

Isolation of a cDNA Clone for Spinach Lipid Transfer Protein and Evidence that the Protein Is Synthesized by the Secretory Pathway 1  

PubMed Central

A cDNA clone encoding a nonspecific lipid transfer protein from spinach (Spinacia oleracea) was isolated by probing a library with synthetic oligonucleotides based on the amino acid sequence of the protein. Determination of the DNA sequence indicated a 354-nucleotide open reading frame which encodes a 118-amino acid residue polypeptide. The first 26 amino acids of the open reading frame, which are not present in the mature protein, have all the characteristics of a signal sequence which is normally associated with the synthesis of membrane proteins or secreted proteins. In vitro transcription of the cDNA and translation in the presence of canine pancreatic microsomes or microsomes from cultured maize endosperm cells indicated that proteolytic processing of the preprotein to the mature form was associated with cotranslational insertion into the microsomal membranes. Because there is no known mechanism by which the polypeptide could be transferred from the microsomal membranes to the cytoplasm, the proposed role of this protein in catalyzing lipid transfer between intracellular membranes is in doubt. Although the lipid transfer protein is one of the most abundant proteins in leaf cells, the results of genomic Southern analysis were consistent with the presence of only one gene. Analysis of the level of mRNA by Northern blotting indicated that the transcript was several-fold more abundant than an actin transcript in leaf and petiole tissue, but was present in roots at less than 1% of the level in petioles. Images Figure 2 Figure 3 Figure 4 Figure 5 Figure 6

Bernhard, Werner R.; Thoma, Sharon; Botella, Jose; Somerville, Chris R.

1991-01-01

233

Electronic Leaf Project  

NSDL National Science Digital Library

This article demonstrates the benefits of a direct application of technology into a science classroom by transferring a traditional activity, such as leaf identification, into an electronic format. The new dynamic medium possesses attributes that can enha

Houston, Carolyn; Hargis, Jace

2000-05-01

234

Leaf Absorbance and Photosynthesis.  

National Technical Information Service (NTIS)

The absorption spectrum of a leaf is often thought to contain some clues to the photosynthetic action spectrum of chlorophyll. Of course, absorption of photons is needed for photosynthesis, but the reverse, photosynthesis when there is absorption, is not ...

K. Schurer

1994-01-01

235

Leaf to Landscape  

Microsoft Academic Search

\\u000a Temporal dynamics and structural complexity of plant canopies strongly affect light harvesting, generating variable spatio-temporal\\u000a distributions of the irradiance on leaf area (Baldocchi and Collineau 1994). Leaf light interception scales linearly with\\u000a incident irradiance, but plant photosynthesis and photomorphogenesis typically exhibit a saturating response to light. Because\\u000a of the inherent nonlinearity in light responses, estimates of the photosynthetic rate at

Alessandro Cescatti; lo Niinemets

236

Leaf to Landscape  

Microsoft Academic Search

\\u000a One fundamental problem for maximizing carbon gain at the leaf and higher organizational levels entails the link between\\u000a light capture and leaf energy budgets. The balance between the two processes, however, depends on the environment. For example,\\u000a shade environments limit carbon gain due to low light levels, and so we would expect plants to display traits that maximize\\u000a light interception

Stanley D. Smith; Elke Naumburg; Lo Niinemets; Matthew J. Germino

237

Deer predation on leaf miners via leaf abscission  

NASA Astrophysics Data System (ADS)

The evergreen oak Quercus gilva Blume sheds leaves containing mines of the leaf miner Stigmella sp. (Lepidoptera: Nepticulidae) earlier than leaves with no mines in early spring in Nara, central Japan. The eclosion rates of the leaf miner in abscised and retained leaves were compared in the laboratory to clarify the effects of leaf abscission on leaf miner survival in the absence of deer. The leaf miner eclosed successfully from both fallen leaves and leaves retained on trees. However, sika deer ( Cervus nippon centralis Kishida) feed on the fallen mined leaves. Field observations showed that deer consume many fallen leaves under Q. gilva trees, suggesting considerable mortality of leaf miners due to deer predation via leaf abscission. This is a previously unreported relationship between a leaf miner and a mammalian herbivore via leaf abscission.

Yamazaki, Kazuo; Sugiura, Shinji

2008-03-01

238

A SPINACH ISOLATE OF COLLETOTRICHUM DEMATIUM FROM THE UNITED STATES AND RISK ASSESSMENT OF C. GLOEOSPORIOIDES FROM RUSSIAN THISTLE IN HUNGARY  

Technology Transfer Automated Retrieval System (TEKTRAN)

An isolate of C. gloeosporioides (Cg) from Hungary is under evaluation for biological control of Russian thistle (Salsola tragus), a major weed pest of the U.S. This pathogen has been found to infect spinach in containment greenhouse studies. To clarify risk to spinach, studies have been initiated...

239

Effect of organic and conventional cropping systems on ascorbic acid, vitamin C, flavonoids, nitrate, and oxalate in 27 varieties of spinach (Spinacia oleracea L.).  

PubMed

This study was undertaken to compare the levels of ascorbic acid, vitamin C, flavonoids, nitrate, and oxalate in 27 spinach varieties grown in certified organic and conventional cropping systems. Liquid chromatography-electrospray ionization-tandem mass spectrometry (LC-(ESI)MS/MS) of methanolic extracts of spinach demonstrated 17 flavonoids, including glucuronides and acylated di- and triglycosides of methylated and methylenedioxyderivatives of 6-oxygenated flavonoids. The mean levels of ascorbic acid and flavonoids were significantly (p < 0.001) higher in the organically grown [40.48 6.16 and 2.83 0.03 mg/kg of fresh weight (FW)] spinach compared to the conventionally grown spinach (25.75 6.12 and 2.27 0.02 mg/kg of FW). Conversely, the mean levels of nitrate were significantly (p < 0.001) higher in the conventionally grown spinach compared to the organically grown spinach. No significant effects were observed in the oxalate content of spinach from either production system. The levels of nitrate correlated negatively with those of ascorbic acid, vitamin C, and total flavonoids and showed a positive correlation with the oxalate content. These results suggest that organic cropping systems result in spinach with lower levels of nitrates and higher levels of flavonoids and ascorbic acid. PMID:22393895

Koh, Eunmi; Charoenprasert, Suthawan; Mitchell, Alyson E

2012-03-20

240

Characterization of a prokaryotic topoisomerase I activity in chloroplast extracts from spinach.  

PubMed

A topoisomerase I activity has been partially purified from crude extracts of spinach chloroplasts. This activity relaxes the supercoiled covalently closed circular DNA of pBR322. The enzyme requires Mg++, but not ATP, and has an apparent molecular weight of about 115,000. It catalyzes a unit change in the linkage number of supercoiled DNA but cannot relax positive supercoiled DNA. These characteristics of the topoisomerase suggest it is of the prokaryotic type and would tend to support the endosymbiotic theory of plastid origin and evolution. PMID:6298746

Siedlecki, J; Zimmermann, W; Weissbach, A

1983-03-11

241

Functional and structural analysis of photosystem II core complexes from spinach with high oxygen evolution capacity  

Microsoft Academic Search

Oxygen-evolving photo system II core complexes were prepared from spinach by solubilizing photosystem II membrane fragments with dodecyl-?-D-maltoside. The core complexes consist of the intrinsic 47-kDa, 43-kDa, D1 and D2 polypeptides, the two subunits of cytochrome b559 and the extrinsic 33-kDa protein. In the presence of 50 mM CaCl2 they exhibit a high oxygen evolution rate of 1.3 0.2

Egbert J. Boekema; Klaus-D. Irrgang; Elisabeth Haag; Gernot Renger

1990-01-01

242

Pendimethalin phytotoxicity and seedling weed control in Indian spinach ( Basella alba L.)  

Microsoft Academic Search

Pot experiments were carried out in a screenhouse to evaluate pendimethalin effectiveness in pre-emergence weed control in Indian spinach (Basella alba L.). In the first trial, pendimethalin was applied at higher doses (0.33, 0.66, 0.99, 1.32, 1.98kgaiha?1), while in the second trial, lower doses (0.066, 0.132, 0.198, 0.264, 0.330kgaiha?1) were used. The treatments were arranged in a completely randomized design

M. A. K Smith

2004-01-01

243

Acetate Binding of Spinach Chloroplasts as a Facet of Fatty Acid Synthesis  

PubMed Central

A particulate fraction of spinach chloroplasts is the major site of binding when either acetate or acetyl-CoA is used as substrate. The acetate is linked covalently, and the binding is inhibited by reagents which react with sulfhydryl groups. The amount of acetate bound is lowered by both citrate and oxaloacetate; however, the binding is not reversed by oxaloacetate. Reversal of binding is also not brought about by the addition of unlabeled acetyl-CoA. If cofactors for fatty acid synthesis and cold acetyl-CoA are added, the binding of labeled acetate is reversed. Acyl carrier protein from E. coli increases the binding of labeled acetate.

Devor, K. A.; Mudd, J. B.

1968-01-01

244

Quantification of L-ascorbic acid and total ascorbic acid in fruits and spinach by capillary zone electrophoresis.  

PubMed

A standard curve for the quantification of L-ascorbic acid (L-AA) by capillary zone electrophoresis (CZE) was established, and the quantification of ascorbic acid and total ascorbic acid in fruits (lemon, Sunkist, and pineapple) and spinach were performed using D-isoascorbic acid (D-IAA) as an internal standard. The minimum detection limits (MDLs) for L-AA and D-IAA were determined to be 1 and 2 microg/mL, respectively, at 265 nm. Dehydroascorbic acid (DHAA) in fruits and spinach was quantified in the presence of DL-homocysteine. The recoveries for L-AA in these juices were between 95 and 105%. PMID:11386660

Liao, T; Jiang, C M; Wu, M C; Hwang, J Y; Chang, H M

2001-05-01

245

Buffer Capacities of Leaves, Leaf Cells, and Leaf Cell Organelles in Relation to Fluxes of Potentially Acidic Gases 1  

PubMed Central

Since environmental pollution by potentially acidic gases such as SO2 causes proton release inside leaf tissues, homogenates of needles of spruce (Picea abies) and fir (Abies alba) and of leaves of spinach (Spinacia oleracea) and barley (Hordeum vulgare) were titrated and buffer capacities were determined as a function of pH. Titration curves of barley leaves were compared with titration curves of barley mesophyll protoplasts. From the protoplasts, chloroplasts and vacuoles were isolated and subjected to titration experiments. From the titration curves, the intracellular distribution of buffering capacities could be deduced. Buffering was strongly pH-dependent. It was high at the extremes of pH but still significant close to neutrality. Owing to its large size, the vacuole was mainly responsible for cellular buffering. However, on a unit volume basis, the cytoplasm was much more strongly buffered than the vacuole. Potentially acidic gases are trapped in the anionic form. They release protons when trapped. The magnitude of diffusion gradients from the atmosphere into the cells, which determines flux, depends on intracellular pH. In the light, the chloroplast stroma, as the most alkaline leaf compartment, has the highest trapping potential. Acidification of the chloroplast stroma inhibits photosynthesis. The trapping potential of the chloroplast is followed by that of the cytosol. Compared with the cytoplasm, the vacuole possesses little trapping potential in spite of its large size. It is particularly small in the acidic vacuoles of conifer needles. In the physiological pH range (slightly above neutrality), chloroplast buffering was about 1 microequivalents H+ per milligram chlorophyll per pH unit or 35 microequivalents H+ per milliliter per pH unit in barley or spinach chloroplasts. This compares with SO2-generated H+ production of somewhat more than 1 microequivalent H+ per milligram chlorophyll per hour, which results from observed SO2 uptake of leaves when stomata were open and the atmospheric SO2 concentration was 0.4 microliters per liter (GE Taylor Jr, DT Tingey 1983 Plant Physiol 72: 237-244). At lower SO2 concentrations, similar H+ generation inside the cells requires correspondingly longer exposure times.

Pfanz, Hardy; Heber, Ulrich

1986-01-01

246

Cleared Leaf Collection  

NSDL National Science Digital Library

The University of California-Berkeley Museum of Paleontology has recently launched this online database of the Daniel I. Axelrod and the Berkeley leaf collections, which contain over 2000 modern leaf specimens bleached and stained to make their venation patterns more visible. Data records for both collections are now online, and images (including a higher resolution mode) will eventually become available for each specimen beginning with those in the Axelrod collection. Using the database is somewhat tricky, but a detailed help page is provided.

247

Effects of Pb 2+ on energy distribution and photochemical activity of spinach chloroplast  

NASA Astrophysics Data System (ADS)

Lead (Pb 2+) is a well-known highly toxic element. The mechanisms of the Pb 2+ toxicity are not well understood for photosynthesis. In this paper, we reported the effect of Pb 2+ on light absorption, distribution and conversion of spinach chloroplast by spectroscopy, and photochemical reaction activities. Several effects of Pb 2+ were observed: (1) the absorption peak intensity of chloroplast obviously decreased in red and blue region and produced optical flattering; (2) fluorescence quantum yield nearby 680 nm of chloroplast greatly declined; (3) the excitation band nearby 440 nm of chloroplast significantly descended; (4) Pb 2+ treatments reduced of the rate of whole chain electron transport, photochemical activities of PSII DCPIP photoreduction and oxygen evolution, but the photoreduction activities of PSI were little changed. Together, the studies of the experiments showed that Pb 2+ decreased absorption of light on spinach chloroplast and inhibited excitation energy to be absorbed by LHCII and transferred to PSII, then reduced the conversion from light energy to electron energy, and decelerated electron transport, water photolysis and oxygen evolution.

Wu, Xiao; Hong, Fashui; Liu, Chao; Su, Mingyu; Zheng, Lei; Gao, Fengqing; Yang, Fan

2008-03-01

248

Low Temperature STM Manipulation and Spectroscopy of Chlorophyll-a Single Molecules from Spinach  

NASA Astrophysics Data System (ADS)

We interrogate single chlorophyll-a, a molecule produced from Spinach, on Cu(111) surface to check its mechanical stability and electronic properties using an ultra-high-vacuum low-temperature scanning-tunneling-microscope (UHV-LT-STM) at liquid helium temperatures. The measured results of isolated single chlorophyll-a molecules are then compared with that of self-assembled molecular layer. The tunneling I/V and dI/dV spectroscopy techniques are used to probe the electronic properties of the chlorophyll-a molecule with atomic precision (1). These spectroscopic investigations elucidate properties of the single molecule such as the band gap and additional molecular orbital states. Mechanical stability of the chlorophyll-a molecule is examined using lateral manipulation techniques with the STM tip (2). In this procedure, the STM tip is placed in close proximity to the molecule (just a few angstrom separation) to increase the tip-molecule interaction. Then the tip is laterally moved across the surface, which results in pulling of the chlorophyll-a molecule to relocate to the specific surface sites. The detailed molecule movement during this manipulation is directly monitored through the corresponding STM-tip height signals. Our results highlight that the Spinach molecule is a promising candidate for environmental friendly nano-electronic device applications. (1) F. Moresco et al, Phy. Rev. Lett. 86, 672-675, (2001) (2) S-W. Hla, K-H. Rieder, Ann. Phy. Chem. 54, 307-330, (2003)

Benson, Jessica J.; Iancu, Violeta; Deshpande, Aparna; Hla, Saw-Wai

2004-04-01

249

Single Molecule Manipulation and Spectroscopy of Chlorophyll-a from Spinach  

NASA Astrophysics Data System (ADS)

Chlorophyll-a, a molecule produced from `Spinach', adsorbed on a Au(111) surface has been investigated by using an ultra-high-vacuum low-temperature scanning-tunneling-microscope (UHV-LT-STM) at liquid helium temperatures. Studies are carried out both on isolated single molecules and on self-assembled molecular layers. The tunneling I-V and dI-dV spectroscopy of chlorophyll-a elucidate electronic properties of single molecule, such as the HOMO-LOMO gap and molecular orbital states. Mechanical stability of the chlorophyll-a is examined by using STM lateral manipulation (1,2). Here, the STM tip is placed just a few angstrom separation from the molecule to increase the tip-molecule interaction. Then the tip is laterally scanned across the surface resulting in pulling of the molecule. The detailed molecule movement is directly monitored through the corresponding STM-tip height signals. Our results reveal that the spinach molecule is a promising candidate for environmental friendly nano-device applications. (1). S.-W. Hla, K.-H. Rieder, Ann. Rev. Phys. Chem. 54 (2003) 307-330. (2). S.-W. Hla, et al. Phys. Rev. Lett. 93 (2004), 208302. This work is financially supported by the US-DOE grant DE-FG02-02ER46012.

Benson, Jessica-Jones

2005-03-01

250

Active site histidine in spinach ribulosebisphosphate carboxylase/oxygenase modified by diethyl pyrocarbonate  

SciTech Connect

(TH) Diethyl pyrocarbonate was synthesized from (TH) ethanol prepared by the reduction of acetaldehyde by NaB3H4. Ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBisCO) from spinach was inactivated with this reagent at pH 7.0 the presence of 20 mM MgS , and tryptic peptides that contained modified histidine residues were isolated by reverse-phase high-performance liquid chromatography. Labeling of the enzyme was conducted in the presence and absence of the competitive inhibitor sedoheptulose 1,7-bisphosphate. The amount of one peptide that was heavily labeled in the absence of this compound was reduced 10-fold in its presence. The labeled residue was histidine-298. This result, in combination with earlier experiments, suggests that His-298 in spinach RuBisCO is located in the active site domain and is essential to enzyme activity. This region of the primary structure is strongly conserved in seven other ribulosebisphosphate carboxylases from divergent sources.

Igarashi, Y.; McFadden, B.A.; el-Gul, T.

1985-07-16

251

Solution Structures of Spinach Acyl Carrier Protein with Decanoate and Stearate  

PubMed Central

Acyl carrier protein (ACP) is a cofactor in a variety of biosynthetic pathways, including fatty acid metabolism. Thus it is of interest to determine structures of physiologically relevant ACP-fatty acid complexes. We report here the NMR solution structures of spinach ACP with decanoate (10:0-ACP) and stearate (18:0-ACP) attached to the 4? phosphopantetheine prosthetic group. The protein in the fatty acid complexes adopts a single conformer, unlike apo- and holo-ACP, which interconvert in solution between two major conformers. The protein component of both 10:0- and 18:0-ACP adopts the four-helix bundle topology characteristic of ACP, and a fatty acid binding cavity was identified in both structures. Portions of the protein close in space to the fatty acid and the 4? phosphopantetheine were identified using filtered/edited NOESY experiments. A docking protocol was used to generate protein structures containing bound fatty acid for 10:0- and 18:0-ACP. In both cases, the predominant structure contained fatty acid bound down the center of the helical bundle, in agreement with the location of the fatty acid binding pockets. These structures demonstrate the conformational flexibility of spinach-ACP and suggest how the protein changes to accommodate its myriad binding partners.

Zornetzer, Gregory A.; Fox, Brian G.; Markley, John L.

2008-01-01

252

Effects of Mg 2+on spectral characteristics and photosynthetic functions of spinach photosystem II  

NASA Astrophysics Data System (ADS)

In the present paper we report the results obtained with the photosystem II (PSII) isolated from spinach treated by MgCl 2, and studied the effect of Mg 2+ on spectral characteristics and photosynthetic functions of PSII. The results showed that Mg 2+ treatment at a suitable concentration could significantly increase the absorption intensity of PSII and the intensity ratio of Soret band to Q band of chlorophyll-a. The treatment also elevated the excited peak intensity at 230, 278 and 343 nm, and the emitted peak intensity at 304 and 682 nm, and the ratio of F278/ F230, respectively. The results implied that Mg 2+ increased absorbance for visible light, improving energy transfer among amino acids within PSII protein complex and accelerating energy transport from tyrosine residue to chlorophyll-a. The photochemical activity and oxygen evolving rate of PSII were also enhanced by Mg 2+. This is viewed as evidence that Mg 2+ can promote energy transfer and oxygen evolution in PSII of spinach.

Liang, Chen; Xiao, Wu; Hao, Huang; Xiaoqing, Liu; Chao, Liu; Lei, Zheng; Fashui, Hong

2009-03-01

253

Oral administration of monogalactosyl diacylglycerol from spinach inhibits colon tumor growth in mice.  

PubMed

Previously, we observed that purified monogalactosyl diacylglycerol (MGDG), a major glycoglycerolipid from spinach, selectively inhibits the activities of mammalian replicative DNA polymerases (?, ? and ?). However, the function of MGDG following ingestion is not well-known. In the present study, spinach MGDG suppressed the proliferation of Colon26 mouse colon cancer cells with an LD(50) of 24 ?g/ml in vitro. ?-cyclodextrin (CD)-MGDG complex was prepared and administered orally following Colon26 mouse tumor adhesion for 26 days. It was observed that 20 mg/kg equivalent (eq.) of the CD-MGDG complex reduced tumor volume by ?60% compared with that of the vehicle-treated controls. In immunohistochemical analysis, the CD-MGDG complex group showed a decreased number of proliferating cell nuclear antigen (PCNA)-positive cells and reduction of mitosis in the tumor cells compared with the control group. In addition, the CD-MGDG complex increased the number of terminal deoxynucleotidyl transferase dUTP nick-end labeling (TUNEL)-positive apoptotic cells and inhibited CD31-positive tumor blood vessel growth significantly. These results suggest that MGDG has the potential for cancer prevention and health promotion. PMID:23251235

Maeda, Naoki; Kokai, Yasuo; Hada, Takahiko; Yoshida, Hiromi; Mizushina, Yoshiyuki

2012-11-01

254

Ribosomes pause during the expression of the large ATP synthase gene cluster in spinach chloroplasts.  

PubMed Central

The large ATP synthase gene cluster from spinach (Spinacia oleracea) chloroplasts encodes five genes, the last four of which encode subunits of the ATP synthase complex. In preliminary experiments (J.K. Kim, M.J. Hollingsworth [1992] Anal Biochem 206: 183-188) it was shown that ribosomes pause during translation of these open reading frames. We have examined ribosome pausing in the four ATP synthase open reading frames of this gene cluster to determine whether it could affect the final ratio of the ATP synthase polypeptides derived from the cluster. Ribosome pauses were mapped and found to be distributed in a nonuniform manner. We have quantitated the relative extent of ribosome pausing within each open reading frame. There is a general but not absolute correlation between the extent of ribosomal pausing and the protein levels found within the ATP synthase complex. We conclude that although it is not the sole factor, ribosome pausing may be a significant posttranscriptional mechanism affecting the expression of the large ATP synthase gene cluster in spinach chloroplasts.

Stollar, N E; Kim, J K; Hollingsworth, M J

1994-01-01

255

Ramularia Leaf Spot  

Technology Transfer Automated Retrieval System (TEKTRAN)

Ramularia leaf spot of sugar beet, a disease caused by Ramularia beticola, is a sporadic problem in the United States, particularly in seed production. It is a more common problem in parts of Europe. Symptoms include light brown, angular spots on the leaves and can cause death of leaves. Epidemiol...

256

Leaf area index measurements  

Microsoft Academic Search

Leaf area index (LAI) is a key structural characteristic of forest ecosystems because of the role of green leaves in controlling many biological and physical processes in plant canopies. Accurate LA1 estimates are required in studies of ecophysiology , atmosphere-ecosystem interactions, and global change. The objective of this paper is to evaluate LA1 values obtained by several research teams using

Jing M. Chen; Paul Steven Plummer; M. Rich; Stith T. Gower; John M. Norman

1997-01-01

257

Effect of Nd3+ ion on carboxylation activity of ribulose-1,5-bisphosphate carboxylase/oxygenase of spinach.  

PubMed

Neodymium (Nd), as a member of rare earth elements, proved to enhance the photosynthesis rate and organic substance accumulation of spinach through the increase in carboxylation activity of Rubisco. Although the oxygenase activity of spinach Rubisco was slightly changed with the Nd(3+) treatment, the specific factor of Rubisco was greatly increased. It was partially due to the promotion of Rubisco activase (R-A) activity but mainly to the formation of Rubisco-Rubisco activase super-complex, a heavier molecular mass protein (about 1200kD) comprising both Rubisco and Rubisco activase. This super-complex was found during the extraction procedure of Rubisco by the gel electrophoresis and Western-blot studies. The formation of Rubisco-R-A super-complex suggested that the secondary structure of the protein purified from the Nd(3+)-treated spinach was different from that of the control. Extended X-ray absorption fine structure study of the 'Rubisco' purified from the Nd(3+)-treated spinach revealed that Nd was bound with four oxygen atoms and two sulfur atoms of amino acid residues at the Nd-O and Nd-S bond lengths of 2.46 and 2.89A, respectively. PMID:16469293

Liu, Chao; Hong, Fa-shui; Wu, Kang; Ma, Hong-bing; Zhang, Xue-guang; Hong, Cheng-jiao; Wu, Cheng; Gao, Feng-qing; Yang, Fan; Zheng, Lei; Wang, Xue-feng; Liu, Tao; Xie, Ya-ning; Xu, Jian-hua; Li, Zhong-rui

2006-02-02

258

VITAMIN A VALUE OF SPINACH AND CARROTS AS ASSESSED USING A STABLE ISOTOPE REFERENCE METHOD IN ADULTS  

Technology Transfer Automated Retrieval System (TEKTRAN)

In order to understand the biological effects of beta-carotene (beta-carotene) in food sources, a stable isotope method was used to investigate the serum response to food provitamin A carotenoids and its conversion to vitamin A. Well- nourished adults were fed spinach and carrots that were hydroponi...

259

Effect of surface characteristics on retention and removal of Escherichia coli O157:H7 on surfaces of spinach  

Technology Transfer Automated Retrieval System (TEKTRAN)

The topography and the spatial heterogeneity of produce surfaces may impact the attachment of microbial cells onto produce surfaces and affect disinfection efficacy. In this study, the effects of produce surface characteristics on the removal of bacteria were studied. Fresh spinach leaves were sp...

260

Comparative survival of Escherichia coli O157:H7, Salmonella Typhimurium, and Murine Norovirus on spinach plants  

Technology Transfer Automated Retrieval System (TEKTRAN)

Introduction: Outbreaks resulting from the consumption of leafy greens contaminated with E. coli O157:H7, Salmonella spp., and norovirus have occurred. It is unclear how the stress response factor rpoS in E. coli O157:H7 and Salmonella spp. affects their survival on spinach. Purpose: A comparison ...

261

Effect of home processing on ascorbic acid and ?-carotene content of spinach ( Spinacia oleracia ) and amaranth ( Amaranthus tricolor ) leaves  

Microsoft Academic Search

The present investigation was conducted to study the concentration of ascorbic acid and -carotene in spinach and amaranth leaves as affected by various domestic processing and cooking methods which included storage of leaves in polythene bags or without packing for 24 and 48 hours in refrigerator at 5 C; at 30 C in polythene bags; drying (sun and oven); blanching

Shashi Kala Yadav; Salil Sehgal

1995-01-01

262

Comparison of Photosynthetic Electron Transport Activities of Spinach Chloroplasts with Those of Corn Mesophyll and Corn Bundle Sheath Tissue.  

National Technical Information Service (NTIS)

Rates of oxygen evolution and electron transport from water and DAD to viologen were comparable for both bundle sheath and mesophyll corn chloroplasts, but these activities were approximately one-third to one-half of the ratio observed for spinach chlorop...

H. Hardt B. Kok

1977-01-01

263

Escherichia coli O157:H7 in feral swine near spinach fields and cattle, central California coast.  

