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1

Site-directed mutagenesis of serine 158 demonstrates its role in spinach leaf sucrose-phosphate synthase modulation  

NASA Technical Reports Server (NTRS)

Site-directed mutagenesis of spinach sucrose-phosphate synthase (SPS) was performed to investigate the role of Ser158 in the modulation of spinach leaf SPS. Tobacco plants expressing the spinach wild-type (WT), S158A, S158T and S157F/S158E SPS transgenes were produced. Expression of transgenes appeared not to reduce expression of the tobacco host SPS. SPS activity in the WT and the S158T SPS transgenics showed light/dark modulation, whereas the S158A and S157F/S158E mutants were not similarly light/dark modulated: the S158A mutant enzyme was not inactivated in the dark, and the S157F/S158E was not activated in the light. The inability to modulate the activity of the S158A mutant enzyme by protein phosphorylation was demonstrated in vitro. The WT spinach enzyme immunopurified from dark transgenic tobacco leaves had a low initial activation state, and could be activated by PP2A and subsequently inactivated by SPS-kinase plus ATP. Rapid purification of the S158A mutant enzyme from dark leaves of transgenic plants using spinach-specific monoclonal antibodies yielded enzyme that had a high initial activation state, and pre-incubation with leaf PP2A or ATP plus SPS-kinase (the PKIII enzyme) caused little modulation of activity. The results demonstrate the regulatory significance of Ser158 as the major site responsible for dark inactivation of spinach SPS in vivo, and indicate that the significance of phosphorylation is the introduction of a negative charge at the Ser158 position.

Toroser, D.; McMichael, R. Jr; Krause, K. P.; Kurreck, J.; Sonnewald, U.; Stitt, M.; Huber, S. C.; Davies, E. (Principal Investigator)

1999-01-01

2

Site-specific regulatory interaction between spinach leaf sucrose-phosphate synthase and 14-3-3 proteins  

NASA Technical Reports Server (NTRS)

We report an Mg2+-dependent interaction between spinach leaf sucrose-phosphate synthase (SPS) and endogenous 14-3-3 proteins, as evidenced by co-elution during gel filtration and co-immunoprecipitation. The content of 14-3-3s associated with an SPS immunoprecipitate was inversely related to activity, and was specifically reduced when tissue was pretreated with 5-aminoimidazole-4-carboxamide riboside, suggesting metabolite control in vivo. A synthetic phosphopeptide based on Ser-229 was shown by surface plasmon resonance to bind a recombinant plant 14-3-3, and addition of the phosphorylated SPS-229 peptide was found to stimulate the SPS activity of an SPS:14-3-3 complex. Taken together, the results suggest a regulatory interaction of 14-3-3 proteins with Ser-229 of SPS.

Toroser, D.; Athwal, G. S.; Huber, S. C.; Davies, E. (Principal Investigator)

1998-01-01

3

Expression of a maize sucrose phosphate synthase in tomato alters leaf carbohydrate partitioning.  

PubMed Central

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 enzymatic activity, we can conclude that SPS enzyme activity is conferred by a single gene product. Sequence comparisons showed that SPS is distantly related to the enzyme sucrose synthase. When expressed from a ribulose bisphosphate carboxylase small subunit promoter in transgenic tomatoes, total SPS activity was boosted up to sixfold in leaves and appeared to be physiologically uncoupled from the tomato regulation mechanism. The elevated SPS activity caused a reduction of starch and increase of sucrose in the tomato leaves. This result clearly demonstrates that SPS is involved in the regulation of carbon partitioning in the leaves.

Worrell, A C; Bruneau, J M; Summerfelt, K; Boersig, M; Voelker, T A

1991-01-01

4

Antibodies That Distinguish between the and Dephospho-Form of Spinach Leaf Synthase  

Microsoft Academic Search

Serum antibodies were raised against a synthetic peptide corre- sponding to the amino acid sequence surrounding the major inac- tivating phosphorylation site (serine-158) of spinach (Spinacia ol- eracea) leaf sucrose-phosphate synthase (SPS). lhe anti-peptide antibodies precipitated highly activated SPS preferentially to ATP- inactivated SPS and interacted only weakly with the sodium dodecyl sulfate-denatured enzyme bound to a membrane. The antibodies

Hendrik Weiner

5

Diurnal Regulation of Leaf Blade Elongation in Rice by CO2 (Is it Related to Sucrose-Phosphate Synthase Activity?).  

PubMed Central

The relationship between leaf blade elongation rates (LER) and sucrose-phosphate synthase (SPS) activity was investigated at different times during ontogeny of rice (Oryza sativa L. cv Jarrah) grown in flooded soil at either 350 or 700 [mu]L CO2 L-1. High CO2 concentrations increased LER of expanding blades and in vivo activity (Vlimiting) SPS activity of expanded blades during the early vegetative stage (21 d after planting [DAP]), when tiller number was small and growing blades were strong carbohydrate sinks. Despite a constant light environment, there was a distinct diurnal pattern in LER, Vlimiting SPS activity, and concentration of soluble sugars, with an increase in the early part of the light period and a decrease later in the light period. The strong correlation (r = 0.65) between LER and Vlimiting SPS activity over the diurnal cycle indicated that SPS activity played an important role in controlling blade growth. The higher Vlimiting SPS activity at elevated CO2 at 21 DAP was caused by an increase in the activation state of the enzyme rather than an increase in Vmax. Fructose and glucose accumulated to a greater extent than sucrose at high CO2 and may have been utilized for synthesis of cell-wall components, contributing to higher specific leaf weight. By the mid-tillering stage (42 DAP), CO2 enrichment enhanced Vlimiting and Vmax activities of source blades. Nevertheless, LER was depressed by high CO2, probably because tillers were stronger carbohydrate sinks than growing blades.

Seneweera, S. P.; Basra, A. S.; Barlow, E. W.; Conroy, J. P.

1995-01-01

6

Freezing Tolerance of Citrus, Spinach, and Petunia Leaf Tissue 1  

PubMed Central

Seasonal variations in freezing tolerance, water content, water and osmotic potential, and levels of soluble sugars of leaves of field-grown Valencia orange (Citrus sinensis) trees were studied to determine the ability of citrus trees to cold acclimate under natural conditions. Controlled environmental studies of young potted citrus trees, spinach (Spinacia pleracea), and petunia (Petunia hybrids) were carried out to study the water relations during cold acclimation under less variable conditions. During the coolest weeks of the winter, leaf water content and osmotic potential of field-grown trees decreased about 20 to 25%, while soluble sugars increased by 100%. At the same time, freezing tolerance increased from lethal temperature for 50% (LT50) of ?2.8 to ?3.8°C. In contrast, citrus leaves cold acclimated at a constant 10°C in growth chambers were freezing tolerant to about ?6°C. The calculated freezing induced cellular dehydration at the LT50 remained relatively constant for field-grown leaves throughout the year, but increased for leaves of plants cold acclimated at 10°C in a controlled environment. Spinach leaves cold acclimated at 5°C tolerated increased cellular dehydration compared to nonacclimated leaves. Cold acclimated petunia leaves increased in freezing tolerance by decreasing osmotic potential, but had no capacity to change cellular dehydration sensitivity. The result suggest that two cold acclimation mechanisms are involved in both citrus and spinach leaves and only one in petunia leaves. The common mechanism in all three species tested was a minor increase in tolerance (about ?1°C) resulting from low temperature induced osmotic adjustment, and the second in citrus and spinach was a noncolligative mechanism that increased the cellular resistance to freeze hydration.

Yelenosky, George; Guy, Charles L.

1989-01-01

7

Cloning and expression analysis of sucrose-phosphate synthase from sugar beet ( Beta vulgaris L.)  

Microsoft Academic Search

A cDNA clone encoding a sucrose-phosphate synthase from sugar beet (BvSPS 1) has been isolated by screening a tap root-specific cDNA library using a heterologous SPS cDNA from spinach. The 3635 by sugar beet cDNA codes for a 1045 amino acid polypeptide with a predicted molecular mass of 118 kDa. The deduced amino acid sequence of sugar beet SPS shows

Holger Hesse; Uwe Sonnewald; Lothar Willmitzer

1995-01-01

8

A Simple Method for Estimating Intactness of Spinach Leaf Protoplasts by Glycolate Oxidase Assay 1  

PubMed Central

A method was developed for the quantitative analysis of intactness of spinach leaf protoplasts using glycolate oxidase activity as an index. Since glycolate does not penetrate into protoplasts at neutral pH, the increase of O2 consumption by the addition of glycolate to protoplast suspension was due to the glycolate oxidase activity released from damaged protoplasts. The proportion of damaged protoplasts in the whole preparation was calculated from the ratio of released and total glycolate oxidase activity. Freshly prepared spinach leaf protoplasts were found to be 80 to 90% intact as estimated by the method. The effect of osmolarity on the respiratory activities of spinach leaf protoplasts was also examined by applying the same principle.

Nishimura, Mikio; Douce, Roland; Akazawa, Takashi

1985-01-01

9

Antioxidant capacity and phenolic content in leaf extracts of tree spinach (Cnidoscolus spp.).  

PubMed

Total phenolic content and antioxidant capacity of two tree spinach species (Cnidoscolus chayamansa McVaugh and C. aconitifolius Miller.) were determined in raw and cooked leaf extracts. Antioxidant capacity was assessed by the oxygen radical absorbance capacity (ORAC) assay, and flavonoid glycoside composition was quantified by HPLC and identified by GC. Total phenolics and antioxidant capacity were higher in raw than in cooked leaf extracts. The ORAC values were strongly correlated with total phenolic content (r = 0.926) in all leaf extracts. The major flavonoids isolated from the leaf extracts were kaempferol-3-O-glycosides and quercetin-3-O-glycosides. C. aconitifolius leaves contained more varieties of the flavonoid glycosides than C. chayamansa. Cooking reduced antioxidant activity and phenolic content and resulted in losses of some kaempferol glycoside and quercetin glycoside residues in leaf extracts. The results of this study indicate that tree spinach leaves are a rich source of natural antioxidants for foods. PMID:14709023

Kuti, Joseph O; Konuru, Hima B

2004-01-14

10

Biosynthesis of Ribulose-1,5-Bisphosphate Carboxylase in Spinach Leaf Protoplasts 1  

PubMed Central

Spinach leaf (Spinacia oleracea L. var. Kyoho) protoplasts sustain protein-synthesizing activity as measured by the incorporation of [14C]-leucine into the protein fraction both in the light and in the dark. By the immunoprecipitation of ribulose-1,5-bisphosphate (RuP2) carboxylase with rabbit antibody raised against the purified spinach enzyme preparation, it was found that approximately 7% of the total radiocarbon incorporated into the protein fraction in the light was in the carboxylase molecules. However, there was no measurable net increase observed in the content of the enzyme protein in the experimental conditions employed. It was found that both chloramphenicol and cycloheximide inhibited the incorporation of [14C]leucine into RuP2 carboxylase and its constituent subunits, as measured by the immunoprecipitation of the enzyme molecule and its subunits, A and B.

Nishimura, Mikio; Akazawa, Takashi

1978-01-01

11

Subcellular Metabolite Levels in Spinach Leaves 1  

PubMed Central

The alterations of subcellular metabolite levels during the day in spinach leaves have been investigated using nonaqueous density gradient centrifugation to separate chloroplasts, cytosol, and vacuole. The results provide direct evidence for the role of sucrose phosphate synthase and cytosolic fructose 1,6-bisphosphatase in regulating sucrose synthesis in leaves and also show that the phosphate translocator is kinetically limiting in vivo.

Gerhardt, Richard; Stitt, Mark; Heldt, Hans W.

1987-01-01

12

Spinach Leaf Chloroplast CO2 and NO2? Photoassimilations Do Not Compete for Photogenerated Reductant  

PubMed Central

Potential competition between CO2 and NO2? 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 CO2 and/or NO2? to produce the highest demand for reductant by CO2 and/or NO2? assimilatory processes (enzymes). Even in the presence of CO2 fixation, NO2? 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 CO2 assimilation. Regardless of the magnitude of the incident light energy, CO2 assimilation did not repress NO2? 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 CO2 as well as with inorganic nitrogen photoassimilation.

Robinson, J. Michael

1988-01-01

13

Purification, properties and substrate specificity of adenosine triphosphate sulphurylase from spinach leaf tissue  

PubMed Central

1. ATP sulphurylase was purified up to 1000-fold from spinach leaf tissue. Activity was measured by sulphate-dependent [32P]PPi–ATP exchange. The enzyme was separated from Mg2+-requiring alkaline pyrophosphatase (which interferes with the PPi–ATP-exchange assay) and from other PPi–ATP-exchange activities. No ADP sulphurylase activity was detected. 2. Sulphate was the only form of inorganic sulphur that catalysed PPi–ATP exchange; Km (sulphate) was 3.1mm, Km (ATP) was 0.35mm and the pH optimum was 7.5–9.0. The enzyme was insensitive to thiol-group reagents and required either Mg2+ or Co2+ for activity. 3. The enzyme catalysed [32P]PPi–dATP exchange; Km (dATP) was 0.84mm and V (dATP) was 30% of V (ATP). Competition between ATP and dATP was demonstrated. 4. Selenate catalysed [32P]PPi–ATP exchange and competed with sulphate; Km (selenate) was 1.0mm and V (selenate) was 30% of V (sulphate). No AMP was formed with selenate as substrate. Molybdate did not catalyse PPi–ATP exchange, but AMP was formed. 5. Synthesis of adenosine 5?-[35S]sulphatophosphate was demonstrated by coupling purified ATP sulphurylase and Mg2+-dependent alkaline pyrophosphatase (also prepared from spinach) with [35S]sulphate and ATP as substrates; adenosine 5?-sulphatophosphate was not synthesized in the absence of pyrophosphatase. Some parameters of the coupled system are reported.

Shaw, W. H.; Anderson, J. W.

1972-01-01

14

Identification of Ser-543 as the major regulatory phosphorylation site in spinach leaf nitrate reductase  

NASA Technical Reports Server (NTRS)

Spinach leaf NADH:nitrate reductase (NR) responds to light/dark signals and photosynthetic activity in part as a result of rapid regulation by reversible protein phosphorylation. We have identified the major regulatory phosphorylation site as Ser-543, which is located in the hinge 1 region connecting the cytochrome b domain with the molybdenum-pterin cofactor binding domain of NR, using recombinant NR fragments containing or lacking the phosphorylation site sequence. Studies with NR partial reactions indicated that the block in electron flow caused by phosphorylation also could be localized to the hinge 1 region. A synthetic peptide (NR6) based on the phosphorylation site sequence was phosphorylated readily by NR kinase (NRk) in vitro. NR6 kinase activity tracked the ATP-dependent inactivation of NR during several chromatographic steps and completely inhibited inactivation/phosphorylation of native NR in vitro. Two forms of NRk were resolved by using anion exchange chromatography. Studies with synthetic peptide analogs indicated that both forms of NRk had similar specificity determinants, requiring a basic residue at P-3 (i.e., three amino acids N-terminal to the phosphorylated serine) and a hydrophobic residue at P-5. Both forms are strictly calcium dependent but belong to distinct families of protein kinases because they are distinct immunochemically.

Bachmann, M.; Shiraishi, N.; Campbell, W. H.; Yoo, B. C.; Harmon, A. C.; Huber, S. C.; Davies, E. (Principal Investigator)

1996-01-01

15

Spinach leaf 70-kilodalton heat-shock cognate stabilizes bovine adrenal glucose-6-phosphate dehydrogenase in vitro without apparent stable binding  

Microsoft Academic Search

Spinach (Spinacia oleracea L.) leaf tissue 70-kilodalton heat-shock cognate was purified by ATP-agarose affinity and gel filtration. Gel filtration of the affinity-purified protein resolved it into three forms: monomer, dimer, and oligomer. In the absence of ATP, the majority of the heat-shock cognate existed as a monomeric form with lesser amounts of dimer and oligomer. Addition of 3 mM ATP

James V. Anderson; Charles L. Guy

1995-01-01

16

Sucrose-phosphate synthase steady-state mRNA increases in ripening kiwifruit  

Microsoft Academic Search

Early during fruit ripening in kiwifruit (Actinidia deliciosa var. deliciosa [A. Chev.], C.F. Liang and A.R. Ferguson cv. Hayward), starch is broken down to sucrose and hexose sugars. Concomitantly, sucrose-phosphate synthase (SPS, EC 2.3.1.14) activity measured with saturating substrate increased, suggesting that SPS is induced in response to a higher requirement for sucrose synthesis [29]. A 2584 bp long partial

Georg Langenkämper; Ronnie McHale; Richard C. Gardner; Elspeth MacRae

1998-01-01

17

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

PubMed

Escherichia coli O157:H7 contamination of leafy green vegetables is an ongoing concern for consumers. Biofilm-associated pathogens are relatively resistant to chemical treatments, but little is known about their response to irradiation. Leaves of Romaine lettuce and baby spinach were dip inoculated with E. coli O157:H7 and stored at 4 degrees C for various times (0, 24, 48, 72 h) to allow biofilms to form. After each time, leaves were treated with either a 3-min wash with a sodium hypochlorite solution (0, 300, or 600 ppm) or increasing doses of irradiation (0, 0.25, 0.5, 0.75, or 1 kGy). Viable bacteria were recovered and enumerated. Chlorine washes were generally only moderately effective, and resulted in maximal reductions of 1.3 log CFU/g for baby spinach and 1.8 log CFU/g for Romaine. Increasing time in storage prior to chemical treatment had no effect on spinach, and had an inconsistent effect on 600 ppm applied to Romaine. Allowing time for formation of biofilm-like aggregations reduced the efficacy of irradiation. D(10) values (the dose required for a 1 log reduction) significantly increased with increasing storage time, up to 48 h postinoculation. From 0 h of storage, D(10) increased from 0.19 kGy to a maximum of 0.40 to 0.43 kGy for Romaine and 0.52 to 0.54 kGy for spinach. SEM showed developing biofilms on both types of leaves during storage. Bacterial colonization of the stomata was extensive on spinach, but not on Romaine. These results indicate that the protection of bacteria on the leaf surface by biofilm formation and stomatal colonization can reduce the antimicrobial efficacy of irradiation on leafy green vegetables. PMID:20629883

Niemira, Brendan A; Cooke, Peter H

2010-06-01

18

Summer (subarctic) versus winter (subtropic) production affects spinach (Spinacia oleracea L.) leaf bionutrients: vitamins (C, E, Folate, K1, provitamin A), lutein, phenolics, and antioxidants.  

PubMed

Comparison of spinach (Spinacia oleracea L.) cultivars Lazio and Samish grown during the summer solstice in the subarctic versus the winter solstice in the subtropics provided insight into interactions between production environment (light intensity), cultivar, and leaf age/maturity/position affecting bionutrient concentrations of vitamins (C, E, folate, K1, provitamin A), lutein, phenolics, and antioxidants. Growing spinach during the winter solstice in the subtropics resulted in increased leaf dry matter %, oxidized (dehydro) ascorbic acid (AsA), ?- and ?-tocopherol, and total phenols but lower reduced (free) AsA, ?-carotene, folate, and antioxidant capacity compared to summer solstice-grown spinach in the subarctic. Both cultivars had similar bionutrients, except for higher dehydroAsA, and lower ?- and ?-tocopherol in 'Samish' compared to 'Lazio'. For most bionutrients measured, there was a linear, and sometimes quadratic, increase in concentrations from bottom to top canopy leaves. However, total phenolics and antioxidant capacity increased basipetally. The current study has thus demonstrated that dehydroAsA, ?-tocopherol, and ?-tocopherol were substantially lower in subarctic compared to subtropical-grown spinach, whereas the opposite relationship was found for antioxidant capacity, ?-carotene, and folates (vitamin B9). The observations are consistent with previously reported isolated effects of growth environment on bionutrient status of crops. The current results clearly highlight the effect of production environment (predominantly radiation capture), interacting with genetics and plant phenology to alter the bionutrient status of crops. While reflecting the effects of changing growing conditions, these results also indicate potential alterations in the nutritive value of foods with anticipated shifts in global climatic conditions. PMID:23834651

Lester, Gene E; Makus, Donald J; Hodges, D Mark; Jifon, John L

2013-07-24

19

Relationship between fresh-packaged spinach leaves exposed to continuous light or dark and bioactive contents: effects of cultivar, leaf size, and storage duration.  

PubMed

Current retail marketing conditions allow produce to receive artificial light 24 h per day during its displayed shelf life. Essential human-health vitamins [ascorbic acid (vit C), folate (vit B(9)), phylloquinone (vit K(1)), alpha-tocopherol (vit E), and the carotenoids lutein, violaxanthin, zeaxanthin, and beta-carotene (provit A)] also are essential for photosynthesis and are biosynthesized in plants by light conditions even under chilling temperatures. Spinach leaves, notably abundant in the aforementioned human-health compounds, were harvested from flat-leaf 'Lazio' and crinkle-leafed 'Samish' cultivars at peak whole-plant maturity as baby (top- and midcanopy) and larger (lower-canopy) leaves. Leaves were placed as a single layer in commercial, clear-polymer retail boxes and stored at 4 degrees C for up to 9 days under continuous light (26.9 micromol.m(2 ).s) or dark. Top-canopy, baby-leaf spinach generally had higher concentrations of all bioactive compounds, on a dry weight basis, with the exception of carotenoids, than bottom-canopy leaves. All leaves stored under continuous light generally had higher levels of all bioactive compounds, except beta-carotene and violaxanthin, and were more prone to wilting, especially the flat-leafed cultivar. All leaves stored under continuous darkness had declining or unchanged levels of the aforementioned bioactive compounds. Findings from this study revealed that spinach leaves exposed to simulated retail continuous light at 4 degrees C, in clear plastic containers, were overall more nutritionally dense (enriched) than leaves exposed to continuous darkness. PMID:20131793

Lester, Gene E; Makus, Donald J; Hodges, D Mark

2010-03-10

20

Light/Dark Profiles of Sucrose Phosphate Synthase, Sucrose Synthase, and Acid Invertase in Leaves of Sugar Beets  

PubMed Central

The activity of sucrose phosphate synthase, sucrose synthase, and acid invertase was monitored in 1- to 2-month-old sugar beet (Beta vulgaris L.) leaves. Sugar beet leaves achieve full laminar length in 13 days. Therefore, leaves were harvested at 2-day intervals for 15 days. Sucrose phosphate synthase activity was not detectable for 6 days in the dark-grown leaves. Once activity was measurable, sucrose phosphate synthase activity never exceeded half that observed in the light-grown leaves. After 8 days in the dark, leaves which were illuminated for 30 minutes showed no significant change in sucrose phosphate synthase activity. Leaves illuminated for 24 hours after 8 days in darkness, however, recovered sucrose phosphate synthase activity to 80% of that of normally grown leaves. Sucrose synthase and acid invertase activity in the light-grown leaves both increased for the first 7 days and then decreased as the leaves matured. In contrast, the activity of sucrose synthase oscillated throughout the growth period in the dark-grown leaves. Acid invertase activity in the dark-grown leaves seemed to be the same as the activity found in the light-grown leaves.

Vassey, Terry L.

1989-01-01

21

Sucrose-phosphate synthase in tree species: light/dark regulation involves a component of protein turnover in Prosopis juliflora (SW DC).  

PubMed

Light dependent modulation of sucrose-phosphate synthase activity (SPS; EC 2.4.1.14) was studied in a tree species, namely Prosopis juliflora. In this paper we demonstrate that cycloheximide, an inhibitor of cytoplasmic protein synthesis, when fed to detached leaves of P. juliflora through transpiration stream in the dark or in light completely prevents in vivo light activation of Vlim and Vmax activities of SPS. In case of spinach, however, cycloheximide feeding affects only Vlim activity while Vmax activity remained unchanged. In contrast, chloramphenicol, an inhibitor of protein synthesis in chloroplast has no effect on the light activation of SPS in Prosopis. The treatment with cycloheximide showed slight reduction in the rate of O2 evolution indicating that cycloheximide had very little effect on overall photosynthesis. These results indicate that short term protein turnover of the SPS protein and some other essential component(s) (e.g., a putative protein that modifies SPS activity) is one of the primary steps in a complex and unique regulatory cascade effecting the reversible light activation of SPS. PMID:9350350

Sinha, A K; Shirke, P A; Pathre, U; Sane, P V

1997-10-01

22

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

23

Nectar secretion requires sucrose phosphate synthases and the sugar transporter SWEET9.  

PubMed

Angiosperms developed floral nectaries that reward pollinating insects. Although nectar function and composition have been characterized, the mechanism of nectar secretion has remained unclear. Here we identify SWEET9 as a nectary-specific sugar transporter in three eudicot species: Arabidopsis thaliana, Brassica rapa (extrastaminal nectaries) and Nicotiana attenuata (gynoecial nectaries). We show that SWEET9 is essential for nectar production and can function as an efflux transporter. We also show that sucrose phosphate synthase genes, encoding key enzymes for sucrose biosynthesis, are highly expressed in nectaries and that their expression is also essential for nectar secretion. Together these data are consistent with a model in which sucrose is synthesized in the nectary parenchyma and subsequently secreted into the extracellular space via SWEET9, where sucrose is hydrolysed by an apoplasmic invertase to produce a mixture of sucrose, glucose and fructose. The recruitment of SWEET9 for sucrose export may have been a key innovation, and could have coincided with the evolution of core eudicots and contributed to the evolution of nectar secretion to reward pollinators. PMID:24670640

Lin, I Winnie; Sosso, Davide; Chen, Li-Qing; Gase, Klaus; Kim, Sang-Gyu; Kessler, Danny; Klinkenberg, Peter M; Gorder, Molly K; Hou, Bi-Huei; Qu, Xiao-Qing; Carter, Clay J; Baldwin, Ian T; Frommer, Wolf B

2014-04-24

24

The Structure of Sucrose Phosphate Synthase from Halothermothrix orenii Reveals Its Mechanism of Action and Binding Mode  

Microsoft Academic Search

Sucrose phosphate synthase (SPS) catalyzes the transfer of a glycosyl group from an activated donor sugar, such as uridine diphosphate glucose (UDP-Glc), to a saccharide acceptor D-fructose 6-phosphate (F6P), resulting in the formation of UDP and D-sucrose-6'-phosphate (S6P). This is a central regulatory process in the production of sucrose in plants, cyanobacteria, and proteobacteria. Here, we report the crystal structure

Teck Khiang Chua; Janusz M. Bujnicki; T.-C. Tan; F. Huynh; B. K. Patel; J. Sivaraman; Y. Ogimoto; K. Miyano; H. Sawa

2008-01-01

25

Induction of genes encoding plastidic phosphorylase from spinach ( Spinacia oleracea L.) and potato ( Solanum tuberosum L.) by exogenously supplied carbohydrates in excised leaf discs  

Microsoft Academic Search

.  A full-length cDNA encoding plastidic phosphorylase (Pho1, EC 2.4.1.1) from spinach (Spinacia oleracea L.) has been isolated. Analysis of the deduced protein sequence revealed considerable homologies with the corresponding proteins\\u000a from other plants, animals and prokaryotes. Escherichia coli cells carrying the entire cDNA for Pho1 expressed an active phosphorylase, which resembled the properties of the plastidic isozyme of spinach with

Elke Duwenig; Martin Steup; Jens Kossmann

1997-01-01

26

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

27

Effects of excessive photon on the photosynthetic pigments and violaxanthin de-epoxidase activity in the xanthophyll cycle of spinach leaf  

Microsoft Academic Search

Excessive photon effects on the photosynthetic pigments and violaxanthin de-epoxidase activity in the xanthophyll cycle of two-month-old spinach leaves were investigated. The leaves were exposed to an excessive photon flux of 1300?molm?2s?1 for 24h. Photosynthetic pigments such as chlorophylls and carotenoids were quantified and purified by high-performance liquid chromatography. The results showed that the high irradiance induced the dynamic conversion

Dev Mani Pandey; Kyung-Hong Kang; Up-Dong Yeo

2005-01-01

28

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

29

Promoter strength and tissue specificity effects on growth of tomato plants transformed with maize sucrose-phosphate synthase.  

PubMed

When sucrose-phosphate synthase (SPS; EC 2.4.1.14) is expressed in tomato (Lycopersicon esculentum Mill.) from a ribulose-1,5-bisphosphate carboxylase-oxygenase (Rubisco) small subunit (rbcS) promoter, yields are often unchanged but when SPS is expressed from a Cauliflower Mosaic Virus 35S promoter, yield is enhanced up to 80%. Two explanations for this phenomenon are (i) that expression of SPS in tissues other than leaves accounts for the increased yield or (ii) that the lower level of expression directed by the 35S promoter is more beneficial than the high level of expression directed by the rbcS promoter. To test the first hypothesis, we conducted a reciprocal graft experiment, which showed that root SPS activity did not substantially affect growth. To test the second hypothesis, we conducted a field trial using a backcrossed, segregating, population of SPS-transformed plants derived from 35S and rbcS lines. The optimal dose of SPS activity for growth was approximately twice that of the wild type regardless of which promoter was used. The effect of SPS on growth was the result of a shift in partitioning of carbon among starch, sucrose, and ionic compounds (primarily amino acids), rather than of an increase in net photosynthesis. Excessive SPS activity resulted in a decreased rate of amino acid synthesis, which could explain the non-linear response of plant growth to the level of SPS expression. PMID:11346956

Laporte, M M; Galagan, J A; Prasch, A L; Vanderveer, P J; Hanson, D T; Shewmaker, C K; Sharkey, T D

2001-04-01

30

Sucrose Phosphate Synthase, Sucrose Synthase, and Invertase Activities in Developing Fruit of Lycopersicon esculentum Mill. and the Sucrose Accumulating Lycopersicon hirsutum Humb. and Bonpl. 1  

PubMed Central

The green-fruited Lycopersicon hirsutum Humb. and Bonpl. accumulated sucrose to concentrations of about 118 micromoles per gram fresh weight during the final stages of development. In comparison, Lycopersicon esculentum Mill. cultivars contained less than 15 micromoles per gram fresh weight of sucrose at the ripe stage. Glucose and fructose levels remained relatively constant throughout development in L. hirsutum at 22 to 50 micromoles per gram fresh weight each. Starch content was low even at early stages of development, and declined further with development. Soluble acid invertase (EC 3.2. 1.26) activity declined concomitant with the rise in sucrose content. Acid invertase activity, which was solubilized in 1 molar NaCl (presumably cell-wall bound), remained constant throughout development (about 3 micromoles of reducing sugars (per gram fresh weight) per hour. Sucrose phosphate synthase (EC 2.4.1.14) activity was present at about 5 micromoles of sucrose (per gram fresh weight) per hour even at early stages of development, and increased sharply to about 40 micromoles of sucrose (per gram fresh weight) per hour at the final stages of development studied, parallel to the rise in sucrose content. In comparison, sucrose phosphate synthase activity in L. esculentum remained low throughout development. The possible roles of the sucrose metabolizing enzymes in determining sucrose accumulation are discussed.

Miron, Daphne; Schaffer, Arthur A.

1991-01-01

31

Nitrogen Uptake in Spinach  

NASA Astrophysics Data System (ADS)

A plant's absorption of nitrogen can be encouraged by a variety of environmental factors, especially the application of fertilizers. As a common limiting factor in plant growth, not up taking enough nitrogen can be a result of an unhealthy plant. Moreover, as farmers seek out methods to increase growth of plants, fertilizers are used as a solution to the issue of nitrogen deficiency to incorporate additional nitrogen from chemical or organic sources, by not using the right fertilizer can greatly affect the plats. The point of this research project is to determine the effect of various fertilizers on the plant growth, and to correlate the measured nitrogen, water and chlorophyll content in spinach leaves. Spinach leaves were used because they are known to quickly uptake chemicals in the environment. The spinach plants were exposed to four different growing parameters, which are referred to as control, ammonium nitrate, MiracleGro , and organic. The spinach was originally placed in nitrogen deficient soil with only 2.2x10 4 weight percent (wt. %) nitrogen. The leaves in the control group were grown in this nitrogen deficient soil without any fertilizer added. Ammomium nitrate and MiracleGro were added to the spinach in the A and MG groups, respectively, and organic chicken stool was used for the O group. By using a spectral imaging system and flame combustion techniques, the chlorophyll content can be related to the nitrogen content in the spinach leaves. In these spinach leaves, nitrogen and chlorophyll content were measured, chlorophyll is a green pigment that plays a crucial role in producing nutrients for green plants. The lack of chlorophyll will allow the plant to become susceptible to diseases, so it is extremely important that the plants have a high content of chlorophyll. The role of nitrogen in chlorophyll is very important and helps in the creation of chlorophyll; therefore it is necessary that an appropriate amount of nitrogen is added for optimal growth and nutrient content. A common method of increasing nitrogen's availability is by adding fertilizer to plants. Fertilizers come in many varieties, ranging from organic to synthetic. Organic fertilizers differ from their synthetic counterparts in that they contain less artificial substances. Preliminary results of this study show that the organic fertilizer promoted growth of chlorophyll in the spinach leaves. The highest peaks in our results are due to the light absorbance of chlorophyll. The spectra also showed the organic fertilizer had the highest chlorophyll content, unlike the ammonium sulfate which had the last amount. Surprisingly, the control performed slightly better than the MiracleGro, which would not be expected, since MiracleGro is a widely used fertilizer, it was expected that this would lead to the highest chlorophyll content. It is unexpected the soil with trace nitrogen content was able to produce spinach with this relatively high content of chlorophyll. It is imperative to examine how different types of nitrogen additives affect spinach growth. The consequences of fertilizer overuse are destructive to both the plant and its environment, as well as to the humans that consume the resulting produce. The preliminary results of this experiment gave insight into the effectiveness of various kinds of fertilizers and may be able to encourage farmers to use organic fertilizers from natural sources for optimal nutrients and growth of their crops.

Ramirez, J.; VanBenthem, P.

2013-12-01

32

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

2012-04-01

33

Sucrose biosynthesis in a prokaryotic organism: Presence of two sucrose-phosphate synthases in Anabaena with remarkable differences compared with the plant enzymes  

PubMed Central

Biosynthesis of sucrose-6-P catalyzed by sucrose-phosphate synthase (SPS), and the presence of sucrose-phosphate phosphatase (SPP) leading to the formation of sucrose, have both been ascertained in a prokaryotic organism: Anabaena 7119, a filamentous heterocystic cyanobacterium. Two SPS activities (SPS-I and SPS-II) were isolated by ion-exchange chromatography and partially purified. Four remarkable differences between SPSs from Anabaena and those from higher plants were shown: substrate specificity, effect of divalent cations, native molecular mass, and oligomeric composition. Both SPS-I and SPS-II accept Fru-6-P (Km for SPS-I = 0.8 ± 0.1 mM; Km for SPS-II = 0.7 ± 0.1 mM) and UDP-Glc as substrates (Km for SPS-I = 1.3 ± 0.4 mM; Km for SPS-II = 4.6 ± 0.4 mM), but unlike higher plant enzymes, they are not specific for UDP-Glc. GDP-Glc and TDP-Glc are also SPS-I substrates (Km for GDP-Glc = 1.2 ± 0.2 mM and Km for TDP-Glc = 4.0 ± 0.4 mM), and ADP-Glc is used by SPS-II (Km for ADP-Glc = 5.7 ± 0.7 mM). SPS-I has an absolute dependence toward divalent metal ions (Mg2+ or Mn2+) for catalytic activity, not found in plants. A strikingly smaller native molecular mass (between 45 and 47 kDa) was determined by gel filtration for both SPSs, which, when submitted to SDS/PAGE, showed a monomeric composition. Cyanobacteria are, as far as the authors know, the most primitive organisms that are able to biosynthesize sucrose as higher plants do.

Porchia, Andrea C.; Salerno, Graciela L.

1996-01-01

34

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

35

Spinach Nitrate Reductase 1  

PubMed Central

Initial velocity studies of immunopurified spinach nitrate reductase have been performed under conditions of controlled ionic strength and pH and in the absence of chloride ions. Increased ionic strength stimulated NADH:ferricyanide reductase and reduced flavin:nitrate reductase activities and inhibited NADH:nitrate reductase, NADH:cytochrome c reductase and reduced methyl viologen:nitrate reductase activities. NADH:dichlorophenolindophenol reductase activity was unaffected by changes in ionic strength. All of the partial activities, expressed in terms of micromole 2 electron transferred per minute per nanomole heme, were faster than the overall full, NADH:nitrate reductase activity indicating that none of the partial activities included the rate limiting step in electron transfer from NADH to nitrate. The pH optimum for NADH:nitrate reductase activity was determined to be 7 while values for the various partial activities ranged from 6.5 to 7.5. Chlorate, bromate, and iodate were determined to be alternate electron acceptors for the reduced enzyme. These results indicate that unlike the enzyme from Chlorella vulgaris, intramolecular electron transfer between reduced heme and Mo is not rate limiting for spinach nitrate reductase.

Barber, Michael J.; Notton, Brian A.

1990-01-01

36

Along-vein necrosis as indicator symptom on water spinach caused by nickel in water culture  

Microsoft Academic Search

Water spinach (Ipomoea aquatica Forsk, cv. Bamboo-Leaf) grown in aerated nutrient solution in green- house was treated with various levels of nickel, copper, zinc, chromium, cadmium, manganese, arsenic, aluminum, and lead. Injury symptoms caused by these metals were compared with each other. Among these metals, only nickel produced specific symptoms of along-vein necrosis on leaves and stems. Leaf yellowing or

En-Jang Sun; Fen-Yi Wu

1998-01-01

37

The role of tryptophan in the ferredoxin-dependent nitrite reductase of spinach  

Microsoft Academic Search

A system has been developed for expressing a His-tagged form of the ferredoxin-dependent nitrite reductase of spinach in Escherichia coli. The catalytic and spectral properties of the His-tagged, recombinant enzyme are similar, but not identical, to those previously\\u000a observed for nitrite reductase isolated directly from spinach leaf. A detailed comparison of the spectral, catalytic and fluorescence\\u000a properties of nitrite reductase

Jatindra N. Tripathy; Masakazu Hirasawa; Sung-Kun Kim; Aaron T. Setterdahl; James P. Allen; David B. Knaff

2007-01-01

38

Expression Patterns, Activities and Carbohydrate-Metabolizing Regulation of Sucrose Phosphate Synthase, Sucrose Synthase and Neutral Invertase in Pineapple Fruit during Development and Ripening.  

PubMed

Differences in carbohydrate contents and metabolizing-enzyme activities were monitored in apical, medial, basal and core sections of pineapple (Ananas comosus cv. Comte de paris) during fruit development and ripening. Fructose and glucose of various sections in nearly equal amounts were the predominant sugars in the fruitlets, and had obvious differences until the fruit matured. The large rise of sucrose/hexose was accompanied by dramatic changes in sucrose phosphate synthase (SPS) and sucrose synthase (SuSy) activities. By contrast, neutral invertase (NI) activity may provide a mechanism to increase fruit sink strength by increasing hexose concentrations. Furthermore, two cDNAs of Ac-sps (accession no. GQ996582) and Ac-ni (accession no. GQ996581) were first isolated from pineapple fruits utilizing conserved amino-acid sequences. Homology alignment reveals that the amino acid sequences contain some conserved function domains. Transcription expression analysis of Ac-sps, Ac-susy and Ac-ni also indicated distinct patterns related to sugar accumulation and composition of pineapple fruits. It suggests that differential expressions of multiple gene families are necessary for sugar metabolism in various parts and developmental stages of pineapple fruit. A cycle of sucrose breakdown in the cytosol of sink tissues could be mediated through both Ac-SuSy and Ac-NI, and Ac-NI could be involved in regulating crucial steps by generating sugar signals to the cells in a temporally and spatially restricted fashion. PMID:22949808

Zhang, Xiu-Mei; Wang, Wei; Du, Li-Qing; Xie, Jiang-Hui; Yao, Yan-Li; Sun, Guang-Ming

2012-01-01

39

Expression Patterns, Activities and Carbohydrate-Metabolizing Regulation of Sucrose Phosphate Synthase, Sucrose Synthase and Neutral Invertase in Pineapple Fruit during Development and Ripening  

PubMed Central

Differences in carbohydrate contents and metabolizing-enzyme activities were monitored in apical, medial, basal and core sections of pineapple (Ananas comosus cv. Comte de paris) during fruit development and ripening. Fructose and glucose of various sections in nearly equal amounts were the predominant sugars in the fruitlets, and had obvious differences until the fruit matured. The large rise of sucrose/hexose was accompanied by dramatic changes in sucrose phosphate synthase (SPS) and sucrose synthase (SuSy) activities. By contrast, neutral invertase (NI) activity may provide a mechanism to increase fruit sink strength by increasing hexose concentrations. Furthermore, two cDNAs of Ac-sps (accession no. GQ996582) and Ac-ni (accession no. GQ996581) were first isolated from pineapple fruits utilizing conserved amino-acid sequences. Homology alignment reveals that the amino acid sequences contain some conserved function domains. Transcription expression analysis of Ac-sps, Ac-susy and Ac-ni also indicated distinct patterns related to sugar accumulation and composition of pineapple fruits. It suggests that differential expressions of multiple gene families are necessary for sugar metabolism in various parts and developmental stages of pineapple fruit. A cycle of sucrose breakdown in the cytosol of sink tissues could be mediated through both Ac-SuSy and Ac-NI, and Ac-NI could be involved in regulating crucial steps by generating sugar signals to the cells in a temporally and spatially restricted fashion.

Zhang, Xiu-Mei; Wang, Wei; Du, Li-Qing; Xie, Jiang-Hui; Yao, Yan-Li; Sun, Guang-Ming

2012-01-01

40

Analysis of gene-disruption mutants of a sucrose phosphate synthase gene in rice, OsSPS1, shows the importance of sucrose synthesis in pollen germination.  

PubMed

The molecular function of an isoform of sucrose phosphate synthase (SPS) in rice, OsSPS1, was investigated using gene-disruption mutant lines generated by retrotransposon insertion. The progeny of the heterozygote of disrupted OsSPS1 (SPS1(+/-)) segregated into SPS1(+/+), SPS1(+/-), and SPS1(-/-) at a ratio of 1:1:0. This distorted segregation ratio, together with the expression of OsSPS1 in the developing pollen revealed by quantitative RT-PCR analysis and promoter-beta-glucuronidase (GUS) fusion assay, suggested that the disruption of OsSPS1 results in sterile pollen. This hypothesis was reinforced by reciprocal crosses of SPS1(+/-) plants with wild-type plants in which the disrupted OsSPS1 was not paternally transmitted to the progeny. While the pollen grains of SPS(+/-) plants normally accumulated starch during their development, pollen germination on the artificial media was reduced to half of that observed in the wild-type control. Overall, our data suggests that sucrose synthesis via OsSPS1 is essential in pollen germination in rice. PMID:25017165

Hirose, Tatsuro; Hashida, Yoichi; Aoki, Naohiro; Okamura, Masaki; Yonekura, Madoka; Ohto, Chikara; Terao, Tomio; Ohsugi, Ryu

2014-08-01

41

Diurnal Changes in Maize Leaf Photosynthesis 1  

PubMed Central

Maize (Zea mays L. cv. Pioneer 3184) leaf elongation rate was measured diurnally and was related to diurnal changes in the activities of sucrose metabolizing enzymes and carbohydrate content in the elongating portion of the leaf. The rate of leaf elongation was greatest at midday (1300 hours) and was coincident with the maximum assimilate export rate from the distal portion of the leaf. Leaf elongation during the light period accounted for 70% of the total observed increase in leaf length per 24 hour period. Pronounced diurnal fluctuations were observed in the activities of acid and neutral invertase and sucrose phosphate synthase. Maximum activities of sucrose phosphate synthase and acid invertase were observed at 0900 hours, after which activity declined rapidly. The activity of sucrose phosphate synthase was substantially lower than that observed in maize leaf source tissue. Neutral invertase activity was greatest at midday (1200 hours) and was correlated positively with diurnal changes in leaf elongation rate. There was no significant change in the activity of sucrose synthase over the light/dark cycle. Sucrose accumulation rate increased during a period when leaf elongation rate was maximal and beginning to decline. Maximum sucrose concentration was observed at 1500 hours, when the activities of sucrose metabolizing enzymes were low. At no time was there a significant accumulation of hexose sugars. The rate of starch accumulation increased after the maximum sucrose concentration was observed, continuing until the end of the light period. There was no delay in the onset of starch mobilization at the beginning of the dark period, and essentially all of the starch was depleted by the end of the night. Mobilization of starch in the elongating tissue at night could account for a significant proportion of the calculated increase in the tissue dry weight due to growth. Collectively, the results suggested that leaf growth may be controlled by the activities of certain sucrose metabolizing enzymes and may be coordinated with assimilate export from the distal, source portion of the leaf. Results are discussed with reference to diurnal photoassimilation and export in the distal, source portion of the leaf.

Kalt-Torres, Willy; Huber, Steven C.

1987-01-01

42

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

43

Water spinach (Ipomoea aquatic Forsk.) reduced the absorption of heavy metals in an in vitro bio-mimicking model system.  