PubMed

We investigated involvement of feral swine in contamination of agricultural fields and surface waterways with Escherichia coli O157:H7 after a nationwide outbreak traced to bagged spinach from California. Isolates from feral swine, cattle, surface water, sediment, and soil at 1 ranch were matched to the outbreak strain. PMID:18258044

Jay, Michele T; Cooley, Michael; Carychao, Diana; Wiscomb, Gerald W; Sweitzer, Richard A; Crawford-Miksza, Leta; Farrar, Jeff A; Lau, David K; O'Connell, Janice; Millington, Anne; Asmundson, Roderick V; Atwill, Edward R; Mandrell, Robert E

2007-12-01

264

Effect of peroxyacetyl nitrate on C¹⁴O fixation by spinach chloroplasts and pinto bean plants  

Microsoft Academic Search

Photosynthetic CO fixation in pinto bean plants and in intact spinach chloroplasts was inhibited by peroxyacetyl nitrate, a component of photochemical smog. Addition of ascorbate to the chloroplast-containing reaction mixtures virtually eliminated this inhibition. Exposing the chloroplasts or other components of the reaction, either separately or as a mixture, to peroxyacetyl nitrate in the dark followed by a light period

W. M. Jr. Dugger; J. Koukol; W. D. Reed; R. L. Palmer

1963-01-01

265

Ca 2+ depletion modifies the electron transfer on both donor and acceptor sides in Photosystem II from spinach  

Microsoft Academic Search

Ca2+ depletion of Photosystem II from spinach results in reversible retardation of electron transfer on both donor and acceptor sides. On the donor side, a decrease of the electron transfer rate from TyrZ results in an enhanced charge recombination between the oxidized primary donor, P680+, and the reduced acceptor quinone, QA?, which in turn leads to a decrease in the

Lars-Erik Andrasson; Imre Vass; Stenbjrn Styring

1995-01-01

266

Coaction of light, nitrate and a plastidic factor in controlling nitrite-reductase gene expression in spinach  

Microsoft Academic Search

It is well established that nitrite reductase (NIR; EC 1.7.7.1) a key enzyme of nitrate reduction is induced by nitrate and light. In the present study with the spinach (Spinacia oleracea L.) seedling the dependency of NIR appearance on nitrate, light and a plastidic factor was investigated to establish the nature of the coaction between these controlling factors. A

B. Seith; C. Schuster; H. Mohr

1991-01-01

267

Characterization of the cultivable microbial community in a spinach-processing plant using MALDI-TOF MS.  

PubMed

A better and regular control of the production chain of fresh fruits and vegetables is necessary, because a contamination of the product by human- and phyto-pathogenic microorganisms may result in high losses during storage and poses a threat to human health. Therefore, detailed knowledge about the occurrence and the diversity of microorganisms within single processing steps is required to allow target-oriented produce safety control. Recently, matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) was successfully used to identify bacterial colonies. Bacteria can be identified with high accuracy by comparing them with generated spectra of a reference database. In this study, spinach and wash water samples were taken of the complete process line of a spinach-washing plant. Bacteria in the samples were grown on plate-count, Arcobacter selective, marine and blood agar. In total, 451 colonies were evaluated by MALDI-TOF MS, 16S rRNA gene sequence and phylogenetic analysis. 50% of the detected species belonged to the class of Gammaproteobacteria. Firmicutes were present with 22%. Mostly, the detected species showed 16S rRNA gene sequence dissimilarities larger than 1% to known reference species and, hence, could not be assigned to a distinct species. However, many isolated species belonged to genera which contain pathogenic or opportunistic pathogenic bacteria. In addition, the bacterial diversity on the spinach surface increased after the first washing step indicating a process-borne contamination of the spinach. PMID:23541209

Hausdorf, Lena; Mundt, Kerstin; Winzer, Michaela; Cordes, Christiana; Frhling, Antje; Schlter, Oliver; Klocke, Michael

2012-11-07

268

INFLUENCE OF DIFFERENT EXTRACTION CONDITIONS AND SAMPLE PRETREATMENTS ON QUANTIFICATION OF NITRATE AND NITRITE IN SPINACH AND LETTUCE  

Microsoft Academic Search

Different sample pretreatment and extraction techniques are often used for analysis of nitrates and nitrites, however, the effects of these variables have not been properly examined. Comparative investigations were carried out with the objective of finding the most suitable conditions for quantification of nitrate and nitrite in spinach and lettuce. A rapid and cost effective RP-HPLC\\/UV method was validated and

Edgar Pinto; Catarina Petisca; Lus F. Amaro; Olvia Pinho; Isabel M. P. L. V. O. Ferreira

2010-01-01

269

Effects of High Temperature Exposure of Spinach Intact Plants and Isolated Thylakoids on Light-Harvesting Complex 2 Protein Phosphorylation  

Microsoft Academic Search

After a 6 min exposure of isolated thylakoids to 43 C, the extent of phosphorylation of light-harvesting complex of photosystem 2 (LHC2) was higher than in control thylakoids kept at 25 C. Similarly, the exposure of intact spinach plants to 43 C in dark for 11 h induced higher extent of thylakoid LHC2 phosphorylation than in control plants kept at

M. Satpathy; P. Mohanty

2000-01-01

270

Chloroplast fructose 1,6-bisphosphatase with changed redox modulation: comparison of the Galdieria enzyme with cysteine mutants from spinach.  

PubMed

Spinach fructose 1,6-bisphosphatase (FBPase, EC 3.1.3.11), a redox-modulated chloroplast enzyme and part of the Calvin cycle, and three different Cys mutants were expressed in E. coli. The properties of the purified proteins were compared to those of native and recombinant chloroplast FBPase from the red alga Galdieria sulphuraria. In spinach chloroplast FBPase, Cys(155) and Cys(174) are engaged in the formation of the disulfide bridge. The corresponding mutants are active when expressed in E. coli, while C179S is inactive and can be reductively activated as can the wild-type enzyme. The active C174S mutant, however, could be inactivated by oxidation, and reactivated, but only by reduction, not alternatively with high pH and high Mg(2+) as is the case for the wild-type enzyme. In the sequence of Galdieria FBPase, the Cys that corresponds to Cys(179) in the spinach enzyme is lacking. However, the Galdieria FBPase, in contrast to the spinach Cys(179) mutant, does not show any indication for a comparable redox modulation of its activity. Instead, oxidation only leads to partial inactivation without any qualitative changes in enzyme properties. Upon reduction, the lost activity can be recovered. PMID:12573251

Reichert, Angelika; Dennes, Andr; Vetter, Susanne; Scheibe, Renate

2003-02-21

271

Effect of lead stress on mineral content and growth of wheat (Triticum aestivum) and spinach (Spinacia oleracea) seedlings.  

PubMed

Lead (Pb) is the most common heavy metal contaminant in the environment. Pb is not an essential element for plants, but they absorb it when it is present in their environment, especially in rural areas when the soil is polluted by automotive exhaust and in fields contaminated with fertilizers containing heavy metal impurities. To investigate lead effects on nutrient uptake and metabolism, two plant species, spinach (Spinacia oleracea) and wheat (Triticum aestivum), were grown under hydroponic conditions and stressed with lead nitrate, Pb(NO3)2, at three concentrations (1.5, 3, and 15mM). Lead is accumulated in a dose-dependent manner in both plant species, which results in reduced growth and lower uptake of all mineral ions tested. Total amounts and concentrations of most mineral ions (Na, K, Ca, P, Mg, Fe, Cu and Zn) are reduced, although Mn concentrations are increased, as its uptake is reduced less relative to the whole plant's growth. The deficiency of mineral nutrients correlates in a strong decrease in the contents of chlorophylls a and b and proline in both species, but these effects are less pronounced in spinach than in wheat. By contrast, the effects of lead on soluble proteins differ between species; they are reduced in wheat at all lead concentrations, whereas they are increased in spinach, where their value peaks at 3mM Pb. The relative lead uptake by spinach and wheat, and the different susceptibility of these two species to lead treatment are discussed. PMID:23961216

Lamhamdi, Mostafa; El Galiou, Ouiam; Bakrim, Ahmed; Nvoa-Muoz, Juan Carlos; Arias-Estvez, Manuel; Aarab, Ahmed; Lafont, Ren

2012-09-08

272

The chlorophyll aII reaction in trypsin-treated spinach chloroplasts in the presence of potassium ferricyanide.  

PubMed

In trypsin-treated spinach chloroplasts there is no linear electron flow from water to potassium ferricyanide. The chlorophyll aII reaction, however, is still active but insensitive to 3-(3, 4-dichlorophenyl)-1, 1-dimethylurea. From this we conclude that ferricyanide and trypsin together stimulate a mini-cycle in photosystem II. PMID:132043

Dring, G

273

Distinct transcriptional profiles and phenotypes exhibited by Escherichia coli O157:H7 isolates related to the 2006 spinach-associated outbreak.  

PubMed

In 2006, a large outbreak of Escherichia coli O157:H7 was linked to the consumption of ready-to-eat bagged baby spinach in the United States. The likely sources of preharvest spinach contamination were soil and water that became contaminated via cattle or feral pigs in the proximity of the spinach fields. In this study, we compared the transcriptional profiles of 12 E. coli O157:H7 isolates that possess the same two-enzyme pulsed-field gel electrophoresis (PFGE) profile and are related temporally or geographically to the above outbreak. These E. coli O157:H7 isolates included three clinical isolates, five isolates from separate bags of spinach, and single isolates from pasture soil, river water, cow feces, and a feral pig. The three clinical isolates and two spinach bag isolates grown in cultures to stationary phase showed decreased expression of many ?(S)-regulated genes, including gadA, osmE, osmY, and katE, compared with the soil, water, cow, feral pig, and the other three spinach bag isolates. The decreased expression of these ?(S)-regulated genes was correlated with the decreased resistance of the isolates to acid stress, osmotic stress, and oxidative stress but increases in scavenging ability. We also observed that intraisolate variability was much more pronounced among the clinical and spinach isolates than among the environmental isolates. Together, the transcriptional and phenotypic differences of the spinach outbreak isolates of E. coli O157:H7 support the hypothesis that some variants within the spinach bag retained characteristics of the preharvest isolates, whereas other variants with altered gene expression and phenotypes infected the human host. PMID:22081562

Parker, Craig T; Kyle, Jennifer L; Huynh, Steven; Carter, Michelle Q; Brandl, Maria T; Mandrell, Robert E

2011-11-11

274

Distinct Transcriptional Profiles and Phenotypes Exhibited by Escherichia coli O157:H7 Isolates Related to the 2006 Spinach-Associated Outbreak  

PubMed Central

In 2006, a large outbreak of Escherichia coli O157:H7 was linked to the consumption of ready-to-eat bagged baby spinach in the United States. The likely sources of preharvest spinach contamination were soil and water that became contaminated via cattle or feral pigs in the proximity of the spinach fields. In this study, we compared the transcriptional profiles of 12 E. coli O157:H7 isolates that possess the same two-enzyme pulsed-field gel electrophoresis (PFGE) profile and are related temporally or geographically to the above outbreak. These E. coli O157:H7 isolates included three clinical isolates, five isolates from separate bags of spinach, and single isolates from pasture soil, river water, cow feces, and a feral pig. The three clinical isolates and two spinach bag isolates grown in cultures to stationary phase showed decreased expression of many ?S-regulated genes, including gadA, osmE, osmY, and katE, compared with the soil, water, cow, feral pig, and the other three spinach bag isolates. The decreased expression of these ?S-regulated genes was correlated with the decreased resistance of the isolates to acid stress, osmotic stress, and oxidative stress but increases in scavenging ability. We also observed that intraisolate variability was much more pronounced among the clinical and spinach isolates than among the environmental isolates. Together, the transcriptional and phenotypic differences of the spinach outbreak isolates of E. coli O157:H7 support the hypothesis that some variants within the spinach bag retained characteristics of the preharvest isolates, whereas other variants with altered gene expression and phenotypes infected the human host.

Kyle, Jennifer L.; Huynh, Steven; Carter, Michelle Q.; Brandl, Maria T.; Mandrell, Robert E.

2012-01-01

275

Effect of home processing on total and extractable calcium and zinc content of spinach (Spinach oleracia) and amaranth (Amaranthus tricolor) leaves.  

PubMed

Spinach (Spinacia oleracia) and amaranth (Amaranthus tricolor) leaves were stored in polyethylene bags and without packing for 24 and 48 hours in a refrigerator at 5 and 30 degrees C in polyethylene bags. The fresh leaves were also dried (oven and sun); blanched (5, 10 and 15 min) and cooked in an open pan and a pressure cooker. The processed leaves were analysed for total and extractable calcium and zinc content. The Ca and Zn content of these leaves varied from 1320 to 2120 and 11.70 to 12.60 mg/100 g DM and the percentage HCl-extractability was 77.82 to 81.92 and 85.16 to 86.15, respectively. No significant effects of drying and storage were observed on total Ca and Zn content and HCl-extractability while blanching and cooking resulted in significant improvement of HCl-extractability of these two minerals. Thus, cooking and blanching are good ways to improve the HCl-extractability of Ca and Zn. PMID:8719740

Yadav, S K; Sehgal, S

1995-07-01

276

Microbial quality of bagged baby spinach and romaine lettuce: effects of top versus bottom sampling.  

PubMed

Contamination with Escherichia coli O157:H7 and Salmonella have called into question the safety and microbial quality of bagged ready-to-eat leafy greens. This study expands on previous findings that these goods have high total bacteria counts (TBC) and coliform counts, variation in counts among different lots, that Escherichia coli is present, and disparities in counts when bags are top or bottom sampled. Nearly 100 bags of baby spinach and hearts of romaine lettuce from a single brand were subjected to both top and bottom sampling. Product was blended, and a portion serially diluted and plated to obtain TBC. Total coliform and E. coli levels were estimated by the most-probable-number (MPN) technique with ColiComplete discs. Top-sampled TBC from bags of baby spinach (48 bags, 13 different lots) ranged from 3.9 to 8.1 log CFU/g and bottom-sampled TBC ranged from 4.0 to 8.2 log CFU/g, with 52% of the bags (or 39% of the lots) producing TBC higher in bottom samples. For hearts of romaine (47 bags from 19 different lots), top-sampled bags had TBC ranging from 2.4 to 7.0 log, and bottom-sampled bags had TBC from 3.3 to 7.3 log, with 64% of the bags (or 63% of the lots) showing higher TBC in bottom samples. However, we are unable to reject the hypothesis that the top and bottom samples from either commodity contain the same TBC (P ? 0.08). No E. coli was detected and total coliform bacteria counts were, with few exceptions, ?210 MPN/g, irrespective of TBC. In general, lots with the most number of days before the printed "use-by" date had lower TBC. However, the R(2) values for either baby spinach (0.4085) or hearts of romaine (0.2946) suggest that age might not be a very good predictor of higher TBC. TBC varied widely between lots and even more so within same-lot samples, as indicated by the sum of squares results. This finding, along with higher TBC in bottom samples, suggests further consideration when a microbiological sampling scheme of bagged produce is designed. PMID:22221365

Kase, Julie A; Borenstein, Stacey; Blodgett, Robert J; Feng, Peter C H

2012-01-01

277

Subcellular Localization of the Starch Degradative and Biosynthetic Enzymes of Spinach Leaves 1  

PubMed Central

The subcellular localization of the starch biosynthetic and degradative enzymes of spinach leaves was carried out by measuring the distribution of the enzymes in a crude chloroplast pellet and soluble protein fraction, and by the separation on sucrose density gradients of intact organelles, chloroplasts, peroxisomes, and mitochondria of a protoplast lysate. ADP-Glucose pyrophosphorylase, starch synthase, and starch-branching enzymes are quantitatively associated with the chloroplasts. The starch degradative enzymes amylase, R-enzyme (debranching activity), phosphorylase, and D-enzyme (transglycosylase) are observed both in the chloroplast and soluble protein fractions, the bulk of the degradative enzyme activities reside in the latter fraction. Chromatography of a chloroplast extract on diethylaminoethyl-cellulose resolves the R- and D-enzymes from amylase and phosphorylase activities although the two latter enzyme activities coeluted. The digestion pattern of amylase with amylopectin as a substrate indicates an endolytic activity but displays properties unlike the typical ?-amylase as isolated from endosperm tissue. Images

Okita, Thomas W.; Greenberg, Elaine; Kuhn, David N.; Preiss, Jack

1979-01-01

278

Fast isolation of highly active photosystem II core complexes from spinach.  

PubMed

Purification of photosystem II (PSII) core complexes is a time-consuming and low-efficiency process. In order to isolate pure and active PSII core complexes in large amounts, we have developed a fast method to isolate highly active monomeric and dimeric PSII core complexes from spinach leaves by using sucrose gradient ultracentrifugation. By using a vertical rotor the process was completed significantly faster compared with a swing-out rotor. In order to keep the core complexes in high activity, the whole isolation procedure was performed in the presence of glycine betain and pH at 6.3. The isolated pigment-protein complexes were characterized by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, absorption spectroscopy, 77 K fluorescence spectroscopy and high performance liquid chromatography. Our results show that this method is a better choice for quick and efficient isolation of functionally active PSII core complexes. PMID:20738723

Wang, Zhao-Gai; Xu, Tian-Hua; Liu, Cheng; Yang, Chun-Hong

2010-09-01

279

Electron spin resonance studies of urea-ferricyanide inactivated spinach photosystem I particles  

SciTech Connect

The photosystem I acceptor system of a subchloroplast particle from spinach was investigated by optical and electron spin resonance (ESR) spectroscopy following graduated inactivation of the bound iron-sulfur proteins by urea-ferricyanide. The chemical analysis of iron and sulfur and the ESR properties of centers A, B, and X are consistent with the participation of three iron-sulfur centers in photosystem I. A differential decrease in centers A, B, and X is observed under conditions which induce S= ..-->.. S/sup 0/ conversion in the bound iron-sulfur proteins. Center B is shown to be the most susceptible, while center X is the least susceptible component to oxidative denaturation. Stepwise inactivation experiments suggest that electron transport in photosystem I does not occur sequentially from X ..-->.. B ..-->.. A since there is quantitative photoreduction of center A in the absence of center B. We propose that center A is directly reduced by X.

Golbeck, J.H.; Warden, J.T.

1981-09-01

280

Temperature dependent steady state and picosecond kinetic fluorescence measurements of a photosystem I preparation from spinach  

SciTech Connect

The fluorescence properties of a photosystem I (PSI) preparation from spinach containing approximately 200 chlorophyll (Chl) per reaction center were investigated. The preparation, characterized both spectroscopically and biochemically, contained the peripheral light harvesting antenna associated with PSI. In this study steady state fluorescence measurements were performed as a function of temperature. An emission maximum at 690 nm and a long wavelength shoulder from 710 to 740 nm were observed. The fluorescence yield at 690 nm is temperature independent, while the yield of the long wavelength shoulder increases dramatically with decreasing temperature. Additionally, kinetic measurements using the technique of single photon counting were done at room temperature and 77K. At 295K a four component fit was needed to describe the fluorescence decay; whereas at 77K, an additional 40-50 ps rise component indicative of fluorescence induction was necessary. 28 refs., 13 figs., 1 tab.

Mukerji, I.; Sauer, K.

1988-08-01

281

Characterization of elemental sulfur in isolated intact spinach chloroplasts. [Spinacia oleracea L  

SciTech Connect

Incubation of intact spinach (Spinacia oleracea L.) chloroplasts in the presence of {sup 35}SO{sub 4}{sup 2{minus}} resulted in the light-dependent formation of a chloroform-soluble sulfur-containing compound distinct from sulfolipid. The authors have identified this compound as the most stable form (S{sub 8}) of elemental sulfur (S{sup 0}, valence state for S = O) by mass spectrometry. It is possible that elemental sulfur (S{sup 0}) was formed by oxidation of bound sulfide, i.e. after the photoreduction of sulfate to sulfide by intact chloroplasts, and released as S{sub 8} under the experimental conditions used for analysis.

Joyard, J.; Douce, R. (Laboratoire Mixte CNRS/Rhone-Poulenc, Lyon (France)); Forest, E. (Centre d'Etudes Nucleaires de Grenoble (France)); Blee, E. (Institut de Botanique, Strasbourg (France))

1988-12-01

282

Investigation of detergent effects on the solution structure of spinach Light Harvesting Complex II  

NASA Astrophysics Data System (ADS)

The properties of spinach light harvesting complex II (LHC II), stabilized in the detergents Triton X-100 (TX100) and n-Octyl-?-D-Glucoside (BOG), were investigated by small-angle neutron scattering (SANS). The LHC II-BOG scattering curve overlaid well with the theoretical scattering curve generated from the crystal structure of LHC II indicating that the protein preparation was in its native functional state. On the other hand, the simulated LHC II curve deviated significantly from the LHC II-TX100 experimental data. Analysis by circular dichroism spectroscopy supported the SANS analysis and showed that LHC II-TX100 is inactivated. This investigation has implications for extracting and stabilizing photosynthetic membrane proteins for the development of biohybrid photoconversion devices.

Cardoso, Mateus B.; Smolensky, Dmitriy; Heller, William T.; O'Neill, Hugh

2010-11-01

283

Investigation of Detergent Effects on the Solution Structure of Spinach Light Harvesting Complex II  

SciTech Connect

The properties of spinach light harvesting complex II (LHC II), stabilized in the detergents Triton X-100 (TX100) and n-Octyl-{beta}-D-Glucoside (BOG), were investigated by small-angle neutron scattering (SANS). The LHC II-BOG scattering curve overlaid well with the theoretical scattering curve generated from the crystal structure of LHC II indicating that the protein preparation was in its native functional state. On the other hand, the simulated LHC II curve deviated significantly from the LHC II-TX100 experimental data. Analysis by circular dichroism spectroscopy supported the SANS analysis and showed that LHC II-TX100 is inactivated. This investigation has implications for extracting and stabilizing photosynthetic membrane proteins for the development of biohybrid photoconversion devices.

Cardoso, Mateus B [ORNL; Smolensky, Dmitriy [ORNL; Heller, William T [ORNL; O'Neill, Hugh Michael [ORNL

2010-01-01

284

Formation of ATP by the adenosine triphosphatase complex from spinach chloroplasts reconstituted together with bacteriorhodopsin.  

PubMed

The energy-linked ATPase complex has been isolated from spinach chloroplasts. This protein complex contained all the subunits of the chloroplast coupling factor (CF1) as well as several hydrophobic compoenents. When the activated complex was reconstituted with added soybean phospholipids, it catalyzed the exchange of radioactive inorganic phosphate with ATP. Sonication of the complex into proteoliposomes together with bacteriorhodopsin yield vesicles that catalyzed light-dependent ATP formation. Both the 32Pi-ATP exchange reactions and ATP formation were sensitive to uncouplers such as 3-tert-butyl-5,2'-dichloro-4'-nitrosalicylanilide, bis-(hexafluoroacetonyl)acetone and carbonyl cyanide-p-trifluoromethoxyphenyl-hydrazone, that act to dissipate a proton gradient. The energy transfer inhibitors dicyclohexylcarbodiimide, triphenyltin chloride and 2-beta-D-glucopyranosyl-4,6'-dihydroxydihydrochalcone were also effective inhibitors of both reactions. PMID:141938

Winget, G D; Kanner, N; Racker, E

1977-06-01

285

Probing the donor side of photosystem II in spinach chloroplasts and algae using electron paramagnetic resonance  

SciTech Connect

this work concerns electron transfer reactions in photosystem II (PS II). Investigations carried out in this work examine the redox reaction rates in PS II using EPR. In Tris-washed PS II preparations from spinach, it is observed that the oxidation kinetics of S II/sub f/, the EPR signal formed by Z/sup +/ after deactivation of oxygen evolution, mirror the reduction kinetics of P680/sup +/ seen by EPR in samples poised at a variety of pH's. These data agree with previous data on the optically measured reduction kinetics of P680/sup +/. The oxidation kinetics of S II/sub vf/, the EPR transient seen from Z/sup +/ in samples active in O/sub 2/ evolving samples, were instrument limited (t/sub 1/2/ less than 4 ..mu..s) and thus could not be directly measured. These results taken together support a model where Z donates electrons directly to P680/sup +/. The examination of the oxidation and reduction kinetics of S II in monovalent and divalent salt-washed PS II preparations from spinach correlated most of the change of Z oxidation and re-reduction kinetics seen upon Tris-treatment with the loss of a 33 kDa polypeptide associated with the donor side of PS II. These data coupled with observations of stead-state light-induced amplitude changes in S II give evidence for the existance of an electron carrier between the water-splitting enzyme and Z. Observation of S II amplitude and kinetics in highly resolved PS II protein complexes from Synechoccus sp., consisting of either a 5 polypeptide PS II core complex (E-1) or a 4 polypeptide PS II core complex (CP2b), localize Z and P680 within the 4 polypeptide complex. 187 refs., 17 figs., 7 tabs.

Boska, M.D.

1985-11-01

286

Growth and Yield of Fenugreek (Trigonella foenum graecum L.), Spinach (Spinacea oleracea L.), Coriander (Coriandrum sativum L.) and Lettuce (Lactuca saliva L.) under Continuous Daylight Condition in Antarctica  

Microsoft Academic Search

A study on growth and yield of fenugreek (Trigonellafoenum graecum L,), spinach (Spinacea oleracea L.),coriander (Coriandrum sativum L.) and lettucse(Lactuca sativa L.) during polar summer 1990-91 is described. The plants were grown in peatmoss using NFT culture. The plants maintained a good growth and crops matured within five weeks of emergence. Flowering was observed in fenugreek, coriander and spinach after

A. B. DHAULAKHANDI; R. P. JOSHI; M. C. JOSHI

287

Characterization of a Resistance Locus ( Pfs-1 ) to the Spinach Downy Mildew Pathogen ( Peronospora farinosa f. sp. spinaciae ) and Development of a Molecular Marker Linked to Pfs-1  

Microsoft Academic Search

Irish, B. M., Correll, J. C., Feng, C., Bentley, T., and de los Reyes, B. G. 2008. Characterization of a resistance locus (Pfs-1) to the spinach downy mildew pathogen (Peronospora farinosa f. sp. spinaciae) and develop- ment of a molecular marker linked to Pfs-1. Phytopathology 98:894-900. Downy mildew is a destructive disease of spinach worldwide. There have been 10 races

B. M. Irish; J. C. Correll; C. Feng; T. Bentley; B. G. de los Reyes

2008-01-01

288

Signal transduction in leaf senescence.  

PubMed

Leaf senescence is a complex developmental phase that involves both degenerative and nutrient recycling processes. It is characterized by loss of chlorophyll and the degradation of proteins, nucleic acids, lipids, and nutrient remobilization. The onset and progression of leaf senescence are controlled by an array of environmental cues (such as drought, darkness, extreme temperatures, and pathogen attack) and endogenous factors (including age, ethylene, jasmonic acid, salicylic acid, abscisic acid, and cytokinin). This review discusses the major breakthroughs in signal transduction during the onset of leaf senescence, in dark- and drought-mediated leaf senescence, and in various hormones regulating leaf senescence achieved in the past several years. Various signals show different mechanisms of controlling leaf senescence, and cross-talks between different signaling pathways make it more complex. Key senescence regulatory networks still need to be elucidated, including cross-talks and the interaction mechanisms of various environmental signals and internal factors. PMID:23096425

Zhang, Haoshan; Zhou, Chunjiang

2012-10-25

289

The worldwide leaf economics spectrum.  