PubMed

This study was conducted to investigate the effect of water spinach on bioaccessibility and intestinal uptake of heavy metals (Arsenic (As), Cadmium (Cd), and Lead (Pb)) using an in vitro digestion model with Caco-2 cells. Aliquots of each heavy metal were co-digested with each part of water spinach (stem and leaf) and then cultured with Caco-2 intestinal cells for 1h at 37 °C. Each heavy metal of As, Cd, and Pb was quantified using an ICP-OES. As the amount of stem and leaf (10, 50, 100, and 500 mg) of water spinach increased, bioaccessibility of As, Cd, and Pb decreased to 42.63%, 12.04%, and 26.17% by leaf and 30.37%, 43.27%, 40.07% by stem, respectively. Intestinal uptake of As, Cd, and Pb reduced to 65.8%, 25.7%, and 44.8% for leaf (500 mg) and 48.4%, 51.3%, and 64.3% for stem (500mg), respectively, compared with the control without leaf and stem. The leaf from water spinach was the most effective for decreasing both bioaccessibility and cellular uptake of Cd. PMID:22841954

Yang, Ui-Jeong; Yoon, So-Ra; Chung, Jae-Hwan; Kim, Young Jun; Park, Ki-Hwan; Park, Tae-Sik; Shim, Soon-Mi

2012-10-01

44

Effect of Light and Chilling Temperatures on Chilling-sensitive and Chilling-resistant Plants. Pretreatment of Cucumber and Spinach Thylakoids in Vivo and in Vitro1  

PubMed Central

The effects of chilling temperatures, in light or dark, on the isolated thylakoids and leaf discs of cucumber (Cucumis sativa L. “Marketer”) and spinach (Spinacia oleracea L. “Bloomsdale”) were studied. The pretreatment of isolated thylakoids and leaf discs at 4 C in the dark did not affect the phenazine methosulfate-dependent phosphorylation, proton uptake, osmotic response to sucrose, Ca2+-dependent ATPase activity, or chlorophyll content. Exposure of cucumber cotyledon discs and isolated thylakoids of cucumber and spinach to 4 C in light resulted in a rapid inactivation of the thylakoids. The sequence of activities or components lost during inactivation (starting with the most sensitive) are: phenazine methosulfate-dependent cyclic phosphorylation, proton uptake, osmotic response to sucrose, Ca2+-dependent ATPase activity, and chlorophyll. The rate of loss of proton uptake, osmotic response to sucrose, Ca2+-dependent ATPase activity and chlorophyll is similar for isolated cucumber and spinach thylakoids, whereas spinach thylakoids are more resistant to the loss of phenazine methosulfate-dependent phosphorylation. The thylakoids of spinach leaf discs were unaffected by exposure to 4 C in light. The results question whether the extreme resistance of spinach thylakoids treated in vivo is solely a function of the chloroplast thylakoid membranes and establish the validity of using in vitro results to make inferences about cucumber thylakoids treated in vivo at 4 C in light.

Garber, Melvin P.

1977-01-01

45

Effect of Light and Chilling Temperatures on Chilling-sensitive and Chilling-resistant Plants. Pretreatment of Cucumber and Spinach Thylakoids in Vivo and in Vitro.  

PubMed

The effects of chilling temperatures, in light or dark, on the isolated thylakoids and leaf discs of cucumber (Cucumis sativa L. "Marketer") and spinach (Spinacia oleracea L. "Bloomsdale") were studied. The pretreatment of isolated thylakoids and leaf discs at 4 C in the dark did not affect the phenazine methosulfate-dependent phosphorylation, proton uptake, osmotic response to sucrose, Ca(2+)-dependent ATPase activity, or chlorophyll content. Exposure of cucumber cotyledon discs and isolated thylakoids of cucumber and spinach to 4 C in light resulted in a rapid inactivation of the thylakoids. The sequence of activities or components lost during inactivation (starting with the most sensitive) are: phenazine methosulfate-dependent cyclic phosphorylation, proton uptake, osmotic response to sucrose, Ca(2+)-dependent ATPase activity, and chlorophyll. The rate of loss of proton uptake, osmotic response to sucrose, Ca(2+)-dependent ATPase activity and chlorophyll is similar for isolated cucumber and spinach thylakoids, whereas spinach thylakoids are more resistant to the loss of phenazine methosulfate-dependent phosphorylation. The thylakoids of spinach leaf discs were unaffected by exposure to 4 C in light. The results question whether the extreme resistance of spinach thylakoids treated in vivo is solely a function of the chloroplast thylakoid membranes and establish the validity of using in vitro results to make inferences about cucumber thylakoids treated in vivo at 4 C in light. PMID:16659980

Garber, M P

1977-05-01

46

Evaluation of antioxidant activities of principal carotenoids available in water spinach ( Ipomoea aquatica)  

Microsoft Academic Search

A fundamental study of free radical-scavenging activity of three carotenoids purified from water spinach (Ipomoea aquatica cv. Slim leaf) by thin layer chromatography and identified by high performance liquid chromatography–mass spectroscopy (HPLC–MS), namely violaxanthin, lutein and ?-carotene, was carried out by measuring the ability to scavenge 2,2-diphenyl-1-picrylhydrazyl (DPPH) radicals and 2,2-azobis-3-ethylbenzthiazoline-6-sulphonic acid (ABTS) radicals and by measuring their ability to

Hongfei Fu; Bijun Xie; Shaojun Ma; Xinrong Zhu; Gang Fan; Siyi Pan

2011-01-01

47

Characterization of technetium species induced in spinach  

Microsoft Academic Search

Plants have the ability to accumulate the long-lived fission product ⁹⁹Tc. In this work, an attempt was made to separate and characterize technetium species induced by spinach plants (Spinacia oleracea L.) grown on a TcOâ⁻ 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

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

1999-01-01

48

In vitro modification of spinach plasmalemma thickness  

Microsoft Academic Search

Floral induction in the long day plant spinach (Spinacia oleracea) has been shown to be accompanied by a thickening of plasmalemma. This change was observed at early evocation, in both shoot\\u000a apices and leaves, as well as after inducing GA3 treatment. To get further information on this thickening, plasma membranes from spinach leaves were isolated, in the present\\u000a study, using

P. Crespi; M. Crèvecoeur; C. Penel; H. Greppin

1993-01-01

49

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 10³ CFU/ml. In parallel, the pathogens were inoculated onto the growing leaf surface by pipetting, to give concentrations of 10? and 10³ 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 (10³ 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

50

Functional Metagenomics of Escherichia coli O157:H7 Interactions with Spinach Indigenous Microorganisms during Biofilm Formation  

PubMed Central

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 28°C 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.

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

2012-01-01

51

Proximate composition and mineral content of two edible species of Cnidoscolus (tree spinach).  

PubMed

Proximate composition and mineral content of raw and cooked leaves of two edible tree spinach species (Cnidoscolus chayamansa and C. aconitifolius), known locally as 'chaya', were determined and compared with that of a traditional green vegetable, spinach (Spinicia oleraceae). Results of the study indicated that the edible leafy parts of the two chaya species contained significantly (p<0.05) greater amounts of crude protein, crude fiber, Ca, K, Fe, ascorbic acid and beta-carotene than the spinach leaf. However, no significant (p>0.05) differences were found in nutritional composition and mineral content between the chaya species, except minor differences in the relative composition of fatty acids, protein and amino acids. Cooking of chaya leaves slightly reduced nutritional composition of both chaya species. Cooking is essential prior to consumption to inactivate the toxic hydrocyanic glycosides present in chaya leaves. Based on the results of this study, the edible chaya leaves may be good dietary sources of minerals (Ca, K and Fe) and vitamins (ascorbic acid and beta-carotene). PMID:10540979

Kuti, J O; Kuti, H O

1999-01-01

52

A Spinach molecular beacon triggered by strand displacement.  

PubMed

We have re-engineered the fluorescent RNA aptamer Spinach to be activated in a sequence-dependent manner. The original Spinach aptamer was extended at its 5'- and 3'-ends to create Spinach.ST, which is predicted to fold into an inactive conformation and thus prevent association with the small molecule fluorophore DFHBI. Hybridization of a specific trigger oligonucleotide to a designed toehold leads to toehold-initiated strand displacement and refolds Spinach into the active, fluorophore-binding conformation. Spinach.ST not only specifically detects its target oligonucleotide but can discriminate readily against single-nucleotide mismatches. RNA amplicons produced during nucleic acid sequence-based amplification (NASBA) of DNA or RNA targets could be specifically detected and reported in real-time by conformational activation of Spinach.ST generated by in vitro transcription. In order to adapt any target sequence to detection by a Spinach reporter we used a primer design technique that brings together otherwise distal toehold sequences via hairpin formation. The same techniques could potentially be used to adapt common Spinach reporters to non-nucleic acid analytes, rather than by making fusions between aptamers and Spinach. PMID:24942625

Bhadra, Sanchita; Ellington, Andrew D

2014-08-01

53

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

54

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.

55

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

2006-01-01

56

Growth Conditions To Reduce Oxalic Acid Content of Spinach  

NASA Technical Reports Server (NTRS)

A controlled-environment agricultural (CEA) technique to increase the nutritive value of spinach has been developed. This technique makes it possible to reduce the concentration of oxalic acid in spinach leaves. It is desirable to reduce the oxalic acid content because oxalic acid acts as an anti-nutritive calcium-binding component. More than 30 years ago, an enzyme (an oxidase) that breaks down oxalic acid into CO2 and H2O2 was discovered and found to be naturally present in spinach leaves. However, nitrate, which can also be present because of the use of common nitratebased fertilizers, inactivates the enzyme. In the CEA technique, one cuts off the supply of nitrate and keeps the spinach plants cool while providing sufficient oxygen. This technique provides the precise environment that enables the enzyme to naturally break down oxalate. The result of application of this technique is that the oxalate content is reduced by 2/3 in one week.

Johnson-Rutzke, Corinne

2003-01-01

57

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

58

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

59

Decrease in leaf sucrose synthesis leads to increased leaf starch turnover and decreased RuBP regeneration-limited photosynthesis but not Rubisco-limited photosynthesis in Arabidopsis null mutants of SPSA1.  

PubMed

We investigated the individual effect of null mutations of each of the four sucrose-phosphate synthase (SPS) genes in Arabidopsis (SPSA1, SPSA2, SPSB and SPSC) on photosynthesis and carbon partitioning. Null mutants spsa1 and spsc led to decreases in maximum SPS activity in leaves by 80 and 13%, respectively, whereas null mutants spsa2 and spsb had no significant effect. Consistently, isoform-specific antibodies detected only the SPSA1 and SPSC proteins in leaf extracts. Leaf photosynthesis at ambient [CO?] was not different among the genotypes but was 20% lower in spsa1 mutants when measured under saturating [CO?] levels. Carbon partitioning at ambient [CO?] was altered only in the spsa1 null mutant. Cold treatment of plants (4 °C for 96 h) increased leaf soluble sugars and starch and increased the leaf content of SPSA1 and SPSC proteins twofold to threefold, and of the four null mutants, only spsa1 reduced leaf non-structural carbohydrate accumulation in response to cold treatment. It is concluded that SPSA1 plays a major role in photosynthetic sucrose synthesis in Arabidopsis leaves, and decreases in leaf SPS activity lead to increased starch synthesis and starch turnover and decreased Ribulose 1,5-bisphosphate regeneration-limited photosynthesis but not ribulose 1·5-bisphosphate carboxylase/oxygenase (Rubisco)-limited photosynthesis, indicating a limitation of triose-phosphate utilization (TPU). PMID:21309792

Sun, Jindong; Zhang, Jisen; Larue, Clayton T; Huber, Steven C

2011-04-01

60

Nitrogen Levels Influence Biomass, Elemental Accumulations, and Pigment Concentrations in Spinach  

Microsoft Academic Search

Spinach (Spinacia oleracea L.) has one of the highest United States per capita consumption rates among leafy vegetable crops, and also ranks second for lutein and ?-carotene carotenoid concentration. The objectives of this study were to determine the effects of nitrogen (N) concentration on elemental and pigment accumulation in spinach. Two spinach cultivars (‘Melody’ and ‘Springer F1’) were greenhouse grown

Mark G. Lefsrud; Dean A. Kopsell; David E. Kopsell

2007-01-01

61

3-Ketoacyl-acyl carrier protein synthase III from spinach (Spinacia oleracea) is not similar to other condensing enzymes of fatty acid synthase.  

PubMed Central

A cDNA clone encoding spinach (Spinacia oleracea) 3-ketoacyl-acyl carrier protein synthase III (KAS III), which catalyzes the initial condensing reaction in fatty acid biosynthesis, was isolated. Based on the amino acid sequence of tryptic digests of purified spinach KAS III, degenerate polymerase chain reaction (PCR) primers were designed and used to amplify a 612-bp fragment from first-strand cDNA of spinach leaf RNA. A root cDNA library was probed with the PCR fragment, and a 1920-bp clone was isolated. Its deduced amino acid sequence matched the sequences of the tryptic digests obtained from the purified KAS III. Northern analysis confirmed that it was expressed in both leaf and root. The clone contained a 1218-bp open reading frame coding for 405 amino acids. The identity of the clone was confirmed by expression in Escherichia coli BL 21 as a glutathione S-transferase fusion protein. The deduced amino acid sequence was 48 and 45% identical with the putative KAS III of Porphyra umbilicalis and KAS III of E. coli, respectively. It also had a strong local homology to the plant chalcone synthases but had little homology with other KAS isoforms from plants, bacteria, or animals.

Tai, H; Jaworski, J G

1993-01-01

62

A new endornavirus species infecting Malabar spinach (Basella alba L.).  

PubMed

A putative new endornavirus was isolated from Malabar spinach (Basella alba). The viral dsRNA consisted of 14,027 nt with a single ORF that coded for a polyprotein of 4,508 aa. The genome organization was similar to that of four other endornaviruses. Conserved domains for helicase-1, capsular synthase, UDP-glucose-glycosyltransferase (UGT), and RdRp were detected. Infected plants were phenotypically undistinguishable from healthy ones. The name Basella alba endornavirus is proposed for the virus isolated from Malabar spinach. PMID:24122112

Okada, Ryo; Kiyota, Eri; Moriyama, Hiromitsu; Toshiyuki, Fukuhara; Valverde, Rodrigo A

2014-04-01

63

Light-dependent modification of Photosystem II in spinach leaves  

Microsoft Academic Search

In dark-adapted spinach leaves approximately one third of the Photosystem II (PS II) reaction centers are impaired in their ability to transfer electrons to Photosystem I. Although these ‘inactive’ PS II centers are capable of reducing the primary quinone acceptor, QA, oxidation of QA- occurs approximately 1000 times more slowly than at ‘active’ centers. Previous studies based on dark-adapted leaves

Kevin Oxborough; Ladislav Nedbal; Roger A. Chylla; John Whitmarsh

1996-01-01

64

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 hours…

Devor, Kenneth A.

1979-01-01

65

Role of Ascorbate in Detoxifying Ozone in the Apoplast of Spinach (Spinacia oleracea L.) Leaves.  

PubMed Central

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-1 of ozone resulted in ozone uptake by the leaves close to 0.9 pmol cm-2 of leaf surface area s-1. Apoplastic AA was slowly oxidized by ozone. The initial decrease of apoplastic AA was <0.1 pmol cm-2 s-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. The data show that 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-2 s-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 glutathi-one 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-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.

Luwe, MWF.; Takahama, U.; Heber, U.

1993-01-01

66

Ethylene regulates ascorbic acid content during dark-induced leaf senescence  

Microsoft Academic Search

The aim of this work was to determine if changes in antioxidant contents are directly controlled by ethylene or are indirect effects associated with modulation of leaf senescence. Detached spinach (Spinacia oleracea L. cv Bison) leaves were treated with ethephon to induce ethylene production, placed in polyethylene bags and stored under darkness at 23°C for 3 days. The ethephon treatment

Gustavo Gergoff; Alicia Chaves; Carlos Guillermo Bartoli

2010-01-01

67

Plug-and-play fluorophores extend the spectral properties of Spinach.  

PubMed

Spinach and Spinach2 are RNA aptamers that can be used for the genetic encoding of fluorescent RNA. Spinach2 binds and activates the fluorescence of (Z)-4-(3,5-difluoro-4-hydroxybenzylidene)-1,2-dimethyl-1H-imidazol-5(4H)-one (DFHBI), allowing the dynamic localizations of Spinach2-tagged RNAs to be imaged in live cells. The spectral properties of Spinach2 are limited by DFHBI, which produces fluorescence that is bluish-green and is not optimized for filters commonly used in fluorescence microscopes. Here we characterize the structural features that are required for fluorophore binding to Spinach2 and describe novel fluorophores that bind and are switched to a fluorescent state by Spinach2. These diverse Spinach2-fluorophore complexes exhibit fluorescence that is more compatible with existing microscopy filter sets and allows Spinach2-tagged constructs to be imaged with either GFP or YFP filter cubes. Thus, these "plug-and-play" fluorophores allow the spectral properties of Spinach2 to be altered on the basis of the specific spectral needs of the experiment. PMID:24393009

Song, Wenjiao; Strack, Rita L; Svensen, Nina; Jaffrey, Samie R

2014-01-29

68

Improving spinach, radish, and lettuce growth under red light-emitting diodes (LEDs) with blue light supplementation  

NASA Technical Reports Server (NTRS)

Radish (Raphanus sativus L. cv. Cherriette), lettuce (Lactuca sativa L. cv. Waldmann's Green), and spinach (Spinacea oleracea L. cv. Nordic IV) plants were grown under 660-nm red light-emitting diodes (LEDs) and were compared at equal photosynthetic photon flux (PPF) with either plants grown under cool-white fluorescent lamps (CWF) or red LEDs supplemented with 10% (30 micromoles m-2 s-1) blue light (400-500 nm) from blue fluorescent (BF) lamps. At 21 days after planting (DAP), leaf photosynthetic rates and stomatal conductance were greater for plants grown under CWF light than for those grown under red LEDs, with or without supplemental blue light. At harvest (21 DAP), total dry-weight accumulation was significantly lower for all species tested when grown under red LEDs alone than when grown under CWF light or red LEDs + 10% BF light. Moreover, total dry weight for radish and spinach was significantly lower under red LEDs + 10% BF than under CWF light, suggesting that addition of blue light to the red LEDs was still insufficient for achieving maximal growth for these crops.

Yorio, N. C.; Goins, G. D.; Kagie, H. R.; Wheeler, R. M.; Sager, J. C.

2001-01-01

69

Popeye strikes again: The deep proteome of spinach leaves.  

PubMed

The cytoplasmic proteome of spinach leaves (Spinacia oleracea L) has been investigated with the help of commercially available (ProteoMiner) combinatorial peptide ligand libraries and with home-made ligand beads as prepared in our laboratory. The protein capture had been performed at three pH values (4.0, 7.0 and 9.3) and elution performed in 4% boiling SDS, 20mM DTT. The total number of unique gene products identified amounts to 322 proteins, of which 114 are in common with the control, untreated sample, 18 are present only in the control and 190 represent the new species detected with the help of all combined eluates and likely represent low-abundance species. This is the first in depth exploration of the spinach cytoplasmic proteome and might enable further studies on interaction, regulation and expression of proteins biological processes in combination or not with transcriptomics data. PMID:21056706

Fasoli, Elisa; D'Amato, Alfonsina; Kravchuk, Alexander V; Boschetti, Egisto; Bachi, Angela; Righetti, Pier Giorgio

2011-01-01

70

Water Spinach (Ipomoea aquatica, Convolvulaceae) A food gone wild  

Microsoft Academic Search

Water spinach (Ipomoea aquatica) has been consid- ered native to Africa, Asia, and the southwestern Pacific Islands. The herbs have been a medicinal vegetable in southern Asia since at least A.D. 300, and perhaps since 200 B.C. People still gather plants from the wild and cul- tivate them. With European arrival in these regions in the late 1400s, they became

Daniel F. Austin

2007-01-01

71

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

Microsoft Academic Search

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 (72.83±0.29%), ash (10.83±0.80%), crude lipid (11.00±0.50%), crude fibre (17.67±0.35%) and available carbohydrate (54.20±0.68%), but low in crude

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

2007-01-01

72

Microbiological Quality of Bagged Cut Spinach and Lettuce Mixes  

Microsoft Academic Search

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. Increases in

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

2008-01-01

73

Leaf Shape  

NSDL National Science Digital Library

This illustrated guide is designed to help students recognize and learn the different types of leaf shapes. The single Web page, which can be easily printed for use at field sites, shows five leaf shapes.

74

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.

75

The plasma membrane-associated NADH oxidase of spinach leaves responds to blue light  

NASA Technical Reports Server (NTRS)

The plasma membrane-associated NADH oxidase (NOX) of spinach leaf disks is characterized by oscillations in activity with a regular period length of ca. 24 min. Within a single population of plants exposed to light at the same time, NOX activities of all plants function synchronously. Exposure of plants transferred from darkness to blue light (495 nm, 2 min, 50 micromoles m-2 s-1) resulted in a complex response pattern but with a new maximum in the rate of NOX activity 36 (24+12) min after illumination and then with maxima in the rate of NOX activity every 24 min thereafter. Transient maxima in NOX activity were observed as well after 9.3 + /- 1.4 and 20.7 +/- 2.1 min. The blue light response differed from the response to red (650 nm, 10 min, 50 micromoles m-2 s-1) or white light where activity maxima were initiated 12 min after the light exposure followed by maxima every 24 min thereafter. Green or yellow light was ineffective. The light response was independent of the time in the 24-min NOX cycle when the light was given. The net effects of blue and red light were ultimately the same with a new maximum in the rate of NOX activity at 12+24=36 min (and every 24 min thereafter), but the mechanisms appear to be distinct.

Morre, D. James; Penel, Claude; Greppin, Hubert; Morre, Dorothy M.

2002-01-01

76

Nitrogen removal from eutrophic water by floating-bed-grown water spinach ( Ipomoea aquatica Forsk.) with ion implantation  

Microsoft Academic Search

The aim of this study was to investigate the use of water spinach (Ipomoea aquatica Forsk.) with N+ ion-beam implantation for removal of nutrient species from eutrophic water. The mutated water spinach was grown on floating beds, and growth chambers were used to examine the growth of three cultivars of water spinach with ion implantation for 14 days in simulated

Miao Li; Yue-Jin Wu; Zeng-Liang Yu; Guo-Ping Sheng; Han-Qing Yu

2007-01-01

77

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

2013-12-01

78

A superfolding Spinach2 reveals the dynamic nature of trinucleotide repeat-containing RNA.  

PubMed

Imaging RNA in living cells is a challenging problem in cell biology. One strategy for genetically encoding fluorescent RNAs is to express them as fusions with Spinach, an 'RNA mimic of GFP'. We found that Spinach was dimmer than expected when used to tag constructs in living cells owing to a combination of thermal instability and a propensity for misfolding. Using systematic mutagenesis, we generated Spinach2 that overcomes these issues and can be used to image diverse RNAs. Using Spinach2, we detailed the dynamics of the CGG trinucleotide repeat-containing 'toxic RNA' associated with Fragile X-associated tremor/ataxia syndrome, and show that these RNAs form nuclear foci with unexpected morphological plasticity that is regulated by the cell cycle and by small molecules. Together, these data demonstrate that Spinach2 exhibits improved versatility for fluorescently labeling RNAs in living cells. PMID:24162923

Strack, Rita L; Disney, Matthew D; Jaffrey, Samie R

2013-12-01

79

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

80

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

81

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

82

Leaf Activities.  

ERIC Educational Resources Information Center

Leaf activities can provide a means of using basic concepts of outdoor education to learn in elementary level subject areas. Equipment needed includes leaves, a clipboard with paper, and a pencil. A bag of leaves may be brought into the classroom if weather conditions or time do not permit going outdoors. Each student should pick a leaf, examine…

Mingie, Walter

83

A superfolding Spinach2 reveals the dynamic nature of trinucleotide repeat RNA  

PubMed Central

Fluorescent imaging of RNA in living cells is a technically challenging problem in cell biology. One strategy for genetically encoding fluorescent RNAs is to express them as fusions with ‘RNA mimics of GFP’. These are short aptamer tags that exhibit fluorescence upon binding otherwise nonfluorescent fluorophores that resemble those found in GFP. We find that the brightest of these aptamers, Spinach, often exhibits reduced fluorescence after it is fused to RNAs of interest. We show that a combination of thermal instability and a propensity for misfolding account for the low fluorescence of various Spinach-RNA fusions. Using systematic mutagenesis, we identified nucleotides that account for the poor folding of Spinach, and generated Spinach2, which exhibits markedly improved thermal stability and folding in cells. Furthermore, we show that Spinach2 largely retains its fluorescence when fused to various RNAs. Using Spinach2, we detail the cellular dynamics of the CGG trinucleotide-repeat containing “toxic RNA” associated with Fragile-X tremor/ataxia syndrome, and show that these RNAs form nuclear foci with unexpected morphological plasticity that is regulated by the cell cycle and by small molecules. Together, these data demonstrate that Spinach2 exhibits improved versatility for fluorescently labeling RNAs in living cells.

Strack, Rita L.; Disney, Matthew D.; Jaffrey, Samie R.

2013-01-01

84

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.

85

Reversible Swelling and Contraction of Isolated Spinach Chloroplasts  

PubMed Central

By use of a micro technique for producing extracts of spinach mesophyll cells, chloroplasts were isolated in a state wherein they displayed microscopically visible, reversible osmotic properties. Swollen spherical chloroplasts treated with hypertonic sucrose or mannitol media, but not NaCl, could be shrunken to a state resembling their disk appearance in living cells. Reversible osmotic behavior was more easily demonstrated when the chloroplasts were initially isolated from cells in a relatively low osmolar concentration in contrast to using 0.25 m sucrose or more concentrated media. Individual chloroplasts could be swollen and contracted repeatedly through as many as 4 cycles. The relationship between the capacity for osmotic behavior and chloroplast appearance in cell extracts is discussed. Images Fig. 1A Fig. 1B Fig. 2

Hongladarom, Tasani; Honda, Shigeru I.

1966-01-01

86

Effect of selected coumarins on spinach chloroplast photosynthesis.  

PubMed

Xanthyletin (1), 3-(1',1'-dimethylallyl)xanthyletin (2), and chalepensin (3), the major coumarins isolated from Stauranthus perforatus, inhibit ATP synthesis from water to methylviologen in spinach thylakoids in a concentration-dependent manner. At low concentration chalepensin (3) inhibits basal and phosphorylating electron flow from water to K(3)[Fe(CN)(6)] without affecting uncoupled electron flow but accelerating Mg(2+)-ATPase activity. Thus, at low concentration the compound behaves as an energy transfer inhibitor. However, at higher concentrations this coumarin acts as an uncoupler because it enhances basal and phosphorylating electron transfer. On the other hand, coumarins 1 and 2 act as Hill reaction inhibitors, although 2 exhibited also uncoupler properties because it induces stimulation of basal and phosphorylating electron flow from water to ferricyanide. The site of interference of xanthyletin was located at the b(6)f-PC level of the electron transport chain. PMID:10552509

Macias, M L; Rojas, I S; Mata, R; Lotina-Hennsen, B

1999-05-01

87

Sulfur Dioxide Inhibition of Photosynthesis in Isolated Spinach Chloroplasts  

PubMed Central

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 negligible inhibition of apparent photosynthesis. The mode of action of sulfur dioxide and related sulfur anions in inhibiting photosynthesis was found to be essentially independent of direct hydrogen-ion effects. Supplements of inorganic pyrophosphate lessened the inhibition of oxygen evolution caused by sulfur dioxide and the sulfur anions. Sulfur dioxide and the sulfur anions were almost equally effective in inhibiting cyclic and noncyclic photophosphorylation in chloroplast suspensions. However, the extent of the inhibition of these photosynthetic reactions does not appear sufficient to account for the inhibition of photosynthetic oxygen evolution by sulfur dioxide.

Silvius, John E.; Ingle, Morris; Baer, Charles H.

1975-01-01

88

Use of the systems approach to determine the fate of Escherichia coli O157:H7 on fresh lettuce and spinach.  

PubMed

Lettuce and spinach inoculated with Escherichia coli O157:H7 were processed and handled in ways that might occur in commercial situations, including variations in holding times before and after product cooling, transportation conditions and temperatures, wash treatments, and product storage temperatures and times. Populations of background microflora and E. coli O157:H7 were enumerated after each step in the system. Data analysis was done to predict response variables with a combination of independent categorical variables. Field temperature, time before cooling, and wash treatment significantly affected E. coli O157:H7 populations on both products. The lowest populations of E. coli O157:H7 were encountered when precool time was minimal, lettuce was washed with chlorine, and storage temperature was 4 degrees C. For lettuce, field and transportation temperature were not important once the storage period started, whereas after 2 days E. coli O157:H7 populations on packaged baby spinach were not affected by field temperature. On chopped iceberg lettuce and whole leaf spinach that was packaged and stored at 4 degrees C, E. coli O157:H7 contamination could still be detected after typical handling practices, although populations decreased from initial levels in many cases by at least 1.5 log units. In abusive cases, where populations increased, the product quality quickly deteriorated. Although E. coli O157:H7 levels decreased on products handled and stored under recommended conditions, survivors persisted. This study highlights practices that may or may not affect the populations of E. coli O157:H7 on the final product. PMID:19681286

Doering, Helga J; Harrison, Mark A; Morrow, Ruth A; Hurst, William C; Kerr, William L

2009-07-01

89

The electron-transfer site of spinach plastocyanin.  

PubMed

Two sites for electron transfer have been proposed for plastocyanin: one near the copper ion and the other close to the acid patch formed by residues 42-45. Calculations of electrostatic properties of spinach plastocyanin and ionic strength dependences of electron-transfer reactions of this protein have been used to distinguish between these two sites. Calculations show that the electric potential field of spinach plastocyanin is highly asymmetric and that the protein has a dipole moment of 360 D. The negative end of the dipole axis emerges between the negative patches formed by residues 42-45, which is though to be the cation binding site, and residues 59-61. The angles between the dipole vector and vectors from the center of mass to the copper ion and to the acid patch are 90 degrees and 30 degrees, respectively. The angle between the dipole vector and a line from the center of mass to the site of electron transfer is evaluated from the ionic strength dependence of electron-transfer rates at pH 7.8 with the help of equations developed by Van Leeuwen et al. [van Leeuwen, J.W., Mofers, F.J.M., & Veerman, E.C.I. (1981) Biochim. Biophys. Acta 635, 434] and Van Leeuwen [van Leeuwen, J.W. (1983) Biochim. Biophys. Acta 743, 408]. The angles found are 85 degrees, 110 degrees, and 75 +/- 15 degrees for reactions with tris(1,10-phenanthroline)cobalt(III), hexacyanoferrate(III), and ferrocytochrome c, respectively. The electric potential field calculations suggest that the hexacyanoferrate(III) interaction angle corresponds to a unique site of minimum repulsion at the hydrophobic region of the protein surface, close to the copper ion.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:2847776

Rush, J D; Levine, F; Koppenol, W H

1988-08-01

90

Microbial antagonists of Escherichia coli O157:H7 on fresh-cut lettuce and spinach.  

PubMed

Fresh-cut lettuce and spinach can become contaminated with pathogens at numerous points from the field to the retail market. Natural microflora present on fresh produce may help reduce the pathogen load. The objective of this study was to isolate natural microflora from fresh-cut iceberg lettuce and baby spinach and to determine whether these bacteria were antagonistic toward Escherichia coli O157:H7. Samples were collected under conditions that mimicked actual practices between production and retail sale. Evidence of naturally occurring microorganisms on fresh lettuce (295 isolates) and spinach (200 isolates) and of possible antagonistic activity toward E. coli O157:H7 was documented. Inhibitory activity by several isolates was due to either acid production or antimicrobial peptides. Bacteria with inhibitory activity were isolated from every step in the processing and handling of the fresh-cut iceberg lettuce and baby spinach. PMID:19681287

Johnston, Michael A; Harrison, Mark A; Morrow, Ruth A

2009-07-01

91

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

92

Inactivation effect of newly developed low concentration electrolyzed water and other sanitizers against microorganisms on spinach  

Microsoft Academic Search

The efficacy of newly developed low concentration electrolyzed water (LcEW) was investigated to inactivate the pathogens on spinach leaves as a convenient and safe alternative sanitizer and it was compared to other sanitizers. Spinach leaves were inoculated with Escherichia coli O157:H7 and Listeria monocytogenes and dip treated with deionized water (DIW), LcEW, strong acid electrolyzed water (SAEW), aqueous ozone (AO),

S. M. E. Rahman; Tian Ding; Deog-Hwan Oh

2010-01-01

93

Bioavailability of iron from spinach using an in vitro/human Caco-2 cell bioassay model  

NASA Technical Reports Server (NTRS)

Spinach (Spinacia oleracea) cv Whitney was tested for iron bioavailabilty using an in vitro human intestinal cell culture ferritin bioassay technique previously developed. Spinach was cultured in a growth chamber for 33 days, harvested, and freeze-dried. Total iron in the samples was an average of 71 micrograms/g dry weight. Spinach was digested in vitro (pepsin and 0.1 M HCl followed by pancreatin and 0.1 M NaHCO3) with and without the addition of supplemental ascorbic acid. Caco-2 cell cultures were used to determine iron bioavailability from the spinach mixtures. Production of the iron-binding protein ferritin in the Caco-2 cells showed the supplemental ascorbic acid doubled bioavailability of iron from spinach. The data show fresh spinach is a poor source of iron, and emphasize the importance of evaluation of whole meals rather than single food items. The data support the usefulness of the in vitro/Caco-2 cell ferritin bioassay model for prescreening of space flight diets for bioavailable iron.

Rutzke, Corinne J.; Glahn, Raymond P.; Rutzke, Michael A.; Welch, Ross M.; Langhans, Robert W.; Albright, Louis D.; Combs, Gerald F Jr; Wheeler, Raymond M.

2004-01-01

94

Diurnal Changes in Maize Leaf Photosynthesis 1  

PubMed Central

Diurnal changes in photosynthetic parameters and enzyme activities were characterized in greenhouse grown maize plants (Zea mays L. cv Pioneer 3184). Rates of net photosynthesis and assimilate export were highest at midday, coincident with maximum irradiance. During the day, assimilate export accounted for about 80% of net carbon fixation, and the maximum export rate (35 milligrams CH2O per square decimeter per hour) was substantially higher than the relatively constant rate maintained through the night (5 milligrams CH2O per square decimeter per hour). Activities of sucrose phosphate synthase and NADP-malate dehydrogenase showed pronounced diurnal fluctuations; maximum enzyme activities were generally coincident with highest light intensity. Reciprocal light/dark transfers of plants throughout the diurnal cycle revealed that both enzymes were deactivated by 30 minutes of darkness during the day, and they could both be substantially activated by 30 minutes of illumination at night. During 24 hours of extended darkness, sucrose phosphate synthase activity declined progressively to an almost undetectable level, but was activated after 1.5 hours of illumination. Thus, the diurnal fluctuation in maize sucrose phosphate synthase can be explained by some form of light modulation of enzyme activity and is not due to an endogenous rhythm in activity. No diurnal fluctuations were observed in the activities of NADP-malic enzyme or fructose 6-phosphate-2-kinase. Phosphoenolpyruvate carboxylase was activated by light to some extent (about 50%) when activity was measured under suboptimal conditions in vitro. The results suggested that the rates of sucrose formation and assimilate export were closely aligned with the rate of carbon fixation and the activation state of sucrose phosphate synthase.

Kalt-Torres, Willy; Kerr, Phillip S.; Usuda, Hideaki; Huber, Steven C.

1987-01-01

95

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

96

Leaf Development  

PubMed Central

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.

2013-01-01

97

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

2013-01-01

98

Detection of genome DNA methylation change in spinach induced by 5-azaC.  

PubMed

DNA methylation has been implicated in the regulation of gene expression, genome imprinting, and chromatin remodeling in eukaryotes. In this study, we analyzed possible alterations in levels and patterns of cytosine methylation in male and female spinach plants after treatment with demethylation agent 5-azacytidine (5-azaC) using two methods: (1) direct determination of 5-methylcytidine (5 mC) amounts in genomic DNA by high-performance liquid chromatography (HPLC) separation and quantification of nucleosides and (2) methylation-sensitive inter-simple sequence repeat (MS-ISSR) technique. HPLC analysis revealed that the DNA methylation events in male and female spinach leaves markedly decreased upon 30 ?M 5-azaC treatment, and the methylation level gradually decreased with the increase in 5-azaC concentration. To study the altered DNA methylation patterns in spinach after 5-azaC treatment, untreated and 500 ?M 5-azaC-treated samples were analyzed by MS-ISSR assay. A total of 385 informative profiles were resolved using 35 ISSR primer sets. MS-ISSR analysis showed various altered methylation patterns between untreated and 5-azaC-treated spinach plants. These alterations were mainly demethylation events, which were largely consistent with the HPLC results. Both HPLC and MS-ISSR analyses showed that the changes in DNA methylation levels and patterns were similar in male and female spinach leaves, which implies that sex was not the main factor influencing DNA methylation levels and patterns in the vegetative organs of spinach. This study could provide a molecular basis of the altered DNA methylation induced by 5-azaC, and lay a foundation for further investigation of the relationship between methylation and sex determination and development in this dioecious plant spinach. PMID:24556376

Gao, Wujun; Li, Shufen; Li, Zhongxia; Huang, Yingying; Deng, Chuanliang; Lu, Longdou

2014-08-01

99

Leaf Type  

NSDL National Science Digital Library

This illustrated guide to leaf types is designed to help students understand the differences between compound and simple leaves. This single Web page can be easily printed for use at field sites. Along with an explanation of both types, the guide includes a short description of related terms.

100

The Role of Galactolipids in Spinach Chloroplast Lamellar Membranes  

PubMed Central

A galactolipid lipase has been isolated and partially purified from the chloroplast fraction of the primary leaves of Phaseolus vulgaris var. Kentucky Wonder. The lipase hydrolyzed monogalactosyl diglyceride rapidly and phosphatidyl choline relatively slowly. Triolein and p-nitrophenyl stearate were not hydrolyzed. Spinach subchloroplast particles were excellent substrates for the lipase. Initial rates of fatty acid release from subchloroplast particles at 30 C by the lipase as high as 60 microequivalents per minute per milligram protein were observed. At completion of the reaction, about 2.7 microequivalents of fatty acid were liberated per milligram of chlorophyll in the subchloroplast particles, indicating that major amounts of lipid in the particles were rapidly attacked by the lipase. The treatment of subchloroplast particles with the lipase resulted in a rapid inhibition of light-dependent electron flow. This inhibition was largely prevented when the incubation was carried out in the presence of high concentrations of defatted bovine serum albumin. These results suggest that when precautions are taken to prevent the binding of fatty acids to the subchloroplast particles, large amounts of lipid may be removed without a marked effect on electron flow.

Anderson, Mark M.; McCarty, Richard E.; Zimmer, Elizabeth A.

1974-01-01

101

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

102

The Simultaneous Determination of Carbon Dioxide Release and Oxygen Uptake in Suspensions of Plant Leaf Mitochondria Oxidizing Glycine 1  

PubMed Central

The construction and operation of a device for continuous measurement of CO2 release by suspensions of respiring mitochondria is described. A combination of this device with a Clark-type O2 electrode was used for simultaneous measurement of respiration and of CO2 release by spinach and pea leaf mitochondria with glycine as substrate. Both mitochondrial preparations showed high rates of respiration and high respiratory control ratios. The addition of oxaloacetate not only inhibited O2 uptake substantially, but also greatly stimulated glycine oxidation as monitored by CO2 release. In spinach leaf mitochondria, the maximal rates of glycine oxidation thus obtained, were two times higher than the rate of glycine oxidation required at average rates of photorespiration. It is concluded from these results that under saturating conditions the capacity of glycine oxidation by intact mitochondria exceeds the capacity of glycine-dependent respiration.

Lilley, Ross McC.; Ebbighausen, Holger; Heldt, Hans W.

1987-01-01

103

Shelf life and sensory characteristics of baby spinach subjected to electron beam irradiation.  

PubMed

The use of ionizing radiation for the control of foodborne pathogens and extending the shelf life of fresh iceberg lettuce and fresh spinach has recently been approved by the U.S. Food and Drug Administration. The efficacy of electron beam irradiation for controlling foodborne pathogens has been reported. For this experiment, the effectiveness of electron beam irradiation on the microbiological and sensory characteristics of fresh spinach was studied. Total aerobic plate counts were reduced by 2.6 and 3.2 log CFU/g at 0.7 and 1.4 kGy, respectively. Lactic acid bacteria were reduced at both doses of e-beam but grew slowly over the 35 d of the experiment. Yeasts and molds were not reduced in samples exposed to 0.7 kGy whereas 1.4 kGy significantly reduced microbial counts. Gas compositions (O(2) and CO(2)) were significantly different than controls. Oxygen levels inside the spinach sample bags decreased over time; however, O(2) levels did not drop below 1% that can induce anaerobic fermentation. CO(2) levels for all treatments increased through day 4; yet 7 d after irradiation, CO(2) level differences were not significant in both control and irradiated samples. Irradiation dose did not affect the basic tastes, aromatics, or mouth feels of fresh spinach, however; hardness attributes decreased as irradiated dose increased and slimy attributes of fresh spinach were higher in control samples compared to irradiated samples. PMID:20722955

Neal, Jack A; Booren, Betsy; Cisneros-Zevallos, Luis; Miller, Rhonda K; Lucia, Lisa M; Maxim, Joseph E; Castillo, Alejandro

2010-08-01

104

Dietary supplementation with blueberries, spinach, or spirulina reduces ischemic brain damage.  

PubMed

Free radicals are involved in neurodegenerative disorders, such as ischemia and aging. We have previously demonstrated that treatment with diets enriched with blueberry, spinach, or spirulina have been shown to reduce neurodegenerative changes in aged animals. The purpose of this study was to determine if these diets have neuroprotective effects in focal ischemic brain. Adult male Sprague-Dawley rats were fed with equal amounts of diets (blueberry, spinach, and spirulina) or with control diet. After 4 weeks of feeding, all animals were anesthetized with chloral hydrate. The right middle cerebral artery was ligated with a 10-O suture for 60 min. The ligature was later removed to allow reperfusional injury. Animals were sacrificed and brains were removed for caspase-3 enzymatic assays and triphenyltetrazolium chloride staining at 8 and 48 h after the onset of reperfusion. A subgroup of animals was used for locomotor behavior and biochemical assays. We found that animals which received blueberry, spinach, or spirulina enriched diets had a significant reduction in the volume of infarction in the cerebral cortex and an increase in post-stroke locomotor activity. There was no difference in blood biochemistry, blood CO2, and electrolyte levels among all groups, suggesting that the protection was not indirectly mediated through the changes in physiological functions. Animals treated with blueberry, spinach, or spirulina had significantly lower caspase-3 activity in the ischemic hemisphere. In conclusion, our data suggest that chronic treatment with blueberry, spinach, or spirulina reduces ischemia/reperfusion-induced apoptosis and cerebral infarction. PMID:15817266

Wang, Yun; Chang, Chen-Fu; Chou, Jenny; Chen, Hui-Ling; Deng, Xiaolin; Harvey, Brandon K; Cadet, Jean Lud; Bickford, Paula C

2005-05-01

105

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

106

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

107

Purification of intact chloroplasts from Arabidopsis and spinach leaves by isopycnic centrifugation.  

PubMed

Chloroplasts are plant-specific organelles. They are the site of photosynthesis but also of many other essential metabolic pathways, such as syntheses of amino acids, vitamins, lipids, and pigments. This unit describes the isolation and purification of chloroplasts from Arabidopsis and spinach leaves. Differential centrifugation is first used to obtain a suspension enriched in chloroplasts (crude chloroplasts extract). In a second step, Percoll density gradient centrifugation is used to recover pure and intact chloroplasts. The Basic Protocol describes the purification of chloroplasts from Arabidopsis leaves. This small flowering plant is now widely used as a model organism in plant biology as it offers important advantages for basic research in genetics and molecular biology. The Alternate Protocol describes the purification of chloroplasts from spinach leaves. Spinach, easily available all through the year, remains a model of choice for the large-scale preparation of pure chloroplasts with a high degree of intactness. PMID:18819091

Seigneurin-Berny, Daphné; Salvi, Daniel; Joyard, Jacques; Rolland, Norbert

2008-09-01

108

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

109

Leaf Carbohydrate Status and Enzymes of Translocate Synthesis in Fruiting and Vegetative Plants of Cucumis sativus L. 1  

PubMed Central

Carbon partitioning in the leaves of Cucumis sativus L., a stachyose translocating plant, was influenced by the presence or absence of a single growing fruit on the plant. Fruit growth was very rapid with rates of fresh weight gain as high as 3.3 grams per hour. Fruit growth was highly competitive with vegetative growth as indicated by lower fresh weights of leaf blades, petioles, stem internodes and root systems on plants bearing a single growing fruit compared to plants not bearing a fruit. Carbon exchange rates, starch accumulation rates and carbon export rates were higher in leaves of plants bearing a fruit. Dry weight loss from leaves was higher at night from fruiting plants, and morning starch levels were consistently lower in leaves of fruiting than in leaves of vegetative plants indicating rapid starch mobilization at night from the leaves of fruiting plants. Galactinol, the galactosyl donor for stachyose biosynthesis, was present in the leaves of fruit-bearing plants at consistently lower concentration than in leaves of vegetative plants. Galactinol synthase, and sucrose phosphate synthase activities were not different on a per gram fresh weight basis in leaves from the two plant types; however, stachyose synthase activity was twice as high in leaves from fruiting plants. Thus, the lower galactinol pools may be associated with an activation of the terminal step in stachyose biosynthesis in leaves in response to the high sink demand of a growing cucumber fruit.

Pharr, David M.; Huber, Steven C.; Sox, Harriet N.

1985-01-01

110

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

111

Carbon Dioxide Fixation in the Light and in the Dark by Isolated Spinach Chloroplasts 1  

PubMed Central

Factors affecting CO2 fixation in the spinach (Spinacia oleracea) chloroplast were investigated. Free magnesium ions are shown to be highly inhibitory for photosynthetic CO2 fixation in isolated intact spinach chloroplasts. The pH optimum for CO2 fixation is about 8.5 but is dependent upon the reaction medium. Conditions are defined under which chloroplasts illuminated in the absence of CO2 accumulate ribulose 1,5-diphosphate, and fix CO2 in a subsequent dark period when high magnesium ion concentrations are provided. The regulation of photosynthetic CO2 assimilation by these factors is discussed.

Avron, Mordhay; Gibbs, Martin

1974-01-01

112

Differences in biofilm formation of produce and poultry Salmonella enterica isolates and their persistence on spinach plants.  

PubMed

Spinach plants were irrigated biweekly with water containing 2.1 log CFU Salmonella/100 ml water (the maximum Escherichia coli MPN recommended by the Leafy Greens Marketing Agreement; LGMA), or 4.1 CFU Salmonella/100 ml water to determine Salmonella persistence on spinach leaves. Green Fluorescent protein expressing Salmonella were undetectable by most-probable number (MPN) at 24 h and 7 days following each irrigation event. This study indicates that Salmonella are unlikely to persist on spinach leaves when irrigation water is contaminated at a level below the LGMA standards. In a parallel study, persistence of Salmonella isolated from poultry or produce was compared following biweekly irrigation of spinach plants with water containing 6 log CFU Salmonella/100 ml. Produce Salmonella isolates formed greater biofilms on polystyrene, polycarbonate and stainless steel surfaces and persisted at significantly higher numbers on spinach leaves than those Salmonella from poultry origin during 35 days study. Poultry Salmonella isolates were undetectable (<1 log CFU/g) on spinach plants 7 days following each irrigation event when assayed by direct plating. This study indicates that Salmonella persistence on spinach leaves is affected by the source of contamination and the biofilm forming ability of the strain. PMID:24010621

Patel, Jitendra; Singh, Manpreet; Macarisin, Dumitru; Sharma, Manan; Shelton, Daniel

2013-12-01

113

A novel copper-containing protein from spinach: a blue oxidase with unique properties.  

PubMed

A copper-containing protein resembling in its optical and EPR spectra stellacyanin from latex was isolated from spinach leaves. The protein oxidizes ferrocyanide and catechol. The activity was highest at acidic pH. It was shown that similar proteins isolated from cucumber and squash also possess the oxidase activity to ferrocyanide. PMID:6317078

Sarkissian, L K; Nalbandyan, R M

1983-10-01

114

Phytoextraction of cadmium by Ipomoea aquatica (water spinach) in hydroponic solution: Effects of cadmium speciation  

Microsoft Academic Search

Phytoextraction is a promising technique to remediate heavy metals from contaminated wastewater. However, the interactions of multi-contaminants are not fully clear. This study employed cadmium, Triton X-100 (TX-100), and EDTA to investigate their interactions on phytotoxicity and Cd phytoextraction of Ipomoea aquatica (water spinach) in simulated wastewater. The Cd speciation was estimated by a chemical equilibrium model and MINEQL+. Statistic

Kai-Sung Wang; Lung-Chiu Huang; Hong-Shen Lee; Pai-Ye Chen; Shih-Hsien Chang

2008-01-01

115

Water spinach (Ipomoea aquatica) as a feed resource for growing rabbits  

Microsoft Academic Search

SUMMARY Rabbits are herbivores which efficiently convert forages to food for human beings. On the other hand, water spinach can be fed alone as the sole diet of rabbits as it appears to supply all the nutrient requirements including minerals, vitamins and water. In this case the feeding level should not be above 8% of the body weight (DM basis)

Pok Samkol

2009-01-01

116

Random Amplified Polymorphic DNA Analysis of Water Spinach ( Ipomoea aquatica ) in Florida  

Microsoft Academic Search

The genetic relationship between three biotypes of water spinach ( Ipomoea aquatica Forsk.), including one 'upland' agricultural cultivar and two floating wild biotypes collected from Hillsborough County, Florida, were evaluated using Random Amplified Polymorphic DNA (RAPD) markers. Forty-eight decamer primers were screened; eighteen of these were informative and yielded 188 resolvable bands, of which 58 (31%) were polymorphic. Five primers

THAI K. VAN; P. T. MADEIRA

117

Antioxidant and antiproliferative activities of water spinach (Ipomoea aquatica Forsk) constituents  

Microsoft Academic Search

The aim of this study was to examine possible antioxidant and antiproliferative activities of 95% ethanol or water extract from water spinach (Ipomoea aquatica Forsk) organs. DPPH staining, total phenolic compounds, total flavonoid content, DPPH radical, reducing power method, FTC method, and inhibition of cancer cell prolifera- tion were employed. Ethanol extract of stem demonstrated a positive effect in DPPH

Dong-Jiann HUANG; Hsien-Jung CHEN; Chun-Der LIN; Yaw-Huei LIN

2005-01-01

118

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. Crèvecoeur; E. Lesniewska; V. Vié; J. P. Goudonnet; H. Greppin; C. Le Grimellec

2000-01-01

119

Iron bioavailability of rats fed liver, lentil, spinach and their mixtures.  

PubMed

To study the effects of dietary iron source (basal diet-FeSO4 x 7H2O, liver, lentil, spinach, liver + lentil, liver+spinach and lentil+spinach) on iron bioavailability, fifty-six Albino Sprague Dawley derived male 21 days old rats were fed on iron-deficient diet (7.8 mg Fe kg(-1) diet) and the mentioned seven iron containing diets (40 mg Fe kg(-1) diet) for 10 days. Rats fed liver diet showed higher iron apparent absorption (52.1%), hemoglobin (Hb) gain (0.94 g/100 mL), Hb-iron gain (1.2 mg), Hb-regeneration efficiency (HRE%) (50.8%), relative efficiency of HRE% (106.5%), packed cell volume gain (2.22%) and mean corpuscular hemoglobin concentration (0.64 g dL(-1)). Liver resulted in an increase in these parameters when mixed with lentil and spinach diets. However, rats fed iron free diet showed the higher dry matter absorption. PMID:19579971

Rewashdeh, Abdullah Y; El-Qudah, Jafar M; Al-Dmoor, Hanee; Al-Qudah, Maisa M; Mamkagh, Amer M; Tarawneh, Khaled A; Hawari, Azmi D; Dababneh, Basem F; Al-Bakheit, Alaa A; Haddad, Moawya A

2009-02-15

120

Effect of Bio and Chemical Fertilizers on Seed Production and Quality of Spinach (Spinacia oleracea L.)  

Microsoft Academic Search

The present investigation was carried out during two successive winter seasons (2002-2003 & 2003-2004) at Kaha Vegetable Farm, Horticulture Research Institute, ARC. It studies the effect of bio-fertilizers (Azotobacter chroccocum & phosphorein) singly or in combination with different rates of N and P chemical fertilizers on growth, yield, sex ratio, seeds (yield & quality) of spinach plants cv. Dokki. Results

F. M. M. EL-ASSIOUTY; S. A. ABO-SEDERA; Dokki Giza

121

24-Epibrassinolide and 20-hydroxyecdysone affect photosynthesis differently in maize and spinach.  

PubMed

The aim of the work was to examine the effect of brassinosteroid (24-epibrassinolide; 24E) and ecdysteroid (20-hydroxyecdysone; 20E) on various parts of primary photosynthetic processes in maize and spinach. Additionally, the effect of steroids on gaseous exchange, pigment content and biomass accumulation was studied. The efficiency of the photosynthetic whole electron-transport chain responded negatively to the 24E or 20E treatment in both species, but there were interspecific differences regarding Photosystem (PS) II response. A positive effect on its oxygen-evolving complex and a slightly better energetical connectivity between PSII units were observed in maize whereas the opposite was true for spinach. The size of the pool of the PSI end electron acceptors was usually diminished due to 24E or 20E treatment. The treatment of plants with 24E or 20E applied individually positively influenced the content of photosynthetic pigments in maize (not in spinach). On the other hand, it did not affect gaseous exchange in maize but resulted in its reduction in spinach. Plants treated with combination of both steroids mostly did not significantly differ from the control plants. We have demonstrated for the first time that 20E applied in low (10nM) concentration can affect various parts of photosynthetic processes similarly to 24E and that brassinosteroids regulate not only PSII but also other parts of the photosynthetic electron transport chain - but not necessarily in the same way. PMID:24769061

Rothová, Olga; Holá, Dana; Ko?ová, Marie; T?mová, Lenka; Hnili?ka, František; Hnili?ková, Helena; Kamlar, Marek; Macek, Tomáš

2014-07-01

122

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

123

Changes in quality, liking, and purchase intent of irradiated fresh-cut spinach during storage.  

PubMed

The use of ionizing radiation to enhance microbial safety of fresh spinach at a maximum dose of 4 kGy has been approved by the U.S. Food and Drug Administration (FDA). However, whether spinach can tolerate those high doses of radiation is unclear. Therefore, this study was conducted to investigate the effects of irradiation and storage on quality, liking, and purchase intent of fresh-cut spinach. The oxygen radical absorbance capacity values and total phenolic content were not consistently affected by irradiation. However, the ascorbic acid content of irradiated sample decreased rapidly during storage, resulting in these samples being lower in ascorbic acid content than controls after 7 and 14 d of storage at 4 °C. Sensory evaluation by a 50-member panel revealed that purchase intent and ratings for liking of appearance, aroma, texture, flavor, and overall were not affected by irradiation at doses up to 2 kGy. Therefore, irradiation at doses up to 2 kGy may be used to enhance microbial safety without affecting consumer acceptance or overall antioxidant values of irradiated spinach. PMID:21623783

Fan, Xuetong; Sokorai, Kimberly J B

2011-08-01

124

Laser Activation of Rapid Absorption Changes in Spinach Chloroplasts and Chlorella 1  

PubMed Central

The kinetics of the 520 m? absorption change in spinach chloroplasts and Chlorella vulgaris following a flash from the ruby laser have been determined as follows: rise halftime ? 0.3 × 10?6 second; rapid recovery halftime = 5 to 6 × 10?6 second; intermediate recovery halftime = 4 × 10?4 second (spinach chloroplasts only); slow recovery halftime = 12 to 170 × 10?3 second, dependent on the measuring light intensity and aerobicity of the suspension. The rapid phase of the 520 m? reaction is approximately independent of temperature, from 295° to 77° Absolute. With increasing oxygenation of the sample, the extent of the rapid phase decreases, the extent of the slow phase increases, while the extent of the intermediate phase in spinach chloroplasts remains constant. In spinach chloroplasts, no recovery halftime of the 3 recovery phases for the 520 m? absorption change was observed to correspond to the halftime for oxidation of cytochrome f (t½ = 1.3 × 10?3 second).

Hildreth, W. W.; Avron, M.; Chance, B.

1966-01-01

125

Reinvestigation of the Structure of Acyl Galactosyl Diglyceride from Spinach Leaves.  

National Technical Information Service (NTIS)

Shown by nuclear magnetic resonance spectroscopy and by synthesis is that the acyl galactosyl diglyceride from spinach leaves is 1',2'-di-O-acyl-3'-O-(6-O-acyl-beta-D-galactopyranosyl)-sn-glycerol and not a mixture of isomers as reported previously. (Auth...

E. Heinz A. P. Tulloch

1969-01-01

126

Assessing Soybean Leaf Area and Leaf Biomass by Spectral Measurements.  

National Technical Information Service (NTIS)

Red and photographic infrared spectral radiances were correlated with soybean total leaf area index, green leaf area index, chlorotic leaf area index, green leaf biomass, chlorotic leaf biomass, and total biomass. The most significant correlations were fo...

B. N. Holben C. J. Fan C. J. Tucker

1979-01-01

127

Generic Escherichia coli Contamination of Spinach at the Preharvest Stage: Effects of Farm Management and Environmental Factors  

PubMed Central

The objective of this study was to determine the effects of farm management and environmental factors on preharvest spinach contamination with generic Escherichia coli as an indicator of fecal contamination. A repeated cross-sectional study was conducted by visiting spinach farms up to four times per growing season over a period of 2 years (2010 to 2011). Spinach samples (n = 955) were collected from 12 spinach farms in Colorado and Texas as representative states of the Western and Southwestern United States, respectively. During each farm visit, farmers were surveyed about farm-related management and environmental factors using a questionnaire. Associations between the prevalence of generic E. coli in spinach and farm-related factors were assessed by using a multivariable logistic regression model including random effects for farm and farm visit. Overall, 6.6% of spinach samples were positive for generic E. coli. Significant risk factors for spinach contamination with generic E. coli were the proximity (within 10 miles) of a poultry farm, the use of pond water for irrigation, a >66-day period since the planting of spinach, farming on fields previously used for grazing, the production of hay before spinach planting, and the farm location in the Southwestern United States. Contamination with generic E. coli was significantly reduced with an irrigation lapse time of >5 days as well as by several factors related to field workers, including the use of portable toilets, training to use portable toilets, and the use of hand-washing stations. To our knowledge, this is the first report of an association between field workers' personal hygiene and produce contamination with generic E. coli at the preharvest level. Collectively, our findings support that practice of good personal hygiene and other good farm management practices may reduce produce contamination with generic E. coli at the preharvest level.

Navratil, Sarah; Gregory, Ashley; Bauer, Arin; Srinath, Indumathi; Jun, Mikyoung; Szonyi, Barbara; Nightingale, Kendra; Anciso, Juan; Ivanek, Renata

2013-01-01

128

Antioxidant Effects of Spinach (Spinacia oleracea L.) Supplementation in Hyperlipidemic Rats  

PubMed Central

Increased consumption of fresh vegetables that are high in polyphenols has been associated with a reduced risk of oxidative stress-induced disease. The present study aimed to evaluate the antioxidant effects of spinach in vitro and in vivo in hyperlipidemic rats. For measurement of in vitro antioxidant activity, spinach was subjected to hot water extraction (WE) or ethanol extraction (EE) and examined for total polyphenol content (TPC), oxygen radical absorbance capacity (ORAC), cellular antioxidant activity (CAA), and antigenotoxic activity. The in vivo antioxidant activity of spinach was assessed using blood and liver lipid profiles and antioxidant status in rats fed a high fat-cholesterol diet (HFCD) for 6 weeks. The TPC of WE and EE were shown as 1.5±0.0 and 0.5±0.0 mg GAE/g, respectively. Increasing the concentration of the extracts resulted in increased ORAC value, CAA, and antigenotoxic activity for all extracts tested. HFCD-fed rats displayed hyperlipidemia and increased oxidative stress, as indicated by a significant rise in blood and liver lipid profiles, an increase in plasma conjugated diene concentration, an increase in liver thiobarbituric acid reactive substances (TBARS) level, and a significant decrease in manganese superoxide dismutase (Mn-SOD) activity compared with rats fed normal diet. However, administration of 5% spinach showed a beneficial effect in HFCD rats, as indicated by decreased liver TBARS level and DNA damage in leukocyte and increased plasma conjugated dienes and Mn-SOD activity. Thus, the antioxidant activity of spinach may be an effective way to ameliorate high fat and cholesterol diet-induced oxidative stress.

Ko, Sang-Heui; Park, Jae-Hee; Kim, So-Yun; Lee, Seon Woo; Chun, Soon-Sil; Park, Eunju

2014-01-01

129

Automated immunomagnetic separation for the detection of Escherichia coli O157:H7 from spinach.  

PubMed

Escherichia coli O157:H7 is a major cause of foodborne illness and methods for rapid and sensitive detection of this deadly pathogen are needed to protect consumers. The use of immunomagnetic separation (IMS) for capturing and detecting foodborne pathogens has gained popularity, partially due to the introduction of automated and high throughput IMS instrumentation. Three methods for automated IMS that test different sample volumes, Kingfisher® mL, Pathatrix® Auto, and Pathatrix® Ultra, were compared using microbiological detection of E. coli O157:H7 from buffered peptone water (BPW), in the presence of background microbial flora derived from spinach leaves, and from culture enrichments from artificially contaminated spinach leaves. The average efficiencies of capture of E. coli O157:H7 using the three methods were 32.1%, 3.7%, and 1.3%, respectively, in BPW; 43.4%, 8.8%, 2.9%, respectively, in the presence of spinach microbial flora; and 63.0%, 7.0%, and 6.3%, respectively, from artificially contaminated spinach. Despite the large differences in IMS capture efficiencies between the KingFisher® and two Pathatrix® methods, all three methods allowed the detection of E. coli O157:H7 from spinach that was artificially contaminated with the pathogen at relatively high (25cfu/30g sample) and low (1cfu/30g sample) levels after 4-6h of culture enrichment. The differences in capture efficiency were compensated for by the differences in sample volume used by the KingFisher® mL (1mL), Pathatrix® Auto (50mL) and Pathatrix® Ultra (250mL) instruments. Thus, despite the reduced capture efficiencies observed for the Pathatrix® methods, the large increase in sample volume results in a greater number of captured cells for downstream detection resulting in improved detection sensitivity. PMID:24718031

Chen, Jing; Shi, Xianming; Gehring, Andrew G; Paoli, George C

2014-06-01

130

Antioxidant Effects of Spinach (Spinacia oleracea L.) Supplementation in Hyperlipidemic Rats.  

PubMed

Increased consumption of fresh vegetables that are high in polyphenols has been associated with a reduced risk of oxidative stress-induced disease. The present study aimed to evaluate the antioxidant effects of spinach in vitro and in vivo in hyperlipidemic rats. For measurement of in vitro antioxidant activity, spinach was subjected to hot water extraction (WE) or ethanol extraction (EE) and examined for total polyphenol content (TPC), oxygen radical absorbance capacity (ORAC), cellular antioxidant activity (CAA), and antigenotoxic activity. The in vivo antioxidant activity of spinach was assessed using blood and liver lipid profiles and antioxidant status in rats fed a high fat-cholesterol diet (HFCD) for 6 weeks. The TPC of WE and EE were shown as 1.5±0.0 and 0.5±0.0 mg GAE/g, respectively. Increasing the concentration of the extracts resulted in increased ORAC value, CAA, and antigenotoxic activity for all extracts tested. HFCD-fed rats displayed hyperlipidemia and increased oxidative stress, as indicated by a significant rise in blood and liver lipid profiles, an increase in plasma conjugated diene concentration, an increase in liver thiobarbituric acid reactive substances (TBARS) level, and a significant decrease in manganese superoxide dismutase (Mn-SOD) activity compared with rats fed normal diet. However, administration of 5% spinach showed a beneficial effect in HFCD rats, as indicated by decreased liver TBARS level and DNA damage in leukocyte and increased plasma conjugated dienes and Mn-SOD activity. Thus, the antioxidant activity of spinach may be an effective way to ameliorate high fat and cholesterol diet-induced oxidative stress. PMID:24772405

Ko, Sang-Heui; Park, Jae-Hee; Kim, So-Yun; Lee, Seon Woo; Chun, Soon-Sil; Park, Eunju

2014-01-01

131

Understanding the photophysics of the spinach-DFHBI RNA aptamer-fluorogen complex to improve live-cell RNA imaging.  

PubMed

The use of aptamer-fluorogen complexes is an emerging strategy for RNA imaging. Despite its promise for cellular imaging and sensing, the low fluorescence intensity of the Spinach-DFHBI RNA aptamer-fluorogen complex hampers its utility in quantitative live-cell and high-resolution imaging applications. Here we report that illumination of the Spinach-fluorogen complex induces photoconversion and subsequently fluorogen dissociation, leading to fast fluorescence decay and fluorogen-concentration-dependent recovery. The fluorescence lifetime of Spinach-DFHBI is 4.0 ± 0.1 ns irrespective of the extent of photoconversion. We detail a low-repetition-rate illumination scheme that enables us to maximize the potential of the Spinach-DFHBI RNA imaging tag in living cells. PMID:24286188

Han, Kyu Young; Leslie, Benjamin J; Fei, Jingyi; Zhang, Jichuan; Ha, Taekjip

2013-12-18

132

77 FR 29588 - Notice of Decision To Issue Permits for the Importation of Fresh Celery, Arugula, and Spinach...  

Federal Register 2010, 2011, 2012, 2013

...huidobrensis without significant pest issues. Spinach, for example, has been permitted entry into the United States from Belize, Costa Rica, El Salvador, Guatemala, Honduras, Nicaragua, and Panama with only visual inspection, and L....

2012-05-18

133

Multiresidue pesticide analysis in ginseng and spinach by nontargeted and targeted screening procedures.  

PubMed

Five different mass spectrometers interfaced to GC or LC were evaluated for their application to targeted and nontargeted screening of pesticides in two foods, spinach and ginseng. The five MS systems were capillary GC/MS/MS, GC-high resolution time-of-flight (GC/HR-TOF)-MS, TOF-MS interfaced with a comprehensive multidimensional GC (GCxGC/TOF-MS), an MS/MS ion trap hybrid mass (qTrap) system interfaced with an ultra-performance liquid chromatograph (UPLC-qTrap), and UPLC interfaced to an orbital trap high resolution mass spectrometer (UPLC/Orbitrap HR-MS). Each MS system was tested with spinach and ginseng extracts prepared through a modified quick, easy, cheap, effective, rugged, and safe (QuEChERS) procedure. Each matrix was fortified at 10 and 50 ng/g for spinach or 25 and 100 ng/g for ginseng with subsets of 486 pesticides, isomers, and metabolites representing most pesticide classes. HR-TOF-MS was effective in a targeted search for characteristic accurate mass ions and identified 97% of 170 pesticides in ginseng at 25 ng/g. A targeted screen of either ginseng or spinach found 94-95% of pesticides fortified for analysis at 10 ng/g with GC/MS/MS or LC/MS/MS using multiple reaction monitoring (MRM) procedures. Orbitrap-MS successfully found 89% of 177 fortified pesticides in spinach at 25 ng/g using a targeted search of accurate mass pseudomolecular ions in the positive electrospray ionization mode. A comprehensive GCxGC/TOF-MS system provided separation and identification of 342 pesticides and metabolites in a single 32 min acquisition with standards. Only 67 or 81% of the pesticides were identified in ginseng and spinach matrixes at 25 ng/g or 10 ng/g, respectively. MS/MS or qTrap-MS operated in the MRM mode produced the lowest false-negative rates, at 10 ng/g. Improvements to instrumentation, methods, and software are needed for efficient use of nontargeted screens in parallel with triple quadrupole MS. PMID:22320080

Hayward, Douglas G; Wong, Jon W; Zhang, Kai; Chang, James; Shi, Feng; Banerjee, Kaushik; Yang, Paul

2011-01-01

134

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

Microsoft Academic Search

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, Cys155 and Cys174 are engaged in the formation

Angelika Reichert; André Dennes; Susanne Vetter; Renate Scheibe

2003-01-01

135

Light activation and molecular-mass changes of NAD(P)-glyceraldehyde 3-phosphate dehydrogenase of spinach and maize leaves  

Microsoft Academic Search

Light modulation of chloroplast glyceraldehyde 3-phosphate dehydrogenase (NAD(P)-GAPDH; EC 1.2.1.13) has been investigated. Complete activation of NADPH-dependent activity is achieved at 25 W.m-2 photosynthetically active radiation in spinach (Spinacia oleracea L.) and 100 W.m-2 in maize (Zea mays L.) leaves. Light activation is stronger in spinach (fivefold on average) than in maize (twofold), which shows higher “dark” activity. The NADH

Sandra Scagliarini; Paolo Trost; Paolo Pupillo; Vincenzo Valenti

1993-01-01

136

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

137

Element contents and food safety of water spinach ( Ipomoea aquatica Forssk.) cultivated with wastewater in Hanoi, Vietnam  

Microsoft Academic Search

Extensive aquatic or semi-aquatic production of water spinach (Ipomoea aquatica Forssk.) for human consumption takes place in Southeast Asia. The aim of this study was to assess the concentrations of 38\\u000a elements in soil and water spinach cultivated under different degrees of wastewater exposure in Hanoi, Vietnam. The results\\u000a showed no effect of wastewater use on the overall element concentrations

Helle Marcussen; Karin Joergensen; Peter E. Holm; Daniela Brocca; Robert W. Simmons; Anders Dalsgaard

2008-01-01

138

Methods for Observing Microbial Biofilms Directly on Leaf Surfaces and Recovering Them for Isolation of Culturable Microorganisms  

PubMed Central

Epifluorescence microscopy, scanning electron microscopy, and confocal laser scanning microscopy were used to observe microbial biofilms directly on leaf surfaces. Biofilms were observed on leaves of all species sampled (spinach, lettuce, Chinese cabbage, celery, leeks, basil, parsley, and broad-leaved endive), although the epifluorescent images were clearest when pale green tissue or cuticle pieces were used. With these techniques, biofilms were observed that were about 20 (mu)m in depth and up to 1 mm in length and that contained copious exopolymeric matrices, diverse morphotypes of microorganisms, and debris. The epifluorescence techniques described here can be used to rapidly determine the abundance and localization of biofilms on leaves. An additional technique was developed to recover individual biofilms or portions of single biofilms from leaves and to disintegrate them for isolation of the culturable microorganisms they contained. Nineteen biofilms from broad-leaved endive, spinach, parsley, and olive leaves were thus isolated and characterized to illustrate the applications of this technique.

Morris, C. E.; Monier, J.; Jacques, M.

1997-01-01

139

Detection of nutrient elements and contamination by pesticides in spinach and rice samples using laser-induced breakdown spectroscopy (LIBS).  

PubMed

The laser-induced breakdown spectroscopy (LIBS) technique was applied to quantify nutrients (Mg, Ca, Na, and K) in spinach and rice and to discriminate pesticide-contaminated products in a rapid manner. Standard reference materials (spinach leaves and unpolished rice flour) were used to establish a relationship between LIBS intensity and the concentration of each element (Mg, Ca, Na, and K) (i.e., calibration line). The limits of detection (LODs) for Mg, Ca, Na, and K were found to be 29.63, 102.65, 36.36, and 44.46 mg/kg in spinach and 7.54, 1.76, 4.19, and 6.70 mg/kg in unpolished rice, respectively. Concentrations of those nutrient elements present in spinach and unpolished rice from a local market were determined by using the calibration lines and compared with those measured with ICP-OES, showing good agreement. The data also suggested that the LIBS technique with the chemometric method (PLS-DA) could be a great tool to distinguish pesticide-contaminated samples from pesticide-free samples in a rapid manner even though they have similar elemental compositions. Misclassification rates were found to be 0 and 2% for clean spinach and pesticide-contaminated spinach, respectively, by applying the PLS-DA model established from the training set of data to predict the classes of test samples. PMID:22148630

Kim, Gibaek; Kwak, Jihyun; Choi, Jeunghwan; Park, Kihong

2012-01-25

140

Eubacterial origin of nuclear genes for chloroplast and cytosolic glucose-6-phosphate isomerase from spinach: sampling eubacterial gene diversity in eukaryotic chromosomes through symbiosis 1 The sequences reported in this paper have been deposited with GenBank under the accession numbers AJ000265 (spinach chloroplast GPI) and AJ000266 (spinach cytosolic GPI). 1  

Microsoft Academic Search

Higher plants possess two distinct nuclear-encoded glucose-6-phosphate isomerase (GPI) isoenzymes, a cytosolic enzmye of the Embden–Meyerhof pathway and a chloroplast enzyme essential to storage and mobilization of carbohydrate fixed by the Calvin cycle. We have purified spinach chloroplast GPI to homogeneity, determined amino acid sequences from the active enzyme, and cloned cDNAs for chloroplast and cytosolic GPI isoenzymes from spinach.

Ulrich Nowitzki; Anke Flechner; Josef Kellermann; Masami Hasegawa; Claus Schnarrenberger; William Martin

1998-01-01

141

Rapid induction of frost hardiness in spinach seedlings under salt stress  

Microsoft Academic Search

The frost hardiness of many plant species can be increased by exposing plants to low, non-freezing temperatures. It has been shown that at least in some herbaceous mono- and dicotyledonous species, hardening can also be induced by treating plants with NaCl at otherwise non-hardening temperatures. In the present investigation, the roots of approximately six-week-old spinach (Spinacia oleracea L.) seedlings were

Dirk K. Hincha

1994-01-01

142

EFFECT OF DIFFERENT TYPES OF SURFECTANTS ON ZINC EFFICIENCY IN SPINACH YIELD  

Microsoft Academic Search

A field experiment was conducted at Agriculture Research Institute Tarnab, Peshawar during 2010 to study the effect of different types of surfactants on Zinc efficiency in spinach yield and uptake of other nutrients. The experiment consisted of two different rates of Zinc Sulphate (ZnSO4) (0.5% and 1%) with three different surfactants (Aerial, Bonus and surf excel) and control without ZnSO4

Zia-ul-haq Kakar; Sajida Parveen; Sabir Gul Khattak; Zahid Saleem

2014-01-01

143

?-Cyanoalanine Synthase Is a Mitochondrial Cysteine Synthase-Like Protein in Spinach and Arabidopsis1  

PubMed Central

?-Cyano-alanine synthase (CAS; EC 4.4.1.9) plays an important role in cyanide metabolism in plants. Although the enzymatic activity of ?-cyano-Ala synthase has been detected in a variety of plants, no cDNA or gene has been identified so far. We hypothesized that the mitochondrial cysteine synthase (CS; EC 4.2.99.8) isoform, Bsas3, could actually be identical to CAS in spinach (Spinacia oleracea) and Arabidopsis. An Arabidopsis expressed sequence tag database was searched for putative Bsas3 homologs and four new CS-like isoforms, ARAth;Bsas1;1, ARAth;Bsas3;1, ARAth;Bsas4;1, and ARAth;Bsas4;2, were identified in the process. ARAth;Bsas3;1 protein was homologous to the mitochondrial SPIol;Bsas3;1 isoform from spinach, whereas ARAth;Bsas4;1 and ARAth;Bsas4;2 proteins defined a new class within the CS-like proteins family. In contrast to spinach SPIol;Bsas1;1 and SPIol;Bsas2;1 recombinant proteins, spinach SPIol;Bsas3;1 and Arabidopsis ARAth;Bsas3;1 recombinant proteins exhibited preferred substrate specificities for the CAS reaction rather than for the CS reaction, which identified these Bsas3 isoforms as CAS. Immunoblot studies supported this conclusion. This is the first report of the identification of CAS synthase-encoding cDNAs in a living organism. A new nomenclature for CS-like proteins in plants is also proposed.

Hatzfeld, Yves; Maruyama, Akiko; Schmidt, Ahlert; Noji, Masaaki; Ishizawa, Kimiharu; Saito, Kazuki

2000-01-01

144

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 (260–300 µmol photons·m-2·s-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 Schöner; G. Heinrich Krause

1990-01-01

145

Sexual modification of female spinach seeds ( Spinacia oleracea L.) by irradiation with ion particles  

Microsoft Academic Search

The female seeds of a spinach plant (Spinacia orelacea L.) were exposed to He (12.5 MeV\\/n) and C (18.3 MeV\\/n) ions in order to investigate the effects of ion particles on sex expression. He ions did not affect germination rates or flowering at doses up to 50 Gy. C ions did not affect germination rates or flowering at doses up

F. Komai; N. Shikazono; A. Tanaka

2003-01-01

146

Influence of phosphate and nitrate supply on root hair formation of rape, spinach and tomato plants  

Microsoft Academic Search

Summary Experiments with tomato, rape and spinach in nutrient solutions have shown that the formation of root hairs is strongly influenced by phosphate and nitrate supply. Decreasing the phosphate concentration of the nutrient solution from 100 to 2 ?M P resulted in an increase of root hair length from 0.1–0.2 to 0.7 mm of the three plant species. Root hair

Doris Foehse; A. Jungk

1983-01-01

147

Changes in Mulberry Leaf Metabolism in Response to Water Stress  

Microsoft Academic Search

A series of experiments were conducted to characterize the water stress-induced changes in the activities of RuBP carboxylase (RuBPCO) and sucrose phosphate synthase (SPS), photosystem 2 activity, and contents of chlorophylls, carotenoids, starch, sucrose, amino acids, free proline, proteins and nucleic acids in mulberry (Morus alba L. cv. K-2) leaves. Water stress progressively reduced the activities of RuBPCO and SPS

P. Barathi; D. Sundar; A. Ramachandra Reddy

2001-01-01

148

Conversion of Monogalactosyldiacylglycerols to Triacylglycerols in Ozone-Fumigated Spinach Leaves  

PubMed Central

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 monogalactosyldiacylglycerol (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 ?-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 ozonefumigated 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 concluded that MGDG was converted to 1,2-diacylglycerol and acylated with 18:3 to TG in ozone-fumigated spinach leaves. Images Figure 1

Sakaki, Takeshi; Saito, Kazuki; Kawaguchi, Akihiko; Kondo, Noriaki; Yamada, Mitsuhiro

1990-01-01

149

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

150

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

151

Element concentrations in water spinach (Ipomoea aquatica Forssk.), fish and sediment from a wetland production system that receives wastewater from Phnom Penh, Cambodia  

Microsoft Academic Search

The Cheung Ek Lake, which is located south of Phnom Penh, Cambodia, receives most of the industrial and domestic wastewater that is produced in the city. The lake is used for fishing and production of water spinach (Ipomoea aquatica Forssk). Concentrations of 35 elements were determined in water spinach and sediment that were collected along transects of two wastewater inlets

Helle Marcussen; Anders Dalsgaard; Peter E. Holm

2009-01-01

152

Acyl Carrier Protein Is Conjugated to Glutathione in Spinach Seed 1  

PubMed Central

Acyl carrier protein (ACP) contains an essential sulfhydryl group in its phosphopantetheine prosthetic group. We have investigated the state of this sulfhydryl in developing and mature spinach seed (Spinacia oleracea). Seed extracts were separated on sodium dodecyl sulfate or native polyacrylamide gels, blotted to nitrocellulose, and probed with antibodies raised against spinach ACP-I. In extracts of mature seeds prepared with reducing agents, ACP-II migrated as a single major band, whereas extracts prepared without reducing agents gave two major bands. The additional band was identified as a conjugate of ACP-II to glutathione (ACP-S-S-G) on the basis of its sensitivity to reducing agents and its comigration with standards in both native and sodium dodecyl sulfate gel electrophoresis. In developing spinach seeds ACP-II exists primarily in its free sulfhydryl form or as acyl derivatives, with essentially no ACP-S-S-G present. During later stages of seed development, as seed water content declines, ACP-S-S-G accumulates to approximately 50% of the total ACP. Seed imbibition results in a rapid decline in ACP-S-S-G levels. The ACP-S-S-G:ACP-SH ratio of seeds during storage was found to be a function of seed water content and this could be manipulated by controlling the relative humidity under which the seeds were stored. We speculate that conjugation of ACP to glutathione protects the ACP from sulfhydryl oxidative damage in dry seeds. ImagesFigure 1Figure 2Figure 3Figure 4Figure 5

Butt, Adrian D.; Ohlrogge, John B.

1991-01-01

153

Differential expression of ribosome-inactivating protein genes during somatic embryogenesis in spinach (Spinacia oleracea).  

PubMed

Root segments from spinach (Spinacia oleracea L. cv. Jiromaru) seedlings form embryogenic callus (EC) that responded to exogenous GA(3) by accumulating a 31-kDa glycoprotein [BP31 or S. oleracea ribosome-inactivating protein (EC 3.2.2.22) (SoRIP1)] in association with the expression of embryogenic potential. Microsequencing of this protein revealed significant similarity with type 1 RIPs. We identified cDNAs for SoRIP1 and S. oleracea RIP2 (SoRIP2), a novel RIP having a consensus shiga/ricin toxic domain and performed a comparative analysis of the expression of SoRIPs during somatic embryogenesis. Western blotting and quantitative polymerase chain reaction analyses revealed that the expression of SoRIP1 in calli increased remarkably in association with the acquisition of embryogenic potential, although the expression in somatic embryos decreased moderately with their development. However, the expression of SoRIP2 in calli remained low and constant but increased markedly with the development of somatic embryos. Treatment of callus with GA(3) and/or ABA for 24 h, or with ABA for a longer period, failed to stimulate the expression of either gene. Immunohistochemistry showed that SoRIP1 preferentially accumulated in the proembryos and peripheral meristem of somatic embryos early in development. Appreciable expression of SoRIP2 was not detected in the callus, but intense expression was found in the epidermis of somatic embryos. These results suggest that the expression of spinach RIP genes is differentially regulated in a development-dependent fashion during somatic embryogenesis in spinach. PMID:18494862

Kawade, Kensuke; Ishizaki, Takuma; Masuda, Kiyoshi

2008-10-01

154

Biosynthesis and Desaturation of Prokaryotic Galactolipids in Leaves and Isolated Chloroplasts from Spinach 1  

PubMed Central

Mono- and digalactosyldiacylglycerol (MGDG and DGDG) were isolated from the leaves of sixteen 16:3 plants. In all of these plant species, the sn-2 position of MGDG was more enriched in C16 fatty acids than sn-2 of DGDG. The molar ratios of prokaryotic MGDG to prokaryotic DGDG ranged from 4 to 10. This suggests that 16:3 plants synthesize more prokaryotic MGDG than prokaryotic DGDG. In the 16:3 plant Spinacia oleracea L. (spinach), the formation of prokaryotic galactolipids was studied both in vivo and in vitro. In intact spinach leaves as well as in chloroplasts isolated from these leaves, radioactivity from [1-14C]acetate accumulated 10 times faster in MGDG than in DGDG. After 2 hours of incorporation, most labeled galactolipids from leaves and all labeled galactolipids from isolated chloroplasts were in the prokaryotic configuration. Both in vivo and in vitro, the desaturation of labeled palmitate and oleate to trienoic fatty acids was higher in MGDG than in DGDG. In leaves, palmitate at the sn-2 position was desaturated in MGDG but not in DGDG. In isolated chloroplasts, palmitate at sn-2 similarly was desaturated only in MGDG, but palmitate and oleate at the sn-1 position were desaturated in MGDG as well as in DGDG. Apparently, palmitate desaturase reacts with sn-1 palmitate in either galactolipid, but does not react with the sn-2 fatty acid of DGDG. These results demonstrate that isolated spinach chloroplasts can synthesize and desaturate prokaryotic MGDG and DGDG. The finally accumulating molecular species, MGDG(18:3/16:3) and DGDG(18:3/16:0), are made by the chloroplasts in proportions similar to those found in leaves.

Heemskerk, Johan W. M.; Schmidt, Hermann; Hammer, Ute; Heinz, Ernst

1991-01-01

155

In vivo and in vitro effects of ethephon on some oxidative enzymes in spinach leaves  

Microsoft Academic Search

In vivo and in vitro effects of ethephon, an ethylene-generating compound, on some oxidative enzymes; polyphenol oxidase (PPO,\\u000a 1.10.3.1), peroxidase (POD, 1.11.1.7) and catalase (CAT, 1.11.1.6) in spinach leaves were investigated. The plants were grown\\u000a under controlled conditions in sand culture in 60 days. Ethephon was applied as two doses at 0.1 and 1 mM. The leaves were\\u000a harvested in the first

Lokman Öztürk; Ö. ?rfan Küfrevio?lu; Yavuz Demir

2008-01-01

156

Light-Induced Nuclear Synthesis of Spinach Chloroplast Fructose-1,6-bisphosphatase 1  

PubMed Central

Etiolated spinach (Spinacia oleracea L. var Winter Giant) seedlings show a residual photosynthetic fructose-1,6-bisphosphatase activity, which sharply rises under illumination. This increase in activity is due to a light-induced de novo synthesis, as it has been demonstrated by enzyme labeling experiments with 2H2O and [35S]methionine. The rise of bisphosphatase activity under illumination is strongly inhibited by cycloheximide, but not by the 70S ribosome inhibitor lincocin, which shows the nuclear origin of this chloroplastic enzyme. Images Fig. 3

Chueca, Ana; Lazaro, Juan Jose; Gorge, Julio Lopez

1984-01-01

157

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

Microsoft Academic Search

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-\\u000a d-ido-octulose are the active 8-carbon ketosugar intermediates of the L-type pentose pathway, it was proposed that they may also\\u000a be reactants in a modified Calvin–Benson–Bassham pathway reaction scheme. This investigation therefore initially focussed\\u000a only on the ido-epimer

John F. Williams; John K. MacLeod

2006-01-01

158

Diverse mechanisms of plant resistance to cauliflower mosaic virus revealed by leaf skeleton hybridization.  

PubMed

Plants not hosts for cauliflower mosaic virus (CaMV) may prevent systemic CaMV infection by interfering with dissemination of infection through the plant or by preventing viral replication and maturation. Leaf skeleton hybridization allows distinction between these two barriers. The technique assesses the spatial distribution of CaMV in an inoculated leaf by hybridization of a skeleton of the leaf with a CaMV DNA probe. Leaves or leaflets of soybean, cucumber, peanut, tomato, lettuce, spinach, pepper, onion, wheat, maize and barley, inoculated with CaMV DNA or CaMV virions were processed for leaf skeleton hybridization either immediately after inoculation or two weeks thereafter. Autoradiographic images of soybean and cucumber skeletons had many dark spots suggesting that CaMV DNA replication and local spread had occurred. Images of onion leaf skeletons prepared two weeks after inoculation with CaMV DNA had fewer spots. To test whether these spots resulted from CaMV replication, DNA was extracted from inoculated onion leaves and analyzed by electrophoresis, blotting and hybridization. Molecules recovered two weeks after inoculation resembled those inoculated, indicating absence of replication. For the other species, we found no evidence of local spread of CaMV infections. Thus, many plant species resist systemic CaMV infection by preventing replication or local spread of CaMV, while others solely prevent systemic movement of infection. PMID:1562237

Melcher, U; Brannan, C M; Gardner, C O; Essenberg, R C

1992-01-01

159

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.

160

Introduction and expression of foreign DNA in isolated spinach chloroplasts by electroporation.  

PubMed

An electroporation-mediated method for the study of foreign gene expression within chloroplasts has been developed. The chloroplast expression vector pHD203-GUS, which consists of coding regions for beta-glucuronidase (GUS) and chloramphenicol acetyltransferase (CAT) separated by a double psbA promoter fragment from pea (in opposite orientation) was electroporated into spinach chloroplasts and the transient gene expression was examined. Conditions for the expression of the reporter genes have been optimized. Both CAT and GUS activities were detected in chloroplasts electroporated with pHD203-GUS, but not with nuclear expression vector pBI221 or negative control pUC18. No GUS activity was detected when pHD203-GUS was electroporated into spinach protoplasts. Dot immunoblot analysis using anti-GUS antibody confirmed the existence of GUS protein in chloroplasts electroporated with chloroplast-specific vector but not the negative controls, excluding the possibilities of endogenous GUS or bacterial contamination. The expression of GUS protein in treated chloroplasts was further confirmed by Western blot analysis. PMID:8893549

To, K Y; Cheng, M C; Chen, L F; Chen, S C

1996-10-01

161

Recombinant nucleases CEL I from celery and SP I from spinach for mutation detection  

PubMed Central

Background The detection of unknown mutations is important in research and medicine. For this purpose, a mismatch-specific endonuclease CEL I from celery has been established as a useful tool in high throughput projects. Previously, CEL I-like activities were described only in a variety of plants and could not be expressed in an active form in bacteria. Results We describe expression of active recombinant plant mismatch endonucleases and modification of their activities. We also report the cloning of a CEL I ortholog from Spinacia oleracea (spinach) which we termed SP I nuclease. Active CEL I and SP I nucleases were expressed as C-terminal hexahistidine fusions and affinity purified from the cell culture media. Both recombinant enzymes were active in mutation detection in BRCA1 gene of patient-derived DNA. Native SP nuclease purified from spinach is unable to incise at single-nucleotide substitutions and loops containing a guanine nucleotide, but the recombinant SP I nuclease can cut at these sites. Conclusion The insect cell-expressed CEL I orthologs may not be identical to their native counterparts purified from plant tissues. The present expression system should facilitate further development of CEL I-based mutation detection technologies.