PubMed

Bringing together leaf trait data spanning 2,548 species and 175 sites we describe, for the first time at global scale, a universal spectrum of leaf economics consisting of key chemical, structural and physiological properties. The spectrum runs from quick to slow return on investments of nutrients and dry mass in leaves, and operates largely independently of growth form, plant functional type or biome. Categories along the spectrum would, in general, describe leaf economic variation at the global scale better than plant functional types, because functional types overlap substantially in their leaf traits. Overall, modulation of leaf traits and trait relationships by climate is surprisingly modest, although some striking and significant patterns can be seen. Reliable quantification of the leaf economics spectrum and its interaction with climate will prove valuable for modelling nutrient fluxes and vegetation boundaries under changing land-use and climate. PMID:15103368

Wright, Ian J; Reich, Peter B; Westoby, Mark; Ackerly, David D; Baruch, Zdravko; Bongers, Frans; Cavender-Bares, Jeannine; Chapin, Terry; Cornelissen, Johannes H C; Diemer, Matthias; Flexas, Jaume; Garnier, Eric; Groom, Philip K; Gulias, Javier; Hikosaka, Kouki; Lamont, Byron B; Lee, Tali; Lee, William; Lusk, Christopher; Midgley, Jeremy J; Navas, Marie-Laure; Niinemets, Ulo; Oleksyn, Jacek; Osada, Noriyuki; Poorter, Hendrik; Poot, Pieter; Prior, Lynda; Pyankov, Vladimir I; Roumet, Catherine; Thomas, Sean C; Tjoelker, Mark G; Veneklaas, Erik J; Villar, Rafael

2004-04-22

290

Salt allocation during leaf development and leaf fall in mangroves  

Microsoft Academic Search

By taking samples along individual branches and measuring leaf size, thickness and Na+ and K+ concentrations, we have shown in Bruguiera cylindrica, Avicennia rumphiana and Avicennia marina that there are two phases of salt accumulation by leaves. This is confirmed by re-analysis of published data for other species. The first phase is a rapid increase in leaf content as it

John W. Cram; Peter G. Torr; Derek A. Rose

2002-01-01

291

Photoregulation of Fructose and Glucose Respiration in the Intact Chloroplasts of Chlamydomonas reinhardtii F-60 and Spinach.  

PubMed Central

The photoregulation of chloroplastic respiration was studied by monitoring in darkness and in light the release of 14CO2 from whole chloroplasts of Chlamydomonas reinhardtii F-60 and spinach (Spinacia oleracea L.) supplied externally with [14C] glucose and [14C]-fructose, respectively. CO2 release was inhibited more than 90% in both chloroplasts by a light intensity of 4 W m-2. Oxidants, oxaloacetate in Chlamydomonas, nitrite in spinach, and phenazine methosulfate in both chloroplasts, reversed the inhibition. The onset of the photoinhibitory effect on CO2 release was relatively rapid compared to the restoration of CO2 release following illumination. In both darkened chloroplasts, dithiothreitol inhibited release. Of the four enzymes (fructokinase, phosphoglucose isomerase, glucose-6-P dehydrogenase, and gluconate-6-P dehydrogenase) in the pathway catalyzing the release of CO2 from fructose, only glucose-6-P dehydrogenase was deactivated by light and by dithiothreitol.

Singh, K. K.; Chen, C.; Gibbs, M.

1993-01-01

292

Effects of Nitrogen Levels and Nitrate\\/Ammonium Ratios on Oxalate Concentrations of Different Forms in Edible Parts of Spinach  

Microsoft Academic Search

Two hydroponic experiments were carried out to investigate the effects of nitrogen (N) levels and forms on the oxalate concentrations of different form in edible parts of spinach. Nitrogen was supplied at five levels (4, 8, 12, 16, 20 mM) in Experiment 1 and five ratios of nitrate (NO3 ) to ammonium (NH4 ) (100\\/0, 75\\/25, 50\\/50, 25\\/75, 0\\/100) at

Yingpeng Zhang; Xianyong Lin; Yongsong Zhang; Shao Jian Zheng; Shaoting Du

2005-01-01

293

Influence of State2 transition on the proton motive force across the thylakoid membrane in spinach chloroplasts  

Microsoft Academic Search

The proton motive force (pmf) across the thylakoid membrane is composed of the proton gradient and the membrane potential, which promotes millisecond-delayed light emission (ms-DLE). In this study, the time courses of LHC II phosphorylation and ms-DLE were investigated in spinach chloroplast during State-2 transition. Red light illumination resulted in an exponential rise in LHC II phosphorylation and a biphasic

Ji-Hu Su; Yun-Kang Shen

2005-01-01

294

The Effects of lllumination on the Xanthophyll Composition of the Photosystem II Light-Harvesting Complexes of Spinach Thylakoid Membranes  

Microsoft Academic Search

~~ lhe xanthophyll composition of the light-harvesting chlorophyll a\\/b proteins of photosystem II (LHCII) has been determined for spinach (Spinacia oleracea 1.) leaves after dark adaptation and following illumination under conditions optimized for conversion of violaxanthin into zeaxanthin. Each of the four LHCll components was found to have a unique xanthophyll composition. lhe major carotenoid was lutein, comprising 60% of

Alexander V. Ruban; Andrew J. Young; Andrew A. Pascal; Peter Horton

1994-01-01

295

Effects of high temperatures on the photosynthetic systems in spinach: Oxygen-evolving activities, fluorescence characteristics and the denaturation process  

Microsoft Academic Search

Activities of oxygen evolution, fluorescence Fv (a variable part of chlorophyll fluorescence) values, and amounts of the 33 kDa protein remaining bound to the thylakoids in intact spinach chloroplasts were measured during and after high-temperature treatment. The following results were obtained. (1) Both the Fv value and the flash-induced oxygen evolution measured by an oxygen electrode were decreased at high

Yoshihiro Yamane; Yasuhiro Kashino; Hiroyuki Koike; Kazuhiko Satoh

1998-01-01

296

Bioconversion of spinach beta-carotene to vitamin A in Chinese children with normal or marginal vitamin A status  

Technology Transfer Automated Retrieval System (TEKTRAN)

To investigate the vitamin A conversion value of spinach beta-carotene (beta -C) in healthy school children with normal or marginal vitamin A status, we recruited 32 school children aged 7-9 y (7.8 0.6 y) with serum retinol '30 mug/dL or <30mug/dL. Subjects were given 5 gram cooked and pureed deut...

297

Bacteriophages Reduce Experimental Contamination of Hard Surfaces, Tomato, Spinach, Broccoli, and Ground Beef by Escherichia coli O157:H7  

Microsoft Academic Search

A bacteriophage cocktail (designated ECP-100) containing three Myoviridae phages lytic for Escherichia coli O157:H7 was examined for its ability to reduce experimental contamination of hard surfaces (glass coverslips and gypsum boards), tomato, spinach, broccoli, and ground beef by three virulent strains of the bacterium. The hard surfaces and foods contaminated by a mixture of three E. coli O157:H7 strains were

Tamar Abuladze; Manrong Li; Marc Y. Menetrez; Timothy Dean; Andre Senecal; Alexander Sulakvelidze

2008-01-01

298

Gravitational water flow enhances the colonization of spinach roots in soil by plant growth-promoting Pseudomonas  

Microsoft Academic Search

Root colonization by a plant growth-promoting Pseudomonas (H3R strain) was examined to determine whether gravitational water flow affects the bacterial distribution on spinach roots. Firstly, the effect of the amount of irrigation water or soil moisture content on the distribution of the H3R strain resistant to three antibiotics was examined using a rhizobox, Pseudomonas When a large amount of water

Yasufumi Urashima; Masao Sakai; Yuko Suga; Ayako Fukunaga; Kaneaki Hori

2004-01-01

299

Use of Spinach, Radish, and Perennial Ryegrass to Assess the Availability of Metals in Waste Foundry Sands  

Microsoft Academic Search

Plant uptake is a major pathway by which toxic metals can enter the food chain. In this laboratory study we grew spinach,\\u000a radish, and perennial ryegrass on sand blends containing 50% waste foundry sand (WFS) to assess the availability of Al, B,\\u000a Ba, Be, Cd, Co, Cr, Cu, Fe, Mg, Mn, Mo, Ni, Pb, V, and Zn. The WFSs utilized

Robert S. Dungan; Nikki H. Dees

2007-01-01

300

Interactions of plant zinc and plant species on the bioavailability of plant cadmium to Japanese quail fed lettuce and spinach  

SciTech Connect

Many cadmium-contaminated environments contain high levels of zinc. The effects of plant Zn and plant species on plant Cd bioavailability were tested in Japanese quail fed lettuce and spinach. Four groups of birds received 10% of their diets as lettuce or spinach leaves intrinsically labeled with {sup 109}Cd and containing low or high intrinsic Zn. Two other groups were fed control diets containing {sup 109}Cd as CdSO{sub 4} and low or high Zn as ZnCO{sub 3}. Cadmium concentrations in diets ranged from 0.857 to 1.05 {mu}g/g dry wt. Zinc concentrations in low-Zn diets ranged from 21.2 to 22.8, and in high-Zn diets from 56.0 to 63.3 {mu}g/g dry wt. Increased lettuce and spinach Zn decreased plant Cd retention in kidney, liver, and jejunum-ileum of Japanese quail. Spinach Cd was less absorbed than lettuce Cd at both Zn levels. Inorganic Zn produced a lesser decrease in Cd retention in kidney, liver, and jejunum-ileum than did plant Zn. The authors conclude that (1) crops that transport Zn and Cd readily into edible tissues show lower Cd bioavailability when grown in Zn-Cd contaminated environments than in Cd-only polluted sites, (2) plant species differ in Cd bioavailability for identical concentrations of Zn and Cd in edible tissues, and (3) toxicological studies with animals exposed to Cd salts and Zn supplements do not assess Cd bioavailability of Zn-Cd contaminated crops.

McKenna, I.M.; Keach, R.M. Jr; Williams, F.M. (Pennsylvania State Univ., University Park (United States)); Chaney, R.L. (Pennsylvania State Univ., University Park (United States) Dept. of Agriculture, Beltsville, MD (United States)); Tao, Shyy-Hwa (Food and Drug Administration, Washington, DC (United States))

1992-02-01

301

UV-C doses to reduce pathogen and spoilage bacterial growth in vitro and in baby spinach  

Microsoft Academic Search

The aim of this work was to investigate the use of different doses of UV-C (0, 2.4, 7.2, 12 and 24kJm?2) radiation treatments to inhibit microbial growth of Listeria monocytogenes and Salmonella enterica. The spoilage bacteria Pseudomonas marginalis (gram negative) was also tested. These bacteria were studied under in vitro conditions and in baby spinach leaves (in vivo conditions) for

Vctor H. Escalona; Encarna Aguayo; Gins B. Martnez-Hernndez; Francisco Arts

2010-01-01

302

The artificial leaf.  

PubMed

To convert the energy of sunlight into chemical energy, the leaf splits water via the photosynthetic process to produce molecular oxygen and hydrogen, which is in a form of separated protons and electrons. The primary steps of natural photosynthesis involve the absorption of sunlight and its conversion into spatially separated electron-hole pairs. The holes of this wireless current are captured by the oxygen evolving complex (OEC) of photosystem II (PSII) to oxidize water to oxygen. The electrons and protons produced as a byproduct of the OEC reaction are captured by ferrodoxin of photosystem I. With the aid of ferrodoxin-NADP(+) reductase, they are used to produce hydrogen in the form of NADPH. For a synthetic material to realize the solar energy conversion function of the leaf, the light-absorbing material must capture a solar photon to generate a wireless current that is harnessed by catalysts, which drive the four electron/hole fuel-forming water-splitting reaction under benign conditions and under 1 sun (100 mW/cm(2)) illumination. This Account describes the construction of an artificial leaf comprising earth-abundant elements by interfacing a triple junction, amorphous silicon photovoltaic with hydrogen- and oxygen-evolving catalysts made from a ternary alloy (NiMoZn) and a cobalt-phosphate cluster (Co-OEC), respectively. The latter captures the structural and functional attributes of the PSII-OEC. Similar to the PSII-OEC, the Co-OEC self-assembles upon oxidation of an earth-abundant metal ion from 2+ to 3+, may operate in natural water at room temperature, and is self-healing. The Co-OEC also activates H(2)O by a proton-coupled electron transfer mechanism in which the Co-OEC is increased by four hole equivalents akin to the S-state pumping of the Kok cycle of PSII. X-ray absorption spectroscopy studies have established that the Co-OEC is a structural relative of Mn(3)CaO(4)-Mn cubane of the PSII-OEC, where Co replaces Mn and the cubane is extended in a corner-sharing, head-to-tail dimer. The ability to perform the oxygen-evolving reaction in water at neutral or near-neutral conditions has several consequences for the construction of the artificial leaf. The NiMoZn alloy may be used in place of Pt to generate hydrogen. To stabilize silicon in water, its surface is coated with a conducting metal oxide onto which the Co-OEC may be deposited. The net result is that immersing a triple-junction Si wafer coated with NiMoZn and Co-OEC in water and holding it up to sunlight can effect direct solar energy conversion via water splitting. By constructing a simple, stand-alone device composed of earth-abundant materials, the artificial leaf provides a means for an inexpensive and highly distributed solar-to-fuels system that employs low-cost systems engineering and manufacturing. Through this type of system, solar energy can become a viable energy supply to those in the non-legacy world. PMID:22475039

Nocera, Daniel G

2012-04-04

303

Subcellular fractionation of polyprenyl diphosphate synthase activities responsible for the syntheses of polyprenols and dolichols in spinach leaves.  

PubMed

Polyisoprenoid alcohols occurring in spinach leaves were analyzed by a two-plate TLC method. Z,E-mixed polyprenols (C(55-60)), glycinoprenols (C(50-55)), and solanesol (C(45)) were mainly found in chloroplasts, whereas dolichols (C(70-80)) were mainly found in microsomes. Analysis of enzymatic products derived from [1-(14)C]isopentenyl diphosphate and farnesyl diphosphate (FPP) with subcellular fractions revealed that chloroplasts and microsomes had the ability to synthesize Z,E-mixed polyprenyl (C(50-65)) and all E-polyprenyl (C(45-50)) diphosphates, and Z,E-mixed polyprenyl (C(70-85)) diphosphates, respectively. FPP and geranylgeranyl diphosphate (GGPP) were both accepted for these enzymatic reactions, the former being a better substrate than the latter. NMR analysis of naturally occurring spinach Z,E-mixed polyprenol (C(55)) and dolichol (C(75)) revealed that the number of internal trans isoprene residues in the former was three in comparison with two internal trans residues found for the latter. These results indicate that two kinds of polyprenyl diphosphate synthases occur in spinach: One is the chloroplast enzyme involved in the synthesis of the shorter-chain (C(50-65)) Z,E-mixed polyprenols and the other is the microsomal enzyme involved in the synthesis of longer-chain (C(70-85)) Z,E-mixed polyprenols, which is converted to dolichols. PMID:11098151

Sakaihara, T; Honda, A; Tateyama, S; Sagami, H

2000-12-01

304

The worldwide leaf economics spectrum  

Microsoft Academic Search

Bringing together leaf trait data spanning 2,548 species and 175 sites we describe, for the first time at global scale, a universal spectrum of leaf economics consisting of key chemical, structural and physiological properties. The spectrum runs from quick to slow return on investments of nutrients and dry mass in leaves, and operates largely independently of growth form, plant functional

Ian J. Wright; Peter B. Reich; Mark Westoby; David D. Ackerly; Zdravko Baruch; Frans Bongers; Jeannine Cavender-Bares; Terry Chapin; Johannes H. C. Cornelissen; Matthias Diemer; Jaume Flexas; Eric Garnier; Philip K. Groom; Javier Gulias; Kouki Hikosaka; Byron B. Lamont; Tali Lee; William Lee; Christopher Lusk; Jeremy J. Midgley; Marie-Laure Navas; lo Niinemets; Jacek Oleksyn; Noriyuki Osada; Pieter Poot; Lynda Prior; Vladimir I. Pyankov; Catherine Roumet; Sean C. Thomas; Mark G. Tjoelker; Erik J. Veneklaas; Rafael Villar

2004-01-01

305

Leaf retention and cassava productivity  

Microsoft Academic Search

Increased longevity of leaves, or improved leaf retention, has been suggested as a possible means to increase productivity of cassava (Manihot esculenta Crantz). This study evaluated variation in leaf retention and its relation to cassava productivity under irrigated and stressed conditions. In the first trial 1350 clones were evaluated on the North Coast of Colombia with a 5-month dry period

J. I. Lenis; F. Calle; G. Jaramillo; J. C. Perez; H. Ceballos; J. H. Cock

2006-01-01

306

Simulating Leaf Appearance in Rice  

Microsoft Academic Search

Most rice (Oryza sativa L.) simulation models assume that only temperature aff ects leaf appearance rate (LAR). Th is assumption ignores results from controlled environment studies that show that LAR in rice is not constant with time (calendar days) under constant temperature. Th e Streck model, which takes into account age eff ects on LAR, improved the prediction of leaf

Nereu Augusto Streck; Leosane Cristina Bosco; Isabel Lago

2008-01-01

307

Effects of Irrigation Treatments and Rates of Nitrogen Fertilization on Young Hass Avocado Trees. II. Relation to Leaf Tipburn, Tree Sunburn, Shoot Dieback, Leaf Scorch, Leaf Color, Leaf Size, Tree Vigor, and Leaf Moisture Deficits  

Microsoft Academic Search

Periodic observations were made during the years 1955 and 1956. The presence and extent of leaf tipburn, tree sunburn, shoot dieback, leaf scorch, leaf color, leaf size, and tree vigor were noted. Leal: moisture deficits were determined during part of the 1956 irrigation season. LEAF TIPBURN Leaf tipburn, due to the accumulation of Cl and SO4 in mature leaves, is

P. W. Moore; S. J. Richards

308

The metabolic significance of octulose phosphates in the photosynthetic carbon reduction cycle in spinach  

PubMed Central

14C-Labelled octulose phosphates were formed during photosynthetic 14CO2 fixation and were measured in spinach leaves and chloroplasts. Because mono- and bisphosphates of d-glycero-d-ido-octulose are the active 8-carbon ketosugar intermediates of the L-type pentose pathway, it was proposed that they may also be reactants in a modified CalvinBensonBassham pathway reaction scheme. This investigation therefore initially focussed only on the ido-epimer of the octulose phosphates even though 14C-labelled d-glycero-d-altro-octulose mono- and bisphosphates were also identified in chloroplasts and leaves. 14CO2 predominantly labelled positions 5 and 6 of d-glycero-d-ido-octulose 1,8-P2 consistent with labelling predictions of the modified scheme. The kinetics of 14CO2 incorporation into ido-octulose was similar to its incorporation into some traditional intermediates of the path of carbon, while subsequent exposure to 12CO2 rapidly displaced the 14C isotope label from octulose with the same kinetics of label loss as some of the confirmed Calvin pathway intermediates. This is consistent with octulose phosphates having the role of cyclic intermediates rather than synthesized storage products. (Storage products dont rapidly exchange isotopically labelled carbons with unlabelled CO2.) A spinach chloroplast extract, designated stromal enzyme preparation (SEP), catalysed and was used to measure rates of CO2 assimilation with Calvin cycle intermediates and octulose and arabinose phosphates. Only pentose (but not arabinose) phosphates and sedoheptulose 7-phosphate supported CO2 fixation at rates in excess of 120?molh?1mg?1 Chl. Rates for octulose, sedoheptulose and fructose bisphosphates, octulose, hexose and triose monophosphates were all notably less than the above rate and arabinose 5-phosphate was inactive. Altro-octulose phosphates were more active than phosphate esters of the ido-epimer. The modified scheme proposed a specific phosphotransferase and SEP unequivocally catalysed reversible phosphate transfer between sedoheptulose bisphosphate and d-glycero-d-ido-octulose 8-phosphate. It was also initially hypothesized that arabinose 5-phosphate, an L-Type pentose pathway reactant, may have a role in a modified Calvin pathway. Arabinose 5-phosphate is present in spinach chloroplasts and leaves. Radiochromatography showed that 14C-arabinose 5-phosphate with SEP, but only in the presence of an excess of unlabelled ribose 5-phosphate, lightly labelled ribulose 5-phosphate and more heavily labelled hexose and sedoheptulose mono- and bisphosphates. However, failure to demonstrate any CO2 fixation by arabinose 5-phosphate as sole substrate suggested that the above labelling may have no metabolic significance. Despite this arabinose and ribose 5-phosphates are shown to exhibit active roles as enzyme co-factors in transaldolase and aldolase exchange reactions that catalyse the epimeric interconversions of the phosphate esters of ido- and altro-octulose. Arabinose 5-phosphate is presented as playing this role in a New Reaction Scheme for the path of carbon, where it is concluded that slow reacting ido-octulose 1,8 bisphosphate has no role. The more reactive altro-octulose phosphates, which are independent of the need for phosphotransferase processing, are presented as intermediates in the new scheme. Moreover, using the estimates of phosphotransferase activity with altro-octulose monophosphate as substrate allowed calculation of the contributions of the new scheme, that ranged from 11% based on the intact chloroplast carboxylation rate to 80% using the carboxylation rate required for the support of octulose phosphate synthesis and its role in the phosphotransferase reaction.

MacLeod, John K.

2006-01-01

309

Functional expression of a Delta12 fatty acid desaturase gene from spinach in transgenic pigs.  

PubMed

Linoleic acid (18:2n-6) and alpha-linolenic acid (18:3n-3) are polyunsaturated fatty acids that are essential for mammalian nutrition, because mammals lack the desaturases required for synthesis of Delta12 (n-6) and n-3 fatty acids. Many plants can synthesize these fatty acids and, therefore, to examine the effects of a plant desaturase in mammals, we generated transgenic pigs that carried the fatty acid desaturation 2 gene for a Delta12 fatty acid desaturase from spinach. Levels of linoleic acid (18:2n-6) in adipocytes that had differentiated in vitro from cells derived from the transgenic pigs were approximately 10 times higher than those from wild-type pigs. In addition, the white adipose tissue of transgenic pigs contained approximately 20% more linoleic acid (18:2n-6) than that of wild-type pigs. These results demonstrate the functional expression of a plant gene for a fatty acid desaturase in mammals, opening up the possibility of modifying the fatty acid composition of products from domestic animals by transgenic technology, using plant genes for fatty acid desaturases. PMID:15067141

Saeki, Kazuhiro; Matsumoto, Kazuya; Kinoshita, Mikio; Suzuki, Iwane; Tasaka, Yasushi; Kano, Koichiro; Taguchi, Yoshitomo; Mikami, Koji; Hirabayashi, Masumi; Kashiwazaki, Naomi; Hosoi, Yoshihiko; Murata, Norio; Iritani, Akira

2004-04-05

310

beta. -carotene synthesis in spinach chloroplasts is tightly linked to photosynthetic carbon metabolism  

SciTech Connect

When purified, highly intact spinach chloroplasts were illuminated in the presence of NaH/sup 14/CO/sub 3/, the largest portion of acetate derived compounds formed was ..beta..-carotene and not fatty acids (20 and 2.5 natoms C incorporated/mg chlorophyll x h when 5 mM NaH /sup 14/CO/sub 3/ was used). From isotopic dilution experiments applying glyceraldehyde 3-P, dihydroxyacetone-P, 3-phosphoglycerate (3-PGA), 2-PGA, phosphoenolpyruvate (PEP) and pyruvate, respectively, evidence was obtained that acetyl-CoA to form isopentenyl-PP (IPP) originates from a low capacity but highly effective flow from photosynthetic CO/sub 2/-fixation via 3-PGA - 2-PGA - PEP - pyruvate. Phosphoglycerate mutase in chloroplasts, of which the presence hitherto was not unequivocally proven, was detected by (i) latency technique and (ii) feeding/1-/sup 14/C/glycerate and following 3-PGA, 2-PGA, PEP and pyruvate level in chloroplasts and suspension medium. From highly effective synthesis of ..beta..-carotene from CO/sub 2/ conclusion may be drawn that pathways for both, acetyl compounds and IPP, to form isoprenoids must exist in chloroplasts.

Schulze-Siebert, D.; Schultz, G.

1987-04-01

311

Evidence for a reactive cysteine at the nucleotide binding site of spinach ribulose-5-phosphate kinase  

SciTech Connect

Ribulose-5-phosphate kinase from spinach was rapidly inactivated by N-bromoacetylethanolamine phosphate in a bimolecular fashion with a k2 of 2.0 m s at 2C and pH 8.0. Ribulose 5-phosphate had little effect on the rate of inactivation, whereas complete protection was afforded by ADP or ATP. The extent of incorporation as determined with UC-labeled reagent was about 1 molar equivalent per subunit in the presence of ATP with full retention of enzymatic activity, and about 2 molar equivalents per subunit in the completely inactivated enzyme. Amino acid analyses of enzyme derivatized with UC-labeled reagent reveal that all of the covalently incorporated reagent was associated with cysteinyl residues. Hence, two sulfhydryls are reactive, but the inactivation correlates with alkylation of one cysteinyl residue at or near the enzyme's nucleotide binding site. The kinase was also extremely sensitive to the sulfhydryl reagents 5,5'-dithiobis(2-nitrobenzoic acid) and N-ethylmaleimide. The reactive sulfhydryl groups are likely to be those generated by reduction of a disulfide during activation. 20 references, 3 figures, 2 tables.

Omnaas, J.; Porter, M.A.; Hartman, F.C.

1985-02-01

312

Partial purification of gibberellin oxidases from spinach leaves. [Spinacia oleracea L  

SciTech Connect

Four enzyme activities catalyzing the following oxidative steps in the gibberellin (GA) biosynthetic pathway have been extracted from spinach (Spinacia oleracea L.) leaves after exposure to 8 long days: GA/sub 12/ ..-->.. GA/sub 53/ ..-->.. GA/sub 44/ ..-->.. GA/sub 19/ ..-->.. GA/sub 20/. Two of these, GA/sub 53/ oxidase and GA/sup 19/ oxidase, were separable from the other two, GA/sub 44/ oxidase and GA/sub 12/ 13-hydroxylase, by anion exchange high performance liquid chromatography (HPLC). Apparent molecular weights of the four enzymes as determined by gel filtration HLPL are: GA/sub 12/ 13-hydroxylase, 28,400; GA/sub 43/ oxidase, 42,500; GA/sub 44/ oxidase, 38,100; GA/sub 19/ oxidase, 39,500. GA/sub 44/ oxidase was purified approximately 100-fold in 0.3% yield by a combination of ammonium sulfate fractionation, anion exchange HPLC, phenyl-Sepharose chromatography and gel filtration HLPC.

Gilmour, S.J.; Bleecker, A.B.; Zeevaart, J.A.D.

1987-09-01

313

Spectral characterization in a supersonic beam of neutral chlorophyll a evaporated from spinach leaves  

NASA Astrophysics Data System (ADS)

The observation of the light absorption of neutral biomolecules has been made possible by a method implemented for their preparation in the gas phase, in supersonically cooled molecular beams, based upon the work of Focsa et al. [C. Mihesan, M. Ziskind, B. Chazallon, E. Therssen, P. Desgroux, S. Gurlui, and C. Focsa, Appl. Surf. Sci. 253, 1090 (2006)]. The biomolecules diluted in frozen water solutions are entrained in the gas plume of evaporated ice generated by an infrared optical parametric oscillators (OPO) laser tuned close to its maximum of absorption, at ~3 ?m. The biomolecules are then picked up in the flux of a supersonic expansion of argon. The method was tested with indole dissolved in water. The excitation spectrum of indole was found cold and large clusters of indole with water were observed up to n = 75. Frozen spinach leaves were examined with the same method to observe the chlorophyll pigments. The Qy band of chlorophyll a has been observed in a pump probe experiment. The Qy bands of chlorophyll a is centred at 647 nm, shifted by 18 nm from its position in toluene solutions. The ionization threshold could also be determined as 6.1 +/- 0.05 eV.

Shafizadeh, N.; Ha-Thi, M. H.; Soep, B.; Gaveau, M. A.; Piuzzi, F.; Pothier, C.

2011-09-01

314

Effects of inorganic phosphate on the light dependent thylakoid energization of intact spinach chloroplasts  

SciTech Connect

The light dependent energization of the thylakoid membrane was analyzed in isolated intact spinach (Spinacia oleracea L.) chloroplasts incubated with different concentrations of inorganic phosphate (Pi). Two independent methods were used: (a) the accumulation of ({sup 14}C)5,5-dimethyl-2,4-oxazolidinedione and ({sup 14}C)methylamine; (b) the energy dependent chlorophyll fluorescence quenching. The inhibition of CO{sub 2} fixation by superoptimal medium Pi or by adding glyceraldehyde - an inhibitor of the Calvin cycle - leads to an increased energization of the thylakoid membrane; however, the membrane energization decreases when chloroplasts are inhibited by suboptimal Pi. This specific low phosphate effect could be partially reversed by adding oxaloacetate, which regenerates the electron acceptor NADP{sup +} and stimulates linear electron transport. The energization seen in low Pi is, however, always lower than in superoptimal Pi, even in the presence of oxaloacetate. Energization recovers in the presence of low amounts of N,N{prime}-dicyclohexylcarbodiimide, which reacts with proton channels including the coupling factor 1 ATP synthase. N,N{prime}-Dicyclohexylcarbodiimide has no effect on energization of chloroplasts in superoptimal Pi. These results suggest there is a specific low phosphate proton leak in the thylakoids, and its origin is discussed.

Heineke, D.; Heldt, H.W. (Universitaet Goettingen (West Germany)); Stitt, M. (Universitaet Bayreuth (West Germany))

1989-09-01

315

Spinach thylakoid polyphenol oxidase isolation, activation, and properties of the native chloroplast enzyme  

SciTech Connect

Polyphenol oxidase activity (E.C. 1.14,18.1) has been found in two enzyme species isolated from thylakoid membranes of spinach chloroplasts. The proteins were released from the membrane by sonication and purified >900-fold by ammonium sulfate precipitation, gel filtration, and ion-exchange chromatography. The enzymes appear to be the tetramer and monomer of a subunit with a molecular weight of 42,500 as determined by lithium dodecyl sulfate gel electrophoresis. Sonication releases polyphenol oxidase from the membrane largely in the latent state. In the absence of added fatty acids, the isolated enzyme spontaneously, but slowly, activates with time. Purified polyphenol oxidase utilizes o-diphenols as substrates and shows no detectable levels of monophenol or p-diphenol oxidase activities. Suitable substrates include chlorogenic acid, catechol, caffeic acid, pyrogallol, and dopamine; however, the enzyme is substrate-inhibited by the last four at concentrations near their K/sub m/. A large seasonal variation in polyphenol oxidase activity may result from a decrease in enzyme content rather than inhibition of the enzyme present.

Golbeck, J.H.; Cammarata, K.V.

1981-05-01

316

Expression of Spinach Ascorbate Peroxidase Isoenzymes in Response to Oxidative Stresses1  

PubMed Central

We studied the response of each ascorbate peroxidase (APX) isoenzyme in spinach leaves under stress conditions imposed by high light intensity, drought, salinity, and applications of methyl viologen and abscisic acid. The steady-state transcript level of cytosolic APX remarkably increased in response to high-light stress and methyl viologen treatment, but not in response to the other stress treatments. The transcript levels of the chloroplastic (stromal and thylakoid-bound) and microbody-bound APX isoenzymes were not changed in response to any of the stress treatments. To explore the responses of the APX isoenzymes to photooxidative stress, the levels of transcript and protein and activities of each isoenzyme were studied during high-light stress and following its recovery. The cytosolic APX activity increased in parallel with transcript abundance during high-light stress, while the protein level was not altered. The other isoenzymes showed no significant changes in transcript and protein levels and activities, except for the gradual decrease in chloroplastic isoenzyme activities.

Yoshimura, Kazuya; Yabuta, Yukinori; Ishikawa, Takahiro; Shigeoka, Shigeru

2000-01-01

317

Effect of 7Li (45MeV) ions on spinach leaves studied by thermoluminescence technique  

NASA Astrophysics Data System (ADS)

In the present work, we have studied the effect of different fluences of 7Li (45MeV) (104-5x107 particles/cm2) on the photosynthetic apparatus of spinach (Spinacia oleracia L.) leaves using the thermoluminescence (TL) technique. Fitting of the recorded TL glow curves using the general order kinetics theory for the control sample showed the presence of the standard TL bands i.e. A(I), D(II), Q(III), B(IV) and C(V) at around -20 degC, -5 degC, 10 degC, 30 degC and 50 degC respectively. The irradiation with fluence of 104 particles/cm2 resulted in the induction of a new TL band at around 16 degC along with the other bands, while the sample irradiated with 105 particles/cm2 showed a splitting of the B band into its components B1 (20 degC) and B2 (30 degC) in addition to the new band. On irradiation with 5x107 particles/cm2, an apparent shift of all the bands towards the lower temperature side was observed. These findings suggest that exposure to 7Li (45MeV) ions results in an alteration of the characteristic trap distribution which represents the energy levels of the various electron transport components within the photosynthetic apparatus.

Gaikwad, Jyoti; Thomas, S.; Kamble, S.; Vidyasagar, P. B.; Sarma, A.

318

Organellar and Cytosolic Localization of Four Phosphoribosyl Diphosphate Synthase Isozymes in Spinach  

PubMed Central

Four cDNAs encoding phosphoribosyl diphosphate (PRPP) synthase were isolated from a spinach (Spinacia oleracea) cDNA library by complementation of an Escherichia coli ?prs mutation. The four gene products produced PRPP in vitro from ATP and ribose-5-phosphate. Two of the enzymes (isozymes 1 and 2) required inorganic phosphate for activity, whereas the others were phosphate independent. PRPP synthase isozymes 2 and 3 contained 76 and 87 amino acid extensions, respectively, at their N-terminal ends in comparison with other PRPP synthases. Isozyme 2 was synthesized in vitro and shown to be imported and processed by pea (Pisum sativum) chloroplasts. Amino acid sequence analysis indicated that isozyme 3 may be transported to mitochondria and that isozyme 4 may be located in the cytosol. The deduced amino acid sequences of isozymes 1 and 2 and isozymes 3 and 4 were 88% and 75% identical, respectively. In contrast, the amino acid identities of PRPP synthase isozyme 1 or 2 with 3 or 4 was modest (22%25%), but the sequence motifs for binding of PRPP and divalent cation-nucleotide were identified in all four sequences. The results indicate that PRPP synthase isozymes 3 and 4 belong to a new class of PRPP synthases that may be specific to plants.

Krath, Britta N.; Hove-Jensen, Bjarne

1999-01-01

319

Defining the Far-Red Limit of Photosystem II in Spinach[C][W  

PubMed Central

The far-red limit of photosystem II (PSII) photochemistry was studied in PSII-enriched membranes and PSII core preparations from spinach (Spinacia oleracea) after application of laser flashes between 730 and 820 nm. Light up to 800 nm was found to drive PSII activity in both acceptor side reduction and oxidation of the water-oxidizing CaMn4 cluster. Far-red illumination induced enhancement of, and slowed down decay kinetics of, variable fluorescence. Both effects reflect reduction of the acceptor side of PSII. The effects on the donor side of PSII were monitored using electron paramagnetic resonance spectroscopy. Signals from the S2-, S3-, and S0-states could be detected after one, two, and three far-red flashes, respectively, indicating that PSII underwent conventional S-state transitions. Full PSII turnover was demonstrated by far-red flash-induced oxygen release, with oxygen appearing on the third flash. In addition, both the pheophytin anion and the Tyr Z radical were formed by far-red flashes. The efficiency of this far-red photochemistry in PSII decreases with increasing wavelength. The upper limit for detectable photochemistry in PSII on a single flash was determined to be 780 nm. In photoaccumulation experiments, photochemistry was detectable up to 800 nm. Implications for the energetics and energy levels of the charge separated states in PSII are discussed in light of the presented results.

Thapper, Anders; Mamedov, Fikret; Mokvist, Fredrik; Hammarstrom, Leif; Styring, Stenbjorn

2009-01-01

320

Histamine, cadaverine, and putrescine produced in vitro by enterobacteriaceae and pseudomonadaceae isolated from spinach.  

PubMed

A total of 364 bacterial isolates, obtained from spinach leaves, were assayed in a decarboxylase broth containing histidine, lysine, and ornithine to check their ability to produce biogenic amines, and then quantified by high-performance liquid chromatography. Among these isolates, 240 formed cadaverine, 208 formed putrescine, and 196 formed histamine, in widely varying amounts. They frequently produced more than one biogenic amine. Klebsiella pneumoniae subsp. pneumoniae and Morganella morganii were the main histamine producers, with mean values of 1,600 and 2,440 mg/liter, respectively, followed by Pantoea spp. 3 (1,710 mg/liter) and Hafnia alvei (2,500 mg/liter). Enterobacter amnigenus and Enterobacter cloacae produced particularly high amounts of putrescine, with mean values of 2,340 and 2,890 mg/liter, respectively. The strongest cadaverine formation was shown by Serratia liquefaciens (3,300 mg/liter), Serratia marcescens (3,280 mg/liter), and Stenotrophomonas maltophilia (1,000 mg/liter). PMID:20132689

Lavizzari, T; Breccia, M; Bover-Cid, S; Vidal-Carou, M C; Veciana-Nogus, M T

2010-02-01

321

X-ray absorption spectroscopy and EPR studies of oriented spinach thylakoid preparations  

SciTech Connect

In this study, oriented Photosystem II (PS II) particles from spinach chloroplasts are studied with electron paramagnetic resonance (EPR) and x-ray absorption spectroscopy (XAS) to determine more details of the structure of the oxygen evolving complex (OEC). The nature of halide binding to Mn is also studied with Cl K-edge and Mn EXAFS (extended x-ray absorption fine structure) of Mn-Cl model compounds, and with Mn EXAFS of oriented PS II in which Br has replaced Cl. Attention is focused on the following: photosynthesis and the oxygen evolving complex; determination of mosaic spread in oriented photosystem II particles from signal II EPR measurement; oriented EXAFS--studies of PS II in the S{sub 2} state; structural changes in PS II as a result of treatment with ammonia: EPR and XAS studies; studies of halide binding to Mn: Cl K-edge and Mn EXAFS of Mn-Cl model compounds and Mn EXAFS of oriented Br-treated photosystem II.

Andrews, J.C. [Univ. of California, Berkeley, CA (United States). Dept. of Chemistry]|[Lawrence Berkeley Lab., CA (United States). Structural Biology Div.

1995-08-01

322

Heterologous C-terminal signals effectively target fluorescent fusion proteins to leaf peroxisomes in diverse plant species.  

PubMed

Peroxisomes are functionally diverse organelles that are wholly dependent on import of nuclear-encoded proteins. The signals that direct proteins into these organelles are either found at the C-terminus (type 1 peroxisomal targeting signal; PTS1) or N-terminus (type 2 peroxisomal targeting signal; PTS2) of the protein. Based on a limited number of tests in heterologous systems, PTS1 signals appear to be conserved across species. To further test the generality of this conclusion and to establish the extent to which the PTS1 signals can be relied on for biotechnological purposes across species, we tested two PTS1 signals for their ability to target fluorescent proteins in diverse plant species. Transient assays following microprojectile bombardment showed that the six amino acid PTS1 sequence (RAVARL) from spinach glycolate oxidase effectively targets green fluorescent fusion protein to the leaf peroxisomes in all 20 crops tested, including four monocots (sugarcane, wheat, corn and onion) and 16 dicots (carrot, cucumber, broccoli, tomato, lettuce, turnip, radish, cauliflower, cabbage, capsicum, celery, tobacco, petunia, beetroot, eggplant and coriander). Similarly, results indicated that the 10 amino acid PTS1 sequence (IHHPRELSRL) from pumpkin malate synthase effectively targets red fluorescent fusion protein to the leaf peroxisomes in all four crops tested including monocot (sugarcane) and dicot (cabbage, celery and pumpkin) species. These signal sequences should be useful metabolic engineering tools to direct recombinant proteins to the leaf peroxisomes in diverse plant species of biotechnological interest. PMID:22386008

Gnanasambandam, Annathurai; Anderson, David J; Mills, Edwina; Brumbley, Stevens M

2012-03-03

323

Leaf death and decomposition during pasture regrowth  

Microsoft Academic Search

Data are presented that describe the pattern of leaf death per ramet and per unit area. Leaf death per ramet was influenced by the number of leaves that died and the weight of the dead leaves. Leaf weight was important in determining differences in seasonal and species death rate per ramet.Leaf death rates reached a maximum of 56 lb D.M.

W. F. Hunt

1971-01-01

324

Retrieval of spinach crop parameters by microwave remote sensing with back propagation artificial neural networks: A comparison of different transfer functions  

NASA Astrophysics Data System (ADS)

Back propagation artificial natural network (BPANN) is a well known and widely used machine learning methodology in the field of remote sensing. In this paper an attempt is made to retrieve the spinach crop parameters like biomass, leaf area index, average plant height and soil moisture content by using the X-band scattering coefficients with BPANN at different growth stages of this crop. The maturity age of this crop was found to be 45 days from the date of sowing. After 45 days from the date of sowing, this crop was cut at a certain height for production. Then, it is a point of interest to investigate the microwave response of variation in production. Significant variations in all the crop parameters were observed after cutting the crop and consequently made the problem more critical. Our work confirms the utility of BPANN in handling such a non-linear data set. The BPANN is essentially a network of simple processing nodes arranged into different layers as input, hidden and the output. The input layer propagates components of a particular input vector after weighting these with synaptic weights to each node in the hidden layer. At each node, these weighted input vector components are added. Each hidden layer computes output corresponding to these weighted sum through a non-linear/linear function (e.g. LOGSIG, TANSIG and PURLIN). These functions are known as transfer functions. Thus, each of the hidden layer nodes compute output values, which become inputs to the nodes of the output layer. At nodes of output layer also a weighted sum of outputs of previous layer (hidden layer) are obtained and processed through a transfer function. Thus, the output layer nodes compute the network output for the particular input vector. In this paper, output nodes use linear transfer function. Different transfer functions e.g. TANSIG, LOGSIG and PURELIN were used and the performance of the ANN was optimized by changing the number of neurons in the hidden layers. The present analysis suggests the need of critical analysis of the BPANN in terms of selection of the best transfer function and other network parameters for the better results.

Prasad, Rajendra; Pandey, A.; Singh, K. P.; Singh, V. P.; Mishra, R. K.; Singh, D.

2012-08-01

325

Why do leaf-tying caterpillars abandon their leaf ties?  

PubMed Central

Leaf-tying caterpillars act as ecosystem engineers by building shelters between overlapping leaves, which are inhabited by other arthropods. Leaf-tiers have been observed to leave their ties and create new shelters (and thus additional microhabitats), but the ecological factors affecting shelter fidelity are poorly known. For this study, we explored the effects of resource limitation and occupant density on shelter fidelity and assessed the consequences of shelter abandonment. We first quantified the area of leaf material required for a caterpillar to fully develop for two of the most common leaf-tiers that feed on white oak, Quercus alba. On average, Psilocorsis spp. caterpillars consumed 21.65 0.67 cm2 leaf material to complete development. We also measured the area of natural leaf ties found in a Maryland forest, to determine the distribution of resources available to caterpillars in situ. Of 158 natural leaf ties examined, 47% were too small to sustain an average Psilocorsis spp. caterpillar for the entirety of its development. We also manipulated caterpillar densities within experimental ties on potted trees to determine the effects of cohabitants on the likelihood of a caterpillar to leave its tie. We placed 1, 2, or 4 caterpillars in ties of a standard size and monitored the caterpillars twice daily to track their movement. In ties with more than one occupant, caterpillars showed a significantly greater propensity to leave their tie, and left sooner and at a faster rate than those in ties as single occupants. To understand the consequences of leaf tie abandonment, we observed caterpillars searching a tree for a site to build a shelter in the field. This is a risky behavior, as 17% of the caterpillars observed died while searching for a shelter site. Caterpillars that successfully built a shelter traveled 110 20 cm and took 28 7 min to find a suitable site to build a shelter. In conclusion, leaf-tying caterpillars must frequently abandon their leaf tie due to food limitation and interactions with other caterpillars, but this is a costly behavior.

Sliwinski, Michelle

2013-01-01

326

Stem-and-Leaf Plots  

NSDL National Science Digital Library

This lesson is designed to introduce students to stem-and-leaf plots as a graphical way to represent a data set. The lesson also reviews measures of central tendency. This lesson provides links to discussions and activities related to stem-and-leaf plots as well as suggested ways to integrate them into the lesson. Finally, the lesson provides links to follow-up lessons designed for use in succession with the current one.

2010-01-01

327

Leaf exsertion, leaf elongation, and leaf senescence in Eriophorum vaginatum and Carex Bigelowii  

SciTech Connect

Most of the common sedges of arctic vegetation show a pattern of leaf production in which the exsertion and elongation of new leaves is more or less simultaneous with the senescence of old leaves. The present study was designed to increase our understanding of the variability sequential leaf production by arctic sedges, and to determine some of the controls on that variability. We did this in two ways: first, we compared the sequential patterns of leaf growth and senescence in E. vaginatum with those of Carex Bigelowii Torr. at two tussock tundra sites near Toolik Lake on the North Slope of Alaska. Second, we compared the responses of leaf growth in these species in control and fertilized plots and in two microenvironments thought to differ sharply in nutrient availability and total productivity. 29 refs., 28 figs., 2 tabs.

Shaver, G.R.; Yandow, T.; Laundre, J.

1990-01-01

328

Formation of the Fe-S cluster of ferredoxin in lysed spinach chloroplasts. [Spinacia oleracea  

SciTech Connect

In vitro formation of the {sup 35}S-labeled Fe-S cluster of ferredoxin (Fd) has been achieved by incubating apo-Fd and ({sup 35}S)cysteine with osmotically lysed chloroplasts of spinach (Spinacia oleracea). Correct integration of the {sup 35}S-labeled Fe-S cluster into Fd was verified on the basis of the following: (a) Under nondenaturing conditions, {sup 35}S-labeled holo-Fd showed the same electrophoretic mobility as authentic holo-Fd; (b) {sup 35}S-labeled holo-Fd showed an ability to bind Fd-NADP{sup +} reductase; (c) the {sup 35}S-labeled moiety was removed from the Fd polypeptide by TCA treatment but not by 2-mercaptoethanol treatment; (d) externally added pea II apo-Fd was converted to {sup 35}S-labeled holo-Fd. This reconstitution was dependent on both ATP and light, and formation of the {sup 35}S-labeled Fe-S cluster was observed upon addition of ATP or when an ATP generation-system was constructed in the light. In contrast, ATP-consuming systems abolished the Fe-S cluster formation. A non-hydrolyzable ATP analog was unable to serve as an ATP substitute, indicating the requirement of ATP hydrolysis for cluster formation. GTP was able to substitute for ATP, but CTP and UTP were less effective. Fe-S cluster formation in lysed chloroplasts was stimulated by light even in the presence of added ATP. Light stimulation was inhibited by DCMU or methyl viologen but not by NH{sub 4}{sup +}. NADPH was able to substitute for light, indicating that light energy is required for the production of reducing compounds such as NADPH in addition to the generation of ATP.

Takahashi, Yasuhiro; Mitsui, Akira; Matsubara, Hiroshi (Osaka Univ. (Japan))

1991-01-01

329

Spinach SoHXK1 is a mitochondria-associated hexokinase.  

PubMed

Hexokinase, a hexose-phosphorylating enzyme, has emerged as a central enzyme in sugar-sensing processes. A few HXK isozymes have been identified in various plant species. These isozymes have been classified into two major groups; plastidic (type A) isozymes located in the plastid stroma and those containing a membrane anchor domain (type B) located mainly adjacent to the mitochondria, but also found in the nucleus. Of all the hexokinases that have been characterized to date, the only exception to this rule is a spinach type B HXK (SoHXK1) that, by means of subcellular fractionation, has been localized to the outer membrane of plastids. However, SoHXK1 has a membrane anchor domain that is almost identical to that of the other type B HXKs. To determine the localization of SoHXK1 enzyme by other means, we expressed SoHXK1::GFP fusion protein in tobacco and Arabidopsis protoplasts and compared its localization with that of the Arabidopsis AtHXK1::GFP fusion protein that shares a similar N-terminal membrane anchor domain. SoHXK1::GFP is localized adjacent to the mitochondria, similar to AtHXK1::GFP and all other previously examined type B HXKs. Proteomic analysis had previously identified AtHXK1 on the outside of the mitochondrial membrane. We, therefore, suggest that SoHXK1 enzyme is located adjacent to the mitochondria like the other type B HXKs that share the same N-terminal membrane anchor domain. PMID:17530285

Damari-Weissler, Hila; Ginzburg, Alexandra; Gidoni, David; Mett, Anahit; Krassovskaya, Inga; Weber, Andreas P M; Belausov, Eddy; Granot, David

2007-05-26

330

Low Temperature Spectral Properties of Subchloroplast Fractions Purified from Spinach 1  

PubMed Central

Spinach (Spinacia oleracea L.) chloroplasts solubilized by digitonin were separated into five fractions by sucrose density gradient centrifugation. Three of the fractions, FI, FII, and FIII, corresponding to photosystem I, photosystem II, and the chlorophyll a/b complex, were purified further by two steps of diethylaminoethyl-cellulose chromatography followed by electrofocusing on an Ampholine column. The polypeptide patterns of the fractions were examined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and the spectral properties of the fractions at ?196 C determined by absorption spectra, fourth derivative curves of the absorption spectra, fluorescence emission spectra, and fluorescence excitation spectra. The activity of purified FII (photosystem II) was also assayed by the photoreduction of dichlorophenol-indophenol at room temperature using 1,5-diphenylcarbohydrazine as the electron donor and by the photoreduction of C-550 at ?196 C. The different fractions showed unique polypeptide patterns and unique sets of low temperature-absorbing forms of chlorophyll. The fluorescence emission spectra of FI, FII, and FIII at ?196 C were also unique with maxima at 734, 685 and 681 nm, respectively. FI showed negligible emission at wavelengths shorter than 700 nm and the long wavelength tails of FII and FIII in the 730 nm region were relatively small (approximately 10% of emission of their wavelength maxima). Addition of 0.1% Triton to FI and FII caused the longer wavelength absorbing forms of chlorophyll to shift to 670 nm and the fluorescence emission maxima (of both fractions) to shift to 679 nm at ?196 C with an increase in the yield of fluorescence especially in the case of FI. ImagesFig. 7

Satoh, Kimiyuki; Butler, Warren L.

1978-01-01

331

Formation of the Fe-S Cluster of Ferredoxin in Lysed Spinach Chloroplasts 1  

PubMed Central

In vitro formation of the 35S-labeled Fe-S cluster of ferredoxin (Fd) has been achieved by incubating apo-Fd and [35S]cysteine with osmotically lysed chloroplasts of spinach (Spinacia oleracea). Correct integration of the 35S-labeled Fe-S cluster into Fd was verified on the basis of the following: (a) Under nondenaturing conditions, 35S-labeled holo-Fd showed the same electrophoretic mobility as authentic holo-Fd; (b) 35S-labeled holo-Fd showed an ability to bind Fd-NADP+ reductase; (c) the 35S-labeled moiety was removed from the Fd polypeptide by TCA treatment but not by 2-mercaptoethanol treatment; (d) externally added pea II apo-Fd was converted to 35S-labeled holo-Fd. This reconstitution was dependent on both ATP and light, and formation of the 35S-labeled Fe-S cluster was observed upon addition of ATP or when an ATP generation-system was constructed in the light. In contrast, ATP-consuming systems abolished the Fe-S cluster formation. A non-hydrolyzable ATP analog was unable to serve as an ATP substitute, indicating the requirement of ATP hydrolysis for cluster formation. GTP was able to substitute for ATP, but CTP and UTP were less effective. Fe-S cluster formation in lysed chloroplasts was stimulated by light even in the presence of added ATP. Light stimulation was inhibited by DCMU or methyl viologen but not by NH4+. NADPH was able to substitute for light, indicating that light energy is required for the production of reducing compounds such as NADPH in addition to the generation of ATP. These results confirm the requirement of light for the Fe-S cluster formation observed previously in intact chloroplasts. Images Figure 1 Figure 2 Figure 4 Figure 5 Figure 6 Figure 8

Takahashi, Yasuhiro; Mitsui, Akira; Matsubara, Hiroshi

1991-01-01

332

Electron nuclear double resonance evidence supporting a monomeric nature for P700 in spinach chloroplasts.  

PubMed

Proton electron nuclear double resonance (ENDOR) spectra of P700(+) in spinach chloroplasts and in photosystem I particles have been obtained and compared with the corresponding ENDOR spectrum of monomeric chlorophyl a(+) (Chla(+)) cation radical. The hyperfine couplings for P700(+) can be interpreted in terms of those expected for a monomer Chla(+) radical. The reduction in alpha-carbon spin densities observed for the in vivo species when compared to the in vitro radical is attributed to differences in the composition of the ground-state orbital for the two systems. For P700(+), a mixture of 75% D(0)/25% D(1), in which D(0) and D(1) represent the ground-and first excited-state orbitals calculated by Petke et al. for Chla(+) [Petke, J. D., Maggiora, G. M., Shipman, L. L. & Christoffersen, R. E. (1980) Photochem. Photobiol. 31, 243-257], gives good agreement between calculated and experimental spin-density reduction factors. Interaction of the pigment ion with its protein environment such as through ligation of the central Mg atom, hydrogen bonding to the 9-keto-carbonyl group, and electrostatic interactions with charged amino acid residues are proposed as factors responsible for the lowering in energy of the D(1) level in vivo. Combined with similar previous proposals for P680(+) of photosystem II, the data suggest that both primary donor cation radicals of green plant photosynthesis can be viewed as monomeric Chla(+) species in which the D(1) orbital makes a significant contribution to the spin-density distribution. PMID:16593417

O'malley, P J; Babcock, G T

1984-02-01

333

Electron nuclear double resonance evidence supporting a monomeric nature for P700+ in spinach chloroplasts  

PubMed Central

Proton electron nuclear double resonance (ENDOR) spectra of P700+ in spinach chloroplasts and in photosystem I particles have been obtained and compared with the corresponding ENDOR spectrum of monomeric chlorophyl a+ (Chla+) cation radical. The hyperfine couplings for P700+ can be interpreted in terms of those expected for a monomer Chla+ radical. The reduction in ?-carbon spin densities observed for the in vivo species when compared to the in vitro radical is attributed to differences in the composition of the ground-state orbital for the two systems. For P700+, a mixture of 75% D0/25% D1, in which D0 and D1 represent the ground-and first excited-state orbitals calculated by Petke et al. for Chla+ [Petke, J. D., Maggiora, G. M., Shipman, L. L. & Christoffersen, R. E. (1980) Photochem. Photobiol. 31, 243-257], gives good agreement between calculated and experimental spin-density reduction factors. Interaction of the pigment ion with its protein environment such as through ligation of the central Mg atom, hydrogen bonding to the 9-keto-carbonyl group, and electrostatic interactions with charged amino acid residues are proposed as factors responsible for the lowering in energy of the D1 level in vivo. Combined with similar previous proposals for P680+ of photosystem II, the data suggest that both primary donor cation radicals of green plant photosynthesis can be viewed as monomeric Chla+ species in which the D1 orbital makes a significant contribution to the spin-density distribution.

O'Malley, Padraig J.; Babcock, Gerald T.

1984-01-01

334

NON-DESTRUCTIVE ASSESSMENT OF ARUNDO DONAX (POACEAE) LEAF QUALITY.  