Pimkin, Maxim; Caretti, Elena; Canutescu, Adrian; Yeung, Jeffrey B; Cohn, Heather; Chen, Yibai; Oleykowski, Catherine; Bellacosa, Alfonso; Yeung, Anthony T

2007-01-01

162

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

163

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

164

Leaf Sequencing Method and System.  

National Technical Information Service (NTIS)

A method of delivering radiation treatment using multi-leaf collimation includes the step of providing a radiation fluence map which includes an intensity profile. The fluence map is converted into a preliminary leaf sequence, wherein the preliminary leaf...

J. Palta J. G. Li S. Kamath S. Ranka S. Sahni

2003-01-01

165

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, André; Vetter, Susanne; Scheibe, Renate

2003-02-21

166

Diseases, pests, and abiotic disorders of greenhouse-grown water spinach (Ipomoea aquatica) in Ontario and California  

Microsoft Academic Search

Water spinach, a specialty vegetable and a member of the sweet potato family, is cultivated for Asian markets in California (United States) and Ontario (Canada). Foliar diseases of this vegetable observed in commercial greenhouses of Ontario in 1993 and 1994, as well as in greenhouses of California in 1998, were attributed respectively to Phyllosticta ipomoeae, Cercospora ipomoeae, and Pseudomonas syringae

R. F. Cerkauskas; S. T. Koike; H. R. Azad; D. T. Lowery; L. W. Stobbs

2006-01-01

167

Performance traits of growing rabbits given graded levels of broken rice and water spinach (Ipomoea aquatica) ad libitum  

Microsoft Academic Search

The present investigation was conducted in the ecological farm of CelAgrid-UTA Cambodia, near Phnom Penh. Sixteen crossbreed (Local x New Zealand White) growing rabbits, averaging 961 ± 145 g live weight were used in a randomized block design to study the effect of broken rice supplementation (0, 4, 8 and 12 g\\/day) to water spinach fed ad libitum. The animals

Pok Samkol; T R Preston; J Ly

168

Replacing dried fish with fresh water spinach for growing pigs fed whole sugar cane stalks or cane juice  

Microsoft Academic Search

The experiment was conducted at CelAgrid (UTA, Cambodia), located in Kandal province. Whole sugar cane stalk and sugar cane juice were used as the sources of energy, and the protein source was the level of dry fish to provide 50, 100, 150 or 200 g protein per day. Fresh water spinach was chopped and fed ad libitum on the diets

Sorn Suheang; T R Preston

169

Escherichia coli O157:H7 in Feral Swine near Spinach Fields and Cattle, Central California Coast1  

PubMed Central

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.

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.

2007-01-01

170

Growth Stage Modulates Salinity Tolerance of New Zealand Spinach ( Tetragonia tetragonioides, Pall.) and Red Orach ( Atriplex hortensis L.)  

Microsoft Academic Search

The response of two speciality vegetable crops, New Zealand spinach (Tetragonia tetragonioides Pall.) and red orach (Atriplex hortensis L.), to salt application at three growth stages was investigated. Plants were grown with a base nutrient solution in outdoor sand cultures and salinized at 13 (early), 26 (mid), and 42 (late) d after planting (DAP). For the treatment salt concentrations, we

Clyde Wilson; Scott M. Lesch; Catherine M. Grieve

2000-01-01

171

In vitro binding of bile acids by spinach, kale, brussels sprouts, broccoli, mustard greens, green bell pepper, cabbage and collards  

Microsoft Academic Search

The in vitro binding of bile acids by spinach (Spinacia oleracea), kale (Brassica oleracea acephala), Brussels sprouts (Brassica oleracea gemmifera), broccoli (Brassica oleracea italica), mustard greens (Brassica juncea), green bell peppers (Capsicum annuum), cabbage (Brassica oleracea capitala) and collards (Brassica oleracea acephala) was determined using a mixture of bile acids secreted in human bile at a duodenal physiological pH of

T. S. Kahlon; M. H. Chapman; G. E. Smith

2007-01-01

172

Effects of phosphite, a reduced form of phosphate, on the growth and phosphorus nutrition of spinach (Spinacia oleracea L.)  

Microsoft Academic Search

Phosphite (Phi) may potentially supply phosphorus (P) nutrition to plants and is widely marketed as a super P fertilizer for many crops. This study investigated the effects of Phi on growth and P nutrition in spinach (Spinacia oleracea L.). High-rate foliar application experiments designed to evaluate the phytotoxicity and P nutritional potential of different Phi formulations by foliar application at

Hoang Thi Bich Thao; Takeo Yamakawa; Aung Kyaw Myint; Papa Saliou Sarr

2008-01-01

173

Effects of extraction and high-performance liquid chromatographic conditions on the determination of lutein in spinach.  

PubMed

A major factor in the direct determination of lutein in spinach extracts proved to be obtaining reproducible and stable chromatography of lutein. This was achieved on a C30 column with the mobile phase acetone-0.1M triethylammonium acetate (TEAA) buffer (pH 7) 9:1 (v/v). Extraction of 10mg of lyophilized spinach with 10 mL of extraction solvent (ethanol, acetone, ethanol-ethyl acetate 1:1 (v/v), methanol-THF 1:1 (v/v)) for 15 min with magnetic stirring under nitrogen resulted in equal yields of lutein. The yields were enhanced by addition of 15% of 1M TEAA buffer pH 7 to all four extraction solvents. As confirmed by recovery experiments, no loss of lutein occurred during the extraction. The relative standard deviation from triplicate extractions was less than 5%. The addition of 15% TEAA pH 7 to acetone enhanced the extraction yield of lutein also from unlyophilized spinach. The content of lutein in different spinach samples ranged from 5 to 15 mg/100g of fresh weight. The first separation is reported of all the carotenoids and chlorophylls on a C18 core-shell column and the addition of 15% of 1M TEAA buffer pH 7 to acetone also enhanced the extraction yield of ?-carotene compared to the yield produced by pure acetone. PMID:23312861

Simonovska, Breda; Vovk, Irena; Glavnik, Vesna; Cerneli?, Katarina

2013-02-01

174

Quality of fresh-cut Iceberg lettuce and spinach irradiated at doses up to 4 kGy  

NASA Astrophysics Data System (ADS)

Fresh-cut Iceberg lettuce packaged in modified atmosphere packages and spinach in perforated film bags were irradiated with gamma rays at doses of 0, 1, 2, 3, and 4 kGy. After irradiation, the samples were stored for 14 days at 4 °C. O2 levels in the packages of fresh-cut Iceberg lettuce decreased and CO2 levels increased with increasing radiation dose, suggesting that irradiation increased respiration rates of lettuce. Tissue browning of irradiated cut lettuce was less severe than that of non-irradiated, probably due to the lower O2 levels in the packages. However, samples irradiated at 3 and 4 kGy had lower maximum force and more severe sogginess than the non-irradiated control. In addition, ascorbic acid content of irradiated lettuce was 22-40% lower than the non-irradiated samples after 14 days of storage. The visual appearance of spinach was not affected by irradiation even at a dose of 4 kGy. Consumer acceptance suggested that more people would dislike and would not buy spinach that was treated at 3 and 4 kGy as compared to the non-irradiated sample. Overall, irradiation at doses of 1 and 2 kGy may be employed to enhance microbial safety of fresh-cut Iceberg lettuce and spinach while maintaining quality.

Fan, Xuetong; Guan, Wenqiang; Sokorai, Kimberly J. B.

2012-08-01

175

Survival and transfer of murine norovirus 1, a surrogate for human noroviruses, during the production process of deep-frozen onions and spinach.  

PubMed

The reduction of murine norovirus 1 (MNV-1) on onions and spinach by washing was investigated as was the risk of contamination during the washing procedure. To decontaminate wash water, the industrial sanitizer peracetic acid (PAA) was added to the water, and the survival of MNV-1 was determined. In contrast to onions, spinach undergoes a heat treatment before freezing. Therefore, the resistance of MNV-1 to blanching of spinach was examined. MNV-1 genomic copies were detected with a real-time reverse transcription PCR assay in PAA-treated water and blanched spinach, and PFUs (representing infectious MNV-1 units) were determined with a plaque assay. A < or = 1-log reduction in MNV-1 PFUs was achieved by washing onion bulbs and spinach leaves. More than 3 log PFU of MNV-1 was transmitted to onion bulbs and spinach leaves when these vegetables were washed in water containing approximately 5 log PFU/ml. No decline of MNV-1 occurred in used industrial spinach wash water after 6 days at room temperature. A concentration of 20 ppm of PAA in demineralized water (pH 4.13) and in potable water (pH 7.70) resulted in reductions of 2.88 +/- 0.25 and 2.41 +/- 0.18 log PFU, respectively, after 5 min of exposure, but no decrease in number of genomic copies was observed. No reduction of MNV-1 PFUs was observed on frozen onions or spinach during storage for 6 months. Blanching spinach (80 degrees C for 1 min) resulted in at least 2.44-log reductions of infectious MNV-1, but many genomic copies were still present. PMID:18724752

Baert, Leen; Uyttendaele, Mieke; Vermeersch, Mattias; Van Coillie, Els; Debevere, Johan

2008-08-01

176

Altered Utilization of N-Acetyl-d-Galactosamine by Escherichia coli O157:H7 from the 2006 Spinach Outbreak?  

PubMed Central

In silico analyses of previously sequenced strains of Escherichia coli O157:H7, EDL933 and Sakai, localized the gene cluster for the utilization of N-acetyl-d-galactosamine (Aga) and d-galactosamine (Gam). This gene cluster encodes the Aga phosphoenolpyruvate:carbohydrate phosphotransferase system (PTS) and other catabolic enzymes responsible for transport and catabolism of Aga. As the complete coding sequences for enzyme IIA (EIIA)Aga/Gam, EIIBAga, EIICAga, and EIIDAga of the Aga PTS are present, E. coli O157:H7 strains normally are able to utilize Aga as a sole carbon source. The Gam PTS complex, in contrast, lacks EIICGam, and consequently, E. coli O157:H7 strains cannot utilize Gam. Phenotypic analyses of 120 independent isolates of E. coli O157:H7 from our culture collection revealed that the overwhelming majority (118/120) displayed the expected Aga+ Gam? phenotype. Yet, when 194 individual isolates, derived from a 2006 spinach-associated E. coli O157:H7 outbreak, were analyzed, all (194/194) displayed an Aga? Gam? phenotype. Comparison of aga/gam sequences from two spinach isolates with those of EDL933 and Sakai revealed a single nucleotide change (G:C?A:T) in the agaF gene in the spinach-associated isolates. The base substitution in agaF, which encodes EIIAAga/Gam of the PTS, changes a conserved glycine residue to serine (Gly91Ser). Pyrosequencing of this region showed that all spinach-associated E. coli O157:H7 isolates harbored this same G:C?A:T substitution. Notably, when agaF+ was cloned into an expression vector and transformed into six spinach isolates, all (6/6) were able to grow on Aga, thus demonstrating that the Gly91Ser substitution underlies the Aga? phenotype in these isolates.

Mukherjee, Amit; Mammel, Mark K.; LeClerc, J. Eugene; Cebula, Thomas A.

2008-01-01

177

Gibberellin A[sub 1] is required for stem elongation in spinach  

SciTech Connect

The effects of the growth retardants 2'-isopropyl-4'-(trimethylammonium chloride)-5'-methylphenyl piperidine-1-carboxylate (AMO-1618) and calcium 3,5-dioxo-4-propionylcyclohexanecarboxylate (BX-112) on stem elongation were investigated in the rosette plant spinach (Spinacia oleracea L.) under long-day (LD) conditions. Stem growth induced by a LD treatment was prevented by both retardants. The inhibition caused by AMO-1618 was reversed by gibberellin A[sub 1] (GA[sub 1]) and GA[sub 20], whereas the effects of BX-112 were reversed by GA[sub 1] only. Six GAs (GA[sub 53], GA[sub 44], GA[sub 19], GA[sub 20], GA[sub 1], and GA[sub 8]) were quantified by gas chromatography-selected ion monitoring using internal standards. Plants treated with BX-112 had reduced levels of GA[sub 1], and GA[sub 8] and accumulated GA[sub 53], GA[sub 44], GA[sub 19], and GA[sub 20]. The relative levels of four additional GAs (3-epi-GA[sub 1], GA[sub 29], GA[sub 60], and GA[sub 81]) were compared by ion intensities only. Relative to GA[sub 81], the level of GA[sub 29] was decreased by BX-112, whereas the levels of GA[sub 6] and 3-epi-GA[sub 1] were increased. Transfer of spinach from short-day conditions to LD conditions caused an increase in all identified GAs of the early 13-hydroxylation pathway with GA[sub 20], GA[sub 1], and GA[sub 8] showing the largest increases. These findings support the position that, of the GA[sub s] belonging to the early 13-hydroxylation pathway, GA[sub 1] is the primary GA active per se for stem elongation in spinach. The increase in endogenous GA[sub 1] in plants in LD conditions is most likely the primary factor for stem elongation. 23 refs., 7 figs., 3 tabs.

Zeevaart, J.A.D.; Gage, D.A.; Talon, M. (Michigan State Univ., East Lansing (United States))

1993-08-01

178

Four-Leaf Clover  

NSDL National Science Digital Library

Scientist-in-training Summer Praetorius has an unusual skillâshe 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 observationâa skill Praetorius uses to spot tiny shelled animals called foraminiferaâand 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

179

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

180

The spinach RNA aptamer as a characterization tool for synthetic biology.  

PubMed

Characterization of genetic control elements is essential for the predictable engineering of synthetic biology systems. The current standard for in vivo characterization of control elements is through the use of fluorescent reporter proteins such as green fluorescent protein (GFP). Gene expression, however, involves not only protein production but also the production of mRNA. Here, we present the use of the Spinach aptamer sequence, an RNA mimic of GFP, as a tool to characterize mRNA expression in Escherichia coli. We show how the aptamer can be incorporated into gene expression cassettes and how co-expressing it with a red fluorescent protein (mRFP1) allows, for the first time, simultaneous measurement of mRNA and protein levels from engineered constructs. Using flow cytometry, we apply this tool here to evaluate ribosome binding site sequences and promoters and use it to highlight the differences in the temporal behavior of transcription and translation. PMID:23991760

Pothoulakis, Georgios; Ceroni, Francesca; Reeve, Benjamin; Ellis, Tom

2014-03-21

181

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

182

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; Ülo Niinemets

183

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; ÜLo Niinemets; Matthew J. Germino

184

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

185

Nucleotide sequences of eDNAs encoding the entire precursor polypeptides for subunits II and III of the photosystem I reaction center from spinach  

Microsoft Academic Search

Several cDNA clones encoding the complete subunit II and III precursor polypeptides of the photosystem I reaction center were isolated from two spinach lambda gtll expression libraries by immunoscreening and homologous hybridization. The identity of the recombinant cDNAs was verified by an N-terminal amino acid sequence of 14 and 20 residues for the respective mature spinach proteins. The ca. 880

S. Münch; U. Ljungberg; J. Steppuhn; A. Schneiderbauer; R. Nechushtai; K. Beyreuther; Reinhold G. Herrmanni

1988-01-01

186

Structural organization of the spinach endoplasmic reticulum-luminal 70-kilodalton heat-shock cognate gene and expression of 70-kilodalton heat-shock genes during cold acclimation.  

PubMed Central

The 70-kD heat-shock proteins (HSP70s) are encoded by a multigene family in eukaryotes. In plants, the 70-kD heat-shock cognate (HSC70) proteins are located in organellar and cytosolic compartments of cells in most tissues. Previous work has indicated that HSC70 proteins of spinach (Spinacia oleracea) are actively synthesized during cold-acclimating conditions. We have isolated, sequenced, and characterized cDNA and genomic clones for the endoplasmic reticulum (ER) luminal HSC70 protein (immunoglobulin heavy chain-binding protein; BiP) of spinach. The spinach ER-luminal HSC70 is a constitutively expressed gene consisting of eight exons. Spinach BiP mRNA appears to be up-regulated during cold acclimation but is not expressed during water stress or heat shock. In contrast to the differential regulation of mRNA, the ER-luminal HSC70 protein levels remain constant in response to various environmental stresses. Two other members of the spinach 70-kD heat-shock (HS70) multigene family also show differential expression in response to a variety of environmental stresses. A constitutively expressed cytosolic HSC70 protein in spinach appears also to be up-regulated in response to both cold-acclimating and heat-shock treatments. Spinach also contains a cold-shock-induced HS70 gene that is not expressed during heat shock or water stress. Since HSP70s are considered to be involved with the chaperoning and folding of proteins, the data further support the concept that they may be important for maintaining cellular homeostasis and proper protein biogenesis during cold acclimation of spinach.

Anderson, J V; Li, Q B; Haskell, D W; Guy, C L

1994-01-01

187

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

188

Deer predation on leaf miners via leaf abscission.  

PubMed

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. PMID:18004533

Yamazaki, Kazuo; Sugiura, Shinji

2008-03-01

189

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

PubMed

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 (0.174-3.993ppm) of the Mustard spinach plants were positively correlated with Hg concentration of soils and varied throughout the growing season. Equations relating foliar Hg concentration to spectral reflectance, its first derivative, and selected vegetation indices were generated using stepwise multiple linear regression. Significant correlations are found for limited wavelengths for specific treatments and dates. Ratio Vegetation Index (RVI) and Red Edge Position (REP) values of plants in Hg-spiked and field-contaminated soils are significantly lower relative to control plants during the early and middle portions of the growth cycle which may be related to lower chlorophyll abundance or functioning in Hg-contaminated plants. PMID:17188786

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

2007-07-01

190

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

191

Cadmium Phytoextraction Efficiency of Arum ( Colocasia antiquorum ), Radish ( Raphanus sativus L.) and Water Spinach ( Ipomoea aquatica ) Grown in Hydroponics  

Microsoft Academic Search

Selection of a phytoextraction plant with high Cd accumulation potential based on compatibility with mechanized cultivation\\u000a practice and local environmental conditions may provide more benefits than selection based mainly on high Cd tolerance plants.\\u000a In this hydroponics study, the potential of Cd accumulation by three plant species; arum (Colocasia antiquorum), radish (Raphanus sativus L.) and water spinach (Ipomoea aquatica) were

Bal Ram Singh; S M Imamul Huq; Shigenao Kawai

2008-01-01

192

Molecular cloning, spatial and temporal characterization of spinach SOGA1 cDNA, encoding an ? subunit of G protein  

Microsoft Academic Search

Heterotrimeric G proteins are an important component of signal transduction pathway in animals. Although these proteins have been described in plants, their exact function and action mode are not clearly defined. In order to analyze the relationship between these proteins and the transduction of light signals in spinach, we have isolated by 5? and 3? RACE-PCR a 1660bp cDNA clone

Pierre-François Perroud; Thierry Diogon; Michèle Crèvecoeur; Hubert Greppin

2000-01-01

193

Organization and expression of the nuclear gene coding for the plastid-specific S22 ribosomal protein from spinach  

Microsoft Academic Search

We report here on the genomic organization and expression of a nuclear gene coding for a plastid ribosomal protein. The gene encodes the plastid-specific ribosomal protein S22 (formerly named CS-S5). Southern blot analysis suggests that the gene is present in one copy in the spinach genome. The gene consists of 5 exons of sizes ranging from 108 to 273 bp

Cordelia Bisanz-Seyer; Régis Mache

1992-01-01

194

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

195

Cotranscription of the S10- and spc -like operons in spinach chloroplasts and identification of three of their gene products  

Microsoft Academic Search

The organisation and expression of the rpl22, rps3, rpl16 and rpl14 genes, which belong to the S10- and spc-like operons of spinach chloroplasts, have been studied. Northern experiments and nuclease S1 mapping show that the two operon-like groups of genes are cotranscribed. It is demonstrated that the intron-containing rpl16 gene is spliced in vivo. Based on amino acid composition and

Dao-Xiu Zhou; Françoise Quigley; Olivier Massenet; Régis Mache

1989-01-01

196

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

197

Nano-Anatase Relieves the Inhibition of Electron Transport Caused by Linolenic Acid in Chloroplasts of Spinach  

Microsoft Academic Search

Linolenic acid is an inhibitor of electron transport in chloroplasts of higher plants. It has obvious effects on the structure\\u000a and function of chloroplasts. In the present paper, we investigated the nano-anatase relieving the inhibition of photoreduction\\u000a activity and oxygen evolution caused by linolenic acid in spinach chloroplasts. The results showed that linolenic acid in\\u000a various concentrations could obviously reduce

Su Mingyu; Liu Chao; Qu Chunxiang; Zheng Lei; Chen Liang; Huang Hao; Liu Xiaoqing; Wu Xiao; Hong Fashui

2008-01-01

198

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

PubMed

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 water with and without ultrasound (21.2 kHz) for 2 min at room temperature. The effects of ultrasound treatment time and acoustic energy density (AED) were evaluated at an ASC concentration of 200 mg/L. The effect of ASC concentration, with a fixed AED of 200 W/L, was also examined. Microbial analysis indicated that ASC reduced E. coli O157 : H7 population by 2.2 log cycles over that of water wash, while the reduction from other sanitizers was about 1 log cycle. Ultrasonication significantly enhanced the reduction of E. coli cells on spinach for all treatments by 0.7 to 1.1 log cycle over that of washes with sanitizer alone. An increase in the ASC concentration enhanced the efficacy of the combined treatment of ASC and ultrasonication, especially at ASC concentrations of < 300 mg/L. Increasing the ultrasound treatment time from 0 to 4 min and AED from 0 to 500 W/L were both effective in increasing the effectiveness of the ASC and ultrasound combined treatments. In addition, E. coli O157 : H7 inoculated on the underside of spinach leaves (rough side) were more difficult to remove than those inoculated on the upper side (smooth side). PMID:19723216

Zhou, Bin; Feng, Hao; Luo, Yaguang

2009-08-01

199

Differences in responses of summer and winter spinach to elevated UV-B at varying soil NPK levels.  

PubMed

Seasonal variations in response of spinach to elevated ultraviolet-B (UV-B) during summer and winter were assessed with respect to growth, biomass, yield, NPK uptake and NPK use efficiencies at varying NPK levels. The nutrient amendments were recommended NPK (RNPK) and 1.5 times recommended NPK (1.5 RNPK). Season significantly affected the measured parameters except the number of leaves. Under ambient UV-B, the growth performance of summer spinach was better in both the NPK levels, higher being at 1.5 RNPK leading to higher nutrient uptake. However, more reduction in biomass under elevated UV-B in 1.5 RNPK was recorded during summer, while during winter in RNPK. Reduction in biomass under elevated UV-B was accompanied by the modification in its partitioning with more biomass allocation to root during summer compared to winter at both the NPK levels. NPK uptake was higher in summer, while NPK use efficiencies were higher during winter. At higher than recommended NPK level, better NPK use efficiencies were displayed during both the seasons. Increased NPK supply during winter enabled spinach to capitalize light more efficiently and hence increased biomass accumulation. Strategies for surviving elevated UV-B in winter differ from those that provided protection from the same stress when it occurs in summer. PMID:24474564

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

2014-05-01

200

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 Calvin–Benson–Bassham 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 don’t 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 ?mol h?1 mg?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

201

Functional analysis of B and C class floral organ genes in spinach demonstrates their role in sexual dimorphism  

PubMed Central

Background Evolution of unisexual flowers entails one of the most extreme changes in plant development. Cultivated spinach, Spinacia oleracea L., is uniquely suited for the study of unisexual flower development as it is dioecious and it achieves unisexually by the absence of organ development, rather than by organ abortion or suppression. Male staminate flowers lack fourth whorl primordia and female pistillate flowers lack third whorl primordia. Based on theoretical considerations, early inflorescence or floral organ identity genes would likely be directly involved in sex-determination in those species in which organ initiation rather than organ maturation is regulated. In this study, we tested the hypothesis that sexual dimorphism occurs through the regulation of B class floral organ gene expression by experimentally knocking down gene expression by viral induced gene silencing. Results Suppression of B class genes in spinach resulted in the expected homeotic transformation of stamens into carpels but also affected the number of perianth parts and the presence of fourth whorl. Phenotypically normal female flowers developed on SpPI-silenced male plants. Suppression of the spinach C class floral organ identity gene, SpAG, resulted in loss of reproductive organ identity, and indeterminate flowers, but did not result in additional sex-specific characteristics or structures. Analysis of the genomic sequences of both SpAP3 and SpPI did not reveal any allelic differences between males and females. Conclusion Sexual dimorphism in spinach is not the result of homeotic transformation of established organs, but rather is the result of differential initiation and development of the third and fourth whorl primordia. SpAG is inferred to have organ identity and meristem termination functions similar to other angiosperm C class genes. In contrast, while SpPI and SpAP3 resemble other angiosperms in their essential functions in establishing stamen identity, they also appear to have an additional function in regulating organ number and identity outside of the third whorl. We present a model for the evolution of dioecy in spinach based on the regulation of B class expression.

2010-01-01

202

Stem and Leaf Plot  

NSDL National Science Digital Library

This site, created by Michelle Lacey of Yale University, gives a definition and an example of stem and leaf plots. The author helps to explain how these graphs are used, and in what fields and/or disciplines. Even though brief, this is still a valuable reference item for anyone interested in statistics.

Lacey, Michelle

2009-11-23

203

Maple Leaf Outdoor Centre.  

ERIC Educational Resources Information Center

Maple Leaf Outdoor Centre (Ontario) has added year-round outdoor education facilities and programs to help support its summer camp for disadvantaged children. Schools, youth centers, religious groups, and athletic teams conduct their own programs, collaborate with staff, or use staff-developed programs emphasizing adventure education and personal…

Maguire, Molly; Gunton, Ric

2000-01-01

204

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

205

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

PubMed

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 Q(y) band of chlorophyll a has been observed in a pump probe experiment. The Q(y) 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. PMID:21950858

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

2011-09-21

206

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

207

THE VISUALIZATION OF THE PHOTOSYNTHETIC COUPLING FACTOR IN EMBEDDED SPINACH CHLOROPLASTS  

PubMed Central

Spinach chloroplast lamellae were stained with aqueous uranyl acetate immediately after glutaraldehyde-osmium fixation but before dehydration and embedding. Under these conditions, the lamellae are shown in thin sections to have 95-Å x 115-Å coupling factor particles on their surfaces. The particles can be seen only on the matrix side of nonopposed thylakoids, and are shown to occur on both stromal and granal lamellae, regardless of the organization of the lamellae into stacks. It is estimated that, in native, fully coupled chloroplast lamellae, there is on the average one coupling factor for every 500 chlorophyll molecules. The morphological appearance of the particles is not affected by a variety of buffers, by changes in illumination or temperature, or by alterations in the energy state of the membranes during preparation. The particles can be removed from the membranes with low concentrations of Na2EDTA, and the photophosphorylating activity of the membranes is concomitantly lost. Both the activity and the appearance of the particles can be restored to the membranes by rebinding EDTA-extracted coupling factors to the uncoupled membranes.

Oleszko, Susan; Moudrianakis, Evangelos N.

1974-01-01

208

Sub-plastidial localization of two different phage-type RNA polymerases in spinach chloroplasts  

PubMed Central

Plant plastids contain a circular genome of ?150 kb organized into ?35 transcription units. The plastid genome is organized into nucleoids and attached to plastid membranes. This relatively small genome is transcribed by at least two different RNA polymerases, one being of the prokaryotic type and plastid-encoded (PEP), the other one being of the phage-type and nucleus-encoded (NEP). The presumed localization of a second phage-type RNA polymerase in plastids is still questionable. There is strong evidence for a sequential action of NEP and PEP enzymes during plant development attributing a prevailing role of NEP during early plant and plastid development, although NEP is present in mature chloroplasts. In the present paper, we have analysed two different NEP enzymes from spinach with respect to subcellular and intra-plastidial localization in mature chloroplasts with the help of specific antibodies. Results show the presence of the two different NEP enzymes in mature chloroplasts. Both enzymes are entirely membrane bound but, unlike previously thought, this membrane binding is not mediated via DNA. This finding indicates that NEP enzymes are not found as elongating transcription complexes on the template DNA in mature chloroplasts and raises the question of their function in mature chloroplasts.

Azevedo, Jacinthe; Courtois, Florence; Lerbs-Mache, Silva

2006-01-01

209

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

210

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

211

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

212

Occurrence of biogenic amines and polyamines in spinach and changes during storage under refrigeration.  

PubMed

Biogenic amines and polyamines were studied in 18 market samples of spinach. Histamine and spermidine were detected in relatively high amounts in all samples within the ranges of 9.5-69.7 and 15.6-53.0 mg/kg, respectively. Other biologically active amines were either detected at low levels or not found at all. Changes in amine content during storage at 6 degrees C were studied. The content of most of the amines remained constant during storage, with the exception of spermidine and histamine. Spermidine showed a clear decreasing trend, whereas histamine significantly increased in all trials, but decreased at the end of the storage in two of the trials. Trials showing a decrease in histamine content also showed the highest spermidine decrease and recorded the highest pH values. Microbial loads throughout storage were also followed, with Pseudomonadaceae and Enterobacteriaceae being the predominant bacterial groups. Trials with higher microbial loads in initial samples also showed the highest histamine content in these samples. Potential explanations for both the formation and the degradation of histamine during storage are discussed. PMID:17935290

Lavizzari, Tommaso; Veciana-Nogués, Maria Teresa; Weingart, Oliver; Bover-Cid, Sara; Mariné-Font, Abel; Vidal-Carou, Maria Carmen

2007-11-14

213

Isolation and Quantitation of ?-d-Glucopyranosyl Abscisate from Leaves of Xanthium and Spinach 12  

PubMed Central

From previous work (Zeevaart 1980 Plant Physiol 66: 672-678) Xanthium leaves are known to contain a high level of alkali-hydrolyzable conjugated abscisic acid. This abscisic acid conjugate has been isolated and identified by mass spectrometry, nuclear magnetic resonance, and chemical and enzymic degradation techniques, as the glucosyl ester of abscisic acid, ?-d-glucopyranosyl abscisate. The glucosyl ester of abscisic acid was the only abscisic acid conjugate found in Xanthium leaves. It was also isolated from spinach leaves. An insignificant amount of the glucosyl ester of abscisic acid partitioned into diethyl ether, whereas 12% partitioned into ethyl acetate. Consequently, removal of abscisic acid by partitioning with ethyl acetate will result in considerable losses of the glucosyl ester of abscisic acid from the aqueous phase. Diethyl ether is, therefore, recommended for separation of abscisic acid and the glucosyl ester of abscisic acid by solvent partitioning. A method for quantitation of the glucosyl ester of abscisic acid as the tetraacetate derivative by gas-liquid chromatography with an electron capture detector was developed. The level of ?-d-glycopyranosyl abscisate in Xanthium leaves increased from 3.6 nanomoles per gram fresh weight in turgid leaves to 22.9 nanomoles in leaves from plants subjected to seven wilting-recovery cycles. ?-d-glycopyranosyl abscisate in Xanthium leaves may be a stable end product of abscisic acid metabolism.

Boyer, Gregory L.; Zeevaart, Jan A. D.

1982-01-01

214

Thiol-Dependent Regulation of Glycerate Metabolism in Leaf Extracts 1  

PubMed Central

We have recently reported that the activity of maize leaf glycerate kinase [EC 2.7.1.31] is regulated in vivo by the light/dark transition, possibly involving the ferredoxin/thioredoxin mechanism, and that the stimulating effect of light can be mimicked in vitro by incubation of crude leaf extract with reducing compounds (LA Kleczkowski, DD Randall 1985 Plant Physiol 79: 274-277). In the present study it was found that the time course of thiol activation of the enzyme was substantially dependent on the presence of some low molecular weight inhibitor(s) of activation found both in leaf extracts and mesophyll chloroplasts. Activity of glycerate kinase from maize as well as wheat leaves increased upon greening of etiolated plants and was correlated with the development of photosynthetic apparatus in these species. The maize enzyme was strongly activated by thiols at all stages of development from etiolated to green seedlings. Thiol activation of glycerate kinase was observed for a number of C4 plants, notably of the nicotinamide adenine dinucleotide phosphate-malic enzyme type, with the strongest effect found for the enzyme from leaf extracts of maize and sorghum (10- and 8-fold activation, respectively). Among the C3 species tested, only the enzyme from soybean leaves was affected under the same conditions (1.6-fold activation). This finding was reflected by an apparent lack of cross-reactivity between the enzyme from maize leaves and antibodies raised against purified spinach leaf glycerate kinase. We suggest that, in addition to its role as a final step of photorespiration in leaves, glycerate kinase from C4 species may serve as a part of the facilitative diffusion system for the intercellular transport of 3-phosphoglycerate. Simultaneous operation of both the passive and the facilitative diffusion mechanisms of 3-phosphoglycerate transport in C4 plants is postulated. Images Fig. 6

Kleczkowski, Leszek A.; Randall, Douglas D.

1986-01-01

215

Barley leaf stripe disease.  

PubMed

Leaf stripe is one of the most important diseases of barley in Iran especially in Gorgan, Mazandran and near Tehran (Varamin). Most obvious symptoms of the disease are described. Long pale or yellow stripes become darker as the fungus sporulates on the leaf surface. Infected plants usually are stunted and produce sterile spikes, rarely a few seeds are produced. Infected spikes and late-forming tillers may produce fertile spikes. The fungus is seed brone and survives in the outer layers of infected seed. To study the seed-borne disease, we have used the different methods (ISTA). Coleoptiles of seedlings are infected by the fungus under cool, moist conditions, a soil temperature below 15 degrees C is necessary for seed infection. The fungus penetrates through coleoptiles and grows systemically within the plant, produces toxin and kills cells and discolors leaf tissue between veins, thus causing striped lesions. When conditions are wet or humid, spores are produced on the surface of leaves at above the time spikes of healthy plant. Morphological characteristics of the vegetative and reproductive structures of the fungus show that it is Drechslera graminea (Rabenh) Shoemaker. PMID:12701433

Zad, J; Aghakhani, M; Etebarian, R; Okhovat, M

2002-01-01

216

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

217

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

218

Automatic detection of regions in spinach canopies responding to soil moisture deficit using combined visible and thermal imagery.  

PubMed

Thermal imaging has been used in the past for remote detection of regions of canopy showing symptoms of stress, including water deficit stress. Stress indices derived from thermal images have been used as an indicator of canopy water status, but these depend on the choice of reference surfaces and environmental conditions and can be confounded by variations in complex canopy structure. Therefore, in this work, instead of using stress indices, information from thermal and visible light imagery was combined along with machine learning techniques to identify regions of canopy showing a response to soil water deficit. Thermal and visible light images of a spinach canopy with different levels of soil moisture were captured. Statistical measurements from these images were extracted and used to classify between canopies growing in well-watered soil or under soil moisture deficit using Support Vector Machines (SVM) and Gaussian Processes Classifier (GPC) and a combination of both the classifiers. The classification results show a high correlation with soil moisture. We demonstrate that regions of a spinach crop responding to soil water deficit can be identified by using machine learning techniques with a high accuracy of 97%. This method could, in principle, be applied to any crop at a range of scales. PMID:24892284

Raza, Shan-e-Ahmed; Smith, Hazel K; Clarkson, Graham J J; Taylor, Gail; Thompson, Andrew J; Clarkson, John; Rajpoot, Nasir M

2014-01-01

219

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

220

Automatic Detection of Regions in Spinach Canopies Responding to Soil Moisture Deficit Using Combined Visible and Thermal Imagery  

PubMed Central

Thermal imaging has been used in the past for remote detection of regions of canopy showing symptoms of stress, including water deficit stress. Stress indices derived from thermal images have been used as an indicator of canopy water status, but these depend on the choice of reference surfaces and environmental conditions and can be confounded by variations in complex canopy structure. Therefore, in this work, instead of using stress indices, information from thermal and visible light imagery was combined along with machine learning techniques to identify regions of canopy showing a response to soil water deficit. Thermal and visible light images of a spinach canopy with different levels of soil moisture were captured. Statistical measurements from these images were extracted and used to classify between canopies growing in well-watered soil or under soil moisture deficit using Support Vector Machines (SVM) and Gaussian Processes Classifier (GPC) and a combination of both the classifiers. The classification results show a high correlation with soil moisture. We demonstrate that regions of a spinach crop responding to soil water deficit can be identified by using machine learning techniques with a high accuracy of 97%. This method could, in principle, be applied to any crop at a range of scales.

Raza, Shan-e-Ahmed; Smith, Hazel K.; Clarkson, Graham J. J.; Taylor, Gail; Thompson, Andrew J.; Clarkson, John; Rajpoot, Nasir M.

2014-01-01

221

Chloroplast ATP synthase of spinach contains nine nonidentical subunit species, six of which are encoded by plastid chromosomes in two operons in a phylogenetically conserved arrangement  

Microsoft Academic Search

We describe the nucleotide sequence of a 4.0 kilobase pair (kbp) region of the spinach plastid chromosome that encodes three subunits of the ATP synthase CF0 sector proximal to the gene for CF1 subunit alpha. The four genes are located on the same strand and form a transcriptional unit. Our study presents details about the genes and their products, resolves

Juliane Hennig; Reinhold G. Herrmann

1986-01-01

222

Coordinate and non-coordinate expression of the stress 70 family and other molecular chaperones at high and low temperature in spinach and tomato  

Microsoft Academic Search

Stress 70 molecular chaperones are found in all the major subcellular compartments of plant cells, and they are encoded by a multigene family. Twelve members of this family have been identified in spinach. The expression of the stress 70 molecular chaperones in response to heat shock is well-known and it appears that low temperature exposure can also stimulate their expression.

Qin-Bao Li; Dale W. Haskell; Charles L. Guy

1999-01-01

223

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 µmol photons

Anne Krapp; W. Paul Quick; Mark Stitt

1991-01-01

224

Use of different fluorometric systems in the determination of fluorescence parameters from spinach thylakoid membranes being exposed to atrazine and copper  

Microsoft Academic Search

Sensitivity of photosystem II fluorescence parameters, as indicators of atrazine and copper inhibitory effects, were investigated by using LuminoTox, Pulse Amplitude Modulated (PAM) and Plant Efficiency Analyzer (PEA) fluorometric systems. Inhibition of Photosystem II was induced when samples of spinach thylakoid membranes were treated with atrazine or copper sulphate for 15?min. In those samples we investigated the change of the

D. Dewez; N. Boucher; F. Bellemare; R. Popovic

2007-01-01

225

Market Response to a Food Safety Shock: The 2006 Foodborne Illness Outbreak of E. coli O157:H7 Linked to Spinach  

Microsoft Academic Search

In 2006 FDA announced that consumers should not eat fresh spinach in the wake of a large foodborne illness outbreak of E. coli O157:H7. This paper investigates response of consumers to the announcement. We use an AIDS demand model with 5 food safety shock variables and retail scanner data to analyze market response. Even fifteen months after the outbreak, predicted

Carlos A. Arnade; Linda Calvin; Fred Kuchler

2008-01-01

226

Elements in major raw agricultural crops in the United States. 3. Cadmium, lead, and eleven other elements in carrots, field corn, onions, rice, spinach, and tomatoes  

Microsoft Academic Search

Six raw agricultural crops (carrots, field corn, onions, rice, spinach, and tomatoes) were collected from major U.S. growing areas uncontaminated by human activities other than normal agricultural practices. Handling, preparation, and analysis of the 1215 samples were performed under carefully controlled conditions. Cadmium and lead were determined by differential pulse anodic stripping voltammetry and Ca, Cu, Fe, K, Mg, Mn,

K. A. Wolnik; F. L. Fricke; S. G. Capar; M. W. Meyer; R. D. Satzger; E. Bonnin; C. M. Gaston

2009-01-01

227

Alterations of the phylloepiphytic bacterial community associated with interactions of Escherichia coli O157:H7 during storage of packaged spinach at refrigeration temperatures.  

PubMed

This study investigated the effects of packaging and storage temperature on the spinach phylloepiphytic bacterial community and fate of Escherichia coli O157:H7. Freshly harvested spinach was rinsed and/or disinfected, packaged and stored under typical retail conditions (4 degrees C) or under temperature abuse conditions (10 degrees C) for a period of 15 days. The final population size of culturable epiphytic bacteria after 15 days of storage was not affected by the temperature of storage or the presence of E. coli O157:H7. However, analysis of the bacterial community using denaturing gradient gel electrophoresis of 16s rDNA revealed changes with time of storage and the presence of E. coli O157:H7. Excision and sequencing of prominent DGGE bands identified that the majority of sequences belonged to the phyla Actinobacteria, Bacteroidetes, Firmicutes and Alphaprotebacteria. After 10 days of storage at 4 degrees C or 10 degrees C the population became more dominated by psychrotrophic bacteria. Removal of the epiphytic bacteria resulted in significant increases in numbers of E coli O157:H7 at 10 degrees C and was associated with decreased expression of E. coli O157:H7 virulence (stxA, curli, eaeA) and stress response (rpoS, sodB) genes. In conclusion, storage temperature and time of storage of packaged spinach affected the diversity of the epiphytic spinach microbiota which influenced the growth, establishment, physiology and potentially virulence of E. coli O157:H7. PMID:20417396

Lopez-Velasco, Gabriela; Davis, Marjorie; Boyer, Renee R; Williams, Robert C; Ponder, Monica A

2010-06-01

228

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

229

Mathematical modeling and numerical analysis of the growth of non-O157 Shiga toxin-producing Escherichia coli in spinach leaves.  

PubMed

This study was conducted to investigate the growth of non-O157 Shiga toxin-producing Escherichia coli (STEC) in spinach leaves and to develop kinetic models to describe the bacterial growth. Six serogroups of non-O157 STEC, including O26, O45, O103, O111, O121, and O145, were used in the growth studies conducted isothermally at 4, 8, 15, 20, 25, 30, and 35 °C. Both STEC and background microflora were enumerated to develop kinetic models. Growth of STEC in spinach leaves was observed at elevated temperatures (15-35 °C), but not at 4 and 8 °C. This study considered the dynamic interactions between the STEC cells and the background microflora. A modified Lotka-Volterra and logistic equation was used to simulate the bacterial growth. In combination with an unconstrained optimization procedure, the differential growth equations were solved numerically to evaluate the dynamic interactions between the STEC cells and the background microflora, and to determine the kinetic parameters by fitting each growth curve to the growth equations. A close agreement between the experimental growth curves and the numerical analysis results was obtained. The analytical results showed that the growth of STEC in spinach leaves was unhindered when the population was low, but the growth was suppressed by the background microflora as the STEC population approached the maximum population density. The effect of temperature on the growth of both STEC and background microflora was also evaluated. Secondary models, evaluating the effect of temperature on growth rates, were also developed. The estimated apparent minimum growth temperature for STEC was 11 °C in commercial spinach leaves. The methodology and results of this study can be used to examine the dynamic interactions and growth between different bacteria in foods, and to conduct risk assessments of STEC in spinach leaves. PMID:23141643

Huang, Lihan

2012-11-01

230

Respiration of Sugars in Spinach (Spinacia oleracea), Maize (Zea mays), and Chlamydomonas reinhardtii F-60 Chloroplasts with Emphasis on the Hexose Kinases.  

PubMed Central

The role of hexokinase in carbohydrate degradation in isolated, intact chloroplasts was evaluated. This was accomplished by monitoring the evolution of 14CO2 from darkened spinach (Spinacia oleracea), maize (Zea mays) mesophyll, and Chlamydomonas reinhardtii chloroplasts externally supplied with 14C-labeled fructose, glucose, mannose, galactose, maltose, and ribose. Glucose and ribose were the preferred substrates with the Chlamydomonas and maize chloroplasts, respectively. The rate of CO2 release from fructose was about twice that from glucose in the spinach chloroplast. Externally supplied ATP stimulated the rate of CO2 release. The pH optimum for CO2 release was 7.5 with ribose and fructose and 8.5 with glucose as substrates. Probing the outer membrane polypeptides of the intact spinach chloroplast with two proteases, trypsin and thermolysin, decreased 14CO2 release from glucose about 50% but had little effect when fructose was the substrate. Tryptic digestion decreased CO2 release from glucose in the Chlamydomonas chloroplast about 70%. 14CO2 evolution from [1-14C]-glucose-6-phosphate in both chloroplasts was unaffected by treatment with trypsin. Enzymic analysis of the supernatant (stroma) of the lysed spinach chloroplast indicated a hexokinase active primarily with fructose but with some affinity for glucose. The pellet (membranal fraction) contained a hexokinase utilizing both glucose and fructose but with considerably less total activity than the stromal enzyme. Treatment with trypsin and thermolysin eliminated more than 50% of the glucokinase activity but had little effect on fructokinase activity in the spinach chloroplast. Tryptic digestion of the Chlamydomonas chloroplast resulted in a loss of about 90% of glucokinase activity.