Technology Transfer Automated Retrieval System (TEKTRAN)

Leaf quality information (i.e., leaf C content, leaf N content, leaf C:N ratio) is especially useful for understanding plant-herbivore interactions and may be important in developing control methods for the invasive riparian plant Arundo donax L. We measured leaf C content, leaf N content, leaf C:N ...

335

Differential sensitivity of spinach and amaranthus to enhanced UV-B at varying soil nutrient levels: association with gas exchange, UV-B-absorbing compounds and membrane damage.  

PubMed

The metabolic reasons associated with differential sensitivity of C3 and C4 plant species to enhanced UV-B under varying soil nutrient levels are not well understood. In the present study, spinach (Spinacia oleracea L. var All Green), a C3 and amaranthus (Amaranthus tricolor L. var Pusa Badi Chaulai), a C4 plant were subjected to enhanced UV-B (280-315nm; 7.2kJm(-2)day(-1)) over ambient under varying soil nutrient levels. The nutrient amendments were recommended Nitrogen (N), Phosphorus (P), Potassium (K), 1.5 recommended NPK, 1.5 recommended N and 1.5 recommended K. Enhanced UV-B negatively affected both the species at all nutrient levels, but the reductions varied with nutrient concentration and combinations. Reductions in photosynthetic rate, stomatal conductance and chlorophyll content were significantly more in spinach compared with amaranthus. The reduction in photosynthetic rate was maximum at 1.5 recommended K and minimum in 1.5 NPK amended plants. The oxidative damage to membranes measured in terms of malondialdehyde content was significantly higher in spinach compared with amaranthus. Enhanced UV-B reduced SOD activity in both the plants except in amaranthus at 1.5 recommended K. POX activity increased under enhanced UV-B at all nutrient levels in amaranthus, but only at 1.5 K in spinach. Amaranthus had significantly higher UV-B-absorbing compounds than spinach even under UV-B stress. Lowest reductions in yield and total biomass under enhanced UV-B compared with ambient were observed in amaranthus grown at 1.5 recommended NPK. Enhanced UV-B did not significantly change the nitrogen use efficiency in amaranthus at all NPK levels, but reduced in spinach except at 1.5 K. These findings suggest that the differential sensitivity of the test species under enhanced UV-B at varying nutrient levels is due to varying antioxidative and UV-B screening capacity, and their ability to utilize nutrients. Amaranthus tolerated enhanced UV-B stress more than spinach at all nutrient levels and 1.5 recommended NPK lowered the sensitivity maximally to enhanced UV-B with respect to photosynthesis, biomass and yield. PCA score has also confirmed the lower sensitivity of amaranthus compared with spinach with respect to the measured physiological and biochemical parameters. PMID:23686471

Singh, Suruchi; Agrawal, Madhoolika; Agrawal, S B

2013-05-18

336

Escherichia coli O157:H7 biofilm formation and internalization on lettuce and spinach leaf surfaces reduces efficacy of irradiation and sodium hypochlorite washes  

Technology Transfer Automated Retrieval System (TEKTRAN)

Escherichia coli O157:H7 contamination of leafy green vegetables is an ongoing concern for consumers. Biofilm-associated and internalized pathogens are relatively resistant to chemical treatments, but little is known about the response of these protected pathogens to irradiation. Leaves of Romaine l...

337

Transfer of Escherichia coli O157:H7 to spinach by house flies, Musca domestica (Diptera: Muscidae).  

PubMed

Filth flies are known mechanical vectors of pathogenic bacteria in hospital and restaurant settings, but their role as vectors for disseminating microbes to plants has not been demonstrated. Escherichia coli O157:H7 deposition by flies onto spinach was studied using molecular, microbiological, and microscopy techniques. Relative quantitative polymerase chain reaction studies showed that bacteria acquired by flies from contaminated cattle manure and deposited in regurgitation spots on leaves survived and multiplied. Scanning electron microscopy of the regurgitation spots of flies exposed to manure inoculated with E. coli suggested the multiplication of bacteria-like organisms within the spots. This finding implies that the bacteria were active and is consistent with a hypothesis that regurgitation spots serve as a nutrition source allowing E. coli O157:H7 to survive on the spinach phylloplane. E. coli O157:H7 persisted on fly body surfaces up to 13 days after exposure to acquisition sources, suggesting that fly cuticular surfaces are conducive to the growth of this pathogen. These results are consistent with the hypothesis of bioenhanced transmission of human pathogens by house flies and suggest that filth flies may affect the microbial safety of fresh produce. PMID:23425236

Wasala, Lakmini; Talley, Justin L; Desilva, Udaya; Fletcher, Jacqueline; Wayadande, Astri

2013-04-01

338

Structural basis of efficient electron transport between photosynthetic membrane proteins and plastocyanin in spinach revealed using nuclear magnetic resonance.  

PubMed

In the photosynthetic light reactions of plants and cyanobacteria, plastocyanin (Pc) plays a crucial role as an electron carrier and shuttle protein between two membrane protein complexes: cytochrome b(6)f (cyt b(6)f) and photosystem I (PSI). The rapid turnover of Pc between cyt b(6)f and PSI enables the efficient use of light energy. In the Pc-cyt b(6)f and Pc-PSI electron transfer complexes, the electron transfer reactions are accomplished within <10(-4) s. However, the mechanisms enabling the rapid association and dissociation of Pc are still unclear because of the lack of an appropriate method to study huge complexes with short lifetimes. Here, using the transferred cross-saturation method, we investigated the residues of spinach (Spinacia oleracea) Pc in close proximity to spinach PSI and cyt b(6)f, in both the thylakoid vesicle-embedded and solubilized states. We demonstrated that the hydrophobic patch residues of Pc are in close proximity to PSI and cyt b(6)f, whereas the acidic patch residues of Pc do not form stable salt bridges with either PSI or cyt b(6)f, in the electron transfer complexes. The transient characteristics of the interactions on the acidic patch facilitate the rapid association and dissociation of Pc. PMID:23032988

Ueda, Takumi; Nomoto, Naoko; Koga, Masamichi; Ogasa, Hiroki; Ogawa, Yuuta; Matsumoto, Masahiko; Stampoulis, Pavlos; Sode, Koji; Terasawa, Hiroaki; Shimada, Ichio

2012-10-02

339

Mild Fe-deficiency improves biomass production and quality of hydroponic-cultivated spinach plants (Spinacia oleracea L.).  

PubMed

It is of great practical importance to improve yield and quality of vegetables in soilless cultures. This study investigated the effects of iron-nutrition management on yield and quality of hydroponic-cultivated spinach (Spinacia oleracea L.). The results showed that mild Fe-deficient treatment (1 ?M FeEDTA) yielded a greater biomass of edible parts than Fe-omitted treatment (0 ?M FeEDTA) or Fe-sufficient treatments (10 and 50 ?M FeEDTA). Conversely, mild Fe-deficient treatment had the lowest nitrate concentration in the edible parts out of all the Fe treatments. Interestingly, all the concentrations of soluble sugar, soluble protein and ascorbate in mild Fe-deficient treatments were higher than Fe-sufficient treatments. In addition, both phenolic concentration and DPPH scavenging activity in mild Fe-deficient treatments were comparable with those in Fe-sufficient treatments, but were higher than those in Fe-omitted treatments. Therefore, we concluded that using a mild Fe-deficient nutrition solution to cultivate spinach not only would increase yield, but also would improve quality. PMID:23497875

Jin, Chong-Wei; Liu, Yue; Mao, Qian-Qian; Wang, Qian; Du, Shao-Ting

2012-12-29

340

Expression of the Large ATP Synthase Gene Cluster in Spinach Plastids during Light-Induced Development 1  

PubMed Central

The large ATP synthase gene cluster in spinach (Spinacia oleracea) plastids encodes four of the six chloroplast-encoded ATP synthase subunits. Expression of this cluster was examined to determine its response to light-induced plastid development. Spinach plastid transcripts were isolated from etiolated tissues, etiolated tissues exposed to 24 h of light, young (1-3 cm) leaves, and mature (8-10 cm) leaves. Transcript levels were examined from each developmental stage as a function of either the quantity of total RNA or gene dosage. The relative transcriptional activity of this gene cluster at each of the four developmental stages was also investigated. The stability of these transcripts was deduced by comparing the transcriptional activity with steady-state transcript levels. During the initial 24 h of light-induced development of an etioplast to a chloroplast, transcription decreases in conjunction with increased transcript stability. Transcriptional activity of this cluster per genome then increases between the 24-h and young stages, with a concomitant decrease in the stability of the transcripts. As the young chloroplast matures, the transcripts from this cluster again become markedly more stable, and the transcription of this set of genes declines. Therefore, the regulation of the expression of this cluster is dependent upon a complex interaction between transcriptional and posttranscriptional factors throughout light-induced plastid development. Images Figure 3 Figure 4

Green, Cynthia D.; Hollingsworth, Margaret J.

1992-01-01

341

MicroRNA profiling of carcinogen-induced rat colon tumors and the influence of dietary spinach  

PubMed Central

Scope MicroRNA (miRNA) profiles are altered in chronic conditions such as cardiovascular disease, diabetes, neurological disorders, and cancer. A systems biology approach was used to examine, for the first time, miRNAs altered in rat colon tumors induced by 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP), a heterocyclic amine carcinogen from cooked meat. Methods and Results Among the most highly dysregulated miRNAs were those belonging to the let-7 family. Subsequent computational modeling and target validation identified c-Myc and miRNA-binding proteins Lin28A/Lin28B (Lin28) as key players, along with Sox2, Nanog and Oct-3/4. These targets of altered miRNAs in colon cancers have been implicated in tumor recurrence and reduced patient survival, in addition to their role as pluripotency factors. In parallel with these findings, the tumor-suppressive effects of dietary spinach given post-initiation correlated with elevated levels of let-7 family members and partial normalization of c-myc, Sox2, Nanog, Oct-3/4, HmgA2, Dnmt3b and P53 expression. Conclusion We conclude that the let-7/c-Myc/Lin28 axis is dysregulated in heterocyclic amine-induced colon carcinogenesis, and that the tumor suppressive effects of dietary spinach are associated with partial normalization of this pathway.

Parasramka, Mansi A.; Dashwood, W. Mohaiza; Wang, Rong; Abdelli, Amir; Bailey, George S.; Williams, David E.; Ho, Emily; Dashwood, Roderick H.

2013-01-01

342

Estimating leaf biochemistry using the PROSPECT leaf optical properties model  

Microsoft Academic Search

The biophysical, biochemical, and optical properties of 63 fresh leaves and 58 dry leaves were measured to investigate the potential of remote sensing to estimate the leaf biochemistry from space. Almost 2000 hemispherical reflectance and transmittance spectra were acquired from 400 nm to 2500 nm using a laboratory spectrophotometer. The amount of chlorophyll, water, protein, cellulose, hemicellulose, lignin, and starch

S. Jacquemoud; S. L. Ustin; J. Verdebout; G. Schmuck; G. Andreoli; B. Hosgood

1996-01-01

343

The orientation of membrane bound radicals: an EPR investigation of magnetically ordered spinach chloroplasts.  

PubMed

The orientation of membrane-bound radicals in spinach chloroplasts is examined by electron paramagnetic resonance (EPR) spectroscopy of chloroplasts oriented by magnetic fields. Several of the membrane-bound radicals which possess g-tensor anisotropy display EPR signals with a marked dependence on the orientation of the membranes relative to the applied EPR field. The fraction of oxidized and reduced plastocyanin, P-700, iron-sulfur proteins A and B, and the X center, an early acceptor of Photosystem I, can be controlled by the light intensity during steady-state illumination and can be trapped by cooling. The X center can be photoreduced and trapped in the absence of strong reductants and high pH, conditions previously found necessary for its detection. These results confirm its role as an early electron acceptor in P-700 photo-oxidation. X is oriented with its smallest principal g-tensor axis (gx) predominantly parallel to the normal to the thylakoid membrane, the same orientation as was found for an early electron acceptor based on time-resolved electron spin polarization studies. We propose that the X center is the first example of a high potential iron-sulfur protein which functions in electron transfer in its 'superreduced' state. We present evidence which suggests that iron-sulfur proteins A and B are 4Fe-4S clusters in an 8Fe-8S protein. Center B is oriented with gy predominantly normal to the membrane plane. The spectra of center A and plastocyanin do not show significant changes with sample orientation. In the case of plastocyanin, this may indicate a lack of molecular orientation. The absence of an orientation effect for reduced center A is reconcilable with a 4Fe-4S geometry, provided that the electron obtained upon reduction can be shared between any pair of Fe atoms in the center. Orientation of the 'Rieske' iron-sulfur protein is also observed. It has axial symmetry with g parallel close to the plane of the membrane. A model is proposed for the organization of these proteins in the thylakoid membrane. A new EPR signal was observed in oriented chloroplasts. This broad unresolved resonance displays a g value of 3.2 when the membrane normal is parallel to the field. It shifts to g = 1.9 when the membrane normal is perpendicular to the field. The signal is sensitive to illumination and to washing of the thylakoid membranes of broken chloroplasts. We suggest that there is a relation between this signal and the water-oxidizing enzyme system. PMID:214110

Dismukes, G C; Sauer, K

1978-12-01

344

Amperometric sensor for hydrogen peroxide based on direct electron transfer of spinach ferredoxin on Au electrode.  

PubMed

A protein-based electrochemical sensor for hydrogen peroxide (H(2)O(2)) was developed by an easy and effective film fabrication method where spinach ferredoxin (Fdx) containing [2Fe-2S] metal center was cross linked with 11-mercaptoundecanoic acid (MUA) on a gold (Au) surface. The surface morphology of Fdx molecules on Au electrodes was investigated by atomic force microscopy (AFM). Electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) were employed to study the electrochemical behavior of adsorbed Fdx on Au. The interfacial properties of the modified electrode were evaluated in the presence of Fe(CN)(6)(3-/4-) redox couple as a probe. From CV, a pair of well-defined and quasi-reversible redox peaks of Fdx was obtained in 10mM, pH 7.0 Tris-HCl buffer solution at -170 and -120mV respectively. One electron reduction of the [2Fe-2S](2+) cluster occurs at one of the iron atoms to give the reduced [2Fe-2S](+). The formal reduction potential of Fdx ca. -150mV (vs. Ag/AgCl electrode) at pH 7.0. The electron-transfer rate constant, k(s), for electron transfer between the Au electrode and Fdx was estimated to be 0.12s(-1). From the electrochemical experiments, it is observed that Fdx/MUA/Au promoted direct electron transfer between Fdx and electrode and it catalyzes the reduction of H(2)O(2). The Fdx/MUA/Au electrode displays a linear increase in amperometric current for increasing concentration of H(2)O(2).The sensor calibration plot was linear with r(2)=0.998 with sensitivity approximately 68.24?Am M(-1)cm(-2). Further, the effect of nitrite on the developed sensor was examined which does not interfere with the detection of H(2)O(2). Finally, the addition of H(2)O(2) on MUA/Au electrode was observed which has no effect on amperometric current. PMID:20851693

Yagati, Ajay Kumar; Lee, Taek; Min, Junhong; Choi, Jeong-Woo

2010-08-26

345

7 CFR 30.2 - Leaf tobacco.  

Code of Federal Regulations, 2013 CFR

...2013-01-01 2013-01-01 false Leaf tobacco. 30.2 Section 30.2 Agriculture...STANDARDS AND STANDARD CONTAINER REGULATIONS TOBACCO STOCKS AND STANDARDS Classification of Leaf Tobacco Covering Classes, Types and Groups of...

2013-01-01

346

Optical Spectra of Synechocystis and Spinach Photosystem II Preparations at 1.7 K: Identification of the D1Pheophytin Energies and Stark Shifts  

Microsoft Academic Search

We report and compare highly resolved, simultaneously recorded absorption and CD spectra of active Photosystem II (PSII) samples in the range 440-750 nm. From an appropriately scaled comparison of spinach membrane fragment (BBY) and PSII core spectra, we show that key features of the core spectrum are quantitatively represented in the BBY data. PSII from the cyanobacterium Synechocystis 6803 display

Vanessa M. Masters; Barry J. Prince; Paul J. Smith; Ron J. Pace; Elmars Krausz

2003-01-01

347

Effect of Nd{sup 3+} ion on carboxylation activity of ribulose-1,5-bisphosphate carboxylase/oxygenase of spinach  

SciTech Connect

Neodymium (Nd), as a member of rare earth elements, proved to enhance the photosynthesis rate and organic substance accumulation of spinach through the increase in carboxylation activity of Rubisco. Although the oxygenase activity of spinach Rubisco was slightly changed with the Nd{sup 3+} treatment, the specific factor of Rubisco was greatly increased. It was partially due to the promotion of Rubisco activase (R-A) activity but mainly to the formation of Rubisco-Rubisco activase super-complex, a heavier molecular mass protein (about 1200 kD) comprising both Rubisco and Rubisco activase. This super-complex was found during the extraction procedure of Rubisco by the gel electrophoresis and Western-blot studies. The formation of Rubisco-R-A super-complex suggested that the secondary structure of the protein purified from the Nd{sup 3+}-treated spinach was different from that of the control. Extended X-ray absorption fine structure study of the 'Rubisco' purified from the Nd{sup 3+}-treated spinach revealed that Nd was bound with four oxygen atoms and two sulfur atoms of amino acid residues at the Nd-O and Nd-S bond lengths of 2.46 and 2.89 A, respectively.

Liu Chao [College of Life Sciences, Soochow University, Suzhou 215123 (China); Hong Fashui [College of Life Sciences, Soochow University, Suzhou 215123 (China)]. E-mail: Hongfsh_cn@sina.com; Wu Kang [College of Life Sciences, Soochow University, Suzhou 215123 (China); Ma, Hong-bing [College of Life Sciences, Soochow University, Suzhou 215123 (China); Zhang Xueguang [College of Life Sciences, Soochow University, Suzhou 215123 (China); Hong Chengjiao [College of Radiation and Public Sanitation, Soochow University, Suzhou 215123 (China); Wu Cheng [College of Life Sciences, Soochow University, Suzhou 215123 (China); Gao Fengqing [College of Life Sciences, Soochow University, Suzhou 215123 (China); Yang Fan [College of Life Sciences, Soochow University, Suzhou 215123 (China); Zheng Lei [College of Life Sciences, Soochow University, Suzhou 215123 (China); Wang Xuefeng [College of Life Sciences, Soochow University, Suzhou 215123 (China); Liu Tao [Synchrotron Radiation Laboratory, Institute of High Energy Physics, Chinese Academy of Science, Beijing 100039 (China); Xie Yaning [Synchrotron Radiation Laboratory, Institute of High Energy Physics, Chinese Academy of Science, Beijing 100039 (China); Xu Jianhua [Synchrotron Radiation Laboratory, Institute of High Energy Physics, Chinese Academy of Science, Beijing 100039 (China); Li Zhongrui [School of Chemical, Biological and Materials Engineering, University of Oklahoma (United States)

2006-03-31

348

Isolation of Campylobacter from feral swine (Sus scrofa) on the ranch associated with the 2006 Escherichia coli O157:H7 spinach outbreak investigation in California  

Technology Transfer Automated Retrieval System (TEKTRAN)

We report the isolation of Campylobacter species from the same population of feral swine that was investigated in San Benito County, California during the 2006 spinach-related Escherichia coli O157:H7 outbreak. This is the first survey of Campylobacter in a free-ranging feral swine population in the...

349

Isolation of a cDNA clone for spinach lipid transfer protein and evidence that the protein is synthesized by the secretory pathway  

Microsoft Academic Search

A cDNA clone encoding a nonspecific lipid transfer protein from spinach (Spinacia oleracea) was isolated by probing a library with synthetic oligonucleotides based on the amino acid sequence of the protein. Determination of the DNA sequence indicated a 354-nucleotide open reading frame which encodes a 118-amino acid residue polypeptide. The first 26 amino acids of the open reading frame, which

W. R. Bernhard; S. Thoma; J. Botella; C. R. Somerville

1991-01-01

350

The 110-kDa Polypeptide of Spinach Plastid DNA-Dependent RNA Polymerase: Single-Subunit Enzyme or Catalytic Core of Multimeric Enzyme Complexes?  

Microsoft Academic Search

Highly purified RNA polymerase preparations from spinach chloroplasts contain seven major polypeptides of 150, 145, 110, 102, 80, 75, and 38 kDa. I find that RNA polymerase activity can be separated under defined conditions into three different fractions by heparin-Sepharose chromatography. Immunological analysis has shown that the first fraction contains RNA polymerase activity associated with all seven major polypeptides, and

Silva Lerbs-Mache

1993-01-01

351

The effect of total organic carbon content and repeated irrigation on the persistence of E. coli O157:H7 on baby spinach  

Technology Transfer Automated Retrieval System (TEKTRAN)

Introduction: Contaminated fresh-cut spinach and other leafy greens have caused foodborne illness in the United States. In response, growers are adopting recommendations stated in the California Leafy Greens Marketing Agreement (LGMA). The LGMA permits a maximum population of 126 Most Probable Nu...

352

Ribulose1,5-bisphosphate carboxylase-oxygenase, other Calvin-cycle enzymes, and chlorophyll decrease when glucose is supplied to mature spinach leaves via the transpiration stream  

Microsoft Academic Search

The inhibition of photosynthesis after supplying glucose to detached leaves of spinach (Spinacia oleracea L.) was used as a model system to search for mechanisms which potentially contribute to the sink regulation of photosynthesis. Detached leaves were supplied with 50 mM glucose or water for 7 d through the transpiration stream, holding the leaves in low irradiance (16 mol photons

Anne Krapp; W. Paul Quick; Mark Stitt

1991-01-01

353

Photosystem I-dependent cyclic electron flow in intact spinach chloroplasts: Occurrence, dependence on redox conditions and electron acceptors and inhibition by antimycin A  

Microsoft Academic Search

Photosystem I-dependent cyclic electron transport is shown to operate in intact spinach chloroplasts with oxaloacetate, but not with nitrite or methylviologen as electron acceptors. It is regulated by the redox state of the chloroplast NADP system. Inhibition of cyclic electron transport by antimycin A occurs immediately on addition of this antibiotic in the light. It is unrelated to a different

B. Ivanov; Y. Kobayashi; N. G. Bukhov; U. Heber

1998-01-01

354

Inhibition of E. coli O157:H7 on the surface of Fresh Spinach by bacteriophage ECP-100 and Modified Atmosphere Packaging  

Technology Transfer Automated Retrieval System (TEKTRAN)

The last multistate Escherichia coli O157:H7 (EHEC) outbreak linked to bagged spinach in 2006 has raised concerns about the safety of ready-to-eat vegetables. Since washing alone or in combination with chemicals has been ineffective in completely killing EHEC, there is an urgent need for more effect...

355

The efficacy of sanitizer and ultrasound combined treatments on reduction of Escherichia coli O157:H7 surrogate population on spinach  

Technology Transfer Automated Retrieval System (TEKTRAN)

The recent outbreak of Escherichia coli O157:H7 infections on bagged spinach reaffirmed the importance and challenges of produce safety. Current washing processes in industrial scale operations can only achieve 1- to 2-log CFU/g reduction in microbial populations. More effective post-harvest interve...

356

Intake and digestibility by pigs fed different levels of sweet potato leaves and water spinach as supplements to a mixture of rice bran and cassava root meal  

Microsoft Academic Search

The aim of this experiment, conducted at the Livestock Research Center of the National Agriculture and Forestry Institute (NAFRI), Lao PDR, was to study intake and digestibility in growing pigs fed different levels of sweet potato leaves and water spinach as supplements to a mixture of rice bran and cassava root meal. Three local male pigs of average live weight

Chittavong Malavanh; T R Preston

357

Influence of the interaction between light intensity and CO2 concentration on productivity and quality of spinach (Spinacia oleracea L.) grown in fully controlled environment  

NASA Astrophysics Data System (ADS)

The effects of the factorial combination of two light intensities (200 and 800 ?mol m?2 s?1) and two CO2 concentrations (360 and 800 ppm) were studied on the productivity and nutritional quality of spinach (Spinacia oleracea L.) grown under controlled environment. After 6 weeks within a growth chamber, spinach plants were sampled and analyzed for productivity and quality. There were no statistically significant interactions between the effects of light and CO2 for all of the variables studied, except for the nitrate and oxalic acid content of the leaves. High light and high CO2 independently one from the other, promoted spinach productivity, and the accumulation of ascorbic acid, while their interactive effect limited the accumulation of nitrate and oxalic acid in the spinach leaves. The results highlight the importance of considering the effects of the interaction among environmental variables on maximizing production and the nutritional quality of the food when cultivating and modeling the plant response in controlled environment systems such as for bioregenerative life support.

Proietti, Simona; Moscatello, Stefano; Giacomelli, Gene A.; Battistelli, Alberto

2013-09-01

358

7 CFR 29.3648 - Thin Leaf (C Group).  

Code of Federal Regulations, 2013 CFR

...tolerance. C2F Fine Quality Medium-brown Thin Leaf. ...injury tolerance. C3F Good Quality Medium-brown Thin Leaf. ...injury tolerance. C3G Good Quality Green Thin Leaf. Underripe, medium body, firm leaf...

2013-01-01

359

Deciduous leaf drop reduces insect herbivory  

Microsoft Academic Search

Deciduous leaf fall is thought to be an adaptation that allows plants living in seasonal environments to reduce water loss\\u000a and damage during unfavorable periods while increasing photosynthetic rates during favorable periods. Observations of natural\\u000a variation in leaf shedding suggest that deciduous leaf fall may also allow plants to reduce herbivory. I tested this hypothesis\\u000a by experimentally manipulating leaf retention

Richard Karban

2007-01-01

360

Leaf Photosynthesis Under Drought Stress  

Microsoft Academic Search

The photosynthetic apparatus is resistant to drought. Net CO2 uptake of a leaf submitted to a mild desiccation decreases because of stomatal closure. As aresult, CO2 concentration in the chloroplast decreases in plants exposed to water shortage. This drop in the chloroplast CO2 concentration causes: (i) a decrease in photochemical yield of open PS II centers and, consequently, an increase

Gabriel Cornic; Angelo Massacci

361

CORN LEAF CHLOROPHYLL STATUS FROM HYPERSPECTRAL IMAGES  

Technology Transfer Automated Retrieval System (TEKTRAN)

Leaf chlorophyll concentration is an indicator of plant N status. Subtle differences in canopy reflectance due to changes in leaf chlorophyll concentration are often overwhelmed by the large changes in reflectance associated with soil brightness and leaf area index (LAI). Our objective was to devel...

362

7 CFR 29.2278 - Leaf structure.  

Code of Federal Regulations, 2010 CFR

...2 2010-01-01 2010-01-01 false Leaf structure. 29.2278 Section 29.2278 Agriculture ...Fire-Cured Tobacco (u.s. Type 21) § 29.2278 Leaf structure. The cell development of a leaf as indicated by its...

2010-01-01

363

7 CFR 29.2278 - Leaf structure.  

Code of Federal Regulations, 2010 CFR

...2 2009-01-01 2009-01-01 false Leaf structure. 29.2278 Section 29.2278 Agriculture ...Fire-Cured Tobacco (u.s. Type 21) § 29.2278 Leaf structure. The cell development of a leaf as indicated by its...

2009-01-01

364

Leaf litter decomposition in three Adirondack lakes  

Microsoft Academic Search

Decomposition of terrestrial leaf litter in three Adirondack lakes with water pH values approximately 5, 6, and 7 was studied. Litter bags containing leaves of American beech, sugar maple, red maple, leather leaf, and red spruce were placed in the lakes. Samples were removed periodically over a 3-year period and analyzed for loss in weight, changes in leaf surface area,

A. J. Francis; H. L. Quinby; G. R. Hendrey; C. G. Hoogendyk

1983-01-01

365

Malate Dehydrogenases in the Rusted Bean Leaf.  