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

1993-01-01

231

Characterization of an Electron Transport Pathway Associated with Glucose and Fructose Respiration in the Intact Chloroplasts of Chlamydomonas reinhardtii and Spinach 1  

PubMed Central

The role of an electron transport pathway associated with aerobic carbohydrate degradation in isolated, intact chloroplasts was evaluated. This was accomplished by monitoring the evolution of 14CO2 from darkened spinach (Spinacia oleracea) and Chlamydomonas reinhardtii chloroplasts externally supplied with [14C]fructose and [14C]glucose, respectively, in the presence of nitrite, oxaloacetate, and conventional electron transport inhibitors. Addition of nitrite or oxaloacetate increased the release of 14CO2, but it was shown that O2 continued to function as a terminal electron acceptor. 14CO2 evolution was inhibited up to 30 and 15% in Chlamydomonas and spinach, respectively, by 50 ?m rotenone and by amytal, but at 500- to 1000-fold higher concentrations, indicating the involvement of a reduced nicotinamide adenine dinucleotide phosphate-plastoquinone oxidoreductase. 14CO2 release from the spinach chloroplast was inhibited 80% by 25 ?m 2,5-dibromo-3-methyl-6-isopropyl-p-benzoquinone. 14CO2 release was sensitive to propylgallate, exhibiting approximately 50% inhibition in Chlamydomonas and in spinach chloroplasts of 100 and 250 ?m concentrations, respectively. These concentrations were 20- to 50-fold lower than the concentrations of salicylhydroxamic acid (SHAM) required to produce an equivalent sensitivity. Antimycin A (100 ?m) inhibited approximately 80 to 90% of 14CO2 release from both types of chloroplast. At 75 ?m, sodium azide inhibited 14CO2 evolution about 50% in Chlamydomonas and 30% in spinach. Sodium azide (100 mm) combined with antimycin A (100 ?m) inhibited 14CO2 evolution more than 90%. 14CO2 release was unaffected by uncouplers. These results are interpreted as evidence for a respiratory electron transport pathway functioning in the darkened, isolated chloroplast. Chloroplast respiration defined as 14CO2 release from externally supplied [1-14C]glucose can account for at least 10% of the total respiratory capacity (endogenous release of CO2) of the Chlamydomonas reinhardtii cell.

Singh, Kausal K.; Chen, Changguo; Gibbs, Martin

1992-01-01

232

Spectroscopic and kinetic properties of a recombinant form of the flavin domain of spinach NADH: nitrate reductase.  

PubMed

The C-terminal 268 residues of the spinach assimilatory NADH:nitrate reductase amino acid sequence that correspond to the flavin-containing domain of the enzyme have been selectively amplified and expressed as a recombinant protein in Escherichia coli. The recombinant protein, which was produced in both soluble and insoluble forms, was purified to homogeneity using a combination of ammonium sulfate precipitation, affinity chromatography on 5'-ADP-agarose and FPLC gel filtration. The purified domain exhibited a molecular weight of approximately 30 kDa, estimated by polyacrylamide gel electrophoresis, and a molecular mass of 30,169 for the apoprotein determined by mass spectrometry, which also confirmed the presence of FAD. The UV/visible spectrum was typical of a flavoprotein, with maxima at 272, 386, and 461 nm in the oxidized form while CD spectroscopy yielded both positive and negative maxima at 313 and 382 nm and 461 and 484 nm, respectively. The purified domain showed immunological cross-reactivity with anti-spinach nitrate reductase polyclonal antibodies while both N-terminal and internal amino acid sequencing of isolated peptides confirmed the fidelity of the domain's primary sequence. The protein retained NADH-ferricyanide reductase activity (Vmax=84 micromol NADH consumer/min/nmol FAD) with Km's of 17 and 34 microM for NADH and ferricyanide, respectively, with a pH optimum of approximately 6.5 A variety of NADH-analogs could also function as electron donors, though with decreased efficiency, the most effective being reduced nicotinamide hypoxanthine dinucleotide (V(max) = 35 micromol NHDH consumer/min/nmol FAD) and Km = 22 microM). NAD+ was demonstrated to be a competitive inhibitor (Ki = 1.9 mM) while analysis of inhibition by a variety of NAD+-analogs indicated the most efficient inhibitor to be ADP (Ki = 0.2 mM), with analogs devoid of either the phosphate, ribose, or adenine moieties proving to be markedly less-efficient inhibitors. The isolated domain was also capable of reducing cytochrome b5 directly (V(max) = 1.2 micromol NADH consumed/min/nmol FAD, Km (cyt. b5) = 6 microM), supporting the FAD -> b557 -> Mo electron transfer sequence in spinach nitrate reductase. PMID:8615685

Quinn, G B; Trimboli, A J; Prosser, I M; Barber, M J

1996-03-01

233

Remote Sensing of Leaf Water Content in the Near Infrared.  

National Technical Information Service (NTIS)

A stochastic leaf radiation model was used to predict leaf spectral reflectance as a function of leaf water content for a dicot leaf. Simulated spectral reflectances, corresponding to different leaf water contents or equivalent water thicknesses, were ana...

C. J. Tucker

1979-01-01

234

Deriving leaf chlorophyll content of green-leafy vegetables from hyperspectral reflectance  

NASA Astrophysics Data System (ADS)

Different nitrogen (N) treatments of four common green-leafy vegetable varieties with different leaf color: lettuce ( Lactuca sativa L. var. crispa L.) with yellow green leaves, pakchoi ( Brassica chinensis L.) var. aijiaohuang in Chinese (AJH) with middle green leaves, spinach ( Spinacia oleracea L.) with green leaves and pakchoi ( B. chinensis L.) var. shanghaiqing in Chinese (SHQ) with dark green leaves, were carried out to achieve a wide range of chlorophyll content. The relationship of vegetable leaf hyperspectral response to its chlorophyll content was examined in this study. Almost all reported successful leaf chlorophyll indices in the literature were evaluated for their ability to predict the chlorophyll content in vegetable leaves. Some new indices based on the first derivative curve were also developed, and compared with the chlorophyll indices published. The results showed that most of the indices showed a strong relation with leaf chlorophyll content. In general, modified indices with the blue or near red edge wavelength performed better than their simple counterpart without modification, ratio indices performed a little better than normalized indices when chlorophyll expressed on area basis and reversed when chlorophyll expressed on fresh weight basis. A normalized derivative difference ratio (BND: (D722-D700)/(D722+D700) calibrated by Maire et al. [Maire, G., Francois, C., Dufrene, E., 2004. Towards universal broad leaf chlorophyll indices using PROSPECT simulated database and hyperspectral reflectance measurements. Remote Sensing of Environment 89 (1), 1-28]) gave the best results among all published indices in this study (RMSE=22.1 mg m -2), then the mSR-like indices with the RMSE between 22.6 and 23.0 mg m -2. The new indices EBAR (ratio of the area of red and blue, ? dRE/? dB), EBFN (normalized difference of the amplitude of red and blue, (dRE-dB)/(dRE+dB)) and EBAN (normalized difference of the area of red and blue, (? dRE-? dB)/(? dRE+? dB)) calculated with the derivatives also showed a good performance with the RMSE of 23.3, 24.15 and 24.33 mg m -2, respectively. The study suggests that spectral reflectance measurements hold promise for the assessment of chlorophyll content at the leaf level for green-leafy vegetables. Further investigation is needed to evaluate the effectiveness of such techniques on other vegetable varieties or at the canopy level.

Xue, Lihong; Yang, Linzhang

235

Glucose-6-phosphate dehydrogenase activity in spinach as measured by image analysis: a new approach for plant enzyme histochemistry.  

PubMed

A relatively low-cost computer-assisted image analysis system is described. Software has been specifically written for the continuous monitoring of absorbance readings on cryostat sections of plant tissues incubated in media to reveal enzyme activities. The equipment was tested by quantifying glucose-6-phosphate dehydrogenase activity in cryostat sections from shoot apices of spinach plants. The reaction rate of the dehydrogenase activity was monitored at two incubation temperatures, 20 degrees C and 30 degrees C. Control incubations were performed in media lacking substrate. The specific test minus control reaction at 30 degrees C was twice that at 20 degrees C. Variation of the substrate concentration at 30 degrees C yielded a Km value of 0.37 mM. These preliminary results show that our image analysis system can be used for kinetic measurements of dehydrogenase activity in frozen tissue sections and constitute a new approach for enzyme histochemistry in the shoot apical meristem. PMID:8866645

Crèvecoeur, M; Cissé, M B; Albe, X; Greppin, H

1996-01-01

236

Leaf trait relationships in Australian plant species  

Microsoft Academic Search

Leaf trait data were compiled for 258 Australian plant species from several habitat types dominated by woody perennials. Specific leaf area (SLA), photosynthetic capacity, dark respiration rate and leaf nitrogen (N) and phosphorus (P) concentrations were positively correlated with one another and negatively correlated with average leaf lifespan. These trait relationships were consistent with previous results from global datasets. Together,

Ian J. Wright; Philip K. Groom; Byron B. Lamont; Pieter Poot; Peter B. Reich; E-Detlef Schulze; Erik J. Veneklaas; Mark Westoby; Penrith South

2004-01-01

237

7 CFR 29.3033 - Leaf.  

Code of Federal Regulations, 2010 CFR

...2009-01-01 2009-01-01 false Leaf. 29.3033 Section 29.3033 Agriculture Regulations of the Department of Agriculture...Tobacco (u.s. Type 31 and Foreign Type 93) § 29.3033 Leaf. Whole, unstemmed leaf. Leaf, when...

2009-01-01

238

7 CFR 29.3033 - Leaf.  

Code of Federal Regulations, 2010 CFR

...2010-01-01 2010-01-01 false Leaf. 29.3033 Section 29.3033 Agriculture Regulations of the Department of Agriculture...Tobacco (u.s. Type 31 and Foreign Type 93) § 29.3033 Leaf. Whole, unstemmed leaf. Leaf, when...

2010-01-01

239

The molecular genetic analysis of leaf senescence  

Microsoft Academic Search

The cloning of genes induced during leaf senescence and the study of their modes of regulation conducted in the past two years have revealed some of the molecular mechanisms underlying leaf senescence. The identification of genetic mutants that control leaf senescence in Arabidopsis thaliana opened up new possibilities for genetically analyzing leaf senescence in a model system. Encouraging experimental data

Hong Gil Nam

1997-01-01

240

Leaf photosynthesis, plant growth and nitrogen allocation in rice under different irradiances  

Microsoft Academic Search

.   The photosynthetic rates and various components of photosynthesis including ribulose-1,5-bisphosphate carboxylase (Rubisco;\\u000a EC 4.1.1.39), chlorophyll (Chl), cytochrome (Cyt) f, and coupling factor 1 (CF1) contents, and sucrose-phosphate synthase (SPS; EC 2.4.1.14) activity were examined in young, fully expanded leaves of rice\\u000a (Oryza sativa L.) grown hydroponically under two irradiances, namely, 1000 and 350 ?mol quanta??m?2??s?1, at three N concentrations.

Amane Makino; Tetsuya Sato; Hiromi Nakano; Tadahiko Mae

1997-01-01

241

Changes in leaf hydraulic conductance correlate with leaf vein embolism in Cercis siliquastrum L  

Microsoft Academic Search

The impact of xylem cavitation and embolism on leaf ( K leaf) and stem ( K stem) hydraulic conductance was measured in current-year shoots of Cercis siliquastrum L. (Judas tree) using the vacuum chamber technique. K stem decreased at leaf water potentials (? L) lower than -1.0 MPa, while K leaf started to decrease only at ? L L K leaf

Andrea Nardini; Sebastiano Salleo; Fabio Raimondo

2003-01-01

242

Relationships of leaf dark respiration to leaf nitrogen, specific leaf area and leaf life-span: a test across biomes and functional groups  

Microsoft Academic Search

Based on prior evidence of coordinated multiple leaf trait scaling, we hypothesized that variation among species in leaf\\u000a dark respiration rate (R\\u000a d) should scale with variation in traits such as leaf nitrogen (N), leaf life-span, specific leaf area (SLA), and net photosynthetic\\u000a capacity (A\\u000a max). However, it is not known whether such scaling, if it exists, is similar among

Peter B. Reich; Michael B. Walters; David S. Ellsworth; James M. Vose; John C. Volin; Charles GreshamWilliam; William D. Bowman

1998-01-01

243

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

244

Evaluation of models describing the growth of nalidixic acid-resistant E. coli O157:H7 in blanched spinach and Iceberg lettuce as a function of temperature.  

PubMed

The aim of this study was to model the growth of nalidixic acid-resistant E. coli O157:H7 (E. coli O157:H7NR) in blanched spinach and to evaluate model performance with an independent set of data for interpolation (8.5, 13, 15 and 27 °C) and for extrapolation (broth and fresh-cut iceberg lettuce) using the ratio method and the acceptable prediction zone method. The lag time (LT), specific growth rate (SGR) and maximum population density (MPD) obtained from each primary model were modeled as a function of temperature (7, 10, 17, 24, 30, and 36 °C) using Davey, square root, and polynomial models, respectively. At 7 °C, the populations of E. coli O157:H7NR increased in tryptic soy broth with nalidixic acid (TSBN), blanched spinach and fresh-cut iceberg lettuce, while the populations of E. coli O157:H7 decreased in TSB after 118 h of LT, indicating the risk of nalidixic acid-resistant strain of E. coli O157:H7 contaminated in ready-to-eat produce at refrigerated temperature. When the LT and SGR models of blanched spinach was extended to iceberg lettuce, all relative errors (percentage of RE = 100%) were inside the acceptable prediction zone and had an acceptable Bf and Af values. Thus, it was concluded that developed secondary models for E. coli O157:H7NR in blanched spinach were suitable for use in making predictions for fresh cut iceberg lettuce, but not for static TSBN in this work. PMID:23839062

Kim, Juhui; Chung, Hyunjung; Cho, Joonil; Yoon, Kisun

2013-07-01

245

Evaluation of Models Describing the Growth of Nalidixic Acid-Resistant E. coli O157:H7 in Blanched Spinach and Iceberg Lettuce as a Function of Temperature  

PubMed Central

The aim of this study was to model the growth of nalidixic acid-resistant E. coli O157:H7 (E. coli O157:H7NR) in blanched spinach and to evaluate model performance with an independent set of data for interpolation (8.5, 13, 15 and 27 °C) and for extrapolation (broth and fresh-cut iceberg lettuce) using the ratio method and the acceptable prediction zone method. The lag time (LT), specific growth rate (SGR) and maximum population density (MPD) obtained from each primary model were modeled as a function of temperature (7, 10, 17, 24, 30, and 36 °C) using Davey, square root, and polynomial models, respectively. At 7 °C, the populations of E. coli O157:H7NR increased in tryptic soy broth with nalidixic acid (TSBN), blanched spinach and fresh-cut iceberg lettuce, while the populations of E. coli O157:H7 decreased in TSB after 118 h of LT, indicating the risk of nalidixic acid-resistant strain of E. coli O157:H7 contaminated in ready-to-eat produce at refrigerated temperature. When the LT and SGR models of blanched spinach was extended to iceberg lettuce, all relative errors (percentage of RE = 100%) were inside the acceptable prediction zone and had an acceptable Bf and Af values. Thus, it was concluded that developed secondary models for E. coli O157:H7NR in blanched spinach were suitable for use in making predictions for fresh cut iceberg lettuce, but not for static TSBN in this work.

Kim, Juhui; Chung, Hyunjung; Cho, Joonil; Yoon, Kisun

2013-01-01

246

Digestibility studies in growing pigs fed diets based on full-fat rubber seeds or soya beans supplemented with water spinach  

Microsoft Academic Search

A digestibility trial was conducted to evaluate the nutritive value of diets composed of either Cambodian full-fat rubber (Hevea brasiliensis) seeds or soya beans using 16 Mong Cai*Large White pigs. Rubber seeds of unknown falling day and storing period, and extruded soy beans were used in this study. Water spinach (Ipomoea aquatica) was given ad libitum as a complementary protein-rich

Pok Samkol; Pech Sovanno; T R Preston; J Ly

247

Digestibility indices and N balance in growing rabbits fed a basal diet of water spinach (Ipomoea aquatica) supplemented with broken rice  

Microsoft Academic Search

Four Local and 4 New Zealand White male rabbits with an initial live weight of 1.75 ± 0.10 kg were fed water spinach (Ipomoea aquatica) ad libitum supplemented with broken rice (0, 4, 8 and 12g\\/day) according to a duplicate 4*4 Latin Square design. There were no significant differences for the interaction genotype x diet in any of the indices

Pok Samkol; T R Preston; J Ly

248

Effect of cooking and irradiation on the labile vitamins and antinutrient content of a traditional African sorghum porridge and spinach relish  

Microsoft Academic Search

Irradiation is a potentially useful technology for ensuring the safety and extending the shelf-life of food products in Africa. However, nutritional changes may result. The effects of cooking followed by irradiation (10kGy) on vitamins B1 and C, and the antinutritional factors, phytic acid and nitrates, in a ready-to-eat meal of sorghum porridge and spinach-based relish were investigated. Cooking reduced vitamin

K. G. Duodu; A. Minnaar; J. R. N. Taylor

1999-01-01

249

Characterisation of the effects of Antimycin A upon high energy state quenching of chlorophyll fluorescence (qE) in spinach and pea chloroplasts  

Microsoft Academic Search

High energy state quenching of chlorophyll fluorescence (qE) is inhibited by low concentrations of the inhibitor antimycin A in intact and osmotically shocked chloroplasts isolated from spinach and pea plants. This inhibition is independent of any effect upon ?pH (as measured by 9-aminoacridine fluorescence quenching). A dual control of qE formation, by ?pH and the redox state of an unidentified

Kevin Oxborough; Peter Horton

1987-01-01

250

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

251

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 4°C 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 4°C 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

2012-02-15

252

Cloning, Mapping, and in vitro Transcription--Translation of the Gene for the Large Subunit of Ribulose1,5-bisphosphate Carboxylase from Spinach Chloroplasts  

Microsoft Academic Search

An 11.2-kilobase pair (kbp) BamHI restriction nuclease fragment from spinach chloroplast DNA has been found to contain the gene for the large subunit (LS) of ribulose-1,5-bisphosphate carboxylase [RuP2 carboxylase; 3-phospho-D-glycerate carboxy-lyase (dimerizing), EC 4.1.1.39]. The gene was located by hybridization of cloned chloroplast DNA fragments containing the maize LS gene (Bedbrook, J. R., Coen, D. M., Beaton, A. R., Bogorad,

Jack L. Erion; Joseph Tarnowski; Herbert Weissbach; Nathan Brot

1981-01-01

253

Antioxidant assays - consistent findings from FRAP and ORAC reveal a negative impact of organic cultivation on antioxidant potential in spinach but not watercress or rocket leaves  

PubMed Central

Watercress (Rorippa nasturtium-aquaticum), wild rocket (Diplotaxis tenuifolia), and spinach (Spinacia oleracea) are commercial crops reported to have high concentrations of antioxidants, possibly contributing to disease prevention following human consumption. Following analysis of supermarket-purchased salad leaves, we report the antioxidant content potential of these species using two comparable techniques assessing the consistency between the assays – by the ferric reducing antioxidant power (FRAP) assay and the oxygen radical absorbance capacity (ORAC) assay. The leaves were harvested from both conventionally and organically managed crops, to investigate whether organic agriculture results in improved crop quality. Watercress had the highest FRAP and ability to scavenge free radicals, followed by spinach and rocket. For watercress and rocket, there was no significant effect of organic agriculture on FRAP and ORAC, but for spinach, the antioxidant potential was reduced and this was significant at the 5% level of probability for FRAP but not ORAC, although the trend was clear in both tests. We conclude that there is variation in salad crop antioxidant potential and that FRAP and ORAC are useful techniques for measuring antioxidants in these salad crops with similar ranking for each salad crop studied.

Payne, Adrienne C; Mazzer, Alice; Clarkson, Graham J J; Taylor, Gail

2013-01-01

254

Over-expression of an arabidopsis family A sucrose phosphate synthase (SPS) gene alters plant growth and fibre development  

Microsoft Academic Search

The objective of this study was to manipulate the intracellular pools of sucrose by differentially expressing exogenous sucrose\\u000a phosphate synthase (SPS) and investigating its role in regulating plant growth and fibre development. Tobacco (Nicotiana tabacum cv. Xanthi) plants were transformed with an arabidopsis SPS gene under the regulation of the ubiquitously expressed tandem\\u000a repeat of the 35S cauliflower mosaic virus

Ji-Young Park; Thomas Canam; Kyu-Young Kang; David D. Ellis; Shawn D. Mansfield

2008-01-01

255

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

256

Life in the Leaf Litter  

NSDL National Science Digital Library

Produced by the Center for Biodiversity and Conservation, Life in the Leaf Litter is a guide to the diversity of soil organisms and the crucial role that invertebrates play in woodland ecosystems. The booklet was based, in part, on a leaf litter survey conducted by the CBC's Metro Program and the Museum's Division of Invertebrate Zoology in Central Park's woodlands, which led to the discovery of a new genus and species of centipede, Nannarrup hoffmani. The booklet may be downloaded as a pdf or ordered free of charge.

257

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

258

Effect of Butyl 2-Hydroxy-3-Butynoate on Sunflower Leaf Photosynthesis and Photorespiration 1  

PubMed Central

Detached leaves and whole plants of sunflower were supplied with butyl 2-hydroxy-3-butynoate (BHB), a competitive inactivator of glycolate oxidase, to evaluate the possibility of inhibiting photorespiration and increasing photosynthetic efficiency. In all treatments in vivo and in vitro, BHB inhibited glycolate oxidase. With partially purified glycolate oxidase from spinach leaves, the apparent Ki for BHB was 13.2 micromolar. Low concentrations of BHB neither decreased photorespiration nor increased net photosynthesis. At higher concentrations, either a proportional decrease in photosynthesis and photorespiration or an inhibition of net photosynthesis greater than photorespiration was observed. CO2 evolution in BHB-treated leaves was O2-sensitive and was derived from recent photosynthate. BHB inhibited photosynthesis in 2, 21, or 50% O2 but the ratio of the rates of photosynthesis in these O2 concentrations was the same as in control leaves. BHB treatment resulted in a stimulation of dark respiration. As photosynthesis, photorespiration, and dark respiration were all affected by BHB, the action of BHB on whole leaf metabolism appears to be complex. Substantial inhibition of photorespiration was accompanied by inhibition of photosynthesis and increases in photosynthesis were not observed.

Doravari, Sudarsanam; Canvin, David T.

1980-01-01

259

7 CFR 30.2 - Leaf tobacco.  

Code of Federal Regulations, 2010 CFR

...30.2 Leaf tobacco. Tobacco in the forms in which...manufacturing processes. Leaf tobacco does not include any manufactured or semimanufactured tobacco, stems which have been removed from leaves, cuttings, clippings,...

2009-01-01

260

7 CFR 30.2 - Leaf tobacco.  

Code of Federal Regulations, 2010 CFR

...30.2 Leaf tobacco. Tobacco in the forms in which...manufacturing processes. Leaf tobacco does not include any manufactured or semimanufactured tobacco, stems which have been removed from leaves, cuttings, clippings,...

2010-01-01

261

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

262

Molecular cloning, spatial and temporal characterization of spinach SOGA1 cDNA, encoding an alpha subunit of G protein.  

PubMed

Heterotrimeric G proteins are an important component of signal transduction pathway in animals. Although these proteins have been described in plants, their exact function and action mode are not clearly defined. In order to analyze the relationship between these proteins and the transduction of light signals in spinach, we have isolated by 5' and 3' RACE-PCR a 1660bp cDNA clone called SOGA1. This codes for a 383aa protein, which reveals a very strong homology with other plant Galpha subunit sequences. Genomic analysis suggested that SOGA1 belonged to a small multiple gene family. Northern blots and in-situ hybridization analyses showed that SOGA1 transcripts accumulate in all organs tested with a specific high level associated with the apex, roots and hypocotyls. Finally, a time-course analysis performed on the green tissues showed that accumulation of SOGA1 transcripts follows a circadian rhythm. However, in-situ hybridization analysis of the apex suggested the opposite behavior, while no variation was observed in the hypocotyl. PMID:10806364

Perroud, P F; Diogon, T; Crèvecoeur, M; Greppin, H

2000-05-01

263

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

264

Evidence for a cytochrome f-Rieske protein subcomplex in the cytochrome b6f system from spinach chloroplasts.  

PubMed

The cytochrome b6f complex of spinach chloroplasts was prepared with minor modification according to the method of E. Hurt and G. Hauska (1981) Eur. J. Biochem. 117, 591-599) replacing, however, the final ultracentrifugation step by hydroxyapatite chromatography as suggested by M. F. Doyle and C.-A Yu (1985) Biochem. Biophys. Res. Commun. 131, 700-706). The purified complex was partially dissociated by treatment with 4 M urea or 0.1% sodium dodecyl sulfate (SDS) in the absence of reducing agents. A binary subcomplex consisting of cytochrome f and the Rieske iron-sulfur protein was observed under these conditions by three different methods: (a) hydroxyapatite chromatography; (b) extraction with an isopropanol/water/trifluoroacetic acid mixture; and (c) gel filtration in the presence of low SDS concentrations. The subcomplex dissociated into its components by treatment with mercaptoethanol. These results suggest a close interaction of the cytochrome f with the Rieske protein involving SH groups which under reducing conditions leads to complete dissociation of the subcomplex. PMID:3277532

el-Demerdash, M; Salnikow, J; Vater, J

1988-01-01

265

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 20°C 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

266

LEAF: A Microcomputer Program for Constructing the Tukey Stem and Leaf Graph.  

ERIC Educational Resources Information Center

This paper presents a BASIC microcomputer program that constructs the Tukey (1977) stem and leaf graph. Options within the LEAF program include a modified stem and leaf where the stem is split and a parallel stem and leaf graph where two separate sets of data are displayed from a common stem. (Author)

Pascale, Pietro J.; Smith, Joseph

1986-01-01

267

Modeling Leaf Production and Senescence in Wheat  

Microsoft Academic Search

4 Abstract: A major component in a crop growth model is leaf area development, which has a major influence on photosynthesis and transpiration. The knowledge about the leaf area development of wheat especially in high temperature environments is incomplete. The aim of this study was to quantify leaf production and senescence of 15 spring wheat cultivars. Field experiments were conducted

J. Pourreza; A. Soltani; A. Naderi; A. Aynehband

2009-01-01

268

Hormonal regulation of leaf senescence in Lilium.  

PubMed

In addition to floral senescence and longevity, the control of leaf senescence is a major factor determining the quality of several cut flowers, including Lilium, in the commercial market. To better understand the physiological process underlying leaf senescence in this species, we evaluated: (i) endogenous variation in the levels of phytohormones during leaf senescence, (ii) the effects of leaf darkening in senescence and associated changes in phytohormones, and (iii) the effects of spray applications of abscisic acid (ABA) and pyrabactin on leaf senescence. Results showed that while gibberellin 4 (GA(4)) and salicylic acid (SA) contents decreased, that of ABA increased during the progression of leaf senescence. However, dark-induced senescence increased ABA levels, but did not affect GA(4) and SA levels, which appeared to correlate more with changes in air temperature and/or photoperiod than with the induction of leaf senescence. Furthermore, spray applications of pyrabactin delayed the progression of leaf senescence in cut flowers. Thus, we conclude that (i) ABA plays a major role in the regulation of leaf senescence in Lilium, (ii) darkness promotes leaf senescence and increases ABA levels, and (iii) exogenous applications of pyrabactin inhibit leaf senescence in Lilium, therefore suggesting that it acts as an antagonist of ABA in senescing leaves of cut lily flowers. PMID:22854182

Arrom, Laia; Munné-Bosch, Sergi

2012-10-15

269

Leaf traits and leaf life spans of two xeric-adapted palmettos.  

PubMed

Plants of nutrient-poor, arid environments often have leaf traits that include small size, sclerophylly, long life span, low nutrient concentration, and low photosynthetic rate. Hence, the success of two large-leaved palmettos in peninsular Florida's seasonally xeric, nutrient-impoverished uplands seems anomalous, given that their leaves are orders of magnitude larger than the leaves of sympatric species. An examination of a 16-yr data set of leaf traits and leaf life spans across four vegetative associations differing in available light showed that Serenoa repens and Sabal etonia had low rates of leaf production coupled with long leaf life spans reaching 3.5 yr in heavily shaded plants. The adaptation of these palmettos to xeric, nutrient-poor habitats has generated dwarf statures, diminished leaf sizes and numbers, increased leaf life spans, and reduced rates of leaf production relative to other palms and congeners of more mesic sites. Leaf and petiole size, plant leaf canopy area, and leaf life span increased in both palmettos with decreasing available light, helping to compensate for reduced photosynthetic rates under shaded conditions and for the high leaf construction costs of the large, thick palmetto leaves. Large leaf size in these palmettos, likely due to phylogenetic conservatism, is compensated by other leaf traits (e.g., heavily cutinized epidermises, thick laminas) that increase survival in seasonally xeric, nutrient-impoverished environments. PMID:21636496

Abrahamson, Warren G

2007-08-01

270

Salinity effects on leaf anatomy  

Microsoft Academic Search

Increasing salinity led to substantially higher ratios of mesophyll surface area to leaf area (A\\/sup mes\\/\\/A) for Phaseolus vulgaris and Gossypium hirsutum and a smaller increase for Atriplex patula, a salt-tolerant species. The increase in internal surface for COâ absorption did not lead to higher COâ uptake rates, since the COâ resistance expressed on the basis of mesophyll cell wall

D. J. Longstreth; P. S. Nobel

1979-01-01

271

Biosensor for selective detection of E. coli in spinach using the strong affinity of derivatized mannose with fimbrial lectin.  

PubMed

Escherichia coli (E. coli) contamination in foods and water resources represents a major threat for human health and the environment. This work exploits the strong affinity of mannose-containing oligosaccharides with the fimbrial lectin of E. coli to design novel biosensors. Modified carbohydrate ligands were synthesized by introducing phenyl residues and aliphatic chains to mannose via reductive amination in order to increase both the affinity and selectivity to E. coli compared to other pathogenic bacteria. The synthesized ligands include p-thiolphenyl aminomannose (PTAM), p-carboxyphenyl aminomannose (PCAM), 1-deoxy-1-aminomannopyranoside (DAMP), glucosamine and low molecular weight chitosan bonded to mercapto undecanoic acid. The structures of the ligands were confirmed using (1)H NMR and 1H, (13)C, COZY NMR, and ESI/MS. The ligands were immobilized onto gold electrodes and SPR surfaces using-mercaptoundecanoic acid with glycine as deactivating agent. Two detection mechanisms were tested: (i) metal-enhanced electrochemical detection (MED) and (ii) label-free surface plasmon resonance (SPR) detection. The introduction of phenyl residues and aliphatic side groups to the mannose-containing oligosaccharides produced extremely high affinity for E. coli with detection limit of 1cfu/mL. The relative selectivity of these ligands for E. coli, Citrobacter freundii, Staphylococcus epidermidis were 100%, 2.6% and 8.6% respectively. The biosensors were validated using spinach leaves at 3.0cfu/mL. The work provides a generic biosensor for other pathogenic bacteria by enabling multivalent binding, immediate recognition for pathogens as well as inhibition of bacterial growth. PMID:24906084

Yazgan, Idris; Noah, Naumih M; Toure, Ousmane; Zhang, Siyi; Sadik, Omowunmi A

2014-11-15

272

Alteration of Spinach Ribulose-1,5-Bisphosphate Carboxylase/Oxygenase Activase Activities by Site-Directed Mutagenesis  

PubMed Central

Site-directed mutagenesis was performed on the 1.6 and 1.9 kilobase spinach (Spinacea oleracea) ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) activase cDNAs, encoding the 41 and 45 kilodalton (kD) isoforms of the enzyme, to create single amino acid changes in the putative ATP-binding site of Rubisco activase (Lys-107, Gln-109, and Ser-112) and in an unrelated cysteine residue (Cys-256). Replacement of Lys-107 with Met produced soluble protein with reduced Rubisco activase and ATPase activities in both isoforms. Substituting Ala or Arg for Lys-107 produced insoluble proteins. Rubisco activase activity increased in the 41-kD isoform when Gln-109 was changed to Glu, but activity in the 45-kD isoform was similar to the wild-type enzyme. ATPase activity in the Glu-109 mutations did not parallel the changes in Rubisco activase activity. Rather, a higher ratio of Rubisco activase to ATPase activity occurred in both isoforms. The mutation of Gln-109 to Lys inactivated Rubisco activase activity. Replacement of Ser-112 with Pro created an inactive protein, whereas attempts to replace Ser-112 with Thr were not successful. The mutation of Cys-256 to Ser in the 45-kD isoform reduced both Rubisco activase and ATPase activities. The results indicate that the two activities of Rubisco activase are not tightly coupled and that variations in photosynthetic efficiency may occur in vivo by replacing the wild-type enzyme with mutant enzymes. ImagesFigure 3

Shen, Jennie B.; Ogren, William L.

1992-01-01

273

Reduction of bacteria on spinach, lettuce, and surfaces in food service areas using neutral electrolyzed oxidizing water.  

PubMed

Food safety issues and increases in food borne illnesses have promulgated the development of new sanitation methods to eliminate pathogenic organisms on foods and surfaces in food service areas. Electrolyzed oxidizing water (EO water) shows promise as an environmentally friendly broad spectrum microbial decontamination agent. EO water is generated by the passage of a dilute salt solution ( approximately 1% NaCl) through an electrochemical cell. This electrolytic process converts chloride ions and water molecules into chlorine oxidants (Cl(2), HOCl/ClO(-)). At a near-neutral pH (pH 6.3-6.5), the predominant chemical species is the highly biocidal hypochlorous acid species (HOCl) with the oxidation reduction potential (ORP) of the solution ranging from 800 to 900mV. The biocidal activity of near-neutral EO water was evaluated at 25 degrees C using pure cultures of Escherichia coli, Salmonella typhimurium, Staphylococcus aureus, Listeria monocytogenes, and Enterococcus faecalis. Treatment of these organisms, in pure culture, with EO water at concentrations of 20, 50, 100, and 120ppm total residual chlorine (TRC) and 10min of contact time resulted in 100% inactivation of all five organisms (reduction of 6.1-6.7log(10)CFU/mL). Spray treatment of surfaces in food service areas with EO water containing 278-310ppm TRC (pH 6.38) resulted in a 79-100% reduction of microbial growth. Dip (10min) treatment of spinach at 100 and 120ppm TRC resulted in a 4.0-5.0log(10)CFU/mL reduction of bacterial counts for all organisms tested. Dipping (10min) of lettuce at 100 and 120ppm TRC reduced bacterial counts of E. coli by 0.24-0.25log(10)CFU/mL and reduced all other organisms by 2.43-3.81log(10)CFU/mL. PMID:17993375

Guentzel, Jane L; Liang Lam, Kang; Callan, Michael A; Emmons, Stuart A; Dunham, Valgene L

2008-02-01

274

Roles of ATP and NADPH in formation of the Fe-S cluster of spinach ferredoxin. [Spinacia oleracea  

SciTech Connect

The present study investigated whether ATP and NADPH in the chloroplast system of spinach (Spinacia oleracea) are involved in the supply of ({sup 35}S)sulfide or iron, or in Fe-S cluster formation itself. ({sup 35}S)Sulfide was liberated from ({sup 35}S)cysteine in an NADPH-dependent manner, whereas ATP was not necessary for this process. This desulfhydration of ({sup 35}S)cysteine occurred before the formation of the {sup 35}S-labeled Fe-S cluster, and the amount of radioactivity in ({sup 35}S)sulfide was greater than that in {sup 35}S-labeled holo-Fd by a factor of more than 20. Addition of nonradioactive sulfide (Na{sub 2}S) inhibited competitively formation of the {sup 35}S-labeled Fe-S cluster along with the addition of nonradioactive cysteine, indicating that some of the inorganic sulfide released from cysteine is incorporated into the Fe-S cluster of Fd. ATP hydrolysis was not involved in the production of inorganic sulfide or in the supply of iron for assembly into the Fe-S cluster. However, ATP-dependent Fe-S cluster formation was observed even in the presence of sufficient amounts of ({sup 35}S)sulfide and iron. These results suggest a novel type of ATP-dependent in vivo Fe-S cluster formation that is distinct from in vitro chemical reconstitution. The implications of these results for the possible mechanisms of ATP-dependent Fe-S cluster formation are discussed.

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

1991-01-01

275

Electrostatic sprays of food-grade acids and plant extracts are more effective than conventional sprays in decontaminating Salmonella Typhimurium on spinach.  

PubMed

About 40000 people fall victim to Salmonella infections every year in the United States. Recent occurrences of Salmonella contaminated spinach and its recalls have accelerated the need for efficient antimicrobials targeting these pathogens. Our study was aimed at evaluating the inhibitory properties of malic, tartaric, and lactic acids, and grape seed extract (GSE) alone and in combinations and their application methods against Salmonella Typhimurium-inoculated spinach using a response surface method. Fresh spinach leaves were washed, disinfected with sodium hypochlorite solution (0.04% v/v), rewashed with sterile deionized (DI) water, and inoculated with a 2nd-day culture of S. Typhimurium (7.0 log CFU/mL). Adhered S. Typhimurium population on day 0 were 7.5 log CFU/g. These were treated with individual and combinations of organic acids with GSE or DI water (control) adjusted to the same pH as that of the test solutions with both the modes of application and leaves were refrigerated at 4 °C. Malic acid (2%) in combination with GSE (3%) or lactic acid (3%) sprayed electrostatically showed reductions of 2.6 to 3.3 log CFU/g compared to lower log reductions (0.0 to 0.3 log CFU/g) by day 14 if sprayed conventionally. These findings indicate that malic acid in combination with GSE/lactic acid solutions applied by electrostatic spraying exhibited higher inhibition of pathogens than conventional spraying and can be used for commercial applications to enhance food safety. PMID:21535613

Ganesh, Vijayalakshmi; Hettiarachchy, Navam S; Ravichandran, Madhuram; Johnson, Michael G; Griffis, Carl L; Martin, Elizabeth M; Meullenet, Jean-Francois; Ricke, Steven C

2010-01-01

276

Farm management, environment, and weather factors jointly affect the probability of spinach contamination by generic Escherichia coli at the preharvest stage.  

PubMed

The National Resources Information (NRI) databases provide underutilized information on the local farm conditions that may predict microbial contamination of leafy greens at preharvest. Our objective was to identify NRI weather and landscape factors affecting spinach contamination with generic Escherichia coli individually and jointly with farm management and environmental factors. For each of the 955 georeferenced spinach samples (including 63 positive samples) collected between 2010 and 2012 on 12 farms in Colorado and Texas, we extracted variables describing the local weather (ambient temperature, precipitation, and wind speed) and landscape (soil characteristics and proximity to roads and water bodies) from NRI databases. Variables describing farm management and environment were obtained from a survey of the enrolled farms. The variables were evaluated using a mixed-effect logistic regression model with random effects for farm and date. The model identified precipitation as a single NRI predictor of spinach contamination with generic E. coli, indicating that the contamination probability increases with an increasing mean amount of rain (mm) in the past 29 days (odds ratio [OR] = 3.5). The model also identified the farm's hygiene practices as a protective factor (OR = 0.06) and manure application (OR = 52.2) and state (OR = 108.1) as risk factors. In cross-validation, the model showed a solid predictive performance, with an area under the receiver operating characteristic (ROC) curve of 81%. Overall, the findings highlighted the utility of NRI precipitation data in predicting contamination and demonstrated that farm management, environment, and weather factors should be considered jointly in development of good agricultural practices and measures to reduce produce contamination. PMID:24509926

Park, Sangshin; Navratil, Sarah; Gregory, Ashley; Bauer, Arin; Srinath, Indumathi; Szonyi, Barbara; Nightingale, Kendra; Anciso, Juan; Jun, Mikyoung; Han, Daikwon; Lawhon, Sara; Ivanek, Renata

2014-04-01

277

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

278

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, René; Cepeda, Martha; Mazari-Hiriart, Marisa; Mena, Kristi D; Pillai, Suresh D

2012-02-01

279

Ontogenetic changes in leaf phenology of two co-occurring Mediterranean oaks differing in leaf life span  

Microsoft Academic Search

Large differences in leaf physiology and morphology between ontogenetic stages of a single woody species have often been observed.\\u000a Far less attention, however, has been devoted to studying the ontogenetic changes observed in leaf phenology patterns, despite\\u000a the relevance of leaf phenology in determining the leaf carbon balance and leaf and plant mortality. Leaf emergence patterns\\u000a and leaf longevity were

Sonia Mediavilla; Alfonso Escudero

2009-01-01

280

Leaf wetness within a lily canopy  

NASA Astrophysics Data System (ADS)

A wetness duration experiment was carried out within a lily field situated adjacent to coastal dunes in the Netherlands. A within-canopy model was applied to simulate leaf wetness in three layers, with equal leaf area indices, within the canopy. This simulation model is an extension of an existing model. It appeared that in most cases leaf wetness started in the uppermost layer followed by the middle and bottom layer, respectively. The same occurred during the early morning drying process. Just after sunrise the upper layer started to dry, followed by the middle and bottom layer, respectively. The longest leaf wetness duration occurred in the bottom layer. The calculated leaf wetness durations were within 10 minutes of the results obtained using a leaf wetness sensor.

Jacobs, Adrie F. G.; Heusinkveld, Bert G.; Klok, Elisabeth J.

2005-09-01

281

Response of Leafy Vegetable Kalmi (Water Spinach; Ipomoea aquatica L.) at Elevated Concentrations of Arsenic in Hydroponic Culture  

Microsoft Academic Search

Effects of elevated arsenic (As) concentrations on hydroponic Kalmi (Ipomoea aquatica L.) were investigated. Plants were treated with 0, 10, 25, and 50 ?M As in the greenhouse for 14 days. Arsenic was added\\u000a from sodium meta-arsenite (NaAsO2). Visible toxicity symptom could not easily be recognized without visible growth reduction. Little brown spots on the leaf\\u000a blade were found at 50 ?M As

Molla Rahman Shaibur; Tamanna Islam; Shigenao Kawai

2009-01-01

282

Identification of plastoquinone-C in spinach and maple leaves by reverse-phase high-performance liquid chromatography  

Microsoft Academic Search

To reinvestigate whether the plastoquinone-C (PQ-C) identified in chloroplasts in the 60's is a natural component or an isolation artefact as suggested by some authors, we used a gentle and fast extraction procedure followed by direct RP–HPLC separation of the whole leaf extract in a solvent system which enables separation of both the reduced and oxidised forms of plastoquinone-A (PQ-A,

Jerzy Kruk; Kazimierz Strza?ka

1998-01-01

283

Insect leaf mines from the Eocene Anglesea locality, Victoria, Australia  

Microsoft Academic Search

The first Tertiary leaf mines described from Australia are six mines from the Anglesea locality in Victoria. They are referable to five leaf mining taxa. Two of the mines are associated with a Lauraceae leaf. A third leaf mine is preserved in a ‘mummified’ leaf with affinities to Elaeocarpaceae. The remaining two mines are on leaves that are too poorly

A. C. Rozefelds

1988-01-01

284

7 CFR 28.467 - Leaf Grade 7.  

Code of Federal Regulations, 2010 CFR

... 2009-01-01 2009-01-01 false Leaf Grade 7. 28.467 Section 28.467 Agriculture...Cotton Standards of the United States for the Leaf Grade of American Upland Cotton § 28.467 Leaf Grade 7. Leaf Grade 7 is leaf which...

2009-01-01

285

Classification and quantification of leaf curvature  

PubMed Central

Various mutants of Arabidopsis thaliana deficient in polarity, cell division, and auxin response are characterized by certain types of leaf curvature. However, comparison of curvature for clarification of gene function can be difficult without a quantitative measurement of curvature. Here, a novel method for classification and quantification of leaf curvature is reported. Twenty-two mutant alleles from Arabidopsis mutants and transgenic lines deficient in leaf flatness were selected. The mutants were classified according to the direction, axis, position, and extent of leaf curvature. Based on a global measure of whole leaves and a local measure of four regions in the leaves, the curvature index (CI) was proposed to quantify the leaf curvature. The CI values accounted for the direction, axis, position, and extent of leaf curvature in all of the Arabidopsis mutants grown in growth chambers. Comparison of CI values between mutants reveals the spatial and temporal variations of leaf curvature, indicating the strength of the mutant alleles and the activities of the corresponding genes. Using the curvature indices, the extent of curvature in a complicated genetic background becomes quantitative and comparable, thus providing a useful tool for defining the genetic components of leaf development and to breed new varieties with leaf curvature desirable for the efficient capture of sunlight for photosynthesis and high yields.

Liu, Zhongyuan; Jia, Liguo; Mao, Yanfei; He, Yuke

2010-01-01

286

Structural Basis of Efficient Electron Transport between Photosynthetic Membrane Proteins and Plastocyanin in Spinach Revealed Using Nuclear Magnetic Resonance[C][W][OA  

PubMed Central

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 b6f (cyt b6f) and photosystem I (PSI). The rapid turnover of Pc between cyt b6f and PSI enables the efficient use of light energy. In the Pc-cyt b6f 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 b6f, 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 b6f, whereas the acidic patch residues of Pc do not form stable salt bridges with either PSI or cyt b6f, in the electron transfer complexes. The transient characteristics of the interactions on the acidic patch facilitate the rapid association and dissociation of Pc.

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

2012-01-01

287

Same-day detection of Escherichia coli O157:H7 from spinach by using electrochemiluminescent and cytometric bead array biosensors.  

PubMed

Contamination of fresh produce with Escherichia coli O157:H7 and other pathogens commonly causes food-borne illness and disease outbreaks. Thus, screening for pathogens is warranted, but improved testing procedures are needed to allow reproducible same-day detection of low initial contamination levels on perishable foods, and methods for detecting numerous pathogens in a single test are desired. Experimental procedures were developed to enable rapid screening of spinach for E. coli O157:H7 by using multiplex-capable immunological assays that are analyzed using biosensors. Detection was achieved using an automated electrochemiluminescent (ECL) assay system and a fluorescence-based cytometric bead array. Using the ECL system, less than 0.1 CFU of E. coli O157:H7 per gram of spinach was detected after 5 h of enrichment, corresponding to 6.5 h of total assay time. Using the cytometric bead array, less than 0.1 CFU/g was detected after 7 h of enrichment, with a total time to detection of less than 10 h. These results illustrate that both biosensor assays are useful for rapid detection of E. coli O157:H7 on produce in time frames that are comparable to or better than those of other testing formats. Both methods may be useful for multiplexed pathogen detection in the food industry and other testing situations. PMID:21037307

Leach, Kelly M; Stroot, Joyce M; Lim, Daniel V

2010-12-01

288

Salinity Effects on Leaf Anatomy  

PubMed Central

Increasing salinity led to substantially higher ratios of mesophyll surface area to leaf area (Ames/A) for Phaseolus vulgaris and Gossypium hirsutum and a smaller increase for Atriplex patula, a salt-tolerant species. The increase in internal surface for CO2 absorption did not lead to higher CO2 uptake rates, since the CO2 resistance expressed on the basis of mesophyll cell wall area (rcell) increased even more with salinity. The differences among species in the sensitivity of photosynthesis to salinity in part reflect the different Ames/A and rcell responses.

Longstreth, David J.; Nobel, Park S.

1979-01-01

289

Photoinactivation of the F1-ATPase from spinach chloroplasts by dequalinium is accompanied by derivatization of methionine beta183.  

PubMed

In contrast to the F1-ATPases from bovine mitochondria and the thermophilic Bacillus PS3, which are reversibly inhibited by dequalinium in the absence of irradiation, the Mg2+-ATPase activity of heat- or dithiothreitol-activated chloroplast F1 (CF1) from spinach chloroplasts is slightly stimulated by dequalinium. Conversely, dequalinium is a partial inhibitor (maximal inhibition is 85-90%) of the Ca2+-ATPase of CF1 activated by heat, dithiothreitol, or octylglucoside. The Mg2+- and Ca2+-ATPase activities of CF1 respond differently in the presence of lauryl dimethylamine oxide (LDAO) in the assay medium. Whereas the Mg2+-ATPase activity of heat- or dithiothreitol-activated CF1 is stimulated up to 14-fold by increasing concentrations of LDAO, the Ca2+-ATPase is inhibited in a biphasic manner by increasing concentrations of LDAO. In the presence of LDAO, dequalinium does not stimulate the heat-activated Mg2+-ATPase over that promoted by LDAO alone. That dequalinium slightly stimulates Mg2+-ATPase activity although it inhibits Ca2+-ATPase activity can be reconciled by assuming that dequalinium binds to two sites in CF1, a stimulatory site that also binds LDAO and an inhibitory site. By acting as a partial inhibitor of the Mg2+-ATPase activity that it activates, the combined effect of dequalinium is modest stimulation. Irradiation of heat- or dithiothreitol-activated CF1 or the alpha3beta3gamma subcomplex of CF1 in the presence of 12 microM dequalinium led to rapid photoinactivation. ATP and ADP, separately or in combination with Mg2+, protect against photoinactivation. After photoinactivating the alpha3beta3gamma subcomplex of CF1 with [14C]dequalinium, tryptic and peptic digests of the isolated, derivatized beta subunit were fractionated by high performance liquid chromatography. Sequencing of the isolated, radioactive tryptic and peptic peptides revealed that Metbeta183, which is at or near the catalytic site, is derivatized in a single beta subunit when CF1 is photoinactivated with [14C]dequalinium. PMID:9405435

Ren, H M; Allison, W S

1997-12-19

290

Partial purification and characterization of an insulin-like material from spinach and Lemna gibba G3.  

PubMed

The existence in invertebrates, unicellular eukaryotes, and prokaryotes of materials that resemble several vertebrate peptide hormones led to the suggestion that these peptide messengers may have arisen earlier in evolution than had previously been thought. Consistent with this hypothesis, we describe here material in two plants, spinach and Lemma gibba G3, that is very similar to mammalian insulin, yet distinctive. In each of the early purification steps, which consisted of acidic methanol chloroform extraction and sequential chromatography on C-18 hydrophobic resin, Sephadex G-50, CM-Sepharose, and a short C-3 high performance liquid chromatography column, the immunoactive material from plants resembled the common vertebrate insulins. The protein nature of the material was suggested by its destruction by Pronase but not by the inactivated enzyme. In addition, on TSK chromatography it eluted in a position similar to that of insulin, i.e. equivalent to a protein of 6000 daltons. Using an isocratic high performance liquid chromatography system, the plant immunoactivity eluted earlier, and thus was more hydrophilic, than most of the common mammalian insulins, including pork insulin. The interaction of the plant material with anti-insulin antibodies in a radioimmunoassay was confirmed by using an affinity column of anti-insulin antibodies which adsorbed the plant immunoactivity at neutral pH, and released the material with acid elution. Using a quantitative double radioimmunoassay, the plant insulin-like material was distinguished immunologically from chicken insulin. Although the plant insulin-like material is clearly distinct from pork insulin chromatographically, and from chicken insulin immunologically, it resembles vertebrate insulins in its overall configuration. The plant insulin-like material bound to insulin receptors on IM-9 lymphocytes and stimulated glucose oxidation and lipogenesis in isolated adipocytes from young rats. The bioactivity was neutralized in the presence of anti-insulin antibodies, but not in the presence of normal guinea pig IgG. The role of this insulin-like material in plants is unknown but its existence is consistent with an early evolutionary origin of the insulin messenger peptide family. Alternatively we cannot exclude a later convergent development of this family or introduction of vertebrate DNA into plants. PMID:3553187

Collier, E; Watkinson, A; Cleland, C F; Roth, J

1987-05-01

291

Chloroplast Response to Low Leaf Water Potentials  

PubMed Central

Cyclic and noncyclic photophosphorylation and electron transport by photosystem 1, photosystem 2, and from water to methyl viologen (“whole chain”) were studied in chloroplasts isolated from sunflower (Helianthus annus L. var Russian Mammoth) leaves that had been desiccated to varying degrees. Electron transport showed considerable inhibition at leaf water potentials of ?9 bars when the chloroplasts were exposed to an uncoupler in vitro, and it continued to decline in activity as leaf water potentials decreased. Electron transport by photosystem 2 and coupled electron transport by photosystem 1 and the whole chain were unaffected at leaf water potentials of ?10 to ?11 bars but became progressively inhibited between leaf water potentials of ?11 and ?17 bars. A low, stable activity remained at leaf water potentials below ?17 bars. In contrast, both types of photophosphorylation were unaffected by leaf water potentials of ?10 to ?11 bars, but then ultimately became zero at leaf water potentials of ?17 bars. Although the chloroplasts isolated from the desiccated leaves were coupled at leaf water potentials of ?11 to ?12 bars, they became progressively uncoupled as leaf water potentials decreased to ?17 bars. Abscisic acid and ribonuclease had no effect on chloroplast photophosphorylation. The results are generally consistent with the idea that chloroplast activity begins to decrease at the same leaf water potentials that cause stomatal closure in sunflower leaves and that chloroplast electron transport begins to limit photosynthesis at leaf water potentials below about ?11 bars. However, it suggests that, during severe desiccation, the limitation may shift from electron transport to photophosphorylation.

Keck, R. W.; Boyer, J. S.

1974-01-01

292

"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

293

7 CFR 29.2437 - Heavy Leaf (B Group).  

Code of Federal Regulations, 2010 CFR

...Dark-brown Heavy Leaf. Heavy, mature, close, lean in oil, inelastic, weak...Dark-brown Heavy Leaf. Heavy, mature, close, lean in oil, inelastic, weak...Leaf. Medium to heavy body, mature, close, lean in oil, inelastic,...

2010-01-01

294

7 CFR 29.2437 - Heavy Leaf (B Group).  

Code of Federal Regulations, 2010 CFR

...Dark-brown Heavy Leaf. Heavy, mature, close, lean in oil, inelastic, weak...Dark-brown Heavy Leaf. Heavy, mature, close, lean in oil, inelastic, weak...Leaf. Medium to heavy body, mature, close, lean in oil, inelastic,...

2009-01-01

295

Leaf Morphology Affects Horseradish Regeneration In Vitro  

Microsoft Academic Search

The morphology of horseradish (Armoracia rusticana P. Gaertn., B. Mey & Scherb.) leaves varies through the growing season. The leaves range from laminate (complete) in the summer to pinnate (fern-leaf) toward the end of the growing season in the fall, with intermediate types appearing regularly. The causes of these changes are not understood. To determine whether leaf morphology affects their

A. M. Shehata; R. M. Skirvin; M. A. Norton

2008-01-01

296

Leaf peroxidase isozyme polymorphism of wild apple  

Microsoft Academic Search

The main aims of the study were to reveal the isozyme resemblances in the leaf peroxidase of wild apple and to define the traits related to the identification of Malus sylvestris Mill. The results of the study are based on leaf isozyme analysis of seven progenies selected according to the specific features of mother trees at their natural sites from

R. Petrokas; V. Stanys

2008-01-01

297

Leaf litter decomposition in three Adirondack lakes  

SciTech Connect

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, carbon, nitrogen, and bacterial populations. The rate of decomposition of litter depended on the leaf species tested as well as on the lake water in which they were incubated. Of the five leaf species tested, red maple decomposed much faster and red spruce more slowly, i.e., red maple > sugar maple > beech > leather leaf > red spruce. Further, the data indicated that the rate of decomposition of the leaves differed among the lakes in the order Woods (pH approx. 5) < Sagamore (pH approx. 6) < Panther (pH approx. 7), and that the microbial colonization of some leaf species was affected. Accumulations of leaf litter in acid lakes due to reduction in microbial decomposition may affect nutrient recycling in lake ecosystems. 8 references, 4 tables.

Francis, A.J.; Quinby, H.L.; Hendrey, G.R.; Hoogendyk, C.G.

1983-04-01

298

Leaf and Air Temperature under Hawaii Conditions  

Microsoft Academic Search

During the daylight hours pineapple leaf tem ­ per ature was consistently higher than the air temperature measured in an instrument shelter at the same elevation as the plants. The values usually ranged from 1.5° to 3.5° C. above the air temperature but occasionally a leaf exp osed to direct sunlight had a temperature as mu ch as 7.6 °

T. L. NOFFSINGER

299

Carrot red leaf virus in Israel  

Microsoft Academic Search

Carrot (Daucus carota) plants in commercial fields in Israel quite often evince symptoms of leaf reddening (mainly of older leaves), leaf yellowing, and sometimes plant stunting. These symptoms were observed mainly on plants near the edges of the fields and they were attributed to trace element deficiencies, herbicide drifts and low temperature injuries. Incidence of symptomcarrying plants varied in different

S. Marco

1993-01-01

300

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

301

Leaf epifauna of the seagrass Thalassia testudinum  

Microsoft Academic Search

The abundance, composition and trophic relationships of metazoan leaf epifauna of the marine angiosperm Thalassia testudinum König were studied in Barbados, West Indies. Approximately 90 species from 11 phyla consisted chiefly of nematodes, harpacticoid copepods, crustacean nauplii, ostracods, and turbellarians. Epiflora- and detritus-feeders dominated the epifauna. Increasing leaf epiphytism was accompanied by faunal changes, most notably increased nematode, harpacticoid and

J. B. Lewis; C. E. Hollingworth

1982-01-01

302

Leaf Histology--Two Modern Methods.  

ERIC Educational Resources Information Center

Two methods for examining leaf structure are presented; both methods involve use of "superglue." The first method uses the glue to form a thin, permanent, direct replica of a leaf surface on a microscope slide. The second method uses the glue to examine the three-dimensional structure of spongy mesophyll. (JN)

Freeman, H. E.

1984-01-01

303

The red edge of plant leaf reflectance  

Microsoft Academic Search

The red edge is the sharp change in leaf reflectance between 680 and 750 nm and has been measured on leaves of a variety of species by first derivative reflectance spectrophotometry. A parameter ?re was defined as the wavelength of maximum slope and found to be dependent on chlorophyll concentration (p<0.001), with additional effects of species, developmental stage, leaf layering

D. N. H. Horler; M. Dockray; J. Barber

1983-01-01

304

Comparative enzymology of the adenosine triphosphate sulphurylases from leaf tissue of selenium-accumulator and non-accumulator plants.  

PubMed

1. ATP sulphurylases were partially purified (20-40-fold) from leaf tissue of Astragalus bisulcatus, Astragalus racemosus (selenium-accumulator species) and Astragalus hamosus and Astragalus sinicus (non-accumulator species). Activity was measured by sulphate-dependent PP(i)-ATP exchange. The enzymes were separated from pyrophosphatase and adenosine triphosphatase activities. The properties of the Astragalus ATP sulphurylases were similar to the spinach enzyme. 2. The ATP sulphurylases from both selenium-accumulator and non-accumulator species catalysed selenate-dependent PP(i)-ATP exchange; selenate competed with sulphate. The ratio of V(selenate)/V(sulphate) and K(m)(selenate)/K(m)(sulphate) was approximately the same for the enzyme from each species. 3. Sulphate-dependent PP(i)-ATP exchange was inhibited by ADP, chlorate and nitrate. The kinetics of the inhibition for each enzyme were consistent with an ordered reaction mechanism, in which ATP is the first substrate to react with the enzyme and PP(i) is the first product released. 4. Synthesis of adenosine 5'-[(35)S]sulphatophosphate from [(35)S]sulphate was demonstrated by coupling the Astragalus ATP sulphurylases with Mg(2+)-dependent pyrophosphatase; the reaction was inhibited by selenate. An analogous reaction using [(75)Se]selenate as substrate could not be demonstrated. PMID:4377098

Shaw, W H; Anderson, J W

1974-04-01

305

Physiological, anatomical and leaf hydraulic effects on leaf water ?18O enrichment in different plant species  

NASA Astrophysics Data System (ADS)

Stable oxygen isotope ratios (?18O) of plant and source waters are valuable tools in the analysis of water and carbon fluxes at leaf, plant, and ecosystem scales. Recent improvements in mechanistic models have significantly advanced the understanding of isotopic leaf water enrichment, which is an important source of ?18O variability in plants and ecosystems. However, the marked variability in leaf water ?18O values that have been reported for different plant species hampers efforts to interpret and then apply data on leaf water ?18O values for studies conducted at the ecosystem scale. To improve the understanding and application of ?18O values in leaf water, we tested the interplay of physiological, morphological, anatomical and leaf hydraulic properties as drivers of leaf water ?18O values across 17 Eucalyptus species growing in a common garden. We observed large differences in leaf water ?18O across the 17 species. These differences were only partly driven by physiological and leaf morphological differences across species. A sensitivity analysis using state-of-the-art leaf water enrichment models showed that the parameter - effective path length - (L) is of critical importance for the variability of leaf water ?18O across different species. The data show that L can be related to a suite of leaf properties that include physiology, anatomy and hydraulics. Consequently, consideration of leaf properties will significantly improve the interpretation of ?18O values in leaf water across different plant species and will therefore help in the application of ?18O values in carbon and water cycle assessments at both the plant and the ecosystem scale.

Kahmen, A.; Arndt, S. K.; Dawson, T. E.

2007-12-01

306

Two WUSCHEL-related homeobox genes, narrow leaf2 and narrow leaf3, control leaf width in rice.  

PubMed

Leaf shape is one of the key determinants of plant architecture. Leaf shape also affects the amount of sunlight captured and influences photosynthetic efficiency; thus, it is an important agronomic trait in crop plants. Understanding the molecular mechanisms governing leaf shape is a central issue of plant developmental biology and agrobiotechnology. Here, we characterized the narrow-leaf phenotype of FL90, a linkage tester line of rice (Oryza sativa). Light and scanning electron microscopic analyses of FL90 leaves revealed defects in the development of marginal regions and a reduction in the number of longitudinal veins. The narrow-leaf phenotype of FL90 shows a two-factor recessive inheritance and is caused by the loss of function of two WUSCHEL-related homeobox genes, NAL2 and NAL3 (NAL2/3), which are duplicate genes orthologous to maize NS1 and NS2 and to Arabidopsis PRS. The overexpression of NAL2/3 in transgenic rice plants results in wider leaves containing increased numbers of veins, suggesting that NAL2/3 expression regulates leaf width. Thus, NAL2/3 can be used to modulate leaf shape and improve agronomic yield in crop plants. PMID:23420902

Ishiwata, Aiko; Ozawa, Misa; Nagasaki, Hiroshi; Kato, Makio; Noda, Yusaku; Yamaguchi, Takahiro; Nosaka, Misuzu; Shimizu-Sato, Sae; Nagasaki, Akie; Maekawa, Masahiko; Hirano, Hiro-Yuki; Sato, Yutaka

2013-05-01

307

Verticillium dahliae Race 2-Specific PCR Reveals a High Frequency of Race 2 Strains in Commercial Spinach Seed Lots and Delineates Race Structure.  

PubMed

ABSTRACT Two pathogenic races of Verticillium dahliae have been described on lettuce and tomato. Host resistance to race 1 is governed by plant immune receptors that recognize the race 1-specific fungal effector Ave1. Only partial resistance to race 2 exists in lettuce. Although polymerase chain reaction (PCR) assays are available to identify race 1, no complementary test exists to positively identify race 2, except for lengthy pathogenicity assays on host differentials. Using the genome sequences of two isolates of V. dahliae, one each from races 1 and 2, we identified potential markers and PCR primers to distinguish the two races. Several primer pairs based on polymorphisms between the races were designed and tested on reference isolates of known race. One primer pair, VdR2F-VdR2R, consistently yielded a 256-bp amplicon in all race 2 isolates exclusively. We screened DNA from 677 V. dahliae isolates, including 340 from spinach seedlots, with the above primer pair and a previously published race 1-specific primer pair. DNA from isolates that did not amplify with race 1-specific PCRs amplified with the race 2-specific primers. To validate this, two differential lines of lettuce were inoculated with 53 arbitrarily selected isolates from spinach seed and their pathogenicity and virulence were assessed in a greenhouse. The reactions of the differential cultivars strongly supported the PCR data. V. dahliae race structure was investigated in crops in coastal California and elsewhere using primers specific to the two races. All artichoke isolates from California were race 1, whereas nearly all tomato isolates were race 2. Isolates from lettuce, pepper, and strawberry from California as well as isolates from spinach seed from two of four countries comprised both races, whereas only race 2 was observed in cotton, mint, olive, and potato. This highlights the importance of identifying resistance against race 2 in different hosts. The technique developed in this study will benefit studies in ecology, population biology, disease surveillance, and epidemiology at local and global scales, and resistance breeding against race 2 in lettuce and other crops. PMID:24502204

Short, Dylan P G; Gurung, Suraj; Maruthachalam, Karunakaran; Atallah, Zahi K; Subbarao, Krishna V

2014-07-01

308

Leaf succulence determines the interplay between carboxylase systems and light use during Crassulacean acid metabolism in Kalanchöe species.  

PubMed

The photosynthetic physiology of Crassulacean acid metabolism was investigated in two Kalanchoë species with differing leaf succulence. The magnitude of CAM was higher for the more succulent leaves of K. daigremontiana, compared to the less succulent leaves of K. pinnata. High succulence was related to low mesophyll conductance: K. pinnata was able to maximize diurnal carbon gain by the C(3) pathway, whereas increased succulence is associated with a higher commitment to the CAM cycle in K. daigremontiana. The Rubisco specificity factor, tau, determining selectivity for CO(2) over O(2), was similar for both species (approximately 88), and lower than that of Spinacea (approximately 95), but in contrast to C(4) plants, the Rubisco K(mCO(2)) (determined independently) was also lower in Kalanchoë spp. than in spinach. Differences in light use were related to the nature of the sink strength in each Phase of CAM, with PEPC activity resulting in low electron transport rates. Decarboxylation was marked by high, non-saturated rates of electron transport, with Rubisco activity and activation state increasing in both species during the course of the light period. The degree of succulence, and extent of CAM activity, was associated with a progressive inhibition of PSII photochemistry and potential Rubisco activity during the night in both species. Rubisco could be 'woken up' more rapidly in K. pinnata, whereas 45 min light acclimation was required for full recovery of electron transport and Rubisco activity in K. daigremontiana. Leaf morphology therefore seems to alter the expression of and dependence on CAM, but also the extent of co-regulation of carboxylase networks and light use capacity. PMID:18408219

Griffiths, Howard; Robe, Wendy E; Girnus, Jan; Maxwell, Kate

2008-01-01

309

Are leaf physiological traits related to leaf water isotopic enrichment in restinga woody species?  

PubMed

During plant-transpiration, water molecules having the lighter stable isotopes of oxygen and hydrogen evaporate and diffuse at a faster rate through the stomata than molecules having the heavier isotopes, which cause isotopic enrichment of leaf water. Although previous models have assumed that leaf water is well-mixed and isotopically uniform, non-uniform stomatal closure, promoting different enrichments between cells, and different pools of water within leaves, due to morpho-physiological traits, might lead to inaccuracies in isotopic models predicting leaf water enrichment. We evaluate the role of leaf morpho-physiological traits on leaf water isotopic enrichment in woody species occurring in a coastal vegetation of Brazil known as restinga. Hydrogen and oxygen stable isotope values of soil, plant stem and leaf water and leaf traits were measured in six species from restinga vegetation during a drought and a wet period. Leaf water isotopic enrichment relative to stem water was more homogeneous among species during the drought in contrast to the wet period suggesting convergent responses to deal to temporal heterogeneity in water availability. Average leaf water isotopic enrichment relative to stem water during the drought period was highly correlated with relative apoplastic water content. We discuss this observation in the context of current models of leaf water isotopic enrichment as a function of the Péclet effect. We suggest that future studies should include relative apoplastic water content in isotopic models. PMID:24068091

Rosado, Bruno H P; De Mattos, Eduardo A; Sternberg, Leonel Da S L

2013-09-01

310

Leaf wetness distribution within a potato crop  

NASA Astrophysics Data System (ADS)

The Netherlands has a mild maritime climate and therefore the major interest in leaf wetness is associated with foliar plant diseases. During moist micrometeorological conditions (i.e. dew, fog, rain), foliar fungal diseases may develop quickly and thereby destroy a crop quickly. Potato crop monocultures covering several hectares are especially vulnerable to such diseases. Therefore understanding and predicting leaf wetness in potato crops is crucial in crop disease control strategies. A field experiment was carried out in a large homogeneous potato crop in the Netherlands during the growing season of 2008. Two innovative sensor networks were installed as a 3 by 3 grid at 3 heights covering an area of about 2 hectares within two larger potato crops. One crop was located on a sandy soil and one crop on a sandy peat soil. In most cases leaf wetting starts in the top layer and then progresses downward. Leaf drying takes place in the same order after sunrise. A canopy dew simulation model was applied to simulate spatial leaf wetness distribution. The dew model is based on an energy balance model. The model can be run using information on the above-canopy wind speed, air temperature, humidity, net radiation and within canopy air temperature, humidity and soil moisture content and temperature conditions. Rainfall was accounted for by applying an interception model. The results of the dew model agreed well with the leaf wetness sensors if all local conditions were considered. The measurements show that the spatial correlation of leaf wetness decreases downward.

Heusinkveld, B. G.

2010-07-01

311

An Apparent Anomaly in Peanut Leaf Conductance  

PubMed Central

Conductance to gaseous transfer is normally considered to be greater from the abaxial than from the adaxial side of a leaf. Measurements of the conductance to water vapor of peanut leaves (Arachis hypogaea L.) under well watered and stress conditions in a controlled environment, however, indicated a 2-fold higher conductance from the adaxial side of the leaf than from the abaxial. Studies of conductance as light level was varied showed an increase in conductance from either surface with increasing light level, but conductance was always greater from the adaxial surface at any given light level. In contrast, measurements of soybean (Glycine max [L.] Merr.) and snapbean (Phaseolus vulgaris L.) leaf conductance showed an approximate 2-fold greater conductance from the abaxial surface than from the adaxial. Approximately the same number of stomata were present on both peanut leaf surfaces and stomatal size was similar. Electron microscopic examination of peanut leaves did not reveal any major structural differences between stomata on the two surfaces that would account for the differences in conductance. Light microscope studies of leaf sections revealed an extensive network of bundle sheaths with achloraplastic bundle sheath extensions; the lower epidermis was lined with a single layer of large achloraplastic parenchyma cells. Measurements of net photosynthesis made on upper and lower leaf surfaces collectively and individually indicated that two-thirds of the peanut leaf's total net photosynthesis can be attributed to diffusion of CO2 through the adaxial leaf surface. Possibly the high photosynthetic efficiency of peanut cultivars as compared with certain other C3 species is associated with the greater conductance of CO2 through their upper leaf surfaces. Images

Pallas, James E.

1980-01-01

312

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

313

Fossil leaf economics quantified: calibration, Eocene case study, and implications  

Microsoft Academic Search

Leaf mass per area (MA) is a central ecological trait that is intercorrelated with leaf life span, photosynthetic rate, nutrient concentration, and palatability to herbivores. These coordinated variables form a globally convergent leaf economics spectrum, which represents a general continuum running from rapid resource acquisition to maximized resource retention. Leaf economics are little studied in ancient ecosystems because they cannot

Dana L. Royer; Lawren Sack; Peter Wilf; Christopher H. Lusk; Gregory J. Jordan; Ülo Niinemets; Ian J. Wright; Mark Westoby; Bárbara Cariglino; Phyllis D. Coley; Asher D. Cutter; Kirk R. Johnson; Conrad C. Labandeira; Angela T. Moles; Matthew B. Palmer; Fernando Valladares

2007-01-01

314

7 CFR 28.516 - Leaf Grade No. 6.  

Code of Federal Regulations, 2010 CFR

... 2009-01-01 2009-01-01 false Leaf Grade No. 6. 28.516 Section 28.516...Cotton Standards of the United States for the Leaf Grade of American Pima Cotton § 28.516 Leaf Grade No. 6. Leaf grade No. 6 shall...

2009-01-01

315

7 CFR 28.471 - Below Leaf Grade Cotton.  

Code of Federal Regulations, 2010 CFR

...2009-01-01 2009-01-01 false Below Leaf Grade Cotton. 28.471 Section 28.471...TESTING, AND STANDARDS Standards Below Leaf Grade Cotton § 28.471 Below Leaf Grade Cotton. Below leaf grade cotton is...

2009-01-01

316

7 CFR 28.471 - Below Leaf Grade Cotton.  

Code of Federal Regulations, 2010 CFR

...2010-01-01 2010-01-01 false Below Leaf Grade Cotton. 28.471 Section 28.471...TESTING, AND STANDARDS Standards Below Leaf Grade Cotton § 28.471 Below Leaf Grade Cotton. Below leaf grade cotton is...

2010-01-01

317

7 CFR 28.514 - Leaf Grade No. 4.  

Code of Federal Regulations, 2010 CFR

... 2010-01-01 2010-01-01 false Leaf Grade No. 4. 28.514 Section 28.514...Cotton Standards of the United States for the Leaf Grade of American Pima Cotton § 28.514 Leaf Grade No. 4. Leaf grade No. 4 shall...

2010-01-01

318

7 CFR 28.516 - Leaf Grade No. 6.  

Code of Federal Regulations, 2010 CFR

... 2010-01-01 2010-01-01 false Leaf Grade No. 6. 28.516 Section 28.516...Cotton Standards of the United States for the Leaf Grade of American Pima Cotton § 28.516 Leaf Grade No. 6. Leaf grade No. 6 shall...

2010-01-01

319

7 CFR 28.515 - Leaf Grade No. 5.  

Code of Federal Regulations, 2010 CFR

... 2009-01-01 2009-01-01 false Leaf Grade No. 5. 28.515 Section 28.515...Cotton Standards of the United States for the Leaf Grade of American Pima Cotton § 28.515 Leaf Grade No. 5. Leaf grade No. 5 shall...

2009-01-01

320

NARROW LEAF 7 controls leaf shape mediated by auxin in rice  

Microsoft Academic Search

Elucidation of the genetic basis of the control of leaf shape could be of use in the manipulation of crop traits, leading\\u000a to more stable and increased crop production. To improve our understanding of the process controlling leaf shape, we identified\\u000a a mutant gene in rice that causes a significant decrease in the width of the leaf blade, termed narrow

Kenji Fujino; Yasuyuki Matsuda; Kenjirou Ozawa; Takeshi Nishimura; Tomokazu Koshiba; Marco W. Fraaije; Hiroshi Sekiguchi

2008-01-01

321

Short communication Leaf optical properties and photosynthetic leaf absorptances in several Australian seagrasses  

Microsoft Academic Search

Thisstudyinvestigated within-and among-species variability intheleafoptical properties ofeightlarge-bodiedseagrasses,Posidoniaaustralis, Posidonia sinuosa, Posidonia coriacea, Posidonia angustifolia, Amphibolis antarctica, Amphibolis griffithii, Zostera tasmanica, and Zostera capricorni and the small-bodied Halophila ovalis from the east and west coasts of Australia. Leaf spectral transmittance (TL(l)), reflectance (RL(l)), and non-photosynthetic absorptance (AL(NP)) were measured in order to calculate leaf spectral absorptance (AL(l)) and photosynthetic leaf absorptance (AL(PAR)).

Michael J. Durako

322

Reflectance model of a plant leaf  

NASA Technical Reports Server (NTRS)

A light ray, incident at 5 deg to the normal, is geometrically plotted through the drawing of the cross section of a soybean leaf using Fresnel's Equations and Snell's Law. The optical mediums of the leaf considered for ray tracing are: air, cell sap, chloroplast, and cell wall. The above ray is also drawn through the same leaf cross section considering cell wall and air as the only optical mediums. The values of the reflection and transmission found from ray tracing agree closely with the experimental results obtained using a Beckman DK-2A Spectroreflectometer. Similarly a light ray, incident at about 60 deg to the normal, is drawn through the palisade cells of a soybean leaf to illustrate the pathway of light, incident at an oblique angle, through the palisade cells.

Kumar, R.; Silva, L.

1973-01-01

323

The red edge of plant leaf reflectance  

NASA Technical Reports Server (NTRS)

A detailed study of the red edge spectral feature of green vegetation based on laboratory reflectance spectrophotometry is presented. A parameter lambda is defined as the wavelength is defined as the wavelength of maximum slope and found to be dependent on chlorophyll concentration. Species, development stage, leaf layering, and leaf water content of vegetation also influences lambda. The maximum slope parameter is found to be independent of simulated ground area coverage. The results are interpreted in terms of Beer's Law and Kubelka-Munk theory. The chlorophyll concentration dependence of lambda seems to be explained in terms of a pure absorption effect, and it is suggested that the existence of two lambda components arises from leaf scattering properties. The results indicate that red edge measurements will be valuable for assessment of vegetative chlorophyll status and leaf area index independently of ground cover variations, and will be particularly suitable for early stress detection.

Horler, D. N. H.; Dockray, M.; Barber, J.

1983-01-01

324

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

325

Spectroscopic Measurement of Leaf Water Status  

NASA Technical Reports Server (NTRS)

A leaf drying experiment was carried out in the laboratory in which simultaneous spectral reflectance in the 350-2450 nm region, and leaf weights, were measured at 10 second intervals over a 40 minute period. As the leaf water weight dropped from approximately 60 to 38%. a nearly-linear rise in reflectance at all wavelengths beyond 1000 nm was observed. A principal components analysis of the time series of spectra in the 2000-2500 nm wavelength region showed that over 99% of the variance in the spectra, that were individually scaled to have a sum equal to that of the mean spectrum and subsequently mean corrected, was in the first component. This result shows that it is feasible to determine leaf water content remotely with an imaging spectrometer independent of the surface irradiance effects caused by topography.

Goetz, Alexander F. H.; Boardman, Joseph W.

1995-01-01

326

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

327

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

328

Error Compensation in Leaf Power Problems  

Microsoft Academic Search

The k-Leaf Power recognition problem is a particular case of graph power problems: For a given graph it asks whether there exists an un- rooted tree—the k-leaf root—with leaves one-to-one labeled by the graph vertices and where the leaves have distance at most k iff their correspond- ing vertices in the graph are connected by an edge. Here we study

Michael Dom; Jiong Guo; Falk Hüffner; Rolf Niedermeier

2006-01-01

329

Nutrient influences on leaf photosynthesis  

SciTech Connect

The net rate of CO/sub 2/ uptake for leaves of Gossypium hirsutum L. was reduced when the plants were grown at low concentrations of NO/sub 3//sup -/, PO/sub 4//sup 2 -/, or K/sup +/. The water vapor conductance was relatively constant for all nutrient levels, indicating little effect on stomatal response. Although leaves under nutrient stress tended to be lower in chlorophyll and thinner, the ratio of mesophyll surface area to leaf area did not change appreciably. Thus, the reduction in CO/sub 2/ uptake rate at low nutrient levels was due to a decrease in the CO/sub 2/ conductance expressed per unit mesophyll cell wall area (g/sub CO/sup cell//sub 2/). The use of g/sub CO//sup cell//sub 2/ and nutrient levels expressed per unit of mesophyll cell wall provides a new means of assessing nutrient effects on CO/sub 2/ uptake of leaves. 14 figures, 1 table.

Longstreth, D.J.; Nobel, P.S.

1980-01-01

330

Critique of stepwise multiple linear regression for the extraction of leaf biochemistry information from leaf reflectance data  

Microsoft Academic Search

This study examined the use of stepwise multiple linear regression to quantify leaf carbon, nitrogen, lignin, cellulose, dry weight, and water compositions from leaf level reflectance (R). Two fresh leaf and one dry leaf datasets containing a broad range of native and cultivated plant species were examined using unconstrained stepwise multiple linear regression and constrained regression with wavelengths reported from

Y. L. Grossman; S. L. Ustin; S. Jacquemoud; E. W. Sanderson; G. Schmuck; J. Verdebout

1996-01-01

331

Leaf morphology shift linked to climate change.  

PubMed

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 1-9 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. PMID:22764114

Guerin, Greg R; Wen, Haixia; Lowe, Andrew J

2012-10-23

332

Root Hypoxia Reduces Leaf Growth 1  

PubMed Central

This study examined the potential role of restricted phloem export, or import of substances from the roots in the leaf growth response to root hypoxia. In addition, the effects of root hypoxia on abscisic acid (ABA) and zeatin riboside (ZR) levels were measured and their effects on in vitro growth determined. Imposition of root hypoxia in the dark when transpirational water flux was minimal delayed the reduction in leaf growth until the following light period. Restriction of phloem transport by stem girdling did not eliminate the hypoxia-induced reduction in leaf growth. In vitro growth of leaf discs was inhibited in the presence of xylem sap collected from hypoxic roots, and also by millimolar ABA. Disc growth was promoted by sap from aerated roots and by 0.1 micromolar ZR. The flux of both ABA and ZR was reduced in xylem sap from hypoxic roots. Leaf ABA transiently increased twofold after 24 hours of hypoxia exposure but there were no changes in leaf cytokinin levels. Images Figure 3 Figure 4

Smit, Barbara A.; Neuman, Dawn S.; Stachowiak, Matthew L.

1990-01-01

333

EFFECT OF LEAF ANATOMY ON HYPOSTOMATOUS LEAF GAS EXCHANGE: A THEORETICAL STUDY WITH THE 2DLEAF MODEL  

Microsoft Academic Search

PACHEPSKY L. B. and ACOCK B. Effect of leaf anatomy on hypostomatous leaf gas exchange: A theoretical study with the 2DLEAF model. BIOTRONICS 27, 1-14, 1998. The two-dimensional model of leaf gas exchange, 2DLEAF, which accounts for leaf intercellular structure, was used to study the effect of leaf anatomy on the photosynthesis and transpiration rates of hypostomatous Cg plants. The

L. B. P ACHEPSKYI; B. ACOCK

334

Black leaf streak and viral leaf streak: New banana diseases in East Africa  

Microsoft Academic Search

Black leaf streak, caused by Mycosphaerella fijiensis a virulent pathogen of bananas and plantains, is recorded from Zanzibar. This is the first record of this important pathogen from East Africa. Viral leaf streak of bananas is also identified from Zanzibar. The presence of panama disease and high infestations of root nematode are also noted.

A. J. Dabek; J. M. Waller

1990-01-01

335

Relationships between sclerophylly, leaf biomechanical properties and leaf anatomy in some Australian heath and forest species  

Microsoft Academic Search

A previous study of 19 south-east Australian heath and forest species with a range of leaf textures showed that they varied considerably in leaf biomechanical properties. By using an index of sclerophylly derived from botanists' rankings (botanists' sclerophylly index, BSI) we determined that leaves considered by botanists to be sclerophyllous generally had both high strength and work to fracture (particularly

Cheryl Edwards; Gordon D. Sanson; Nuvan Aranwela; Jennifer Read

2000-01-01

336

Nitrogen Effects on Leaf Anatomy within the Intercalary Meristems of Tall Fescue Leaf Blades  

Microsoft Academic Search

Longitudinal elongation contributes most to leaf area expansion of grasses and its rate is known to be strongly affected by N. Our objective was to determine the effect of two N regimes (N0and N+) on the gradient of leaf tissue formation in meristems of two contrasting tall fescue (Festuca arundinacea Schreb.) genotypes. Proportions of epidermal, mesophyll and vascular tissue as

Ingo F. Rademacher; C. Jerry Nelson

2001-01-01

337

Leaf lifespan as a determinant of leaf structure and function among 23 amazonian tree species  

Microsoft Academic Search

The relationships between resource availability, plant succession, and species' life history traits are often considered key to understanding variation among species and communities. Leaf lifespan is one trait important in this regard. We observed that leaf lifespan varies 30-fold among 23 species from natural and disturbed communities within a 1-km radius in the northern Amazon basin, near San Carlos de

P. B. Reich; C. Uhl; M. B. Walters; D. S. Ellsworth

1991-01-01

338

Cloning of the amphibolic Calvin cycle\\/OPPP enzyme d-ribulose-5-phosphate 3-epimerase (EC 5.1.3.1) from spinach chloroplasts: functional and evolutionary aspects  

Microsoft Academic Search

Exploiting the differential expression of genes for Calvin cycle enzymes in bundle-sheath and mesophyll cells of the C4 plant Sorghum bicolor L., we isolated via subtractive hybridization a molecular probe for the Calvin cycle enzyme d-ribulose-5-phosphate 3-epimerase (R5P3E) (EC 5.1.3.1), with the help of which several full-size cDNAs were isolated from spinach. Functional identity of the encoded mature subunit was

Ulrich Nowitzki; Ralf Wyrich; Peter Westhoff; Katrin Henze; Claus Schnarrenberger; William Martin

1995-01-01

339

Measurement of leaf relative water content by infrared reflectance  

NASA Technical Reports Server (NTRS)

From basic considerations and Beer's law, a leaf water content index incorporating reflectances of wavelengths from 0.76 to 0.90 microns and from 1.55 to 1.75 microns was developed that relates leaf reflectance to leaf relative water content. For the leaf succulent, Agave deserti, the leaf water content index was not significantly different from the relative water content for either individual leaves or an entire plant. Also, the relative water contents of intact plants of Encelia farinosa and Hilaria rigida in the field were estimated by the leaf water content index; variations in the proportion of living to dead leaf area could cause large errors in the estimate of relative water content. Thus, the leaf water content index may be able to estimate average relative water content of canopies when TM4 and TM5 are measured at a known relative water content and fraction of dead leaf material.

Hunt, E. Raymond, Jr.; Rock, Barrett N.; Nobel, Park S.

1987-01-01

340

Role of chloroplastidial proteases in leaf senescence  

PubMed Central

In this report the effect of hydrogen peroxide (H2O2) on peroxidase (POD) activity during leaf senescence was studied with and without phenylmethylsulfonyl fluoride (PMSF) pre-treatment in detached neem (Azadirachta indica A. juss) leaf chloroplasts. Increased POD activity was detected in natural and H2O2-promoted senescent leaf chloroplasts compared to untreated control mature green leaf chloroplasts. However, under H2O2 POD activity markedly increased at 1 day, and then significantly decreased until 4 days. In the presence of H2O2, PMSF, the induction of POD activity was alleviated at 1 day, whereas reduced after 4 days. In contrast, in the presence of H2O2, cycloheximide (CX), the induction of POD activity was reduced at 1 day, whereas alleviated after 4 days. The was a partial reduction in H2O2-induced POD activity with PMSF and CX, indicating the presence of pre-existing inactive PODs in chloroplasts. We also propose a new role for chloroplastidial proteases as activators of pre-existing inactive PODs during leaf senescence.

Goud, Prashanth B

2011-01-01

341

BOREAS TE-9 NSA Leaf Chlorophyll Density  

NASA Technical Reports Server (NTRS)

The BOREAS TE-9 team collected several data sets related to chemical and photosynthetic properties of leaves in boreal forest tree species. These data were collected to help provide an explanation of potential seasonal and spatial changes of leaf pigment properties in boreal forest species at the NSA. At different dates (FFC-Winter, FFC-Thaw, IFC-1, IFC-2, and IMC-3), foliage samples were collected from the upper third of the canopy for five NSA sites (YJP, OJP, OBS, UBS, and OA) near Thompson, Manitoba. Subsamples of 100 needles for black spruce, 20 needles for jack pine, and single leaf for trembling aspen were cut into pieces and immersed in a 20-mL DMF aliquot in a Nalgene test tube. The extracted foliage materials were then oven-dried at 68 C for 48 hours and weighed. Extracted leaf dry weight was converted to a total leaf area basis to express the chlorophyll content in mg/sq cm of total leaf area. The data are provided in tabular ASCII files. The data files are available on a CD-ROM (see document number 20010000884), or from the Oak Ridge National Laboratory (ORNL) Distributed Active Archive Center (DAAC).

Hall, Forrest G. (Editor); Curd, Shelaine (Editor); Margolis, Hank; Sy, Mikailou

2000-01-01

342

Chloroplast Response to Low Leaf Water Potentials  

PubMed Central

Quantum yields were measured for CO2 fixation by sunflower (Helianthus annuus L.) leaves having various water potentials and for dichlorophenolindophenol photoreduction by chloroplasts isolated from similar leaves having various water potentials. In red radiation, the quantum yield for CO2 was 0.076 for an attached sunflower leaf at a water potential of ?3 to ?4 bars but was 0.020 for the same leaf at ?15.3 bars. After recovery to a water potential of ?5 bars, the quantum yield rose to 0.060. Soybean (Glycine max L. [Merr.]) leaves behaved similarly. Chloroplasts from a sunflower leaf with a water potential of ?3.6 bars had a quantum yield for 4 equivalents of 0.079, but when tissue from the same leaf had a water potential of ?14.8 bars, the quantum yield of the chloroplasts decreased to 0.028. The decrease could not be attributed to differences in rates of respiration by the leaves or the chlorophyll content or absorption spectrum of the leaves and chloroplasts. The data are the first to demonstrate an effect of low leaf water potential on the quantum yield and they indicate that changes occurred close to the primary photochemical events of photosynthesis. The similarity in response of the leaves and chloroplasts indicates that certain changes in photosynthesis at low water potentials are attributable to the chloroplasts rather than the stomata.

Mohanty, Prasanna; Boyer, John S.

1976-01-01

343

Pentacyclic triterpenoids from olive fruit and leaf.  