PubMed

Rust growth in the bean leaf was accompanied by the appearance of one new malate dehydrogenase isozyme and continuation of one otherwise lost during the development of the healthy leaf. The new isozyme was contributed by the fungus, the other by the leaf. Both enzymes were cytoplasmic proteins. Rusting caused the loss of a mitochondrial isozyme. PMID:17802172

Staples, R C; Stahmann, M A

1963-06-21

366

Histochemical fluorescence of tissue and brain monoamines: results in 18 minutes using the sucrose-phosphate-glyoxylic acid (SPG) method.  

PubMed

A rapid and sensitive modification of the glyoxylic acid method for the histofluorescent visualization of catecholamines and serotonin in mammalian brain, and other tissues, from cryostat sections is described. The procedure uses a phosphate-sucrose buffer solution combined with 1% glyoxylic acid. Tissues are reacted for 3 s at room temperature. Catecholaminergic cell bodies, pre-terminal, and terminal varicosities, well-localized and brightly fluorescent, are seen throughout cortical and subcortical structures. Serotoninergic cells show a weak fluorescence in rat and mouse brain but a strong fluorescence in dog and monkey brain. PMID:11370236

de la Torre, J C; Surgeon, J W

1976-12-01

367

Sucrose Phosphate Synthase Activity Rises in Correlation with High-Rate Cellulose Synthesis in Three Heterotrophic Systems1  

PubMed Central

Based on work with cotton fibers, a particulate form of sucrose (Suc) synthase was proposed to support secondary wall cellulose synthesis by degrading Suc to fructose and UDP-glucose. The model proposed that UDP-glucose was then channeled to cellulose synthase in the plasma membrane, and it implies that Suc availability in cellulose sink cells would affect the rate of cellulose synthesis. Therefore, if cellulose sink cells could synthesize Suc and/or had the capacity to recycle the fructose released by Suc synthase back to Suc, cellulose synthesis might be supported. The capacity of cellulose sink cells to synthesize Suc was tested by analyzing the Suc phosphate synthase (SPS) activity of three heterotrophic systems with cellulose-rich secondary walls. SPS is a primary regulator of the Suc synthesis rate in leaves and some Suc-storing, heterotrophic organs, but its activity has not been previously correlated with cellulose synthesis. Two systems analyzed, cultured mesophyll cells of Zinnia elegans L. var. Envy and etiolated hypocotyls of kidney beans (Phaseolus vulgaris), contained differentiating tracheary elements. Cotton (Gossypium hirsutum L. cv Acala SJ-1) fibers were also analyzed during primary and secondary wall synthesis. SPS activity rose in all three systems during periods of maximum cellulose deposition within secondary walls. The Z. elegans culture system was manipulated to establish a tight linkage between the timing of tracheary element differentiation and rising SPS activity and to show that SPS activity did not depend on the availability of starch for degradation. The significance of these findings in regard to directing metabolic flux toward cellulose will be discussed.

Babb, V. Michelle; Haigler, Candace H.

2001-01-01

368

Manipulating the Incorporation of [1-14C]Acetate into Different Leaf Glycerolipids in Several Plant Species  

PubMed Central

During short term labeling of expanding leaves of seven plant species with [1-14C]acetate, 35 to 64% of the label incorporated into lipids was found in phosphatidylcholine and 5 to 24% in phosphatidylglycerol. In pumpkin, sunflower, broad bean, and maize, only 4 to 12% of the label was found in diacylgalactosylglycerol, but in tomato, parsley, and spinach, the proportion was 17 to 31%. The latter group was further distinguished by having diacylgalactosylglycerol containing C16:3. The proportions of total incorporated [1-14C]acetate entering the lipids could be manipulated in a predictable manner. Phosphatidylcholine labeling was depressed by treating intact leaves with glycerol or ethylene glycol monomethyl ether or by incubating leaf discs in vitro. An associated increase in phosphatidylglycerol labeling occurred within the first group of plants, whereas an increase in labeling of either diacylgalactosylglycerol, phosphatidylglycerol, or sulfolipid occurred within the second group. Treating intact leaves with glycerol or incubating leaf discs in vitro was shown to elevate cellular concentrations of sn-glycerol 3-phosphate. These results have been interpreted in terms of the two-pathway hypothesis for glycerolipid biosynthesis, in which it is proposed that phosphatidylcholine is synthesized via a different pathway (eukaryotic) to that for synthesis of phosphatidylglycerol (prokaryotic). Both pathways may contribute toward the synthesis of diacylgalactosylglycerol, with the contribution of each being assessed from the proportion of hexadecatrienoic acid found in the particular plant. Images Fig. 1

Gardiner, Susan E.; Roughan, P. Grattan; Slack, C. Roger

1982-01-01

369

Single leaf area estimation models based on leaf weight of eucalyptus in southern China  

Microsoft Academic Search

Leaf area is an important parameter for modeling tree growth and physiological processes of trees. The single young and mature\\u000a leaf area estimation models of eucalyptus were developed based on leaf fresh weight. In total, leaf area and leaf weight were\\u000a measured from 455 fresh leaves of 25 trees of eucalyptus in southern China. The majority of the data (80%)

Jun Diao; Xiang-dong Lei; Ling-xia Hong; Jian-tao Rong; Qiang Shi

2010-01-01

370

Habitat Complexity of Stream Leaf Packs: Effects on Benthic Macroinvertebrates and Leaf Litter Breakdown  

NASA Astrophysics Data System (ADS)

We investigated two attributes of leaf-pack complexity (i.e., leaf-pack mass and leaf surface area) on fish predation, colonization of benthic macroinvertebrates, and leaf breakdown rates in a coldwater Michigan stream. We manipulated three factors using a factorial design: fish (exclusion or control cage), leaf-pack mass (1, 3, or 5 g dry mass), and leaf surface area (<7, 7-10, or >10 cm leaf width). Acer leaves were fastened into leaf packs. Exclusion cages had mesh on all sides; control cages lacked mesh on two sides to provide access to fishes. Two replicate leaf packs were randomly collected after 25-31 d from two sections of the stream (n = 4). Common shredders were Gammarus, Pycnopsyche, and Lepidostoma. We did not detect a significant effect of fish predation on benthic macroinvertebrates or leaf breakdown (i.e., mass loss). Colonization of benthic macroinvertebrates appeared proportional to leaf-pack mass but was unaffected by the surface area of leaves. Leaf breakdown was more rapid among leaf packs with fewer leaves (i.e., leaves with large surface area and leaf packs with low mass) and greater numbers of shredders. We suspect that physical fragmentation is the primary mechanism for higher breakdown rates among leaf packs with fewer leaves.

Ruetz, C. R.; Vanhaitsma, D. L.; Breen, M. J.

2005-05-01

371

The dosimetric impact of leaf interdigitation and leaf width on VMAT treatment planning in Pinnacle: comparing Pareto fronts  

Microsoft Academic Search

To evaluate in an objective way the effect of leaf interdigitation and leaf width on volumetric modulated arc therapy plans in Pinnacle. Three multileaf collimators (MLCs) were modeled: two 10 mm leaf width MLCs, with and without interdigitating leafs, and a 5 mm leaf width MLC with interdigitating leafs. Three rectum patients and three prostate patients were used for the

Z van Kesteren; T M Janssen; E Damen; C van Vliet-Vroegindeweij

2012-01-01

372

Isolation of Mesophyll Cells and Bundle Sheath Cells from Digitaria sanguinalis (L.) Scop. Leaves and a Scanning Microscopy Study of the Internal Leaf Cell Morphology 1  

PubMed Central

A technique is described for the separation of mesophyll and bundle sheath cells from Digitaria sanguinalis leaves and evidence for separation is given with light and scanning electron micrographs. Gentle grinding of fully differentiated leaves in a mortar releases mesophyll cells which are isolated on nylon nets by filtration. More extensive grinding of the remaining tissue yields bundle sheath strands which are isolated by filtration with stainless steel sieves and nylon nets. Further grinding of bundle sheath strands in a tissue homogenizer releases bundle sheath cells which are collected on nylon nets. Percentage of purity derived from cell counts and yield data on a chlorophyll basis are given. The internal leaf cell morphology is presented in scanning electron micrographs and compared with light micrographs of fully-differentiated D. sanguinalis leaves. In leaves of plants which possess the C4-dicarboxylic acid cycle of photosynthesis, the relationship of leaf morphology to photosynthesis in mesophyll and bundle sheath cells is considered, and the hypothesis is presented that as atmospheric CO2 enters a leaf about 85% is fixed by the C4-dicarboxylic acid cycle in the mesophyll cells and 10 to 15% is fixed by the reductive pentose phosphate cycle in the bundle sheath cells. A technique also is given for the isolation of mesophyll cells from spinach leaves. Images

Edwards, Gerald E.; Black, Clanton C.

1971-01-01

373

Biochemical and proton NMR characterization of the isolated functional beta-subunit of coupling factor one from spinach chloroplasts  

SciTech Connect

Beta subunits have been dissociated from CF1 of spinach chloroplasts, purified by HPLC and characterized by two-dimensional electrophoresis and fluorescence emission. The solutions of isolated beta subunits are able to hydrolyze MgATP; this ATPase activity is an intrinsic property of the beta molecule. From proton NMR at 300 and 500 MHz, it is shown that the preparations are fully reproducible and that beta subunits remain monomeric with 75% aliphatic protons associated with rigid parts of the molecule. The other 25% give rise to separate resonances and belong to mobile side-chains and/or to flexible regions. The measurement of the transverse relaxation times T2 has permitted a detailed characterization of the molecular dynamics of the isolated beta subunits.

Roux-Fromy, M.; Neumann, J.M.; Andre, F.; Berger, G.; Girault, G.; Galmiche, J.M.; Remy, R.

1987-04-29

374

Extended-spectrum Beta-lactamase gene sequences in gram-negative saprophytes on retail organic and nonorganic spinach.  

PubMed

A substantial proportion of infections caused by drug-resistant Gram-negative bacteria (GNB) in community and health care settings are recognized to be caused by evolutionarily related GNB strains. Their global spread has been suggested to occur due to human activities, such as food trade and travel. These multidrug-resistant GNB pathogens often harbor mobile drug resistance genes that are highly conserved in their sequences. Because they appear across different GNB species, these genes may have origins other than human pathogens. We hypothesized that saprophytes in common human food products may serve as a reservoir for such genes. Between July 2007 and April 2008, we examined 25 batches of prepackaged retail spinach for cultivatable GNB population structure by 16S rRNA gene sequencing and for antimicrobial drug susceptibility testing and the presence of extended-spectrum beta-lactamase (ESBL) genes. We found 20 recognized GNB species among 165 (71%) of 231 randomly selected colonies cultured from spinach. Twelve strains suspected to express ESBLs based on resistance to cefotaxime and ceftazidime were further examined for bla(CTX-M) and bla(TEM) genes. We found a 712-bp sequence in Pseudomonas teessidea that was 100% identical to positions 10 to 722 of an 876-bp bla(CTX-M-15) gene of an E. coli strain. Additionally, we identified newly recognized ESBL bla(RAHN-2) sequences from Rahnella aquatilis. These observations demonstrate that saprophytes in common fresh produce can harbor drug resistance genes that are also found in internationally circulating strains of GNB pathogens; such a source may thus serve as a reservoir for drug resistance genes that ultimately enter pathogens to affect human health. PMID:21216903

Raphael, Eva; Wong, Lisa K; Riley, Lee W

2011-01-07

375

7 CFR 28.466 - Leaf Grade 6.  

Code of Federal Regulations, 2013 CFR

...2013-01-01 2013-01-01 false Leaf Grade 6. 28.466 Section 28.466 Agriculture Regulations of the Department of Agriculture...for the Leaf Grade of American Upland Cotton § 28.466 Leaf Grade 6. Leaf Grade 6 is leaf which is...

2013-01-01

376

7 CFR 29.1162 - Leaf (B Group).  

Code of Federal Regulations, 2013 CFR

...firm leaf structure, medium body, rich in oil...10 percent. B3LGood Quality Lemon Leaf Ripe, firm leaf structure, medium body, oily, strong...firm leaf structure, medium body, stringy. Uniformity...percent waste. B3SGood Quality Slick Leaf...

2013-01-01

377

7 CFR 29.3647 - Heavy Leaf (B Group).  

Code of Federal Regulations, 2013 CFR

...Medium-brown Heavy Leaf. Ripe, medium body, open leaf structure...injury tolerance. B3F Good Quality Medium-brown Heavy Leaf. Mature...injury tolerance. B3M Good Quality Mixed Heavy Leaf. Mature, medium body, firm leaf...

2013-01-01

378

Efficacy of washing with hydrogen peroxide followed by aerosolized antimicrobials as a novel sanitizing process to inactivate Escherichia coli O157:H7 on baby spinach.  

PubMed

Aerosolization was investigated as a potential way to apply allyl isothiocyanate (AIT), hydrogen peroxide (H(2)O(2)), acetic acid (AA) and lactic acid (LA) on fresh baby spinach to control Escherichia coli O157:H7 during refrigeration storage. In this study, baby spinach leaves were dip-inoculated with E. coli O157:H7 to a level of 6 log CFU/g and stored at 4C for 24 h before treatment. Antimicrobials were atomized into fog-like micro-particles by an ultrasonic nebulizer and routed into a jar and a scale-up model system where samples were treated. Samples were stored at 4C for up to 10 days before the survival of the cells was determined. A 2-min treatment with 5% AIT resulted in a >5-log reduction of E. coli O157:H7 on spinach after 2 days refrigeration regardless if the samples were pre-washed or not; however, this treatment impaired the sensory quality of leaves. Addition of LA to AIT improved the antimicrobial efficacy of AIT. In the jar system, washing with 3% H(2)O(2) followed by a 2-min treatment of 2.5% LA+1% AIT or 2.5% LA+2% AIT reduced E. coli O157:H7 population by 4.7 and >5 log CFU/g, respectively, after 10 days refrigeration. In the scale-up system, up to 4-log reduction of bacterial population was achieved for the same treatments without causing noticeable adverse effect on the appearance of leaves. Thus, this study demonstrates the potential of aerosolized AIT+LA as a new post-washing intervention strategy to control E. coli O157:H7 on baby spinach during refrigeration storage. PMID:22177228

Huang, Yaoxin; Ye, Mu; Chen, Haiqiang

2011-11-27

379

Microsequecing and cDNA cloning of the Calvin cycle\\/OPPP enzyme ribose-5-phosphate isomerase (EC 5.3.1.6) from spinach chloroplasts  

Microsoft Academic Search

Ribose-5-phosphate isomerase (RPI) catalyses the interconversion of ribose-5-phosphate and ribulose-5-phosphate in the reductive and oxidative pentose phosphate pathways in plants. RPI from spinach chloroplasts was purified and microsequenced. Via PCR with degenerate primers designed against microsequenced peptides, a hybridisation probe was obtained and used to isolate several cDNA clones which encode RPI. The nuclear-encoded 239 amino acid mature RPI subunit

William Martin; Katrin Henze; Josef Kellermann; Anke Flechner; Claus Schnarrenberger

1996-01-01

380

Changes in fungal community structure in bulk soil and spinach rhizosphere soil after chemical fumigation as revealed by 18S rDNA PCR-DGGE  

Microsoft Academic Search

To analyze the impact of chloropicrin and 1,3-dichloropropene on fungal community structure in bulk soil and spinach rhizosphere soil in a field, developed a new nested polymerase chain reaction (PCR) method to facilitate the detection of major fungal taxa and we used the method to monitor 18S rDNA PCR-denaturing gradient gel electrophoresis (DGGE) profiles for 3years. The cropping system consisted

Yuko Takada Hoshino; Naoyuki Matsumoto

2007-01-01

381

The influence of metal cations and pH on the heat sensitivity of photosynthetic oxygen evolution and chlorophyll fluorescence in spinach chloroplasts  

Microsoft Academic Search

The heat-sensitivity of photosynthetic oxygen evolution of thylakoids isolated from spinach increases by increasing the pH above neutral value. The temperature for inactivation (transition temperature) is lowered from about 45 C (pH 6.07.4) to 33C (pH 8.5). Similar results are obtained with intact chloroplasts. At pH 7.0 the transition temperature of washed thylakoids decreases by lowering the salt concentration below

Engelbert Weis

1982-01-01

382

Tissue and stage-specific modulation of RNA editing of the psbF and psbL transcript from spinach plastids a new regulatory mechanism?  

Microsoft Academic Search

The psbE operon of spinach chloroplasts, which includes the genes psbE, psbF, psbL and psbJ, encodes two RNA editing sites. One site corresponds to the initiation codon of the psbL transcript, as has been described earlier for the homologous transcript from tobacco, while at a second editing site, newly reported here, an internal phenylalanine codon of the psbF transcript is

Ralph Bock; Rudolf Hagemann; Hans Kssel; Jrg Kudla

1993-01-01

383

D-ribulose-5-phosphate 3-epimerase: Cloning and heterologous expression of the spinach gene, and purification and characterization of the recombinant enzyme  

Microsoft Academic Search

The authors have achieved, to their knowledge, the first high-level heterologous expression of the gene encoding D-ribulose-5-phosphate 3-epimerase from any source, thereby permitting isolation and characterization of the epimerase as found in photosynthetic organisms. The extremely labile recombinant spinach (Spinacia oleracea L.) enzyme was stabilized by DL-α-glycerophosphate or ethanol and destabilized by D-ribulose-5-phosphate or 2-mercaptoethanol. Despite this lability, the unprecedentedly

Y.-R. Chen; F. C. Hartman; T. Y. S. Lu; F. W. Larimer

1998-01-01

384

Daily consumption of Indian spinach (Basella alba) or sweet potatoes has a positive effect on total-body vitamin A stores in  

Microsoft Academic Search

Background: Recent evidence suggests that the vitamin A equiv- alency of -carotene from plant sources is lower than previously estimated. Objective: We assessed the effect of 60 d of daily supplementation with 750g retinol equivalents (RE) of either cooked, pured sweet potatoes; cooked, pured Indian spinach (Basella alba); or synthetic sources of vitamin A or-carotene on total-body vitamin A stores

Marjorie J Haskell; Kazi M Jamil; Ferdaus Hassan; Janet M Peerson; George J Fuchs; Kenneth H Brown

385

Speciation of Cd and Zn in contaminated soils assessed by DGT-DIFS, and WHAM/Model VI in relation to uptake by spinach and ryegrass.  

PubMed

A pot experiment was carried out to investigate the impact of Cd and Zn extractability in soil and speciation in pore water of industrial contaminated soils, on metal concentration in a metal sensitive species like spinach (Spinacia oleracea) and a more metal tolerant species like Italian ryegrass (Lolium multiflorum). For chemical speciation of Cd and Zn in pore water, WHAM/Model VI version 6.0 was used. The DGT technique was used to determine the effective concentration, C(E), of Cd and Zn in soils. The free ion activity in pore water correlated well with the contents in plants, and there was a linear relationship between the C(E) values and the concentration of Cd and Zn in both spinach and ryegrass in the non-toxic range. However, the C(E) values usually overestimated the plant contents when plants, particularly the spinach plants, were subjected to toxic concentration in the pore water. Metal uptake decreased in plants affected by toxicity, whereas metal binding to the Chelex resin did not. Thus, we found no linear relationship between the C(E) and metal contents in spinach, whereas a linear relationship was found between C(E)-Zn and the Zn concentration in ryegrass (r2=0.96, p<0.001). For Cd in ryegrass this relationship was weak (r2=0.53, p=0.18). This study indicates that the transport of metals from labile metal pools to the DGT-resin is linearly related to plant uptake only when plants are growing well, and that the applicability of DGT as an indicator for plant uptake seems species dependent. PMID:16084561

Alms, Asgeir R; Lombnaes, Peder; Sogn, Trine A; Mulder, Jan

2005-08-09

386

A study on skin problems among people engaged in wastewater-fed culture of water spinach in Phnom Penh, Cambodia (preliminary result)  

Microsoft Academic Search

Introduction: Boeng Cheung Ek lake is located west of Phnom Penh city where wastewater from industrial factories, urban area and rain-water run-off is discharged into the lake without any treatment. In the area, the farmers' main income is from growing water spinach (Ipomoea aquatica) in the lake. This study reports preliminary findings of skin problems among people engaged wastewater-fed culture

Vuong Tuan Anh; Phung Dac Cam; Phan Thu Phuong; Wim van der Hoek; Chan Vicheth; Anders Dalsgaard

387

D-Glucosone and L-sorbosone, putative intermediates of L-ascorbic acid biosynthesis in detached bean and spinach leaves. [Phaseolus vulgaris L. ; Spinacia oleracea L  

SciTech Connect

D-(6-{sup 14}C)Glucosone that had been prepared enzymically from D-(6-{sup 14}C)glucose was used to compare relative efficiencies of these two sugars for L-ascorbic acid (AA) biosynthesis in detached bean (Phaseolus vulgaris L., cv California small white) apices and 4-week-old spinach (Spinacia oleracea L., cv Giant Noble) leaves. At tracer concentration, {sup 14}C from glucosone was utilized by spinach leaves for AA biosynthesis much more effectively than glucose. Carbon-14 from (6-{sup 14}C)glucose underwent considerable redistribution during AA formation, whereas {sup 14}C from (6-{sup 14}C)glucosone remained almost totally in carbon 6 of AA. In other experiments with spinach leaves, L-(U-{sup 14}C)sorbosone was found to be equivalent to (6-{sup 14}C)glucose as a source of {sup 14}C for AA. In the presence of 0.1% D-glucosone, conversion of (6-{sup 14}C) glucose into labeled AA was greatly repressed. In a comparable experiment with L-sorbosone replacing D-glucosone, the effect was much less. The experiments described here give substance to the proposal that D-glucosone and L-sorbosone are putative intermediates in the conversion of D-glucose to AA in higher plants.

Saito, Kazumi; Nick, J.A.; Loewus, F.A. (Washington State Univ., Pullman (USA))

1990-11-01

388

The effect of experimental warming on leaf functional traits, leaf structure and leaf biochemistry in Arabidopsis thaliana  

Microsoft Academic Search

BACKGROUND: The leaf is an important plant organ, and how it will respond to future global warming is a question that remains unanswered. The effects of experimental warming on leaf photosynthesis and respiration acclimation has been well studied so far, but relatively little information exists on the structural and biochemical responses to warming. However, such information is very important to

Biao Jin; Li Wang; Jing Wang; Ke-Zhen Jiang; Yang Wang; Xiao-Xue Jiang; Cheng-Yang Ni; Yu-Long Wang; Nian-Jun Teng

2011-01-01

389

Leaf emergence in relation to leaf traits in temperate woody species in East-Chinese Quercus fabri forests  

NASA Astrophysics Data System (ADS)

To determine the effect of leaf traits on leaf emergence phenology, timing of leaf emergence, leaf expansion rate, durations of leaf emergence and expansion, leaf mass per area (LMA) and leaf size were investigated for 48 woody species from 25 families in two closed Chinese white oak ( Quercus fabri) forests of eastern China. Cross-species regression and phylogenetic regression were employed to examine the relationship between leaf phenology and leaf traits. Leaf area, LMA, and leaf expansion rate were found to be significantly greater in canopy trees than in understory shrubs in the oak forests. However, there was no significant difference in timing of leaf emergence and durations of leaf emergence and expansion between canopy and understory species. The large-LMA species leafed out earlier than the species with small LMA. The small-leaved species leafed out earlier than the species with large leaves, but the large-leaved species were greater in leaf expansion rate than their counterparts. Leaf expansion rate was positively correlated with leaf area and timing of leaf emergence, but no significant relationship was found between leaf size and leaf expansion period. These results suggest that large- and small-leaved species possibly employed different strategies to minimize herbivory damage, i.e. early leafing to avoid defoliator damage in small-leaved species and fast expanding and thereby shortening vulnerable time to herbivores in large-leaved species. It could be inferred that the species with small leaves and large-LMA leafed out early in the oak forests, thereby permitting less energy loss than their counterparts under the influence of frost in early spring. In general, early leaf emergence is of significance for high LMA species to increase carbon gain in temperate broad-leaved forests, but it is not related to plant height. Leaf size and leaf expansion period are not necessarily correlated.

Sun, Shucun; Jin, Dongmei; Li, Rongjin

2006-09-01

390

"Breath figures" on leaf surfaces-formation and effects of microscopic leaf wetness.  

PubMed

"Microscopic leaf wetness" means minute amounts of persistent liquid water on leaf surfaces which are invisible to the naked eye. The water is mainly maintained by transpired water vapor condensing onto the leaf surface and to attached leaf surface particles. With an estimated average thickness of less than 1 ?m, microscopic leaf wetness is about two orders of magnitude thinner than morning dewfall. The most important physical processes which reduce the saturation vapor pressure and promote condensation are cuticular absorption and the deliquescence of hygroscopic leaf surface particles. Deliquescent salts form highly concentrated solutions. Depending on the type and concentration of the dissolved ions, the physicochemical properties of microscopic leaf wetness can be considerably different from those of pure water. Microscopic leaf wetness can form continuous thin layers on hydrophobic leaf surfaces and in specific cases can act similar to surfactants, enabling a strong potential influence on the foliar exchange of ions. Microscopic leaf wetness can also enhance the dissolution, the emission, and the reaction of specific atmospheric trace gases e.g., ammonia, SO2, or ozone, leading to a strong potential role for microscopic leaf wetness in plant/atmosphere interaction. Due to its difficult detection, there is little knowledge about the occurrence and the properties of microscopic leaf wetness. However, based on the existing evidence and on physicochemical reasoning it can be hypothesized that microscopic leaf wetness occurs on almost any plant worldwide and often permanently, and that it significantly influences the exchange processes of the leaf surface with its neighboring compartments, i.e., the plant interior and the atmosphere. The omission of microscopic water in general leaf wetness concepts has caused far-reaching, misleading conclusions in the past. PMID:24167510

Burkhardt, Juergen; Hunsche, Mauricio

2013-10-24

391

"Breath figures" on leaf surfaces--formation and effects of microscopic leaf wetness  

PubMed Central

Microscopic leaf wetness means minute amounts of persistent liquid water on leaf surfaces which are invisible to the naked eye. The water is mainly maintained by transpired water vapor condensing onto the leaf surface and to attached leaf surface particles. With an estimated average thickness of less than 1 ?m, microscopic leaf wetness is about two orders of magnitude thinner than morning dewfall. The most important physical processes which reduce the saturation vapor pressure and promote condensation are cuticular absorption and the deliquescence of hygroscopic leaf surface particles. Deliquescent salts form highly concentrated solutions. Depending on the type and concentration of the dissolved ions, the physicochemical properties of microscopic leaf wetness can be considerably different from those of pure water. Microscopic leaf wetness can form continuous thin layers on hydrophobic leaf surfaces and in specific cases can act similar to surfactants, enabling a strong potential influence on the foliar exchange of ions. Microscopic leaf wetness can also enhance the dissolution, the emission, and the reaction of specific atmospheric trace gases e.g., ammonia, SO2, or ozone, leading to a strong potential role for microscopic leaf wetness in plant/atmosphere interaction. Due to its difficult detection, there is little knowledge about the occurrence and the properties of microscopic leaf wetness. However, based on the existing evidence and on physicochemical reasoning it can be hypothesized that microscopic leaf wetness occurs on almost any plant worldwide and often permanently, and that it significantly influences the exchange processes of the leaf surface with its neighboring compartments, i.e., the plant interior and the atmosphere. The omission of microscopic water in general leaf wetness concepts has caused far-reaching, misleading conclusions in the past.

Burkhardt, Juergen; Hunsche, Mauricio

2013-01-01

392

Spinach chloroplast 0-acetylserine (thiol)-lyase exhibits two catalytically non-equivalent pyridoxal-5'-phosphate-containing active sites.  

PubMed

A synthetic gene encoding the mature spinach- chloroplast O-acetylserine (thiol)-lyase was constructed and expressed in an Escherichia coli strain carrying the T7 RNA polymerase system. The pure recombinant protein was obtained at high yield (6 mg/l cell culture) using a new purification procedure that includes affinity chromatography on Green A agarose. Its specific activity was of the order of 1000 U/mg, and its physical properties were similar to those previously reported for the natural enzyme isolated from spinach chloroplasts. In particular the recombinant enzyme, as for the natural enzyme, behaved as a homodimer composed of two identical subunits each of Mr 35000. From steady-state kinetic studies using sulfide or 5-thio(2-nitrobenzoate) (Nbs) as alternative nucleophilic co-substrates, the enzyme exhibited positive kinetic co-operativity with respect to O-acetylserine [Ser(Ac)] in the presence of sulfide and a negative kinetic co-operativity in the presence of Nbs. Binding of Ser(Ac) to the enzyme was also investigated by absorbance and fluorescence measurements to obtain insight into the role of pyridoxal 5'-phosphate and of the single tryptophan residue (Trp176) present in the enzyme molecule. Addition of Ser(Ac) to the enzyme provoked the disappearance of the 409-nm absorbance band of the pyridoxal 5'-phosphate Schiff base and the appearance of two new absorbance bands, the one located between 320 nm and 360 nm and the other centered at 470 nm. Also, the fluorescence emission of the pyridoxal 5'-phosphate Schiff base was quenched upon addition of Ser(Ac) to the enzyme. These changes were most presumably due to the formation of a Schiff base intermediate between alpha-aminoacrylate and the pyridoxal 5'-phosphate cofactor. The fluorescence emission of Trp176 was also quenched upon Ser(Ac) binding to the enzyme. Quantitative analysis of the absorbance and fluorescence equilibrium data disclosed a co-operative behavior in Ser(Ac) binding, in agreement with the steady-state kinetic results. Fluorescence quenching experiments with the acrylamide and iodide revealed that the indole ring of Trp176 was largely exposed and located within the pyridoxal 5'-phosphate active site. These results are consistent with the finding that the native enzyme is composed of two identical subunits. Yet, presumably due to subunit-subunit interactions, the enzyme exhibits two non-equivalent pyridoxal-5'-phosphate-containing active sites. PMID:8617276

Rolland, N; Ruffet, M L; Job, D; Douce, R; Droux, M

1996-02-15

393

7 CFR 29.2438 - Thin Leaf (C Group).  

Code of Federal Regulations, 2013 CFR

...and specifications C1L Choice Light-brown Thin Leaf. Thin to medium body, mature to ripe...Light-brown Thin Leaf. Thin to medium body, mature to ripe...percent injury tolerance. Choice Medium-brown Thin Leaf....

2013-01-01

394

7 CFR 29.1162 - Leaf (B Group).  

Code of Federal Regulations, 2010 CFR

...Ripe, firm leaf structure, medium body, lean in oil, weak color intensity, narrow...Ripe, firm leaf structure, medium body, lean in oil, weak color intensity, stringy... Ripe, firm leaf structure, fleshy, lean in oil, weak color intensity,...

2009-01-01

395

7 CFR 29.1162 - Leaf (B Group).  

Code of Federal Regulations, 2010 CFR

...Ripe, firm leaf structure, medium body, lean in oil, weak color intensity, narrow...Ripe, firm leaf structure, medium body, lean in oil, weak color intensity, stringy... Ripe, firm leaf structure, fleshy, lean in oil, weak color intensity,...

2010-01-01

396

7 CFR 28.471 - Below Leaf Grade Cotton.  

Code of Federal Regulations, 2013 CFR

...2013-01-01 false Below Leaf Grade Cotton. 28.471 Section 28.471 Agriculture...STANDARDS AND STANDARD CONTAINER REGULATIONS COTTON CLASSING, TESTING, AND STANDARDS Standards Below Leaf Grade Cotton § 28.471 Below Leaf Grade...

2013-01-01

397

7 CFR 29.2437 - Heavy Leaf (B Group).  

Code of Federal Regulations, 2013 CFR

...injury tolerance. B3F Good Medium-brown Heavy Leaf. ...injury tolerance. B3M Good Mixed Color Heavy Leaf. Medium to heavy body, mature...injury tolerance. B3G Good Green Heavy Leaf. Medium to heavy body,...

2013-01-01

398

7 CFR 29.2662 - Heavy Leaf (B Group).  

Code of Federal Regulations, 2013 CFR

...injury tolerance. B3F Good Medium-brown Heavy Leaf. Medium...injury tolerance. B3VF Good Greenish Medium-brown Heavy Leaf. Medium...injury tolerance. B3G Good Green Heavy Leaf. Medium to heavy body,...

2013-01-01

399

Efficacy of UV, acidified sodium hypochlorite, and mild heat for decontamination of surface and infiltrated Escherichia coli O157:H7 on green onions and baby spinach.  

PubMed

Produce-associated foodborne illnesses outbreaks have highlighted the need for more effective decontamination methods to ensure the safety of fresh produce. The main objective of this study was to evaluate the individual and combined efficacies of germicidal UV light (12.5 to 500 mJ/cm(2)), acidified sodium hypochlorite (ASC 10 to 200 ppm), and mild heat (40 to 50C) for decontaminating green onions and baby spinach infected with Escherichia coli O157:H7. Samples were inoculated by spot and dip inoculation methods to mimic surface and infiltrated E. coli O157:H7 contamination, respectively. In green onions and baby spinach, the individual efficacies of UV, ASC, and mild-heat treatments varied based on the produce type and contamination method. Following analysis of the efficacies of the single treatments, a combined treatment with 125 mJ/cm(2) UV and 200 ppm of ASC at 50C was selected for spot-inoculated green onions, and a combined treatment with 125 mJ/cm(2) UV and 200 ppm of ASC at 20C was selected for spot- and dip-inoculated baby spinach. While a >5-log reduction was achieved with the combination treatment for spot-inoculated green onions with an initial contamination level of 7.2 log CFU per spot, the same treatment reduced E. coli O157:H7 populations below the detection limit (<1 log) on green onions spot inoculated at a lower contamination level (4.3 log CFU per spot). On spot- and dip-inoculated baby spinach, the combined treatment reduced E. coli O157:H7 populations by 2.8 log CFU per spot and 2.6 log CFU/g, respectively. The combined treatment of 500 mJ/cm(2) UV and 200 ppm of ASC at 50C selected for the decontamination of dip-inoculated green onions resulted in a 2.2-log CFU/g reduction. These findings suggest that when foodborne pathogens contaminate produce and subsequently infiltrate, attach to, or become localized into protected areas, the individual or combined applications of UV, ASC, and mild-heat treatments have limited decontamination efficacies on both green onions and baby spinach (<3 log). However, treatments combining UV, ASC, and mild heat could be a promising application for reducing pathogen populations (>5 log) on E. coli O157:H7 surface-contaminated green onions. This study also highlights the importance of developing and optimizing produce-specific decontamination methods to ensure the safety of fresh produce commodities. PMID:22980001

Durak, M Zeki; Churey, John J; Worobo, Randy W

2012-07-01

400

Automobile leaf springs from composite materials  

Microsoft Academic Search

The automobile industry has shown increased interest in the replacement of steel springs with fiberglass reinforced composite leaf springs. Therefore, the aim of this paper is to present a general study on the analysis, design and fabrication of composite springs. From this viewpoint, the suspension spring of a compact car, a jeep was selected as a prototype.A single leaf, variable

H. A. Al-Qureshi

2001-01-01

401

Identification of Plant Using Leaf Image Analysis  

NASA Astrophysics Data System (ADS)

The trees are basically identified by their leaves. There are different varieties of trees grown throughout the world. Some are important cash crop. Some are used in medicine. The tree identification is very important in day to day life. Their identifications had been studied using various laboratory methods. The morphological and genetically characteristics were employed to classify different leafs. However, the presence of wide morphological varieties through evolution among the various leaf cultivars made it more complex and difficult to classify them. Therefore manual identification as well as classification of these leaves is a tedious task. During the last few decades computational biologists have studied various diversities among leaf due to huge number of evolutionary changes. Leaf structures play a very crucial role in determining the characteristics of a plant. The broad and narrow shaped leaves, leaf arrangement, leaf margin characteristics features which differentiate various leaf of a tree. This project proposed the methods to identify the leaf using an image analysis based approach.

Pramanik, Subhra; Bandyopadhyay, Samir Kumar; Bhattacharyya, Debnath; Kim, Tai-Hoon

402

Leaf Litter Decomposition in Three Adirondack Lakes.  

National Technical Information Service (NTIS)

Decomposition of terrestrial leaf litter in three Adirondack lakes with water pH values approximately 5, 6, and 7 was studied. Litter bags containing leaves of American beech, sugar maple, red maple, leather leaf, and red spruce were placed in the lakes. ...

A. J. Francis H. L. Quinby G. R. Hendrey C. G. Hoogendyk

1983-01-01

403

Photovoltaic Leaf Area Meter Development and Testing  

Microsoft Academic Search

Photovoltaic (PV) panel was used to develop a simple and practical leaf area meter. Components of the developed PV leaf area meter include a PV panel as sensor, a wooden cabinet as enclosure, a flashlight as light source, and a commercial digital multimeter for voltage measurement. The principle of projected area measurement is the voltage generated by the PV panel

C. Igathinathane; B. Chennakesavulu; K. Manohar; A. R. Womac; L. O. Pordesimo

2008-01-01

404

[Photoprotective mechanisms of leaf anthocyanins: research progress].  

PubMed

Anthocyanin is widely distributed in plant organs such as root, stem, leaf, flower and fruit, being a kind of secondary metabolites generated in plant morphogenesis or for stress response. Leaf anthocyanin has special chemical structure and spectral properties, playing important roles in plant photoprotection, and becomes a hotspot in plant photosynthetic physiological ecology. This paper summarized the recent research progress in the effects of leaf anthocyanin on plant photosynthesis, including the distribution of leaf anthocyanin, its spectral properties, and its relationships with photosynthetic pigments, with the focus on the potential mechanisms of anthocyanins photoprotection, including light absorption, antioxidation, and osmotic regulation. The further research directions on the effects of leaf anthocyanin on photoprotection were proposed. PMID:22720633

Wang, Liang-Zai; Hu, Yan-Bo; Zhang, Hui-Hui; Xu, Nan; Zhang, Xiu-Li; Sun, Guang-Yu

2012-03-01

405

Regulation of photosynthetic sucrose synthesis: a role for calcium?  

Microsoft Academic Search

We have investigated whether changes of the cytosolic free-calcium concentration could regulate photosynthetic sucrose synthesis. Partially purified enzymes from spinach (Spinacea oleracea L.) leaves were assayed using calcium-EGTA buffers to obtain defined free-calcium concentrations in the low micromolar and submicromolar ranges. These concentrations of calcium did not directly affect sucrose-phosphate synthase activity. They inhibited the cytosolic fructose-1,6-bisphosphatase, acting competitively to

Monika Brauer; Dale Sanders; Mark Stitt

1990-01-01

406

Partial purification of a spinach thylakoid protein kinase that can phosphorylate light-harvesting chlorophyll a/b proteins  

SciTech Connect

Protein phosphorylation in plant tissues is particularly marked in chloroplasts, protein kinase activity being associated with the outer envelope, the soluble stromal fraction, and the thylakoid membrane. Furthermore, thylakoid-bound activity probably includes several distinct kinases, as suggested by studies of divalent cation specificity and thermal lability carried out with intact thylakoids and by subfractionation of solubilized membranes. Illumination of thylakoids, particularly with red light, promotes the rapid and extensive phosphorylation of the light-harvesting chlorophyll a/b complex (LHCII) on a threonine residue near the amino terminus of the protein. This phosphorylation is thought to be involved in regulating the distribution of absorbed quanta between photosystems II and I and is modulated by the redox state of the thylakoid plastoquinone pool. Neither of the thylakoid kinases reported to date was capable of phosphorylating purified LHCII in vitro or of incorporating phosphate into threonyl residues of exogenous substrates, that some LHCII phosphorylation was catalyzed by a preliminary fraction led workers to suggest that at least one other kinase remained to be isolated. Here, the authors report the solubilization and partial purification of a protein kinase from spinach thylakoids that is capable of phosphorylating LHCII in vitro, and they show that the specific site of phosphorylation is very nearly the same as, if not identical with, the site phosphorylated in organello.

Clark, R.D.; Hind, G.; Bennett, J.

1985-01-01

407

Translocation of the potato 3-deoxy-D-arabino-heptulosonate 7-phosphate synthase into isolated spinach chloroplasts  

SciTech Connect

A cDNA for potato (Solanum tuberosum L.) 3-deoxy-D-arabino-heptulosonate 7-phosphate synthase, the first enzyme of the shikimate pathway, encodes a 56 KD polypeptide whose amino terminus resembles a chloroplast transit sequence. The cDNA was placed downstream of the phage T7 polymerase recognition sequence in plasmid pGEM-3Z. DNA of the resulting plasmid pGEM-DWZ directed T7 polymerase to synthesize potato DAHP synthase mRNA in vitro. The mRNA was used in wheat germ and rabbit reticulocyte lysates for the synthesis of {sup 35}S-labeled pro-DAHP synthase. The predominant translation product is a 59 KD polypeptide that can be immunoprecipitated by rabbit polyclonal antibodies raised against the 53 KD DAHP synthase purified from potato tubers. Isolated spinach chloroplasts process the 59 KD pro-DAHP synthase to a 50 KD polypeptide. The processed polypeptide is protected from protease degradation, suggesting uptake of the enzyme into the cell organelle. Fractionation of reisolated chloroplasts after import of pro-DAHP synthase showed mature enzyme in the stroma. The uptake and processing of DAHP synthase is inhibited by antibodies raised against the mature enzyme. Our results are consistent with the assumption that potato contains a nuclear DNA encoded DAHP synthase that is synthesized as a proenzyme and whose mature form resides in the chloroplasts. Our data provide further evidence that green plants synthesize aromatic amino acids in plastids.

Zhao, Jianmin; Weaver, L.M.; Herrmann, K.M. (Purdue Univ., West Lafayette, IN (USA))

1990-05-01

408

Pressure Equilibrium and Jump Study on Unfolding of 23-kDa Protein from Spinach Photosystem II  

PubMed Central

Pressure-induced unfolding of 23-kDa protein from spinach photosystem II has been systematically investigated at various experimental conditions. Thermodynamic equilibrium studies indicate that the protein is very sensitive to pressure. At 20C and pH 5.5, 23-kDa protein shows a reversible two-state unfolding transition under pressure with a midpoint near 160 MPa, which is much lower than most natural proteins studied to date. The free energy (?Gu) and volume change (?Vu) for the unfolding are 5.9 kcal/mol and ?160 ml/mol, respectively. It was found that NaCl and sucrose significantly stabilize the protein from unfolding and the stabilization is associated not only with an increase in ?Gu but also with a decrease in ?Vu. The pressure-jump studies of 23-kDa protein reveal a negative activation volume for unfolding (?66.2 ml/mol) and a positive activation volume for refolding (84.1 ml/mol), indicating that, in terms of system volume, the protein transition state lies between the folded and unfolded states. Examination of the temperature effect on the unfolding kinetics indicates that the thermal expansibility of the transition state and the unfolded state of 23-kDa protein are closer to each other and they are larger than that of the native state. The diverse pressure-refolding pathways of 23-kDa protein in some conditions were revealed in pressure-jump kinetics.

Tan, Cui-Yan; Xu, Chun-He; Wong, Jun; Shen, Jian-Ren; Sakuma, Shinsuke; Yamamoto, Yasusi; Lange, Reinhard; Balny, Claude; Ruan, Kang-Cheng

2005-01-01

409

Effects of Carbon Dioxide and Oxygen on the Regulation of Photosynthetic Carbon Metabolism by Ammonia in Spinach Mesophyll Cells 1  

PubMed Central

Photosynthetic carbon metabolism of isolated spinach mesophyll cells was characterized under conditions favoring photorespiratory (PR; 0.04% CO2 and 20% O2) and nonphotorespiratory (NPR; 0.2% CO2 and 2% O2) metabolism, as well as intermediate conditions. Comparisons were made between the metabolic effects of extracellularly supplied NH4+ and intracellular NH4+, produced primarily via PR metabolism. The metabolic effects of 14CO2 fixation under PR conditions were similar to perturbations of photosynthetic metabolism brought about by externally supplied NH4+; both increased labeling and intracellular concentrations of glutamine at the expense of glutamate and increased anaplerotic synthesis through ?-ketoglutarate. The metabolic effects of added NH4+ during NPR fixation were greater than those during PR fixation, presumably due to lower initial NH4+ levels during NPR fixation. During PR fixation, addition of ammonia caused decreased pools and labeling of glutamate and serine and increased glycolate, glyoxylate, and glycine labeling. The glycolate pathway was thus affected by increased rates of carbon flow and decreased glutamate availability for glyoxylate transamination, resulting in increased usage of serine for transamination. Sucrose labeling decreased with NH4+ addition only during PR fixation, suggesting that higher photosynthetic rates under NPR conditions can accommodate the increased drain of carbon toward amino acid synthesis while maintaining sucrose synthesis.

Lawyer, Arthur L.; Cornwell, Karen L.; Larsen, Peder O.; Bassham, James A.

1981-01-01

410

Rapid, enhanced detection of Salmonella Typhimurium on fresh spinach leaves using micron-scale, phage-coated magnetoelastic biosensors  

NASA Astrophysics Data System (ADS)

In order to cost-effectively and rapidly detect bacterial food contamination in the field, the potential usefulness of phage-coated magnetoelastic (ME) biosensors has been recently reported. These biosensors are freestanding, mass-sensitive biosensors that can be easily batch-fabricated, thereby reducing the fabrication cost per sensor to a fraction of a cent. In addition, the biosensors can be directly placed on fresh produce surfaces and used to rapidly monitor possible bacterial food contamination without any preceding sample preparation. Previous investigations showed that the limit of detection (LOD) with millimeter-scale ME biosensors was fairly low for fresh produce with smooth surfaces (e.g., tomatoes and shell eggs). However, the LOD is anticipated to be dependent on the size of the biosensors as well as the topography of produce surfaces of interest. This paper presents an investigation into the use of micron-scale, phage-coated ME biosensors for the enhanced detection of Salmonella Typhimurium on fresh spinach leaves.

Horikawa, Shin; Vaglenov, Kiril A.; Gerken, Dana M.; Chai, Yating; Park, Mi-Kyung; Li, Suiqiong; Petrenko, Valery A.; Chin, Bryan A.

2012-05-01

411

Dynamics of the antioxidant system during seed osmopriming, post-priming germination, and seedling establishment in Spinach (Spinacia oleracea).  

PubMed

Osmopriming is a pre-sowing treatment that improves seed germination performance and stress tolerance. To understand osmopriming physiology, and its association with post-priming stress tolerance, we investigated the antioxidant system dynamics during three stages: during osmopriming, post-priming germination, and seedling establishment. Spinach seeds (Spinacia oleracea L. cv. Bloomsdale) were primed with -0.6 MPa PEG at 15C for 8 d, and dried at room temperature for 2 d. Unprimed and primed germinating seeds/seedlings were subjected to a chilling and desiccation stresses. Seed/seedling samples were collected for antioxidant assays and germination performance and stress tolerance were evaluated. Our data indicate that: (1) during osmopriming the transition of seeds from dry to germinating state represses the antioxidant pathways (residing in dry seeds) that involve CAT and SOD enzymes but stimulates another pathway (only detectable in imbibed seeds) involving APX; (2) a renewal of antioxidant system, possibly required by seedling establishment, occurs after roughly 5 d of germination; (3) osmopriming strengthens the antioxidant system and increases seed germination potential, resulting in an increased stress tolerance in germinating seeds. Osmopriming-mediated promotive effect on stress tolerance, however, may diminish in relatively older (e.g. ~5-week) seedlings. PMID:21421363

Chen, Keting; Arora, Rajeev

2010-08-21

412

Comparison of the Levels of Six Endogenous Gibberellins in Roots and Shoots of Spinach in Relation to Photoperiod 1  

PubMed Central

This communication describes the distribution of gibberellins (GAs) in roots and shoots of spinach in relation to photoperiod. From previous work (Metzger, Zeevaart 1980 Plant Physiol 65: 623-626) shoots were known to contain GA53, GA44, GA19, GA17, GA20, and GA29. We now show by combined gas chromatographymass spectrometry that roots contain GA44, GA19, and GA29. Trace amounts of GA53 were detected by combined gas chromatographyselected ion current monitoring. Neither GA17 nor GA20 were detected in root extracts. Analysis by the d-5 corn bioassay also showed no effect of photoperiodic treatment on the levels of GA-like substances in root extracts. Both phloem and xylem exudates had patterns of GA-like activity similar to those found in shoots and roots, respectively. Moreover, foliar application of [3H]GA20 resulted in the transport of label from the shoot to the roots. Over half of the label in the roots represented unmetabolized [3H]GA20, indicating that part of the GA20 in the phloem is transported to the roots. Consequently, if GA20 is made in, or transported to the roots, it is rapidly metabolized in that organ. This is a clear indication that regulation of GA metabolism is greatly different in roots and shoots.

Metzger, James D.; Zeevaart, Jan A. D.

1980-01-01

413

Inhibitory effect of p-nitrothiophenol in the light on the photosystem II activity of spinach chloroplasts.  

PubMed

The treatment of spinach chloroplasts with p-nitrothiophenol in the light at acidic and neutral pH'S caused specific inhibition of the Photosystem II activity, whereas the same treatment in the dark did not affect the activity at all. The photosystem I activity was not inhibited by p-nitrothiophenol both in the light and in the dark. The inhibition was accompanied by changes of fluorescence from chloroplasts. As observed at room temperature, the 685-nm band was lowered by the p-nitrothiophenol treatment in the light and, at liquid nitrogen temperature, the relative height of the 695-nm band to the 685-nm band increased and the 695-nm band shifted to longer wavelengths. The action spectra for these effects of p-nitrothiophenol on the activity and fluorescence showed a peak at 670 nm with a red drop at longer wavelengths. It was concluded that the light absorbed by Photosystem II is responsible for the chemical modification of chloroplasts with p-nitrothiopehnol to causing the specific inhibition of Photosystem II. PMID:2315

Kobayashi, Y; Inoue, Y; Shibata, K

1976-01-15

414

Erythromycin and 5S rRNA binding properties of the spinach chloroplast ribosomal protein CL22.  

PubMed Central

The spinach chloroplast ribosomal protein (r-protein) CL22 contains a central region homologous to the Escherichia coli r-protein L22 plus long N- and C-terminal extensions. We show in this study that the CL22 combines two properties which in E. coli ribosome are split between two separate proteins. The CL22 which binds to the 5S rRNA can also be linked to an erythromycin derivative added to the 50S ribosomal subunit. This latter property is similar to that of the E. coli L22 and suggests a similar localization in the 50S subunit. We have overproduced the r-protein CL22 and deleted forms of this protein in E. coli. We show that the overproduced CL22 binds to the chloroplast 5S rRNA and that the deleted protein containing the N- and C-terminal extensions only has lost the 5S rRNA binding property. We suggest that the central homologous regions of the CL22 contains the RNA binding domain. Images

Carol, P; Rozier, C; Lazaro, E; Ballesta, J P; Mache, R

1993-01-01

415

Derivatives of diterpen labdane-8?,15-diol as photosynthetic inhibitors in spinach chloroplasts and growth plant inhibitors.  

PubMed

In a search of new efficient herbicides of natural origin, four derivatives were prepared from labdane-8?,15-diol (1) and 15-O-acetyl-8?-hydroxy labdane (2) isolated from Croton ciliatoglanduliferus. Their inhibitory activity on photosynthetic electron transport on fresh, broken spinach chloroplasts and on the growth of plants were determined. Derivative 15-O-benzoyl-8?-hydroxy labdane (5) was seven times more active than 2 as reaction Hill inhibitor. Complex of 5 with the adjuvant 2-hydroxypropyl-?-cyclodextrin (5:HPB) (200 ?M) was sprayed on Physalys ixocarpa (green tomato) plants; 48 h later the complex inhibited PS II by transforming the active reaction centers to silent reaction centers or "heat sinks". After 72 h this effect disappeared, probably 5:HPB was metabolized by the plant. Chlorophyll a fluorescence of Trifolium alexandrinum (clover) leaves was affected with 5:HPB at the level of PQ pool reduction. 5:HPB decreases the tomato and clover dry-biomass, without affecting Lolium perenne (grass) plants, suggesting that complex 5 acts as selective herbicide for dicotyledonous plants. PMID:23733160

Morales-Flores, Flix; Aguilar, Mara Isabel; King-Daz, Beatriz; Lotina-Hennsen, Blas

2013-05-15

416

Complementary nutrient effects of separately collected human faeces and urine on the yield and nutrient uptake of spinach (Spinacia oleracea).  

PubMed

A glasshouse experiment was conducted to evaluate the combined use of separately collected human faeces and urine as fertilizer for spinach (Spinacia oleracea) production. Seven human faeces N : urine N combinations (1 : 7 to 7 : 1) each supplying 200 kg N ha(-1) were evaluated along with sole human faeces, sole urine, inorganic fertilizer and an unamended control. Complementary application of the two resources, human faeces and urine, increased fresh and dry matter yields only in treatments having high proportions of urine. Nitrogen uptake followed the same trend but the opposite trend occurred for P uptake indicating that urine was a better source of N whereas human faeces were the better source of P. Potassium uptake was not influenced by the two resources. The minimal improvement observed in the fertilizer value of human faeces when co-applied with urine suggested that co-application of the two resources may not give an added yield advantage when compared with sole human faeces. PMID:20601403

Kutu, Funso R; Muchaonyerwa, Pardon; Mnkeni, Pearson N S

2010-07-02

417

In vitro reconstitution of the spinach chloroplast cytochrome b6 protein from a fusion protein expressed in Escherichia coli.  

PubMed

We have developed a strategy for overproduction of spinach apocytochrome b6 as a fusion protein to maltose-binding protein (MBP) in Escherichia coli, using the expression vector pMal-c2. The fusion protein was purified to virtual homogeneity by gel filtration chromatography and the method of insertion of hemes into fusion protein was elaborated. The ambient and low-temperature absorption spectra of the reconstituted cytochrome b6 were similar to those of cytochrome b6 spectra in isolated proteins or cytochrome b6f complexes and are typical for bis-histidine ligated b-type cytochromes. Optical circular dichroism (CD) spectra of the visible region further confirmed the appropriate binding of hemes by the apocytochrome b6 protein. We found that the incorporation of hemes was required for the refolding of the cytochrome b6 protein into the more compact structure found in the native cytochrome protein. Heme staining experiments suggested that the two hemes in the reconstituted cytochrome b6 protein are bound with different affinities. The reconstituted cytochrome b6 protein was cleaved by Xa factor proteolysis from fusion protein and separated for characterization. The procedure presented in this work for reconstitution of hemes into the cytochrome b6 protein should provide an important tool for structure/function studies of membrane-bound cytochrome proteins. PMID:12147358

Krliczewski, Jaros?aw; Szczepaniak, Andrzej

2002-07-29

418

A model for leaf initiation  

PubMed Central

A biophysical model is proposed for how leaf primordia are positioned on the shoot apical
meristem in both spiral and whorl phyllotaxes. Primordia are initiated by signals that propagate
in the epidermis in both azimuthal directions away from the cotyledons or the most recently
specified primordia. The signals are linear waves as inferred from the spatial periodicity of the
divergence angle and a temporal periodicity. The periods of the waves, which represent actively
transported auxin, are much smaller than the plastochron interval. Where oppositely directed
waves meet at one or more angular positions on the periphery of the generative circle, auxin
concentration builds and as in most models this stimulates local movement of auxin to
underlying cells, where it promotes polarized cell division and expansion. For higher order
spirals the wave model requires asymmetric function of auxin transport; that is, opposite wave
speeds differ. An algorithm for determination of the angular positions of leaves in common leaf
phyllotaxic configurations is proposed. The number of turns in a pattern repeat, number of leaves
per level and per pattern repeat, and divergence angle are related to speed of auxin transport and
radius of the generative circle. The rule for composition of Fibonacci or Lucas numbers
associated with some phyllotaxes is discussed. A subcellular model suggests how the shoot
meristem might specify either symmetric or asymmetric transport of auxin away from the
forming primordia that produce it. Biological tests that could make or break the mathematical
and molecular hypotheses are proposed.