PubMed

This work establishes a new procedure for the extraction and analysis of pentacyclic triterpenes, with which fruits and leaves from three Spanish olive cultivars ("Picual", "Hojiblanca", and "Arbequina") has been studied. The leaf contains important amounts of oleanolic acid (3.0-3.5% DW), followed by significant concentrations of maslinic acid and minor levels of ursolic acid, erythrodiol, and uvaol. The abundance and profile of triterpenoids change during the leaf ontogeny. In the fruit, triterpenes are exclusively located in the epicarp at concentrations 30-fold lower than that in the leaf. Maslinic acid is the main triterpenoid, only accompanied of oleanolic acid. Along the ripening the levels of these triterpenes decreased. All the analyzed leaves and fruits come from the same agricultural estate, with identical climate and culturing conditions. For this reason, the found differences could majorly be attributable to the genetic factors of the olive cultivars. PMID:20712364

Guinda, Angeles; Rada, Mirela; Delgado, Teresa; Gutiérrez-Adánez, Pilar; Castellano, José María

2010-09-01

344

Relationship between Leaf Water and Leaf Waxes in Growing Pine Needles  

NASA Astrophysics Data System (ADS)

There has been an increasing interest in reconstruction of paleoclimate and paleo-environment using hydrogen isotopic ratios of plant lipids extracted from sediments. It has been shown that ?D of plant lipids is related to the ?D of leaf water, which in turn is related to the ?D of precipitation and relative humidity. However, the ?D of leaf water changes significantly through the life of a leaf, it is not clear how the leaf water dynamics affects the bulk isotopic composition of lipids that are synthesized throughout the life of the leaf. This work is a detailed study of the relationship between ?D values in leaf water and in leaf wax n-acids for two species of pine needles, red pine ( Pinus resinosa) and white pine ( Pinus strobus). In an earlier investigation we found that the ?D of leaf water in pine needles increased as they were elongated through the needle-growing season. The leaf water of red pine needles has higher ?D values than that of white pine needles at each comparable stage of growth. In addition, for a given needle, the leaf water ?D also increased from the base to the tip of the needle. To examine the variation of lipid ?D in relation to that of leaf water ?D, we collected 4 sets of needles during their elongation period, obtained the bulk leaf water, then sectioned them into smaller segments along the length, and measured ?D values of n-acids with 24 to 32 carbons. We test how the measured D/H ratios of leaf waxes vary with time, between two species, and with the position in the needle (relative distance from the tip, 0-1). A multiple regression analysis shows the following results. 1) The ?D values of all types of n-acids are significantly correlated with the position of the sample; ?D is lower near the base and higher near the tip. This result is consistent with the along-needle isotopic distribution of leaf water. 2) Leaf waxes of red pine needles are significantly more enriched in D than white pine needles, also consistent with leaf water ?D variation between the two species. 3) Regardless of temporal increases of leaf water ?D, the ?D of 4 out of 5 wax n-acids shows a decreasing trend with time, although only two (C-24, 32) are statistically significant. This may reflect use of stored hydrogen (from stored carbohydrates) at earlier stages of growth. 4) The significance of the overall regression of ?D against time, species and relative position increases from low carbon to high carbon number lipids (for C-24, 26, 28, 30, and 32, r2=0.34, 0.31, 0.56, 0.61, and 0.83), suggesting that longer wax n-acids are more influenced by local leaf water.

Majumdar, S.; Feng, X.; Hou, J.; Faiia, A. M.; Huang, Y.

2007-12-01

345

Perfect is best: low leaf fluctuating asymmetry reduces herbivory by leaf miners.  

PubMed

Fluctuating asymmetry (FA) represents small, random variation from symmetry and can be used as an indicator of plant susceptibility to herbivory. We investigated the effects of FA of two oak species, Quercus laevis and Q. geminata, and the responses of three herbivore guilds: leaf miners, gallers, and chewers. To examine differences in FA and herbivory between individuals, 40 leaves from each tree were collected, and FA indices were calculated. To examine differences in FA and herbivory within-individuals, we sampled pairs of mined and unmined leaves for asymmetry measurements. Differences in growth of leaf miners between leaf types were determined by tracing 50 mines of each species on symmetric leaves and asymmetric leaves. Asymmetric leaves contained significantly lower concentrations of tannins and higher concentrations of nitrogen than symmetric leaves for both plant species. Both frequency of asymmetric leaves on plants and levels of asymmetry positively influenced the abundance of Brachys, Stilbosis and other leaf miners, but no significant relationship between asymmetry and herbivory was observed for Acrocercops. Brachys and Stilbosis mines were smaller on asymmetric leaves, but differences in mine survivorship between symmetric and asymmetric leaves were observed only for Stilbosis mines. This study indicated that leaf miners might use leaf FA as a cue to plant quality, although differential survivorship among leaf types was not observed for all species studied. Reasons for the different results between guilds are discussed. PMID:15378348

Cornelissen, Tatiana; Stiling, Peter

2005-01-01

346

Leaf anatomy of three herbaceous bamboo species.  

PubMed

Fully developed leaves of Cryptochloa capillata (Swallen) Soderstrom, Raddia brasilienses Bertol and Pharus lappulaceus Aublet (Poaceae: Bambusoideae) were collected at Restinga de Jacarepiá, Environment Proctection Area of Massambaba, county of Rio de Janeiro, State of Rio de Janeiro, Brazil, and studied by optical microscope. Leaf anatomy is described in order to contribute to the Poaceae family study. Anatomic features observed in the three studied species such as: midrib with complex vascular system, mesophyll consisting of tabular lobed chlorophyllous elements and fusoid cells, vascular bundles with double sheath, epidermis made up of long cells, short cells, micro-hairs, prickles and silica bodies correspond to the "bambusoid type" of leaf anatomy. PMID:12659043

Vieira, R C; Gomes, D M S; Sarahyba, L S; Arruda, R C O

2002-11-01

347

Leaf Stomata as Bioindicators of Environmental Change  

NSDL National Science Digital Library

Leaf stomatal densities can be determined by a simple laboratory technique and yet have wide application in understanding environmental change. Several researchers have evidence which indicates that stomatal densities change in response to changing atmospheric levels of carbon dioxide. Stomata may also vary in response to the amount of annual rainfall in different localities. Because this investigation involves climatic variations, it requires that many geographically dispersed sites collect and share data. In this experiment, leaves from two species of trees will be collected and the stomatal index on the upper and lower epidermis of each leaf will be determined.

BEGIN:VCARD VERSION:2.1 FN:Steve Case N:Case;Steve ORG:University of Kansas REV:2005-04-13 END:VCARD

1994-07-30

348

Stem and leaf morphoanatomy of Maytenus ilicifolia.  

PubMed

Maytenus ilicifolia is a woody medicinal plant, employed mainly for its antiulcerogenic properties. The stem and leaf morphoanatomy has been studied, aiming to supply knowledge for the pharmacognostic and taxonomic species identification. The vegetative material was fixed, freehand sectioned and stained according to usual microtechniques. The stem organization, in secondary growth, shows periderm beneath the remaining epidermis, conspicuous sclerenchymatic ring in the cortex and cambium forming phloem outside and xylem inside. The leaf is simple, alternate and lanceolate and has sparsely spiny teeth along the margin. Epidermal cells containing calcium oxalate crystals, thick cuticle that forms cuticular flanges, dorsiventral mesophyll and amphicrival bundle in the midrib and petiole are observed. PMID:15664461

Duarte, M R; Debur, M C

2005-01-01

349

Mueller matrix of a dicot leaf  

NASA Astrophysics Data System (ADS)

A better understanding of the information contained in the spectral, polarized bidirectional reflectance and transmittance of leaves may lead to improved techniques for identifying plant species in remotely sensed imagery as well as better estimates of plant moisture and nutritional status. Here we report an investigation of the optical polarizing properties of several leaves of one species, Cannabis sativa, represented by a 3x3 Mueller matrix measured over the wavelength region 400-2,400 nm. Our results support the hypothesis that the leaf surface alters the polarization of incident light - polarizing off nadir, unpolarized incident light, for example - while the leaf volume tends to depolarized incident polarized light.

Vanderbilt, Vern C.; Daughtry, Craig S. T.

2012-05-01

350

Two-dimensional leaf orientation distributions  

NASA Technical Reports Server (NTRS)

Combined inclination/azimuth leaf angle distributions are important for accurate models of vegetation canopy reflectance. It is shown that appropriate mathematical representations can be constructed from beta distributions under most circumstances. This is illustrated by analyzing observational data on soybean leaves and balsam fir needles. There are some problems when the data is imprecise and when correlations between inclination and azimuth angle are induced by heliotropism. Otherwise, the two-dimensional beta-type distribution appears to be a versatile tool for describing complete inclination/azimuth leaf angle distributions.

Strebel, D. E.; Goel, N. S.; Ranson, K. J.

1985-01-01

351

Is leaf dry matter content a better predictor of soil fertility than specific leaf area?  

PubMed Central

Background and Aims Specific leaf area (SLA), a key element of the ‘worldwide leaf economics spectrum’, is the preferred ‘soft’ plant trait for assessing soil fertility. SLA is a function of leaf dry matter content (LDMC) and leaf thickness (LT). The first, LDMC, defines leaf construction costs and can be used instead of SLA. However, LT identifies shade at its lowest extreme and succulence at its highest, and is not related to soil fertility. Why then is SLA more frequently used as a predictor of soil fertility than LDMC? Methods SLA, LDMC and LT were measured and leaf density (LD) estimated for almost 2000 species, and the capacity of LD to predict LDMC was examined, as was the relative contribution of LDMC and LT to the expression of SLA. Subsequently, the relationships between SLA, LDMC and LT with respect to soil fertility and shade were described. Key Results Although LD is strongly related to LDMC, and LDMC and LT each contribute equally to the expression of SLA, the exact relationships differ between ecological groupings. LDMC predicts leaf nitrogen content and soil fertility but, because LT primarily varies with light intensity, SLA increases in response to both increased shade and increased fertility. Conclusions Gradients of soil fertility are frequently also gradients of biomass accumulation with reduced irradiance lower in the canopy. Therefore, SLA, which includes both fertility and shade components, may often discriminate better between communities or treatments than LDMC. However, LDMC should always be the preferred trait for assessing gradients of soil fertility uncoupled from shade. Nevertheless, because leaves multitask, individual leaf traits do not necessarily exhibit exact functional equivalence between species. In consequence, rather than using a single stand-alone predictor, multivariate analyses using several leaf traits is recommended.

Hodgson, J. G.; Montserrat-Marti, G.; Charles, M.; Jones, G.; Wilson, P.; Shipley, B.; Sharafi, M.; Cerabolini, B. E. L.; Cornelissen, J. H. C.; Band, S. R.; Bogard, A.; Castro-Diez, P.; Guerrero-Campo, J.; Palmer, C.; Perez-Rontome, M. C.; Carter, G.; Hynd, A.; Romo-Diez, A.; de Torres Espuny, L.; Royo Pla, F.

2011-01-01

352

Cytokinin Regulates Compound Leaf Development in Tomato[C][W  

PubMed Central

Leaf shape diversity relies on transient morphogenetic activity in leaf margins. However, how this morphogenetic capacity is maintained is still poorly understood. Here, we uncover a role for the hormone cytokinin (CK) in the regulation of morphogenetic activity of compound leaves in tomato (Solanum lycopersicum). Manipulation of CK levels led to alterations in leaf complexity and revealed a unique potential for prolonged growth and morphogenesis in tomato leaves. We further demonstrate that the effect of CK on leaf complexity depends on proper localization of auxin signaling. Genetic analysis showed that reduction of CK levels suppresses the effect of Knotted1 like homeobox (KNOXI) proteins on leaf shape and that CK can substitute for KNOXI activity at the leaf margin, suggesting that CK mediates the activity of KNOXI proteins in the regulation of leaf shape. These results imply that CK regulates flexible leaf patterning by dynamic interaction with additional hormones and transcription factors.

Shani, Eilon; Ben-Gera, Hadas; Shleizer-Burko, Sharona; Burko, Yogev; Weiss, David; Ori, Naomi

2010-01-01

353

DIGITAL IMAGE ANALYSIS OF ZOSTERA MARINA LEAF INJURY  

EPA Science Inventory

Current methods for assessing leaf injury in Zostera marina (eelgrass) utilize subjective indexes for desiccation injury and wasting disease. Because of the subjective nature of these measures, they are inherently imprecise making them difficult to use in quantifying complex leaf...

354

The Role of Mangrove Ecosystems: Mangrove Leaf Area Indices.  

National Technical Information Service (NTIS)

Leaf area index (LAI) on total leaf surface per unit ground area is one parameter which may be used to estimate the photosynthetic capacity of individual plants or entire ecosystems. Techniques used for determining LAI in south Florida mangrove ecosystems...

D. J. Pool

1973-01-01

355

Preconcentration and trace determination of cadmium in spinach and various water samples by temperature-controlled ionic liquid dispersive liquid phase microextraction.  

PubMed

A sensitive and selective method for the preconcentration and separation of sub µg L-1 levels of cadmium ions in aqueous solutions with high salt contents is described. The developed method is based on temperature-controlled ionic liquid dispersive liquid phase microextraction of cadmium using the 1-hexyl-3-methylimidazolium bis (trifluoromethylsulfonyl) imide (ionic liquid (IL)) as an extractant followed by flame atomic absorption spectrometry determination. The extraction of cadmium ions from the aqueous solution into the fine droplets of IL was performed with dithizone as the chelating agent. Some predominant factors affecting the preconcentration of cadmium ions were evaluated and optimized. Under the optimum conditions, the calibration graph was linear over the concentration range from 0.6-20.0 µg L-1 of cadmium and the limit of detection (LOD) was 0.2 µg L-1. The enrichment factor was found to be 25. The developed method was successfully applied to the determination of cadmium in spinach and water samples. PMID:24664344

Rahnama, Reyhaneh; Mansoursamaei, Nazanin; Jamali, Mohammad Reza

2014-01-01

356

Extra-ribosomal function(s) of the plastid ribosomal protein L4 in the expression of ribosomal components in spinach.  

PubMed

We have previously characterised the cDNA corresponding to the nucleus-encoded, plastid ribosomal protein L4 from spinach. The L4 protein belongs to the group of ribosomal proteins for which extra-ribosomal functions have been demonstrated in prokaryotes. In general, these functions are concerned with the expression of ribosomal components. In order to analyse whether the plastid L4 protein might also have (an) extra-ribosomal function(s) we have produced the plastid L4 protein as a thioredoxin fusion protein and analysed its role in both prokaryotic (E. coli) and plastid systems. We found that the plastid L4 protein can replace the E. coli L4 protein in the NusA-dependent attenuation control of the E. coli S10 operon by stabilising stalled transcription complexes in a NusA-dependent reaction. In plastids, the L4 protein inhibits transcription of the rrn operon. Our results thus suggest extra-ribosomal function(s) for the plastid L4 protein in the expression of ribosomal components. PMID:10852486

Trifa, Y; Lerbs-Mache, S

2000-05-01

357

Photoprotective Energy Dissipation Involves the Reorganization of Photosystem II Light-Harvesting Complexes in the Grana Membranes of Spinach Chloroplasts[W  

PubMed Central

Plants must regulate their use of absorbed light energy on a minute-by-minute basis to maximize the efficiency of photosynthesis and to protect photosystem II (PSII) reaction centers from photooxidative damage. The regulation of light harvesting involves the photoprotective dissipation of excess absorbed light energy in the light-harvesting antenna complexes (LHCs) as heat. Here, we report an investigation into the structural basis of light-harvesting regulation in intact spinach (Spinacia oleracea) chloroplasts using freeze-fracture electron microscopy, combined with laser confocal microscopy employing the fluorescence recovery after photobleaching technique. The results demonstrate that formation of the photoprotective state requires a structural reorganization of the photosynthetic membrane involving dissociation of LHCII from PSII and its aggregation. The structural changes are manifested by a reduced mobility of LHC antenna chlorophyll proteins. It is demonstrated that these changes occur rapidly and reversibly within 5 min of illumination and dark relaxation, are dependent on ?pH, and are enhanced by the deepoxidation of violaxanthin to zeaxanthin.

Johnson, Matthew P.; Goral, Tomasz K.; Duffy, Christopher D.P.; Brain, Anthony P.R.; Mullineaux, Conrad W.; Ruban, Alexander V.

2011-01-01

358

Oxidation--reduction midpoint potentials of the flavin, haem and Mo-pterin centres in spinach (Spinacia oleracea L.) nitrate reductase.  

PubMed Central

Oxidation-reduction midpoint potentials have been determined for the flavin, cytochrome b557 and Mo-pterin prosthetic groups of spinach (Spinacia oleracea L.) assimilatory nitrate reductase using visible, c.d. and room-temperature e.p.r. potentiometric titrations. At pH 7 and 25 degrees C, the midpoint potential for the FAD/FADH2 couple was determined by c.d. potentiometry to be -280 +/- 10 mV (n = 2). The redox potential for reduction of the haem was determined by visible potentiometry to be -123 +/- 10 mV (n = 1), significantly lower than the previously published value of -60 mV [Fido, Hewitt, Notton, Jones & Nasrulhaq-Boyce (1979) FEBS Lett. 99, 180-182]. Potentials for the Mo(VI)/Mo(V) and Mo(V)/Mo(IV) redox couples, determined by room-temperature e.p.r. potentiometry, were found to be +2 +/- 20 and -6 +/- 20 mV respectively. These values are very similar to the values previously determined for the FAD, haem and Mo-pterin centres in assimilatory nitrate reductase isolated from the unicellular green alga Chlorella vulgaris and indicate a close thermodynamic similarity between the two enzymes.

Kay, C J; Barber, M J; Notton, B A; Solomonson, L P

1989-01-01

359

Oxidation--reduction midpoint potentials of the flavin, haem and Mo-pterin centres in spinach (Spinacia oleracea L.) nitrate reductase.  

PubMed

Oxidation-reduction midpoint potentials have been determined for the flavin, cytochrome b557 and Mo-pterin prosthetic groups of spinach (Spinacia oleracea L.) assimilatory nitrate reductase using visible, c.d. and room-temperature e.p.r. potentiometric titrations. At pH 7 and 25 degrees C, the midpoint potential for the FAD/FADH2 couple was determined by c.d. potentiometry to be -280 +/- 10 mV (n = 2). The redox potential for reduction of the haem was determined by visible potentiometry to be -123 +/- 10 mV (n = 1), significantly lower than the previously published value of -60 mV [Fido, Hewitt, Notton, Jones & Nasrulhaq-Boyce (1979) FEBS Lett. 99, 180-182]. Potentials for the Mo(VI)/Mo(V) and Mo(V)/Mo(IV) redox couples, determined by room-temperature e.p.r. potentiometry, were found to be +2 +/- 20 and -6 +/- 20 mV respectively. These values are very similar to the values previously determined for the FAD, haem and Mo-pterin centres in assimilatory nitrate reductase isolated from the unicellular green alga Chlorella vulgaris and indicate a close thermodynamic similarity between the two enzymes. PMID:2604699

Kay, C J; Barber, M J; Notton, B A; Solomonson, L P

1989-10-01

360

Pharmacognostic evaluation of Cayratia trifolia (Linn.) leaf  

PubMed Central

Objective To present a detailed pharmacognostic study of the leaf of Cayratia trifolia (C. trifolia) Linn. (Vitaceae), an important plant in the Indian system of medicine. Methods The macroscopy, microscopy, physiochemical analysis, preliminary testing, fluorescence analysis of powder of the plant and other WHO recommended methods for standardization were investigated. Results Leaves are trifoliolated with petioles (2–3 cm) long. Leaflets are ovate to oblong-ovate, (2–8 cm) long, (1.5–5 cm) wide, pointed at the tip. The leaf surface shows the anisocytic type stomata covered with guard cells followed by epidermis layer. Leaf surface contents including veins, vein islet and vein termination were also determined. Transverse section of leaf shows the epidermis layer followed by cuticle layer and vascular bandles (xylem and phloem). The mesophyll is differentiated into palisade and spongy parenchyma. Abundant covering trichomes emerge from the upper epidermis. Trichomes are uniseriate and multicellular. Strips of collenchyma are present below and upper layer of epidermis. Conclusions It can be concluded that the pharmacognostic profile of the C. trifolia is helpful in developing standards for quality, purity and sample identification.

Kumar, Dinesh; Gupta, Jyoti; Kumar, Sunil; Arya, Renu; Kumar, Tarun; Gupta, Ankit

2012-01-01

361

Anatomy of non-uniform leaf photosynthesis  

Microsoft Academic Search

Since 1986, non-uniform photosynthesis over the leaf area that may be attributed to patchy stomatal closure, has been an important issue in stress physiology of photosynthesis. In this review, I first outline the gaseous environment within the intercellular spaces, because this is the most fundamental background of this problem. Then, recent studies approaching non-uniform photosynthesis are reviwed. After examining techniques

Ichiro Terashima

1992-01-01

362

An Outbreak of Foxglove Leaf Poisoning  

Microsoft Academic Search

Comfrey (Symphytum officinale) leaves resemble those of foxglove (Digitalis purpurea) when the plant is not in bloom and, therefore, cardiac glycoside poisoning may occur when people confuse foxglove with comfrey. We report an outbreak of foxglove leaf poisoning following the use of alleged \\

Chun-Chi Lin; Chen-Chang Yang; Dong-Haur Phua; Jou-Fang Deng; Li-Hua Lu

2010-01-01

363

Environmental Correlates of Leaf Stomata Density  

NSDL National Science Digital Library

In this Experiment, students make impressions of leaf stomata (using clear nail polish) and test a hypothesis of their choice about how leaf stomata density might vary under different environmental conditions. Leaf stomata are the principal means of gas exchange in vascular plants. Stomata are small pores, typically on the undersides of leaves, that are opened or closed under the control of a pair of banana-shaped cells called guard cells. When open, stomata allow CO2 to enter the leaf for synthesis of glucose, and also allow for water, H2O, and free oxygen, O2, to escape. In addition to opening and closing the stomata (stomata behavior), plants may exert control over their gas exchange rates by varying stomata density in new leaves when they are produced (such as in the spring or summer). The more stomata per unit area (stomata density) the more CO2 can be taken up, and the more water can be released. Thus, higher stomata density can greatly amplify the potential for behavioral control over water loss rate and CO2 uptake.

Vatnick, Itzick

2010-02-16

364

Plant leaf imaging technique for agronomy  

Microsoft Academic Search

Recent physiological studies on nutrition and growth have shown that leaf area is a reliable index of growth factor determining carbohydrate metabolism, yield and quality of crops. Software was developed using image processing toolbox of MATLAB, for calculating parameters of multiple leaves like area, length, width etc. Sample of 50 leaves of various shapes and sizes were used in measurements

V. D. Shivling; Ajay Singla; C. Ghanshyam; Pawan Kapur; Savita Gupta

2011-01-01

365

Turbine rotor-stator leaf seal and related method  

DOEpatents

A seal assembly for installation between rotating and stationary components of a machine includes a first plurality of leaf spring segments secured to the stationary component in a circumferential array surrounding the rotating component, the leaf spring segments each having a radial mounting portion and a substantially axial sealing portion, the plurality of leaf spring segments shingled in a circumferential direction.

Herron, William Lee (Cincinnati, OH); Butkiewicz, Jeffrey John (Simpsonville, SC)

2003-01-01

366

Mapping vineyard leaf area with multispectral satellite imagery  

Microsoft Academic Search

Vineyard leaf area is a key determinant of grape characteristics and wine quality. As is frequently the case in agriculture, available ground-based leaf area measurements employed by growers are not well suited to larger area mapping. In this study, IKONOS high spatial resolution, multispectral satellite imagery was used to map leaf area throughout two commercial wine grape vineyards (approximately 800

L. F. Johnson; D. E. Roczen; S. K. Youkhana; R. R. Nemani; D. F. Bosch

2003-01-01

367

Systematic vegetative anatomy and ensiform leaf development in Xyris (Xyridaceae)  

Microsoft Academic Search

Ensiform leaf development in monocotyledons follows a broadly similar sequence in a wide range of relatively unrelated taxa, indicating a plastic developmental pattern, possibly associated with stressed environmental conditions, sinceXyrisspecies tend to grow in relatively damp but nutrient-poor environments. The bifacial leaf sheath surrounds the apex and the subadjacent primordium. A conical unifacial leaf tip «Vorläuferspitze» is established at an

M. J. SAJO; P. J. RUDALL

1999-01-01

368

7 CFR 30.31 - Classification of leaf tobacco.  

Code of Federal Regulations, 2010 CFR

...2009-01-01 false Classification of leaf tobacco. 30.31 Section 30.31...STOCKS AND STANDARDS Classification of Leaf Tobacco Covering Classes, Types and Groups of Grades § 30.31 Classification of leaf tobacco. For the purpose of this...

2009-01-01

369

Field estimation of leaf nitrogen by light transmittance  

Microsoft Academic Search

A highly significant negative correlation was found between percentage transmittance of photosynthetically active radiation (%TPAR) through a varied sample of walnut leaves and their extractable chlorophyll content (expressed on a leaf?area basis). The %TPAR was negatively correlated with leaf nitrogen (N) expressed on a leaf?area basis. When leaves were sampled from throughout the canopy of a walnut tree, no correlation

A. Erez; S. A. Weinbaum

1985-01-01

370

Relating Leaf Nitrogen, Leaf Photosynthesis and Canopy CO2 Exchange in a Temperate Winter Barley Field  

NASA Astrophysics Data System (ADS)

Net exchange of CO2 between the atmosphere and the soil-vegetation interface (NEE) is controlled by a wide range of biochemical and biophysical processes where leaf photosynthesis is often the most important. In mechanistically and physically based photosynthesis models (e.g. Farquhar et al. 1980) leaf nutrient status is a limiting factor for the photosynthetic capacity since it is implicitly incorporated through the parameters of maximum rate of carboxylation of CO2 (Vcmax) and the maximum rate of electron transport (Jmax). These are closely related to leaf nitrogen concentration (Na) and leaf chlorophyll content (Cab) and often show a characteristic seasonal dynamic. When simulating CO2 exchange, model outputs are sensitive to leaf photosynthetic capacity, which is labour consuming to verify through field measurements. A less time consuming method is to measure leaf "greenness" (SPAD), which is closely related to chlorophyll content and thus photosynthetic capacity. In the present study field measurements of leaf photosynthesis (LI-6400, LICOR Inc.), leaf reflectance (SPAD-502, Minolta), and LAI (LAI-2000, LICOR Inc.) were conducted on agricultural fields in Western Denmark during one growing season. The leaf photosynthesis measurements provided the basis for estimating photosynthetic capacity. SPAD measurements and LAI was measured with a higher spatial and temporal resolution. SPAD readings were calibrated against Cab and Na analyzed on leaf material in the laboratory and later correlated to photosynthetic capacity. These data were used to parameterize a coupled photosynthesis and stomatal model that was run for the growing season 2012 to estimate NEE. As a part of the hydrological observatory HOBE (hobe.dk), fluxes of greenhouse gasses are continuously measured by eddy covariance systems at three field sites in the Skjern River Catchment, Western Denmark, providing the basis for estimating the exchange of energy, water vapour, and CO2 on canopy scale. One of the sites is situated at the field under investigation in the present study. Here we compare modeled NEE with the measured CO2 fluxes. The presented approach is shown to provide an efficient field sampling method for model parameterization with high temporal and spatial resolution and a physiological basis for scaling fluxes from leaf level to canopy scale. We further evaluate the potential for applying the model approach in connection with upscaling by means of satellite data.

Jensen, R.; Boegh, E.; Herbst, M.; Friborg, T.

2012-12-01

371

Impact of epidermal leaf mining by the aspen leaf miner (Phyllocnistis populiella) on the growth, physiology, and leaf longevity of quaking aspen.  

PubMed

The aspen leaf miner, Phyllocnistis populiella, feeds on the contents of epidermal cells on both top (adaxial) and bottom (abaxial) surfaces of quaking aspen leaves, leaving the photosynthetic tissue of the mesophyll intact. This type of feeding is taxonomically restricted to a small subset of leaf mining insects but can cause widespread plant damage during outbreaks. We studied the effect of epidermal mining on aspen growth and physiology during an outbreak of P. populiella in the boreal forest of interior Alaska. Experimental reduction of leaf miner density across two sites and 3 years significantly increased annual aspen growth rates relative to naturally mined controls. Leaf mining damage was negatively related to leaf longevity. Leaves with heavy mining damage abscised 4 weeks earlier, on average, than leaves with minimal mining damage. Mining damage to the top and bottom surfaces of leaves had different effects on physiology. Mining on the top surface of the leaf had no significant effect on photosynthesis or conductance and was unrelated to leaf stable C isotope ratio (delta(13)C). Mining damage to the bottom leaf surface, where stomata are located, had significant negative effects on net photosynthesis and water vapor conductance. Percent bottom mining was positively related to leaf delta(13)C. Taken together, the data suggest that the primary mechanism for the reduction of photosynthesis by epidermal leaf mining by P. populiella is the failure of stomata to open normally on bottom-mined leaves. PMID:18523809

Wagner, Diane; DeFoliart, Linda; Doak, Patricia; Schneiderheinze, Jenny

2008-08-01

372

Measurements of leaf orientation, light distribution and sunlit leaf area in a boreal aspen forest  

Microsoft Academic Search

A new instrument called a Multiband Vegetation Imager (MVI) (Kucharik et al., 1997), which uses a 16-bit charge-coupled device (CCD) camera and filter exchange mechanism to capture 2-band (visible and near-infrared) image pairs of plant canopies, has been used to measure the light distribution over sunlit leaves and indirectly infer leaf area index (LAI), sunlit LAI and leaf angle distribution

Christopher J Kucharik; John M. Norman; Stith T. Gower

1998-01-01

373

Nitrogen EÄects on Leaf Anatomy within the Intercalary Meristems of Tall Fescue Leaf Blades  

Microsoft Academic Search

Longitudinal elongation contributes most to leaf area expansion of grasses and its rate is known to be strongly aÄected by N. Our objective was to determine the eÄect of two N regimes (N0 and Ná) on the gradient of leaf tissue formation in meristems of two contrasting tall fescue (Festuca arundinacea Schreb.) genotypes. Proportions of epidermal, mesophyll and vascular tissue

INGO F. RADEMACHER; C. JERRY NELSON

2001-01-01

374

Seasonal variation in Daucus carota leaf-surface and leaf-tissue chemical profiles  

Microsoft Academic Search

The purpose of this work was to document seasonal changes in leaf-surface and whole-leaf chemistry of Daucus carota cohorts that differed in life-cycle phenology (winter annual, annual, or biennial), with particular focus on compounds that serve as contact oviposition stimulants for Papilio polyxenes, the black swallowtail butterfly. Cohorts of carrot plants exhibiting different life-cycle phenologies were established, and plants from

Janie S Brooks; Paul Feeny

2004-01-01

375

Leaf optical properties and photosynthetic leaf absorptances in several Australian seagrasses  

Microsoft Academic Search

This study investigated within- and among-species variability in the leaf optical properties of eight large-bodied seagrasses, Posidonia australis, Posidonia sinuosa, Posidonia coriacea, Posidonia angustifolia, Amphibolis antarctica, Amphibolis griffithii, Zostera tasmanica, and Zostera capricorni and the small-bodied Halophila ovalis from the east and west coasts of Australia.Leaf spectral transmittance [TL(?)], reflectance [RL(?)], and non-photosynthetic absorptance [AL(NP)] were measured in order to

Michael J. Durako

2007-01-01

376

Final report on the safety assessment of AloeAndongensis Extract, Aloe Andongensis Leaf Juice,aloe Arborescens Leaf Extract, Aloe Arborescens Leaf Juice, Aloe Arborescens Leaf Protoplasts, Aloe Barbadensis Flower Extract, Aloe Barbadensis Leaf, Aloe Barbadensis Leaf Extract, Aloe Barbadensis Leaf Juice,aloe Barbadensis Leaf Polysaccharides, Aloe Barbadensis Leaf Water, Aloe Ferox Leaf Extract, Aloe Ferox Leaf Juice, and Aloe Ferox Leaf Juice Extract.  

PubMed

Plant materials derived from the Aloe plant are used as cosmetic ingredients, including Aloe Andongensis Extract, Aloe Andongensis Leaf Juice, Aloe Arborescens Leaf Extract, Aloe Arborescens Leaf Juice, Aloe Arborescens Leaf Protoplasts, Aloe Barbadensis Flower Extract, Aloe Barbadensis Leaf, Aloe Barbadensis Leaf Extract, Aloe Barbadensis Leaf Juice, Aloe Barbadensis Leaf Polysaccharides, Aloe Barbadensis Leaf Water, Aloe Ferox Leaf Extract, Aloe Ferox Leaf Juice, and Aloe Ferox Leaf Juice Extract. These ingredients function primarily as skin-conditioning agents and are included in cosmetics only at low concentrations. The Aloe leaf consists of the pericyclic cells, found just below the plant's skin, and the inner central area of the leaf, i.e., the gel, which is used for cosmetic products. The pericyclic cells produce a bitter, yellow latex containing a number of anthraquinones, phototoxic compounds that are also gastrointestinal irritants responsible for cathartic effects. The gel contains polysaccharides, which can be acetylated, partially acetylated, or not acetylated. An industry established limit for anthraquinones in aloe-derived material for nonmedicinal use is 50 ppm or lower. Aloe-derived ingredients are used in a wide variety of cosmetic product types at concentrations of raw material that are 0.1% or less, although can be as high as 20%. The concentration of Aloe in the raw material also may vary from 100% to a low of 0.0005%. Oral administration of various anthraquinone components results in a rise in their blood concentrations, wide systemic distribution, accumulation in the liver and kidneys, and excretion in urine and feces; polysaccharide components are distributed systemically and metabolized into smaller molecules. aloe-derived material has fungicidal, antimicrobial, and antiviral activities, and has been effective in wound healing and infection treatment in animals. Aloe barbadensis (also known as Aloe vera)-derived ingredients were not toxic in acute oral studies using mice and rats. In parenteral studies, the LD(50) using mice was > 200 mg/kg, rats was > 50 mg/kg, and using dogs was > 50 mg/kg. In intravenous studies the LD(50) using mice was > 80 mg/kg, rats was > 15 mg/kg, and dogs was > 10 mg/kg. The 14-day no observed effect level (NOEL) for the Aloe polysaccharide, acemannan, in the diet of Sprague-Dawley rats, was 50,000 ppm or 4.1 to 4.6 g/kg day(-1). In a 3-month study using mice, Aloe vera (extracted in ethanol) given orally in drinking water at 100 mg/kg produced reproductive toxicity, inflammation, and mortality above that seen in control animals. Aloe vera extracted in methanol and given to mice at 100 mg/kg in drinking water for 3 months caused significant sperm damage compared to controls. Aloe barbadensis extracted with water and given to pregnant Charles Foster albino rats on gestational days (GDs) 0 through 9 was an abortifacient and produced skeletal abnormalities. Both negative and positive results were found in bacterial and mammalian cell genotoxicity assays using Aloe barbadensis-derived material, Aloe Ferox-derived material, and various anthraquinones derived from Aloe. Aloin (an anthraquinone) did not produce tumors when included in the feed of mice for 20 weeks, nor did aloin increase the incidence of colorectal tumors induced with 1,2-dimethylhydrazine. Aloe-emodin (an anthraquinone) given to mice in which tumor cells had been injected inhibited growth of malignant tumors. Other animal data also suggest that components of Aloe inhibit tumor growth and improve survival. Various in vitro assays also demonstrated anticarcinogenic activity of aloe-emodin. Diarrhea was the only adverse effect of note with the use of Aloe-derived ingredients to treat asthma, ischemic heart disease, diabetes, ulcers, skin disease, and cancer. Case reports include acute eczema, contact urticaria, and dermatitis in individuals who applied Aloe-derived ingredients topically. The Cosmetic Ingredient Review Expert Panel concluded that anthraquinone levels in the several Aloe Barbaden

2007-01-01

377

Plant size effects on the relationships among specific leaf area, leaf nutrient content, and photosynthetic capacity in tropical woody species  

Microsoft Academic Search

To test whether leaf trait relationships vary with plant size, specific leaf area (SLA), area- and mass-based leaf nutrient contents (Narea and Nmass, Parea and Pmass), and area- and mass-based leaf photosynthetic capacities (Aarea and Amass) of 127 small individuals (woody plants shorter than 2 m) and 47 large trees (taller than 10 m) were measured in a tropical montane rain forest,

Fude Liu; Wenjie Yang; Zhongsheng Wang; Zhen Xu; Hong Liu; Ming Zhang; Yuhong Liu; Shuqing An; Shucun Sun

2010-01-01

378

The assessment of leaf water content using leaf reflectance ratios in the visible, near?, and short?wave?infrared  

Microsoft Academic Search

The common features of spectral reflectance from vegetation foliage upon leaf dehydration are decreasing water absorption troughs in the near?infrared (NIR) and short?wave?infrared (SWIR). We studied which leaf water index in the NIR and SWIR is most suitable for the assessment of leaf water content and the detection of leaf dehydration from the laboratory standpoint. We also examined the influence

A. Hoehn; L. S. Stodieck; D. M. Klaus; W. W. Adams III; W. J. Emery

2008-01-01

379

Xylem Cavitation in the Leaf of Prunus laurocerasus and Its Impact on Leaf Hydraulics1  

PubMed Central

This paper reports how water stress correlates with changes in hydraulic conductivity of stems, leaf midrib, and whole leaves of Prunus laurocerasus. Water stress caused cavitation-induced dysfunction in vessels of P. laurocerasus. Cavitation was detected acoustically by counts of ultrasonic acoustic emissions and by the loss of hydraulic conductivity measured by a vacuum chamber method. Stems and midribs were approximately equally vulnerable to cavitations. Although midribs suffered a 70% loss of hydraulic conductance at leaf water potentials of ?1.5 MPa, there was less than a 10% loss of hydraulic conductance in whole leaves. Cutting and sealing the midrib 20 mm from the leaf base caused only a 30% loss of conduction of the whole leaf. A high-pressure flow meter was used to measure conductance of whole leaves and as the leaf was progressively cut back from tip to base. These data were fitted to a model of hydraulic conductance of leaves that explained the above results, i.e. redundancy in hydraulic pathways whereby water can flow around embolized regions in the leaf, makes whole leaves relatively insensitive to significant changes in conductance of the midrib. The onset of cavitation events in P. laurocerasus leaves correlated with the onset of stomatal closure as found recently in studies of other species in our laboratory.

Nardini, Andrea; Tyree, Melvin T.; Salleo, Sebastiano

2001-01-01

380

Influence of Internal Sugar Levels on Apoplasmic Retrieval of Exogenous Sucrose in Source Leaf Tissue 1  

PubMed Central

Sugar levels in Beta vulgaris leaves were increased by heat-girdling the petiole and returning the plant to the controlled-environment chamber for 10 and 34 hours. After 10 hours, sucrose influx into the treated leaves was similar to the controls, although sucrose levels increased from 2.1 to 5.3 micromoles per milligram chlorophyll. However, after a 34-hour treatment, sucrose levels increased from 2.1 to 11.5 micromoles per milligram chlorophyll. In this instance, sucrose influx decreased relative to the untreated controls. Decreasing sugar levels by DCMU treatment resulted in a small stimulation of sucrose influx. A similar DCMU treatment applied to leaves of Allium cepa also resulted in an increase in sucrose influx. However, in A. cepa we could not attribute this increase to a lowering of sugar levels, as the kinetic profiles obtained from control leaves did not vary from each other throughout the day, despite considerable changes in sugar levels. Additionally, it appeared that sucrose uptake in onion may be set at some point and remains invariant throughout the day. Similar studies were also conducted on discs cut from mature leaves of Spinacia oleracea var America. Between 1 and 8 hours after the onset of the photoperiod, the sucrose content of the spinach leaves increased from 2.6 to 9.3 micromoles per milligram chlorophyll. A comparison of the kinetic profiles obtained from leaf discs, taken at these times, indicated that sucrose uptake was not influenced by these changes in internal sugar levels. The relationship between the above findings and `trans' inhibition of exogenous sucrose uptake is discussed. Although intermediate changes in sugar levels in sugar beet leaves did not appear to affect sucrose influx, autoradiographic studies revealed that these changes dramatically affected the partitioning of exogenously supplied [14C]sucrose. Our results indicate that while intermediate changes in internal sugar levels have little effect on sucrose influx across the plasmalemma, they may dramatically affect partitioning between the phloem and the mesophyll vacuole. Images Fig. 6 Fig. 7

Wilson, Clyde; Lucas, William J.

1987-01-01

381

Leaf abscission phenology of a scrub oak: consequences for growth and survivorship of a leaf mining beetle  

Microsoft Academic Search

Brachys tessellatus is a leaf-mining beetle that attacks Quercus laevis (turkey oak), a deciduous scrub oak in the fall line Sandhills of the southeastern United States. This oak species varies substantially in leaf abscission phenology. In the fall of 1994 we examined leaf abscission patterns at three sites in central South Carolina and found that leaves containing active miners abscised

Kim J. Waddell; Charles W. Fox; Kenneth D. White; Timothy A. Mousseau

2001-01-01

382

Physiological, anatomical and leaf hydraulic effects on leaf water delta18O enrichment in different plant species  

Microsoft Academic Search

Stable oxygen isotope ratios (delta18O) of plant and source waters are valuable tools in the analysis of water and carbon fluxes at leaf, plant, and ecosystem scales. Recent improvements in mechanistic models have significantly advanced the understanding of isotopic leaf water enrichment, which is an important source of delta18O variability in plants and ecosystems. However, the marked variability in leaf

A. Kahmen; S. K. Arndt; T. E. Dawson

2007-01-01

383

Elevated Levels of Both Sucrose-Phosphate Synthase and Sucrose Synthase in Vicia Guard Cells Indicate Cell-Specific Carbohydrate Interconversions.  

PubMed Central

A long series of reports correlate larger stomatal aperture size with elevated concentration of sucrose (Suc) in guard cells. To assess the role and autonomy of guard cells with respect to these changes, we have determined quantitatively the cellular distribution of the synthetic enzyme, Suc-phosphate synthase (SPS) and the degradative enzyme Suc synthase (SS) in Vicia leaflet. As expected for Suc-exporting cells, the photosynthetic parenchyma had a high SPS:SS ratio of approximately 45. Also as expected, in epidermal cells, which had only few and rudimentary plastids, the SPS:SS ratio was low (0.4). Of all cells and tissues measured, those that had the highest specific activity of SPS (about 4.8 [mu]mol mg-1 of protein h-1) were guard cells. Guard cells also had a very high relative specific activity of SS.

Hite, DRC.; Outlaw, W. H.; Tarczynski, M. C.

1993-01-01

384

Elevated levels of both sucrose-phosphate synthase and sucrose synthase in vicia guard cells indicate cell-specific carbohydrate interconversions  

SciTech Connect

A long series of reports correlate larger stomatal aperture size with elevated concentration of sucrose (Suc) in guard cells. To assess the role and autonomy of guard cells with respect to these changes, the authors have determined quantitatively the cellular distribution of the synthetic enzyme, Suc-phosphate synthase (SPS) and the degradative enzyme Suc synthase (SS) in Vicia leaflet. As expected for Suc-exporting cells, the photosynthetic parenchyma had a high SPS:SS ratio of approximately 45. Also as expected, in epdermal cells, which had only few and rudimentary plastids, the SPS:SS ratio was low (0.4). Of all cells and tissues measured, those that had the highest specific activity of SPS (about 4.8 [mu]mol mg[sup [minus]1] of protein h[sup [minus]1]) were guard cells. Guard cells also had a very high relative specific activity of SS. 45 refs., 3 figs.

Hite, D.R.C.; Outlaw, W.H. Jr.; Tarczynski, M.C. (Florida State Univ., Tallahassee (United States))

1993-04-01

385

Using Stream Leaf Packs to Explore Community Assembly  

NSDL National Science Digital Library

In this TIEE experiment, students will explore functional and taxonomic diversity in a stream ecosystem, learn about food web relationships, and learn about the ways in which abiotic and biotic factors determine what organisms are present in a community. Students will make and install artificial leaf packs in a stream, wait for the leaf packs to be colonized by stream organisms, measure abiotic variables that could influence leaf pack colonization, retrieve the leaf packs and classify the organisms they find in both taxonomic and functional ways, and participate in a class discussion of how the leaf pack community is situated within a larger ecosystem.

Hartley, Laurel

2011-08-29

386

The mechanical transmission of euonymus mosaic virus, maple leaf perforation by leaf extract or leaf nucleic acid to herbaceous plants  

Microsoft Academic Search

Conditions for the mechanical transmission of some woody viruses to herbaceous hosts were studied. Viruses from naturally-infected\\u000a spindle tree (Euonymus europaea) and maple (Acer pseudoplatanus) leaves were mechanically transmitted by the homogenate prepared by using charcoal and celite to beans (Phaseolus vulqaris cv. Kocovska and Perlicka). The transmission of Euonymus mosaic virus and maple leaf perforation by nucleic acids prepared

ValÉria ŠUbÍKovÁ

1973-01-01

387

Use of NAP gene to manipulate leaf senescence in plants  

DOEpatents

The present invention discloses transgenic plants having an altered level of NAP protein compared to that of a non-transgenic plant, where the transgenic plants display an altered leaf senescence phenotype relative to a non-transgenic plant, as well as mutant plants comprising an inactivated NAP gene, where mutant plants display a delayed leaf senescence phenotype compared to that of a non-mutant plant. The present invention also discloses methods for delaying leaf senescence in a plant, as well as methods of making a mutant plant having a decreased level of NAP protein compared to that of a non-mutant plant, where the mutant plant displays a delayed leaf senescence phenotype relative to a non-mutant plant. Methods for causing precocious leaf senescence or promoting leaf senescence in a plant are also disclosed. Also disclosed are methods of identifying a candidate plant suitable for breeding that displays a delayed leaf senescence and/or enhanced yield phenotype.

Gan, Susheng; Guo, Yongfeng

2013-04-16

388

Variations in the polarized leaf reflectance of Sorghum bicolor  

NASA Technical Reports Server (NTRS)

The polarized reflectance factor, Rq, of sorghum (Sorghum bicolor, L.) leaves from field-grown plants was measured in situ in the summers of 1983 and 1984. In 1983, three leaves of two randomly selected plants were measured at 2-week intervals. The value of Rq varied, depending on leaf and day of measurement. Measured values of Rq for the adaxial leaf surface ranged from 16 to 53; for the abaxial leaf surface the values ranged from 28 to 69. In 1984, measurements consisted of repeated observations made on the same leaf at biweekly intervals. The values of Rq from the adaxial leaf surface ranged from 26 to 38. Values of Rq from the abaxial leaf surface increased throughout the season, from 16 to 45. Differences in Rq were attributed to changes in surface details of the leaf.

Grant, Lois; Daughtry, C. S. T.; Vanderbilt, V. C.

1987-01-01

389

Leaf-wax n-alkanes record the plant-water environment at leaf flush  

PubMed Central

Leaf-wax n-alkanes 2H/1H ratios are widely used as a proxy in climate reconstruction. Although the broad nature of the relationship between n-alkanes ?2H values and climate is appreciated, the quantitative details of the proxy remain elusive. To examine these details under natural environmental conditions, we studied a riparian broadleaf angiosperm species, Populus angustifolia, growing on water with a constant ?2H value and monitored the ?2H values of leaf-wax n-alkanes and of stem, leaf, stream, and atmospheric waters throughout the entire growing season. Here we found the ?2H values of leaf-wax n-alkanes recorded only a 2-wk period during leaf flush and did not vary for the 19 weeks thereafter when leaves remained active. We found ?2H values of leaf-wax n-alkanes of P. angustifolia record conditions earlier in the season rather than fully integrating the entire growing season. Using these data, we modeled precipitation ?2H values during the time of wax synthesis. We observed that the isotope ratios of this precipitation generally were 2H-enriched compared with mean annual precipitation. This model provides a mechanistic basis of the often-observed 2H-enrichment from the expected fractionation values in studies of broadleaf angiosperm leaf-wax ?2H. In addition, these findings may have implications for the spatial and temporal uses of n-alkane ?2H values in paleoapplications; when both plant community and growth form are known, this study allows the isolation of the precipitation dynamics of individual periods of the growing season.

Tipple, Brett J.; Berke, Melissa A.; Doman, Christine E.; Khachaturyan, Susanna; Ehleringer, James R.

2013-01-01

390

Leaf-wax n-alkanes record the plant-water environment at leaf flush.  

PubMed

Leaf-wax n-alkanes (2)H/(1)H ratios are widely used as a proxy in climate reconstruction. Although the broad nature of the relationship between n-alkanes ?(2)H values and climate is appreciated, the quantitative details of the proxy remain elusive. To examine these details under natural environmental conditions, we studied a riparian broadleaf angiosperm species, Populus angustifolia, growing on water with a constant ?(2)H value and monitored the ?(2)H values of leaf-wax n-alkanes and of stem, leaf, stream, and atmospheric waters throughout the entire growing season. Here we found the ?(2)H values of leaf-wax n-alkanes recorded only a 2-wk period during leaf flush and did not vary for the 19 weeks thereafter when leaves remained active. We found ?(2)H values of leaf-wax n-alkanes of P. angustifolia record conditions earlier in the season rather than fully integrating the entire growing season. Using these data, we modeled precipitation ?(2)H values during the time of wax synthesis. We observed that the isotope ratios of this precipitation generally were (2)H-enriched compared with mean annual precipitation. This model provides a mechanistic basis of the often-observed (2)H-enrichment from the expected fractionation values in studies of broadleaf angiosperm leaf-wax ?(2)H. In addition, these findings may have implications for the spatial and temporal uses of n-alkane ?(2)H values in paleoapplications; when both plant community and growth form are known, this study allows the isolation of the precipitation dynamics of individual periods of the growing season. PMID:23359675

Tipple, Brett J; Berke, Melissa A; Doman, Christine E; Khachaturyan, Susanna; Ehleringer, James R

2013-02-12

391

An AU-rich element in the 3' untranslated region of the spinach chloroplast petD gene participates in sequence-specific RNA-protein complex formation.  

PubMed Central

In chloroplasts, the 3' untranslated regions of most mRNAs contain a stem-loop-forming inverted repeat (IR) sequence that is required for mRNA stability and correct 3'-end formation. The IR regions of several mRNAs are also known to bind chloroplast proteins, as judged from in vitro gel mobility shift and UV cross-linking assays, and these RNA-protein interactions may be involved in the regulation of chloroplast mRNA processing and/or stability. Here we describe in detail the RNA and protein components that are involved in 3' IR-containing RNA (3' IR-RNA)-protein complex formation for the spinach chloroplast petD gene, which encodes subunit IV of the cytochrome b6/f complex. We show that the complex contains 55-, 41-, and 29-kDa RNA-binding proteins (ribonucleoproteins [RNPs]). These proteins together protect a 90-nucleotide segment of RNA from RNase T1 digestion; this RNA contains the IR and downstream flanking sequences. Competition experiments using 3' IR-RNAs from the psbA or rbcL gene demonstrate that the RNPs have a strong specificity for the petD sequence. Site-directed mutagenesis was carried out to define the RNA sequence elements required for complex formation. These studies identified an 8-nucleotide AU-rich sequence downstream of the IR; mutations within this sequence had moderate to severe effects on RNA-protein complex formation. Although other similar sequences are present in the petD 3' untranslated region, only a single copy, which we have termed box II, appears to be essential for in vitro protein binding. In addition, the IR itself is necessary for optimal complex formation. These two sequence elements together with an RNP complex may direct correct 3'-end processing and/or influence the stability of petD mRNA in chloroplasts.

Chen, Q; Adams, C C; Usack, L; Yang, J; Monde, R A; Stern, D B

1995-01-01

392

Cryo-EM study of the spinach chloroplast ribosome reveals the structural and functional roles of plastid-specific ribosomal proteins  

PubMed Central

Protein synthesis in the chloroplast is carried out by chloroplast ribosomes (chloro-ribosome) and regulated in a light-dependent manner. Chloroplast or plastid ribosomal proteins (PRPs) generally are larger than their bacterial counterparts, and chloro-ribosomes contain additional plastid-specific ribosomal proteins (PSRPs); however, it is unclear to what extent these proteins play structural or regulatory roles during translation. We have obtained a three-dimensional cryo-EM map of the spinach 70S chloro-ribosome, revealing the overall structural organization to be similar to bacterial ribosomes. Fitting of the conserved portions of the x-ray crystallographic structure of the bacterial 70S ribosome into our cryo-EM map of the chloro-ribosome reveals the positions of PRP extensions and the locations of the PSRPs. Surprisingly, PSRP1 binds in the decoding region of the small (30S) ribosomal subunit, in a manner that would preclude the binding of messenger and transfer RNAs to the ribosome, suggesting that PSRP1 is a translation factor rather than a ribosomal protein. PSRP2 and PSRP3 appear to structurally compensate for missing segments of the 16S rRNA within the 30S subunit, whereas PSRP4 occupies a position buried within the head of the 30S subunit. One of the two PSRPs in the large (50S) ribosomal subunit lies near the tRNA exit site. Furthermore, we find a mass of density corresponding to chloro-ribosome recycling factor; domain II of this factor appears to interact with the flexible C-terminal domain of PSRP1. Our study provides evolutionary insights into the structural and functional roles that the PSRPs play during protein synthesis in chloroplasts.

Sharma, Manjuli R.; Wilson, Daniel N.; Datta, Partha P.; Barat, Chandana; Schluenzen, Frank; Fucini, Paola; Agrawal, Rajendra K.

2007-01-01

393

Identifying efficacious approaches to chemoprevention with chlorophyllin, purified chlorophylls and freeze-dried spinach in a mouse model of transplacental carcinogenesis  

PubMed Central

The carcinogenic potential of dibenzo[a,l]pyrene (DBP) has been well characterized in numerous animal models. We have previously documented that a single dose of 15 mg/Kg DBP to pregnant mice late in gestation (GD 17) produces an aggressive T-cell lymphoma as well as lung and liver cancer in offspring. The current study examines the chemopreventative properties of chlorophyllin (CHL) and chlorophyll (Chl) in this transplacental carcinogenesis model. Pregnant B6129SF1 females, bred to 129S1/SvIm males, received purified diets incorporated with either 2000 p.p.m. CHL, 2000 p.p.m. Chl or 10% freeze-dried spinach beginning at gestation day 9. Lymphoma-dependent mortality was not significantly altered by maternal consumption of any of the diet and little effect on lung tumor burden in mice surviving to 10 months of age was observed. However, coadministration of CHL at 380 mg/Kg with DBP by gavage (molar ratio of 10:1, CHL:DBP) provided significant protection against DBP-initiated carcinogenesis. Offspring born to dams receiving CHL co-gavaged with DBP exhibited markedly less lymphoma-dependent mortality (P < 0.001). The degree of protection by CHL, compared with controls dosed with DBP in tricaprylin (TCP) as the vehicle, was less marked, but still significant. Coadministration of CHL (TCP as vehicle) also reduced lung tumor multiplicity in mice by ?50% and this was observed throughout the study (P < 0.005). This is the first demonstration that CHL can provide potent chemoprotection in a transplacental carcinogenesis model and support a mechanism involving complex-mediated reduction of carcinogen uptake.

Castro, David J.; Lohr, Christiane V.; Fischer, Kay A.; Waters, Katrina M.; Webb-Robertson, Bobbie-Jo M.; Dashwood, Roderick H.; Bailey, George S.; Williams, David E.

2009-01-01

394

Identifying Efficacious Approaches to Chemoprevention with chlorophyllin, purified chlorophylls and freeze-dried spinach in a Mouse Model of Transplacental Carcinogenesis  

SciTech Connect

The carcinogenic potential of dibenzo[a,l]pyrene (DBP) has been well characterized in numerous animal models. We have previously documented that a single dose of 15 mg/Kg DBP to pregnant mice late in gestation (GD 17) produces an aggressive T-cell lymphoma as well as lung and liver cancer in offspring. The current study examines the chemopreventative properties of chlorophyllin (CHL) and chlorophyll (Chl) in this transplacental carcinogenesis model. Pregnant B6129SF1 females, bred to 129S1/SvIm males, received purified diets incorporated with either 2000 ppm CHL, 2000 ppm Chl, or 10% freeze-dried spinach beginning at gestation day 9. Lymphoma-dependent mortality was not significantly altered by maternal consumption of any of the diet and little effect on lung tumor burden in mice surviving to 10 months of age was observed. However, co-administration of CHL at 380 mg/Kg with DBP by gavage (molar ratio of 10:1, CHL:DBP) provided significant protection against DBP initiated carcinogenesis. Offspring born to dams receiving CHL co-gavaged with DBP exhibited markedly fewer lymphoma-dependent mortalities (p< 0.001). The degree of protection by CHL, compared to controls dosed with DBP in tricaprylin (TCP) as the vehicle, were less marked, but still significant. Co-administration of CHL (TCP as vehicle) also reduced lung tumor multiplicity in mice by approximately 50% and this was observed throughout the study (p< 0.005). This is the first demonstration that CHL can provide potent chemoprotection in a transplacental carcinogenesis model and supports a mechanism involving complex-mediated reduction of carcinogen uptake.

Castro, David J.; Lohr, Christiane V.; Fischer, Kay A.; Waters, Katrina M.; Webb-Robertson, Bobbie-Jo M.; Dashwood, Roderick H.; Bailey, George S.; Williams, David E.

2009-02-01

395

Crystallographic analysis of ribulose 1,5-bisphosphate carboxylase from spinach at 2.4 A resolution. Subunit interactions and active site.  

PubMed

The X-ray structure of the quaternary complex of ribulose 1,5-bisphosphate carboxylase/oxygenase from spinach with CO2, Mg2+ and a reaction-intermediate analogue (CABP) has been determined and refined at 2.4 A resolution. Cyclic non-crystallographic symmetry averaging around the molecular 4-fold axis and phase combination were used to improve the initial multiple isomorphous replacement phases. A model composed of one large subunit and one small subunit was built in the resulting electron density map, which was of excellent quality. Application of the local symmetry gave an initial model of the L8S8 molecule with a crystallographic R-value of 0.43. Refinement of this initial model was performed by a combination of conventional least-squares energy refinement and molecular dynamics simulation using the XPLOR program. Three rounds of refinement, interspersed with manual rebuilding at the graphics display, resulted in a model containing all of the 123 amino acid residues in the small subunit, and 467 of the 475 residues in the large subunit. The R-value for this model is 0.24, with relatively small deviations from ideal stereochemistry. Subunit interactions in the L8S8 molecule have been analysed and are described. The interface areas between the subunits are extensive, and bury almost half of the accessible surface areas of both the large and the small subunit. A number of conserved interaction areas that may be of functional significance have been identified and are described, and biochemical and mutagenesis data are discussed in the structural framework of the model. PMID:2118958

Knight, S; Andersson, I; Brändén, C I

1990-09-01

396

BOREAS TE-5 Leaf Gas Exchange Data  

NASA Technical Reports Server (NTRS)

The BOREAS TE-5 team collected measurements in the NSA and SSA on gas exchange, gas composition, and tree growth. The leaf photosynthetic gas exchange data were collected in the BOREAS NSA and the SSA from 06-Jun- 1994 to 13-Sep- 1994 using a LI-COR 6200 portable photosynthesis system. The data were collected to compare the photosynthetic capacity, stomata] conductance, and leaf intercellular CO, concentrations among the major tree species at the BOREAS sites. The data are average values from diurnal measurements on the upper canopy foliage (sun leaves). The data are available in tabular ASCII files. The data files are available on a CD-ROM (see document number 20010000884), or from the Oak Ridge National Laboratory (ORNL) Distributed Activity Archive Center (DAAC).

Hall, Forrest G. (Editor); Curd, Shelaine (Editor); Ehleriinger, Jim; Brooks, J. Renee; Flanagan, Larry

2000-01-01

397

BOREAS TE-5 Leaf Carbon Isotope Data  

NASA Technical Reports Server (NTRS)

The BOREAS TE-5 team collected measurements in the NSA and SSA on gas exchange, gas composition, and tree growth. This documentation describes leaf carbon isotope data that were collected in 1993 and 1994 at the NSA and SSA OJP sites, the SSA OBS site, and the NSA UBS site. In addition, leaf carbon isotope data were collected in 1994 only at the NSA and SSA OA sites. These data was collected to provide seasonal integrated physiological information for 10 to 15 common species at these 6 BOREAS sites. The data are stored in tabular ASCII files. The data files are available on a CD-ROM (see document number 20010000884), or from the Oak Ridge National Laboratory (ORNL) Distributed Active Archive Center (DAAC).

Hall, Forrest G. (Editor); Curd, Shelaine (Editor); Ehleriinger, Jim; Brooks, J. Renee; Flanagan, Larry

2000-01-01

398

Preventing leaf identity theft with hormones.  

PubMed

Genetic analysis of plant development has begun to demonstrate the importance of hormone synthesis and transport in regulating morphogenesis. In the case of leaf development, for example, auxin pooling determines where a primordium will emerge and leads to the activation of transcription factors, which determine leaf identities by modulating abscisic acid (ABA) and gibberellic acid (GA) concentrations. Signal transduction studies suggest that negative regulation of transcription factors through protein turnover is commonly used as a mechanism of hormone action. Together, these findings suggest that auxin might degrade a repressor that allows the activation of genes that modulate ABA/GA ratios in emerging leaves. With our increased understanding of the molecular basis of hormone signaling, it is becoming possible to overlay important regulators onto signaling modules that determine morphological outputs. PMID:16054431

Lumba, Shelley; McCourt, Peter

2005-10-01

399

Parasitic wasps orient to green leaf volatiles  

Microsoft Academic Search

Summary Undamaged plants emit low levels of green leaf volatiles (GLVs), while caterpillar-damaged and artificially damaged plants emit relatively higher levels of certain GLVs. Female braconid parasitoids,Microplitis croceipes, oriented to both damaged plants and to individual GLVs in no-choice tests in a wind tunnel, but seldom oriented to undamaged plants. Female ichneumonid parasitoids,Netelia heroica, also oriented to individual GLVs in

Douglas W. Whitman; Fred J. Eller

1990-01-01

400

Science Nation: Leaf-cutter Ants  

NSDL National Science Digital Library

In established colonies, millions of leaf-cutter ants cut and carry sections of leaves larger than their own bodies as part of a well choreographed, highly functioning society. With support from the National Science Foundation (NSF),bacteriologist Cameron Currie and his team study ants and their complex, productive societies to help address some of human society's most pressing challenges, such as better drugs and cleaner energy.

401

The effect of variety and maturity on the quality of freeze-dried carrots. The effect of microwave blanching on the nutritional and textural quality of freeze-dried spinach  

NASA Technical Reports Server (NTRS)

Using carrots, the quality of freeze-dried products was studied to determine the optimum varieties and maturation stages for quality attributes such as appearance, flavor, texture, and nutritive value. The quality of freeze-dried carrots is discussed in terms of Gardner color, alcohol insoluble solids, viscosity, and core/cortex ratio. Also, microwave blanching of freeze-dried spinach was studied to determine vitamin interrelationships, anatomical changes, and oxidative deteriorations in terms of preprocessing microwave treatments. Statistical methods were employed in the gathering of data and interpretation of results in both studies.

1979-01-01

402

Ancient pinnate leaf mimesis among lacewings.  

PubMed

Insects have evolved diverse methods of predator avoidance, many of which implicate complex adaptations of their wings (e.g., Phylliidae, Nymphalidae, Notodontidae). Among these, angiosperm leaf mimicry is one of the most dramatic, although the historical origins of such modifications are unclear owing to a dearth of paleontological records. Here, we report evidence of pinnate leaf mimesis in two lacewings (Neuroptera): Bellinympha filicifolia Y. Wang, Ren, Liu & Engel gen. et sp. nov. and Bellinympha dancei Y. Wang, Ren, Shih & Engel, sp. nov., from the Middle Jurassic, representing a 165-million-year-old specialization between insects and contemporaneous gymnosperms of the Cycadales or Bennettitales. Furthermore, such lacewings demonstrate a preangiosperm origin for leaf mimesis, revealing a lost evolutionary scenario of interactions between insects and gymnosperms. The current fossil record suggests that this enigmatic lineage became extinct during the Early Cretaceous, apparently closely correlated with the decline of Cycadales and Bennettitales at that time, and perhaps owing to the changing floral environment resulted from the rise of flowering plants. PMID:20805491

Wang, Yongjie; Liu, Zhiqi; Wang, Xin; Shih, Chungkun; Zhao, Yunyun; Engel, Michael S; Ren, Dong

2010-09-14

403

Stomatal Closure during Leaf Dehydration, Correlation with Other Leaf Physiological Traits1  

PubMed Central

The question as to what triggers stomatal closure during leaf desiccation remains controversial. This paper examines characteristics of the vascular and photosynthetic functions of the leaf to determine which responds most similarly to stomata during desiccation. Leaf hydraulic conductance (Kleaf) was measured from the relaxation kinetics of leaf water potential (?l), and a novel application of this technique allowed the response of Kleaf to ?l to be determined. These “vulnerability curves” show that Kleaf is highly sensitive to ?l and that the response of stomatal conductance to ?l is closely correlated with the response of Kleaf to ?l. The turgor loss point of leaves was also correlated with Kleaf and stomatal closure, whereas the decline in PSII quantum yield during leaf drying occurred at a lower ?l than stomatal closure. These results indicate that stomatal closure is primarily coordinated with Kleaf. However, the close proximity of ?l at initial stomatal closure and initial loss of Kleaf suggest that partial loss of Kleaf might occur regularly, presumably necessitating repair of embolisms.

Brodribb, Tim J.; Holbrook, N. Michele

2003-01-01

404

Leaf morphological effects predict effective path length and enrichment of 18O in leaf water of different Eucalyptus species  

NASA Astrophysics Data System (ADS)

Stable isotopes have been a valuable tool to study water or carbon fluxes of plants and ecosystems. In particular oxygen isotopes (?18O) in leaf water or plant organic material are now beginning to be established as a simple and integrative measure for plant - water relations. Current ?18O models, however, are still limited in their application to a broad range of different species and ecosystems. It remains for example unclear, if species-specific effects such as different leaf morphologies need to be included in the models for a precise understanding and prediction of ?18O signals. In a common garden experiment (Currency Creek Arboretum, South Australia), where over 900 different Eucalyptus species are cultivated in four replicates, we tested effects of leaf morphology and anatomy on ?18O signals in leaf water of 25 different species. In particular, we determined for all species enrichment in 18O of mean lamina leaf water above source water (?18O) as related to leaf physiology as well as leaf thickness, leaf area, specific leaf area and weight and selected anatomical properties. Our data revealed that diurnal ?18O in leaf water at steady state was significantly different among the investigated species and with differences up to 10% at midday. Fitting factors (effective path length) of leaf water ?18O models were also significantly different among the investigated species and were highly affected by species-specific morphological parameters. For example, leaf area explained a high percentage of the differences in effective path length observed among the investigated species. Our data suggest that leaf water ?18O can act as powerful tool to estimate plant - water relations in comparative studies but that additional leaf morphological parameters need to be considered in existing ?18O models for a better interpretation of the observed ?18O signals.

Kahmen, A.; Merchant, A.; Callister, A.; Dawson, T. E.; Arndt, S. K.

2006-12-01

405

The origin of the diversity of leaf venation pattern.  

PubMed

The leaf venation pattern of plants shows remarkable diversity and species-specificity. However, the mechanism underlying the pattern formation and pattern diversity remains unclear. We developed a mathematical model that is based on the positive feedback regulation between plant hormone auxin and its efflux carrier. This system can generate auxin flow pathways by self-organization from an almost homogeneous state. This result explains a well-known experimental phenomenon referred as to "polar auxin transport." The model can produce diverse leaf venation patterns with spatial regularity under similar conditions to those of leaf development, that is, in the presence of leaf expansion and auxin sink. Final venation patterns are strikingly affected by leaf shape and leaf expansion. These results indicate that the positive feedback regulation between auxin and its efflux carrier is a central dynamic in leaf venation pattern formation. The diversity of leaf venation patterns in plant species is probably due to the differences of leaf shape and leaf expansion pattern. PMID:16894601

Fujita, Hironori; Mochizuki, Atsushi

2006-10-01

406

Regulation of leaf senescence and crop genetic improvement.  

PubMed

Leaf senescence can impact crop production by either changing photosynthesis duration, or by modifying the nutrient remobilization efficiency and harvest index. The doubling of the grain yield in major cereals in the last 50 years was primarily achieved through the extension of photosynthesis duration and the increase in crop biomass partitioning, two things that are intrinsically coupled with leaf senescence. In this review, we consider the functionality of a leaf as a function of leaf age, and divide a leaf's life into three phases: the functionality increasing phase at the early growth stage, the full functionality phase, and the senescence and functionality decreasing phase. A genetic framework is proposed to describe gene actions at various checkpoints to regulate leaf development and senescence. Four categories of genes contribute to crop production: those which regulate (I) the speed and transition of early leaf growth, (II) photosynthesis rate, (III) the onset and (IV) the progression of leaf senescence. Current advances in isolating and characterizing senescence regulatory genes are discussed in the leaf aging and crop production context. We argue that the breeding of crops with leaf senescence ideotypes should be an essential part of further crop genetic improvement. PMID:23131150

Wu, Xiao-Yuan; Kuai, Ben-Ke; Jia, Ji-Zeng; Jing, Hai-Chun

2012-12-01

407

Using Leaf Samples to Establish a Library of Tropical Leaf Fingerprints  

NASA Astrophysics Data System (ADS)

Variation in leaf chemistry is directly expressed in spectroscopic patterns of tropical canopies. The goal of the Spectranomics project is to explore this variation in the hopes of developing a method to measure tropical forest diversity remotely from airborne or space-bound spectroscopy in the future. We analyzed tomato leaves for various chemical compositions to better understand the Spectranomics approach to quantifying chemical data of tropical species. We also compared our data to standard data in each analysis. Our results allow us to give the tomato leaves a chemical signature in which we are able to use to compare to other leaf samples. Using this process, we are able to create a library of leaf signatures and document the variety of tree species in tropical forests around the world.

Ngo, P.; Nguyen, R.; Anderson, C.; Weiss, P.

2010-12-01

408

Coordination between leaf and stem traits related to leaf carbon gain and hydraulics across 32 drought-tolerant angiosperms.  

PubMed

We examined 15 traits in leaves and stems related to leaf C economy and water use for 32 co-existing angiosperms at ridge sites with shallow soil in the Bonin Islands. Across species, stem density was positively correlated to leaf mass per area (LMA), leaf lifespan (LLS), and total phenolics and condensed tannins per unit leaf N (N-based), and negatively correlated to leaf osmotic potential and saturated water content in leaves. LMA and LLS were negatively correlated to photosynthetic parameters, such as area-, mass-, and N-based assimilation rates. Although stem density and leaf osmotic potential were not associated with photosynthetic parameters, they were associated with some parameters of the leaf C economy, such as LMA and LLS. In the principal component (PCA) analysis, the first three axes accounted for 74.4% of total variation. Axis 1, which explained 41.8% of the total variation, was well associated with parameters for leaf C and N economy. Similarly, axis 2, which explained 22.3% of the total variation, was associated with parameters for water use. Axis 3, which explained 10.3% of the total variation, was associated with chemical defense within leaves. Axes 1 and 2 separated functional types relatively well, i.e., creeping trees, ruderal trees, other woody plants, C(3) shrubs and forbs, palms, and CAM plants, indicating that plant functional types were characterized by similar attributes of traits related to leaf C and N economy and water use. In addition, when the plot was extended by two unrelated traits, leaf mass-based assimilation rates and stem density, it also separated these functional types. These data indicate that differences in the functional types with contrasting plant strategies can be attributed to functional integration among leaf C economy, hydraulics, and leaf longevity, and that both leaf mass-based assimilation rates and stem density are key factors reflecting the different functions of plant species. PMID:18297313

Ishida, Atsushi; Nakano, Takashi; Yazaki, Kenichi; Matsuki, Sawako; Koike, Nobuya; Lauenstein, Diego L; Shimizu, Michiru; Yamashita, Naoko

2008-05-01

409

Endophytic fungi reduce leaf-cutting ant damage to seedlings  

PubMed Central

Our study examines how the mutualism between Atta colombica leaf-cutting ants and their cultivated fungus is influenced by the presence of diverse foliar endophytic fungi (endophytes) at high densities in tropical leaf tissues. We conducted laboratory choice trials in which ant colonies chose between Cordia alliodora seedlings with high (Ehigh) or low (Elow) densities of endophytes. The Ehigh seedlings contained 5.5 times higher endophyte content and a greater diversity of fungal morphospecies than the Elow treatment, and endophyte content was not correlated with leaf toughness or thickness. Leaf-cutting ants cut over 2.5 times the leaf area from Elow relative to Ehigh seedlings and had a tendency to recruit more ants to Elow plants. Our findings suggest that leaf-cutting ants may incur costs from cutting and processing leaves with high endophyte loads, which could impact Neotropical forests by causing variable damage rates within plant communities.

Bittleston, L. S.; Brockmann, F.; Wcislo, W.; Van Bael, S. A.

2011-01-01

410

Transcriptomic analysis of incised leaf-shape determination in birch.  

PubMed

Plant researchers have focused much attention on leaf shape because of its importance in the identification. To evaluate the impact of intraspecies leaf-shape variation on the transcriptome, a series of Betula pendula 'Dalecarlica' and B. pendula saplings were generated through tissue culture. The leaf shapes and transcriptomes of B. pendula 'Dalecarlica' clones were compared with those of B. pendula clones. The leaf shape of B. pendula 'Dalecarlica' was incised and that of B. pendula was ovate. Transcriptome data revealed numerous changes in gene expression between B. pendula 'Dalecarlica' and B. pendula, including upregulation of 8767 unigenes and downregulation of 8379 unigenes in B. pendula 'Dalecarlica'. A pathway analysis revealed that the transport and signal transduction of auxin were altered in 'Dalecarlica', which may have contributed to its altered leaf shape. These results shed light on variation in birch leaf shape and help identify important genes for the genetic engineering of birch trees. PMID:24013080

Mu, Huaizhi; Lin, Lin; Liu, Guifeng; Jiang, Jing

2013-12-01

411

Opinion: prospects for improving photosynthesis by altering leaf anatomy.  

PubMed

Engineering higher photosynthetic efficiency for greater crop yields has gained significant attention among plant biologists and breeders. To achieve this goal, manipulation of metabolic targets and canopy architectural features has been heavily emphasized. Given the substantial variations in leaf anatomical features among and within plant species, there is large potential to engineer leaf anatomy for improved photosynthetic efficiency. Here we review how different leaf anatomical features influence internal light distribution, delivery of CO(2) to Rubisco and water relations, and accordingly recommend features to engineer for increased leaf photosynthesis under different environments. More research is needed on (a) elucidating the genetic mechanisms controlling leaf anatomy, and (b) the development of a three dimensional biochemical and biophysical model of leaf photosynthesis, which can help pinpoint anatomical features required to gain a higher photosynthesis. PMID:23116676

Tholen, Danny; Boom, Carolina; Zhu, Xin-Guang

2012-12-01

412

Control of wheat leaf growth under saline conditions  

Microsoft Academic Search

\\u000a Water relations parameters in individual cells and the biophysical parameters controlling leaf growth were studied in context\\u000a of salt stress. Various levels of NaCI, ranging from 25 to 250mo1 m-3, were used to salinize the medium. The parameters were measured in growing zone of the first emerged leaf of wheat seedlings\\u000a (cv. Flanders, a British variety). In case of leaf

Hamayun Arif; A. Deri Tomos

413

Quality of paper boards from arecanut leaf sheath  

Microsoft Academic Search

A study was carried on utilizing arecanut leaf sheath for making paper boards. Paper boards were made with various combinations of arecanut leaf sheath with waste paper, 1:1, 1:2, 1:3, 3:1, 2:1, control (100% areca leaf sheath) and the qualities of these paper boards were tested as per the Bureau of Indian Standards (IS: 1060 (part-I)-1966). The paper boards made

R Raghupathy; R Viswanathan

2002-01-01

414

Generality of leaf trait relationships: A test across six biomes  

SciTech Connect

Convergence in interspecific leaf trait relationships across diverse taxonomic groups and biomes would have important evolutionary and ecological implications. Such convergence has been hypothesized to result from trade-offs that limit the combination of plant traits for any species. Here the authors address this issue by testing for biome differences in the slope and intercept of interspecific relationships among leaf traits: longevity, net photosynthetic capacity (A{sub max}), leaf diffusive conductance (G{sub S}), specific leaf area (SLA), and nitrogen (N) status, for more than 100 species in six distinct biomes of the Americas. The six biomes were: alpine tundra-subalpine forest ecotone, cold temperate forest-prairie ecotone, montane cool temperate forest, desert shrubland, subtropical forest, and tropical rain forest. Despite large differences in climate and evolutionary history, in all biomes mass-based leaf N (N{sub mass}), SLA, G{sub S}, and A{sub max} were positively related to one another and decreased with increasing leaf life span. The relationships between pairs of leaf traits exhibited similar slopes among biomes, suggesting a predictable set of scaling relationships among key leaf morphological, chemical, and metabolic traits that are replicated globally among terrestrial ecosystems regardless of biome or vegetation type. However, the intercept (i.e., the overall elevation of regression lines) of relationships between pairs of leaf traits usually differed among biomes. With increasing aridity across sites, species had greater A{sub max} for a given level of G{sub S} and lower SLA for any given leaf life span. Using principal components analysis, most variation among species was explained by an axis related to mass-based leaf traits (A{sub max}, N, and SLA) while a second axis reflected climate, G{sub S}, and other area-based leaf traits.

Reich, P.B. [Univ. of Minnesota, Saint Paul, MN (United States). Dept. of Forest Resources; Ellsworth, D.S. [Brookhaven National Lab., Upton, NY (United States). Dept. of Applied Science; Walters, M.B. [Michigan State Univ., East Lansing, MI (United States). Dept. of Forestry; Vose, J.M. [Forest Service, Otto, NC (United States). Coweeta Hydrological Lab.; Gresham, C. [Clemson Univ., Georgetown, SC (United States). Baruch Forest Inst.; Volin, J.C. [Florida Atlantic Univ., Davie, FL (United States). Div. of Science; Bowman, W.D. [Inst. of Arctic and Alpine Research, Boulder, CO (United States). Mountain Research Station]|[Univ. of Colorado, Boulder, CO (United States). Dept. of Evolutionary, Population, and Organismic Biology

1999-09-01

415

Yield losses caused by leaf roll of potatoes  

Microsoft Academic Search

Summary  The data presented confirm the opinion that the healthy hills adjoined by leaf roll plants on one or on both sides, compensate,\\u000a in part, for the low yield of the leaf roll plants.\\u000a \\u000a The gain in yield of a healthy plant adjoined on both sides by leaf roll plants is approximately double the gain of such plants\\u000a adjoined by a

H. C. Kirkpatrick; F. M. Biodgett

1943-01-01

416

Changes in Pelagic Bacteria Communities Due to Leaf Litter Addition  

Microsoft Academic Search

In many limnetic systems, the input of allochthonous organic matter, e.g., leaf litter, is a substantial source of dissolved\\u000a organic carbon (DOC) for pelagic bacteria, especially in fall and winter when autochthonous DOC production is low. However,\\u000a relatively little is known about community changes of pelagic lake bacteria due to leaf litter input which includes both the\\u000a release of leaf

Kristine Michelle L. Hutalle-Schmelzer; Elke Zwirnmann; Angela Krüger; Hans-Peter Grossart

2010-01-01

417

Predicting tropical plant physiology from leaf and canopy spectroscopy  

Microsoft Academic Search

A broad regional understanding of tropical forest leaf photosynthesis has long been a goal for tropical forest ecologists,\\u000a but it has remained elusive due to difficult canopy access and high species diversity. Here we develop an empirical model\\u000a to predict sunlit, light-saturated, tropical leaf photosynthesis using leaf and simulated canopy spectra. To develop this\\u000a model, we used partial least squares

Christopher E. Doughty; Gregory P. Asner; Roberta E. Martin

2011-01-01

418

Regeneration of peppermint and orange mint from leaf disks  

Microsoft Academic Search

Leaf disks from peppermint, spearmint, orange mint, lavender mint and Scotch spearmint were cultured on various Murashige-Skoog-based media in order to regenerate shoots. A significantly larger average number of orange mint leaf disks regenerated shoots on basal medium containing 44.4 µM benzyladenine (BA) and 250 ml l-1 coconut water (CW). Shoots regenerated from peppermint leaf disks cultured on basal medium

J. M. Van Eck; S. L. Kitto

1992-01-01

419

Clumped distribution of oak leaf miners between and within plants  

Microsoft Academic Search

Leaf miners typically show non-random distributions both between and within plants. We tested the hypothesis that leaf miners on two oak species were clumped on individual host trees and individual branches and addressed whether clumping was influenced by aspects of plant quality and how clumping and\\/or interactions with other oak herbivores affected leaf-miner survivorship. Null models were used to test

Tatiana Cornelissen; Peter Stiling

2008-01-01

420

A worldwide survey of tomato yellow leaf curl viruses  

Microsoft Academic Search

Summary.  ?The name tomato yellow leaf curl virus (TYLCV) has been given to several whitefly-transmitted geminiviruses affecting tomato\\u000a cultures in many tropical and subtropical regions. Hybridization tests with two DNA probes derived from a cloned isolate of\\u000a TYLCV from Israel (TYLCV-ISR) were used to assess the affinities of viruses in naturally infected tomato plants with yellow\\u000a leaf curl or leaf curl

H. Czosnek; H. Laterrot

1997-01-01

421

Protective role of a methanolic extract of spinach (Spinacia oleracea L.) against Pb toxicity in wheat (Triticum aestivum L.) seedlings: beneficial effects for a plant of a nutraceutical used with animals.  

PubMed

Spinach extracts contain powerful natural antioxidants and have been used to improve the response of animal cells to various stress factors. The aim of the present study was to assess the effects of a methanolic extract of spinach (SE) used at two concentrations (21.7 and 217 ppm) on the growth, certain enzymes and antioxidant systems in wheat seedlings under lead stress. When wheat seedlings were grown for 7 days in a solution containing Pb(NO3)2 (3 mM), germination and growth were impaired, while signs of oxidative stress were observed. SE (217 ppm) pretreatment was able to protect seedlings from Pb toxicity by both reducing Pb uptake and Pb-induced oxidative stress. As a consequence, almost normal germination, elongation, biomass and ?-amylase activity were restored by SE (217 ppm) pretreatment of wheat seedlings, in spite of the presence of Pb. Our results support the protective role and the antioxidant effect of SE against Pb. These results show an amazing similarity to the effects of SE in animals, which suggests that providing "nutraceuticals" to plants could improve their "health" status. PMID:23645001

Lamhamdi, Mostafa; Bakrim, Ahmed; Bouayad, Noureddin; Aarab, Ahmed; Lafont, René

2013-10-01

422

Plant Transpiration and its Sensitivity to Increasing Carbon Dioxide Concentration at Leaf, Canopy and Regional Scales  

Microsoft Academic Search

This thesis assembles simulation models for plant transpiration and uses these models to investigate the sensitivity of transpiration rates to the elevation of atmospheric CO_2 concentration at leaf, canopy and regional scales. The leaf transpiration model assembly (LTMA) simulates stomatal conductance, leaf net photosynthesis, leaf boundary layer conductance, mass and energy transfer, leaf energy balance. The stomatal conductance model and

Xiwu Zhan

1995-01-01

423

Ozone-induced ethylene release from leaf surfaces  

SciTech Connect

Ozone-induced stress-ethylene emissions from the adaxial and abaxial leaf surfaces of four plant species (Glycine max (L) Merr. cv. Dare, Lycopersicon esculentum Mill cv. Roma VF, Eucalyptus globulus Labill. and Hedera helix L.) were studied to determine if the stress ethylene diffused through the stomata or cuticle. In plants not exposed to ozone, basal ethylene was detected above both the adaxial and abaxial leaf surfaces of all the plant species examined, indicating that some ethylene can diffuse across the leaf cuticle. Oxone-induced stress ethylene production in all species examined. These data indicate that ozone-induced stress ethylene primarily diffuses from the leaf via the stomata.

Rodecap, K.D.; Tingey, D.T.

1986-01-01

424

Antibacterial activity of various leaf extracts of Merremia emarginata  

PubMed Central

Objective To investigate the antibacterial activity and phytochemical screening of the aqueous, methanol and petroleum ether leaf extracts of Merremia emarginata (M. emarginata). Methods The antibacterial activity of leaf extracts of M. emarginata were evaluated by agar well diffusion method against four selected bacterial species. Results The presence of tannins, flavonoids, amino acids, starch, glycosides and carbohydrates in the different leaf extracts was established. The methanol extract was more effective against Bacillus cereus and Escherichia coli, whereas aqueous extract was more effective against Staphylococcus aureus and Pseudomonas aeruginosa. Conclusions : The results in the present study suggest that M. emarginata leaf can be used in treating diseases caused by the tested organisms.

Elumalai, EK; Ramachandran, M; Thirumalai, T; Vinothkumar, P

2011-01-01

425

Further Studies of the Heat Transfer from a Leaf  

PubMed Central

The resistance to the diffusion of heat and water vapor external to a leaf, can be derived from measurement of the rate of change of the leaf temperature, after a sudden alteration of the intensity of irradiation. The theory of the method has been developed to accommodate the case of a leaf that is freely transpiring, exchanging longwave radiation with the environment and with different internal resistances on the 2 sides of the leaf. It has been successfully applied to measurements on wet blotting paper in the laboratory.

Linacre, E. T.

1967-01-01

426

INTERSPECFIC VARIATION IN SO2 FLUX - LEAF SURFACE 'VERSUS' INTERNAL FLUX, AND COMPONENTS OF LEAF CONDUCTANCE  

EPA Science Inventory

The object of the study was to clarify the relationships among stomatal, residual, and epidermal conductances in determining the flux of SO2 air pollution to leaves. Variations in leaf SO2 and H2O vapor fluxes were determined using four plant species: Pisum sativum L. (garden pea...

427

Replication of tomato yellow leaf curl virus (TYLCV) DNA in agroinoculated leaf discs from selected tomato genotypes  

Microsoft Academic Search

The leaf disc agroinoculation system was applied to study tomato yellow leaf curl virus (TYLCV) replication in explants from susceptible and resistant tomato genotypes. This system was also evaluated as a potential selection tool in breeding programmes for TYLCV resistance. Leaf discs were incubated with a head-to-tail dimer of the TYLCV genome cloned into the Ti plasmid ofAgrobacterium tumefaciens. In

H. Czosnek; A. Kheyr-Pour; B. Gronenborn; E. Remetz; M. Zeidan; A. Altman; H. D. Rabinowitch; S. Vidavsky; N. Kedar; Y. Gafni; D. Zamir

1993-01-01

428

Leaf anatomy during leaf development of photoautotrophically in vitro -grown tobacco plants as affected by growth irradiance  

Microsoft Academic Search

Tobacco (Nicotiana tabacum L.) plants were cultured in vitro photoautotrophically at three levels of irradiance (PAR 400–700 nm): low (LI, 60 µmol m?2 s?1), middle (MI, 180 µmol m?2 s?1) and high (HI, 270 µmol m?2 s?1). Anatomy of the fourth leaf from bottom was followed during leaf development. In HI and MI plants, leaf area expansion started\\u000a earlier as

B. Radochová; I. Tichá

2009-01-01

429

On the temporal variation of leaf magnetic parameters: Seasonal accumulation of leaf-deposited and leaf-encapsulated particles of a roadside tree crown.  

PubMed

Understanding the accumulation behaviour of atmospheric particles inside tree leaves is of great importance for the interpretation of biomagnetic monitoring results. In this study, we evaluated the temporal variation of the saturation isothermal remanent magnetisation (SIRM) of leaves of a roadside urban Platanus × acerifolia Willd. tree in Antwerp, Belgium. We hereby examined the seasonal development of the total leaf SIRM signal as well as the leaf-encapsulated fraction of the deposited dust, by washing the leaves before biomagnetic analysis. On average 38% of the leaf SIRM signal was exhibited by the leaf-encapsulated particles. Significant correlations were found between the SIRM and the cumulative daily average atmospheric PM10 and PM2.5 measurements. Moreover, a steady increase of the SIRM throughout the in-leaf season was observed endorsing the applicability of biomagnetic monitoring as a proxy for the time-integrated PM exposure of urban tree leaves. Strongest correlations were obtained for the SIRM of the leaf-encapsulated particles which confirms the dynamic nature of the leaf surface-accumulated particles. PMID:25000572

Hofman, Jelle; Wuyts, Karen; Van Wittenberghe, Shari; Samson, Roeland

2014-09-15

430

Spectroscopic determination of leaf nutritional, morpholgical, and metabolic traits  

NASA Astrophysics Data System (ADS)

Terrestrial ecosystems, particularly forests, play an important role in the global carbon and water cycles. Remote sensing observations are invaluable to the study of vegetation patterning, ecosystem functioning, and dynamics. This research examined the relationships between leaf optical properties and important leaf structural, biochemical, and metabolic traits that describe the photosynthetic capacity, recalcitrance, and nutrient dynamics of plant canopies. This was done utilizing leaf-level reflectance spectroscopy in conjunction with traditional chemometric statistical techniques designed to handle high-dimensionality data, specifically partial least-squares regression (PLSR). A suite of leaf biochemical and morphological traits were estimated with high accuracy and precision using measurements of dried and ground leaf material with a portable spectroradiometer in conjunction with PLSR modeling. An important result from this study was that a single model could be developed to accurately estimate the variation in leaf traits, including nitrogen and carbon content, lignin, fiber and cellulose, isotopic nitrogen-15, and leaf mass per area, across species, growth environments, throughout the vertical profile of a canopy, and with leaf lifespan. A residual analysis of the model prediction errors showed no significant biases observed by tree species, canopy position, or leaf age. Fresh-leaf reflectance spectroscopy was used to identify the linkages between leaf photosynthetic metabolism and leaf optical properties within controlled and natural environments, and across diverse plant species. Two key parameters controlling photosynthetic rates - the maximum rates of RuBisCO carboxylation (Vcmax) and RuBP regeneration ( Jmax) --- were directly estimated using leaf spectra and concurrent gas-exchange measurements. The models for each variable captured the pronounced temperature sensitivity of plants, and integrated the significant variability in metabolism across species that is related to differences in leaf structure and biochemistry. The PLSR models displayed high accuracy in predictions using independent validation data. Models identified key spectral regions related to leaf biochemistry, including foliar nitrogen and pigments, as well as wavelengths related to the regulation of photosynthesis, dissipation of excess energy and chlorophyll fluorescence. In sum, this research provides a novel empirical basis for estimating parameters critical to the measurement of photosynthetic activity in plants.

Serbin, Shawn P.

431

Proteomic profiling of Tectona grandis L. leaf.  

PubMed

Tectona grandis L. (teak) is one of the premier hardwood timbers in the world, ranking at present in the top five tropical hardwood species in terms of worldwide plantation area. Characteri