Abraham-Shrauner, Barbara; Pickard, Barbara G

2011-01-01

419

S2F, a leaf-specific trans-acting factor, binds to a novel cis-acting element and differentially activates the RPL21 gene.  

PubMed

Tissue-specific factors control the differential expression of nuclear genes encoding plastid proteins. To identify some of these factors, the light-independent spinach RPL21 gene encoding the plastid ribosomal protein L21 was chosen as a model. The RPL21 promoter organization was defined by transient and stable transfections of RPL21 promoter deletion mutants fused to a reporter gene. The following results were obtained. (1) We identified a strong core promoter, spanning the transcription start site region, sufficient to drive high levels of gene expression. (2) We identified two non-overlapping positive and negative domains, located upstream from the core promoter region, that modulate core promoter activity independently of light. (3) We found that the positive domain contains a new cis-acting element, the S2 site, related to but different from the light-responsive GT-1 binding site. We show that the S2 site binds a leaf-specific nuclear factor (named S2F). The S2 site is conserved in the promoter region of many nuclear genes encoding plastid proteins. Experiments with transgenic tobacco plants confirmed that the S2 site is critical for positive domain activity in leaf tissues. The S2 site is thus identified as a new tissue-specific, light-independent regulatory element. PMID:9286115

Lagrange, T; Gauvin, S; Yeo, H J; Mache, R

1997-08-01

420

S2F, a leaf-specific trans-acting factor, binds to a novel cis-acting element and differentially activates the RPL21 gene.  

PubMed Central

Tissue-specific factors control the differential expression of nuclear genes encoding plastid proteins. To identify some of these factors, the light-independent spinach RPL21 gene encoding the plastid ribosomal protein L21 was chosen as a model. The RPL21 promoter organization was defined by transient and stable transfections of RPL21 promoter deletion mutants fused to a reporter gene. The following results were obtained. (1) We identified a strong core promoter, spanning the transcription start site region, sufficient to drive high levels of gene expression. (2) We identified two non-overlapping positive and negative domains, located upstream from the core promoter region, that modulate core promoter activity independently of light. (3) We found that the positive domain contains a new cis-acting element, the S2 site, related to but different from the light-responsive GT-1 binding site. We show that the S2 site binds a leaf-specific nuclear factor (named S2F). The S2 site is conserved in the promoter region of many nuclear genes encoding plastid proteins. Experiments with transgenic tobacco plants confirmed that the S2 site is critical for positive domain activity in leaf tissues. The S2 site is thus identified as a new tissue-specific, light-independent regulatory element.

Lagrange, T; Gauvin, S; Yeo, H J; Mache, R

1997-01-01

421

Why so strong for the lotus leaf?  

NASA Astrophysics Data System (ADS)

The authors discussed the potential reasons why the lotus leaf is so strong by means of scanning electron microscopy (SEM). The results showed that the good mechanical properties of lotus leaf should be attributed to its architecture, such as paralleled microtubes structure, umbrellalike structure, and hierarchically layered hexagon structure. The important observation from this work is that the surface of the rear face of the lotus leaf seems to be constituted by the layers of hexagons whose hierarchical pilling up of size decreases as we go deeper from surface. This is a typical fractal-like phenomenon.

Guo, Zhiguang; Liu, Weimin; Su, Bao-Lian

2008-11-01

422

Key Proliferative Activity in the Junction between the Leaf Blade and Leaf Petiole of Arabidopsis1[W][OA  

PubMed Central

Leaves are the most important, fundamental units of organogenesis in plants. Although the basic form of a leaf is clearly divided into the leaf blade and leaf petiole, no study has yet revealed how these are differentiated from a leaf primordium. We analyzed the spatiotemporal pattern of mitotic activity in leaf primordia of Arabidopsis (Arabidopsis thaliana) in detail using molecular markers in combination with clonal analysis. We found that the proliferative zone is established after a short interval following the occurrence of a rod-shaped early leaf primordium; it is separated spatially from the shoot apical meristem and seen at the junction region between the leaf blade and leaf petiole and produces both leaf-blade and leaf-petiole cells. This proliferative region in leaf primordia is marked by activity of the ANGUSTIFOLIA3 (AN3) promoter as a whole and seems to be differentiated into several spatial compartments: activities of the CYCLIN D4;2 promoter and SPATULA enhancer mark parts of it specifically. Detailed analyses of the an3 and blade-on-petiole mutations further support the idea that organogenesis of the leaf blade and leaf petiole is critically dependent on the correct spatial regulation of the proliferative region of leaf primordia. Thus, the proliferative zone of leaf primordia is spatially differentiated and supplies both the leaf-blade and leaf-petiole cells.

Ichihashi, Yasunori; Kawade, Kensuke; Usami, Takeshi; Horiguchi, Gorou; Takahashi, Taku; Tsukaya, Hirokazu

2011-01-01

423

Global leaf trait relationships: mass, area, and the leaf economics spectrum.  

PubMed

The leaf economics spectrum (LES) describes multivariate correlations that constrain leaf traits of plant species primarily to a single axis of variation if data are normalized by leaf mass. We show that these traits are approximately distributed proportional to leaf area instead of mass, as expected for a light- and carbon dioxide-collecting organ. Much of the structure in the mass-normalized LES results from normalizing area-proportional traits by mass. Mass normalization induces strong correlations among area-proportional traits because of large variation among species in leaf mass per area (LMA). The high LMA variance likely reflects its functional relationship with leaf life span. A LES that is independent of mass- or area-normalization and LMA reveals physiological relationships that are inconsistent with those in global vegetation models designed to address climate change. PMID:23539179

Osnas, Jeanne L D; Lichstein, Jeremy W; Reich, Peter B; Pacala, Stephen W

2013-03-28

424

Relationships between specific leaf weight and mineral concentration among genotypes  

Microsoft Academic Search

Physiological functions are usually expressed on a leaf area basis, whereas leaf mineral concentrations are often expressed on a dry matter basis. If specific leaf weight (SLW; g DM m?2 leaf) differs among genotypes then variability in mineral concentration may depend on the basis of expression. Data from experiments with peanut (Arachis hypogaea L.) and pearl millet [Pennisetum glaucum (L.)

R. Harold Brown; George T. Byrd

1997-01-01

425

Simulating Leaf Area of Corn Plants at Contrasting Water Status  

Technology Transfer Automated Retrieval System (TEKTRAN)

An exponential decay function was fitted with literature data to describe the decrease in leaf expansion rate as leaf water potential decreases. The fitted function was then applied to modify an existing leaf area simulation module in a soil-plant-atmosphere continuum model in order to simulate leaf...

426

Calibration of the Minolta SPAD502 leaf chlorophyll meter  

Microsoft Academic Search

Use of leaf meters to provide an instantaneous assessment of leaf chlorophyll has become common, but calibration of meter output into direct units of leaf chlorophyll concentration has been difficult and an understanding of the relationship between these two parameters has remained elusive. We examined the correlation of soybean (Glycine max) and maize (Zea mays L.) leaf chlorophyll concentration, as

John Markwell; John C. Osterman; Jennifer L. Mitchell

1995-01-01

427

7 CFR 29.2663 - Thin Leaf (C Group).  

Code of Federal Regulations, 2013 CFR

...injury tolerance. C3F Good Medium-brown Thin Leaf...tolerance. C3VF Good Greenish Medium-brown Thin Leaf... C5VF Low Greenish Medium-brown Thin Leaf...injury tolerance. C3G Good Green Thin Leaf....

2013-01-01

428

Assessing the generality of global leaf trait relationships  

Microsoft Academic Search

Summary Global-scale quantification of relationships between plant traits gives insight into the evolution of the world's vegetation, and is crucial for parameterizing vegetation- climate models. A database was compiled, comprising data for hundreds to thousands of species for the core 'leaf economics' traits leaf lifespan, leaf mass per area, photosynthetic capacity, dark respiration, and leaf nitrogen and phosphorus

Ian J. Wright; Peter B. Reich; Johannes H. C. Cornelissen; Daniel S. Falster; Eric Garnier; Kouki Hikosaka; Byron B. Lamont; William Lee; C. H. Lusk; J. Oleksyn; N. Osada; R. Villar; D. I. Warton; M. Westoby

2005-01-01

429

Elevated CO and leaf shape: Are dandelions getting toothier?  

Microsoft Academic Search

Heteroblastic leaf development in Taraxacum officinale is compared between plants grown under ambient (350 ppm) vs. elevated (700 ppm) CO levels. Leaves of elevated CO plants exhibited more deeply incised leaf margins and relatively more slender leaf laminae than leaves of ambient CO plants. These differences were found to be significant in allometric analyses that controlled for differences in leaf

S. C. Thomas; F. A. Bazzaz

1996-01-01

430

RFLP tagging of QTLs conditioning specific leaf weight and leaf size in soybean  

Microsoft Academic Search

Selection for high specific leaf weight (SLW) in soybean [Glycine max (L) Merr.] may increase apparent photosynthetic rate per unit leaf area (AP), which in turn may improve seed yield. In general,\\u000a the SLW and leaf size are negatively correlated in soybean. To maximize total photosynthetic performance, and perhaps the\\u000a seed yield, of a soybean cultivar, it would be necessary

M. A. R. Mian; R. Wells; T. E. Carter Jr.; D. A. Ashley; H. R. Boerma

1998-01-01

431

Effect of Image Processing of a Leaf Photograph on the Calculated Fractal Dimension of Leaf Veins  

Microsoft Academic Search

Digital photography is a promised method for estimating the fractal characteristics of leaf veins. In this study, the effects\\u000a of different threshold levels and image processing methods using Adobe Photoshop software on the fractal dimension values\\u000a were examined from a digital photo of nectarine leaf. The results showed that the nectarine leaf vein has typical fractal\\u000a characteristics and its fractal

Yun Kong; Shaohui Wang; Chengwei Ma; Baoming Li; Yuncong Yao

2007-01-01

432

Leaf Decomposition in a Tropical Rainforest Stream.  

National Technical Information Service (NTIS)

Fungi play an important part in leaf litter decomposition in terrestrial ecosystems in both temperate and tropical regions. There are few published reports dealing with decomposition in running waters, and no work has been done in tropical streams. Result...

D. E. Padgett

1975-01-01

433

Monitoring Air Quality with Leaf Yeasts.  

ERIC Educational Resources Information Center

|Proposes that leaf yeast serve as quick, inexpensive, and effective techniques for monitoring air quality. Outlines procedures and provides suggestions for data analysis. Includes results from sample school groups who employed this technique. (ML)|

Richardson, D. H. S.; And Others

1985-01-01

434

Guava leaf extract and topical haemostasis.  

PubMed

The effects of guava leaf extract on the bleeding time and the three main mechanisms of haemostasis: vasoconstriction, platelet aggregation and blood coagulation, were investigated. The water extract of guava leaves did not shorten bleeding times in rats. Guava leaf extract potentiated the vascular muscle contraction induced in rabbits by phenylephrine, and when given alone it stimulated human platelet aggregation in vitro in a dose-dependent manner. On the other hand, it significantly prolonged blood coagulation; activated partial thromboplastin time (APTT) test (p < 0.05). The higher the concentration of the extract, the longer APTT was observed. Thus, a water extract of guava leaves showed ambiguous effects on the haemostatic system. Guava leaf extract did not affect bleeding times, it stimulated vasoconstriction and platelet aggregation but it inhibited blood coagulation. Therefore, guava leaf extract is not recommended as a haemostatic agent. PMID:10925412

Jaiarj, P; Wongkrajang, Y; Thongpraditchote, S; Peungvicha, P; Bunyapraphatsara, N; Opartkiattikul, N

2000-08-01

435

Photosynthesis and Respiration in Leaf Slices.  

ERIC Educational Resources Information Center

|Demonstrates how leaf slices provide an inexpensive material for illustrating several fundamental points about the biochemistry of photosynthesis and respiration. Presents experiments that illustrate the effects of photon flux density and herbicides and carbon dioxide concentration. (DDR)|

Brown, Simon

1998-01-01

436

Quantifying the reduction in potential health risks by determining the sensitivity of poliovirus type 1 chat strain and rotavirus SA-11 to electron beam irradiation of iceberg lettuce and spinach.  

PubMed

Fresh produce, such as lettuce and spinach, serves as a route of food-borne illnesses. The U.S. FDA has approved the use of ionizing irradiation up to 4 kGy as a pathogen kill step for fresh-cut lettuce and spinach. The focus of this study was to determine the inactivation of poliovirus and rotavirus on lettuce and spinach when exposed to various doses of high-energy electron beam (E-beam) irradiation and to calculate the theoretical reduction in infection risks that can be achieved under different contamination scenarios and E-beam dose applications. The D(10) value (dose required to reduce virus titers by 90%) (standard error) of rotavirus on spinach and lettuce was 1.29 ( 0.64) kGy and 1.03 ( 0.05) kGy, respectively. The D(10) value (standard error) of poliovirus on spinach and lettuce was 2.35 ( 0.20) kGy and 2.32 ( 0.08) kGy, respectively. Risk assessment of data showed that if a serving (?14 g) of lettuce was contaminated with 10 PFU/g of poliovirus, E-beam irradiation at 3 kGy will reduce the risk of infection from >2 in 10 persons to approximately 6 in 100 persons. Similarly, if a serving size (?0.8 g) of spinach is contaminated with 10 PFU/g of rotavirus, E-beam irradiation at 3 kGy will reduce infection risks from >3 in 10 persons to approximately 5 in 100 persons. The results highlight the value of employing E-beam irradiation to reduce public health risks but also the critical importance of adhering to good agricultural practices that limit enteric virus contamination at the farm and in packing houses. PMID:22179244

Espinosa, Ana Cecilia; Jesudhasan, Palmy; Arredondo, Ren; Cepeda, Martha; Mazari-Hiriart, Marisa; Mena, Kristi D; Pillai, Suresh D

2011-12-16

437

Quantifying the Reduction in Potential Health Risks by Determining the Sensitivity of Poliovirus Type 1 Chat Strain and Rotavirus SA-11 to Electron Beam Irradiation of Iceberg Lettuce and Spinach  

PubMed Central

Fresh produce, such as lettuce and spinach, serves as a route of food-borne illnesses. The U.S. FDA has approved the use of ionizing irradiation up to 4 kGy as a pathogen kill step for fresh-cut lettuce and spinach. The focus of this study was to determine the inactivation of poliovirus and rotavirus on lettuce and spinach when exposed to various doses of high-energy electron beam (E-beam) irradiation and to calculate the theoretical reduction in infection risks that can be achieved under different contamination scenarios and E-beam dose applications. The D10 value (dose required to reduce virus titers by 90%) (standard error) of rotavirus on spinach and lettuce was 1.29 ( 0.64) kGy and 1.03 ( 0.05) kGy, respectively. The D10 value (standard error) of poliovirus on spinach and lettuce was 2.35 ( 0.20) kGy and 2.32 ( 0.08) kGy, respectively. Risk assessment of data showed that if a serving (?14 g) of lettuce was contaminated with 10 PFU/g of poliovirus, E-beam irradiation at 3 kGy will reduce the risk of infection from >2 in 10 persons to approximately 6 in 100 persons. Similarly, if a serving size (?0.8 g) of spinach is contaminated with 10 PFU/g of rotavirus, E-beam irradiation at 3 kGy will reduce infection risks from >3 in 10 persons to approximately 5 in 100 persons. The results highlight the value of employing E-beam irradiation to reduce public health risks but also the critical importance of adhering to good agricultural practices that limit enteric virus contamination at the farm and in packing houses.

Espinosa, Ana Cecilia; Jesudhasan, Palmy; Arredondo, Rene; Cepeda, Martha; Mazari-Hiriart, Marisa; Mena, Kristi D.

2012-01-01

438

Leaf Senescence: Gene Expression and Regulation  

Microsoft Academic Search

\\u000a Each autumn leaf senescence leaves its mark on the planet in the form of dramatic changes in color that can be seen from space.\\u000a Annually, leaf senescence mediates the breakdown of 300 million tons of chlorophyll while changing green forests and fields\\u000a to yellow and orange (1). The drama of these color changes is matched by the dramatic nature of

Louis M. Weaver; Edward Himelblau; Richard M. Amasino

439

Leaf Impressions: A Model for Carbonization  

NSDL National Science Digital Library

In this activity students make leaf impressions on paper to illustrate how carbonization works. They use the leaf press method to demonstrate staining as a model for carbonization, when living tissue leaves a carbon film in sediment and rock. The students will discover that many plant fossils are preserved through carbonization and that soft parts of animals including skin and fur have also been preserved as fossils through the process of carbonization.

Greb, Stephen

440

Somatic embryogenesis from leaf cultures of potato  

Microsoft Academic Search

An efficient procedure has been developed for inducing somatic embryogenesis from leaf cultures of potato cv. Jyothi. Leaf sections were initially cultured on 2,4-dichlorophenoxyacetic acid (2,4-D) + benzyladenine (BA) and a-naphthaleneacetic acid (NAA) + BA supplemented Murashige and Skoog (MS) media. Nodular embryogenic callus developed from the cut ends of explants on media containing 2,4-D and BA, whereas compact callus

T. JayaSree; U. Pavan; M. Ramesh; A. V. Rao; K. Jagan Mohan Reddy; A. Sadanandam

2001-01-01

441

Influence of pH upon the Warburg effect in isolated intact spinach chloroplasts. I. Carbon dioxide photoassimilation and glycolate synthesis  

Microsoft Academic Search

The influence of pH upon the O inhibition of ¹⁴CO photoassimilation (Warburg effect) was examined in intact spinach (Spinacia oleracea) chloroplasts. With conditions which favored the Warburg effect, i.e. rate-limiting CO and 100 percent O, O inhibition was greater at pH 8.4 to 8.5 than at pH 7.5 to 7.8. At pH 8.5, as compared with 7.8, there was an

J. M. Robinson; M. Gibbs; D. N. Cotler

1977-01-01

442

The function and properties of the iron-sulfur center in spinach ferredoxin: Thioredoxin reductase: A new biological role for iron-sulfur clusters  

SciTech Connect

Thioredoxin reduction in chloroplasts in catalyzed by a unique class of disulfide reductases which use a [2Fe-2S]{sup 2+/+} ferredoxin as the electron donor and contain an Fe-S cluster as the sole prosthetic group in addition to the active-site disulfide. The nature, properties, and function of the Fe-S cluster in spinach ferredoxin: thioredoxin reductase (FTR) have been investigated by the combination of UV/visible absorption, variable-temperature magnetic circular dichroism (MCD), EPR, and resonance Raman (RR) spectroscopies. 66 refs., 5 figs., 1 tab.

Staples, C.R.; Ameyibor, E.; Fu, Weiguang; Johnson, M.K. [Univ. of Georgia, Athens, GA (United States)] [and others

1996-09-03

443

Relationship between hydraulic resistance and leaf morphology in broadleaf Quercus species: a new interpretation of leaf lobation  

Microsoft Academic Search

We investigated the relationship between leaf shape and leaf hydraulic resistance in a set of broadleaf Quercus tree species (Q. cerris, Q. frainetto, Q. petraea, Q. pyrenaica, Q. robur, Q. rubra, Q. velutina). Seedlings of all the studied species were grown under uniform environmental conditions. A new high-pressure flowmeter was designed to measure leaf-blade hydraulic resistance. Leaf shape was characterised

S. Sis; J. J. Camarero; Eustaquio Gil-Pelegrn

2001-01-01

444

Leaf morphology shift linked to climate change  

PubMed Central

Climate change is driving adaptive shifts within species, but research on plants has been focused on phenology. Leaf morphology has demonstrated links with climate and varies within species along climate gradients. We predicted that, given within-species variation along a climate gradient, a morphological shift should have occurred over time due to climate change. We tested this prediction, taking advantage of latitudinal and altitudinal variations within the Adelaide Geosyncline region, South Australia, historical herbarium specimens (n = 255) and field sampling (n = 274). Leaf width in the study taxon, Dodonaea viscosa subsp. angustissima, was negatively correlated with latitude regionally, and leaf area was negatively correlated with altitude locally. Analysis of herbarium specimens revealed a 2 mm decrease in leaf width (total range 19 mm) over 127 years across the region. The results are consistent with a morphological response to contemporary climate change. We conclude that leaf width is linked to maximum temperature regionally (latitude gradient) and leaf area to minimum temperature locally (altitude gradient). These data indicate a morphological shift consistent with a direct response to climate change and could inform provenance selection for restoration with further investigation of the genetic basis and adaptive significance of observed variation.

Guerin, Greg R.; Wen, Haixia; Lowe, Andrew J.

2012-01-01

445

Chemistry and Biology of Plant Leaf Movements.  

PubMed

The leaves of Mimosa pudica L. are well known for their rapid movement when touched. Recently, we were able to isolate an excitatory substance in small quantities from this plant, which consists of three different components (potassium L-malate, magnesium trans-aconitate, and dimethylammonium salt). Many plants close their leaves in the evening, as if to sleep, and open them early in the morning (nyctinastic leaf movement). This circadian rhythm is known to be controlled by the biological clock of such plants. Extensive studies on other nyctinastic plants led to the isolation of a variety of leaf-opening substances (LOSs) and leaf-closing substances (LCSs). Based on our experiments on these bioactive substances, we found that the circadian rhythmic leaf movement of these plants is initiated by the regulated balance of LOSs and LCSs. The balance of concentration between the two leaf-movement factors (LMFs) is inversed during the day. The glycoside-type LMF is hydrolyzed with beta-glucosidase, the activity of which is regulated by the biological clock. The circadian rhythm observed in the leaf movement is introduced by activation of beta-glucosidase regulated by the biological clock. PMID:10777626

Ueda; Yamamura

2000-04-01

446

Ginseng leaf-stem: bioactive constituents and pharmacological functions  

Microsoft Academic Search

Ginseng root is used more often than other parts such as leaf stem although extracts from ginseng leaf-stem also contain similar active ingredients with pharmacological functions. Ginseng's leaf-stems are more readily available at a lower cost than its root. This article reviews the pharmacological effects of ginseng leaf-stem on some diseases and adverse effects due to excessive consumption. Ginseng leaf-stem

Hongwei Wang; Dacheng Peng; Jingtian Xie

2009-01-01

447

Decline of leaf hydraulic conductance with dehydration: relationship to leaf size and venation architecture.  

PubMed

Across plant species, leaves vary enormously in their size and their venation architecture, of which one major function is to replace water lost to transpiration. The leaf hydraulic conductance (K(leaf)) represents the capacity of the transport system to deliver water, allowing stomata to remain open for photosynthesis. Previous studies showed that K(leaf) relates to vein density (vein length per area). Additionally, venation architecture determines the sensitivity of K(leaf) to damage; severing the midrib caused K(leaf) and gas exchange to decline, with lesser impacts in leaves with higher major vein density that provided more numerous water flow pathways around the damaged vein. Because xylem embolism during dehydration also reduces K(leaf), we hypothesized that higher major vein density would also reduce hydraulic vulnerability. Smaller leaves, which generally have higher major vein density, would thus have lower hydraulic vulnerability. Tests using simulations with a spatially explicit model confirmed that smaller leaves with higher major vein density were more tolerant of major vein embolism. Additionally, for 10 species ranging strongly in drought tolerance, hydraulic vulnerability, determined as the leaf water potential at 50% and 80% loss of K(leaf), was lower with greater major vein density and smaller leaf size (|r| = 0.85-0.90; P < 0.01). These relationships were independent of other aspects of physiological and morphological drought tolerance. These findings point to a new functional role of venation architecture and small leaf size in drought tolerance, potentially contributing to well-known biogeographic trends in leaf size. PMID:21511989

Scoffoni, Christine; Rawls, Michael; McKown, Athena; Cochard, Herv; Sack, Lawren

2011-04-21

448

Pulvinus activity, leaf movement and leaf water-use efficiency of bush bean ( Phaseplus vulgaris L.) in a hot environment  

Microsoft Academic Search

Pulvinus activity of Phaseolus species in response to environmental stimuli plays an essential role in heliotropic leaf movement. The aims of this study\\u000a were to monitor the continuous daily pulvinus movement and pulvinus temperature, and to evaluate the effects of leaf movements,\\u000a on a hot day, on instantaneous leaf water-use efficiency (WUEi), leaf gas exchange, and leaf temperature. Potted plants

Mahmoud Raeini-Sarjaz; Vida Chalavi

2008-01-01

449

Leaf patterns, leaf size and ecologically related traits in high Mediterranean mountain on the Moroccan High Atlas  

Microsoft Academic Search

Leaf traits functional relationship is particularly important in plant ecological strategies, but few data are available from\\u000a Mediterranean high-altitude environments. We analysed leaf general patterns and leaf trait relationships in 84 perennial species\\u000a on the High Atlas, Morocco. We examined the correlation amongst leaf size, leaf width and length, plant height and seed size,\\u000a analysed multi-trait relationships using Structural Equation

Teresa Navarro; Jalal El Oualidi; Mohammed Sghir Taleb; Virginia Pascual; Baltasar Cabezudo; Rubn Milla

2010-01-01

450

Leaf miner-induced changes in leaf transmittance cause variations in insect respiration rates  

Microsoft Academic Search

Very little is known about alterations in microclimate when an herbivore feeds on host plant. Modifications of leaf transmittance properties induced by feeding activity of the leaf miner Phyllonorycter blancardella F. were measured using a spectrometer. Their effects on the herbivore's body temperature and respiration rate have been determined under controlled conditions and varying radiation level employing an infrared gas

Sylvain Pincebourde; Jrme Casas

2006-01-01

451

Leaf alkaloids, phenolics, and coffee resistance to the leaf miner Leucoptera coffeella (Lepidoptera: Lyonetiidae).  

PubMed

Coffee (Coffea spp.) alkaloids (caffeine and related methylxanthines) and phenolics (caffeic and chlorogenic acids) have recognized pestistatic/pesticidal activity and mediate insect-plant interactions. The present investigation assessed the resistance of 12 coffee genotypes to the leaf miner Leucoptera (= Perileucoptera) coffeella (Gurin-Mneville & Perrottet) (Lepidoptera: Lyonetiidae) and correlated such results with the leaf content of coffee alkaloids and phenolics that probably play a role in the interaction between coffee and this leaf miner. The levels of chlorogenic and caffeic acid, caffeine, and related methylxanthines were measured and quantified in leaf extracts of these genotypes before and 7 d after their infestation by the leaf miner. Some coffee genotypes (Coffea canephora L. and Coffea racemosa Lour. and its hybrids with Coffea arabica L.) exhibited high pesticidal activity (100% mortality) toward the L. coffeella, indicating their antibiosis resistance. However, there was no correlation between this activity and the leaf levels of coffee alkaloids and phen