| photoinhibition at chilling temperature : fluorescence characteristics of unhardened and cold-acclimated spinach leaves. | the effects of moderate light at chilling temperature on the photosynthesis of unhardened (acclimated to +18° c) and hardened (cold-acclimated) spinach (spinacea oleracea l.) leaves were studied by means of fluorescence-induction measurements at 20° c and 77k and by determination of quantum yield of o2 evolution. exposure to 550 μmol photons·m(-2)·s(-1) at +4° c induced a strong photoinhibition in the unhardened leaves within a few hours. photoinhibition manifested by a decline in quantum yield ... | 1989 | 24212435 |
| response of photosynthesis and respiration of resurrection plants to desiccation and rehydration. | using non-invasive techniques (co2 gas exchange, light scattering, light absorption, chlorophyll fluorescence, chlorophyll luminescence), we have analysed the response of respiration and photosynthesis to dehydration and rehydration of leaves of the resurrection plants craterostigma plantagineum hochst., ramonda mykoni reichb. and ceterach officinarum lam. et dc. and of the drought-sensitive mesophyte spinach (spinacia oleracea l.). the following observations were made: (i) the rate of water los ... | 1989 | 24212344 |
| evidence for a light dependent increase of phosphoglucomutase activity in isolated, intact spinach chloroplasts. | phosphoglucomutase (pgm) activity was measured in spinach (spinacia oleracea l.) chloroplasts. initial enzyme activity in a chloroplast lysate was 5 to 10% of total activity measured with 1 micromolar glucose 1,6-bisphosphate (glc 1,6-p(2)) in the assay. initial pgm activity increased 2- to 3-fold when chloroplasts were illuminated for 10 minutes prior to enzyme measurement and then decreased slowly in the dark. measurements of total enzyme activity were unchanged by prior light treatment. initi ... | 1989 | 16666582 |
| regulation of sucrose-phosphate-synthase activity in spinach leaves by protein level and covalent modification. | a dot-blot technique was developed using monoclonal antibodies to measure, rapidly and accurately, the amount of sucrose-phosphate synthase (sps; ec 2.4.1.14) protein present in a crude extract from spinach (spinacia oleracea l. cv. dark green bloomsdale) leaves; this was compared with sps activity in this material. during leaf development, increased sps activity followed closely the increase in enzyme-protein level, indicating denovo synthesis or altered turn-over rates for sps. in contrast, ac ... | 1989 | 24212279 |
| changes in the activity of the chloroplastic and cytosolic forms of dihydroxyacetone phosphate reductase during maturation of leaves. | young or mature rosette leaves from spinach (spinacia oleracea l.) plants growing in the field, in the greenhouse, or in a growth chamber under a regimen of 8 hours light and 16 hours dark contained 15 to 50 nanomoles per minute per gram wet weight of nadh:dihydroxyacetone phosphate reductase activity. of this activity, 75 to 87% was the chloroplastic isoform and 25 to 13% was the cytosolic form. when plants were induced to senesce, as measured by stem elongation and flowering, the percentage of ... | 1989 | 16666531 |
| chalcone synthases from spinach (spinacia oleracea l.) : ii. immunofluorescence and immunogold localization. | the distribution of the two chalcone synthases in leaves ofspinacia oleracea l. was studied at both the tissue and the subcellular level using immunofluorescence and immunogold techniques. neither technique differentiated between the two enzyme forms. the chalcone synthases are located in the upper and the lower epidermis and to a minor extent in the subepidermal layers. traces of the two enzyme forms may be present in the residual mesophyll. this distribution is independent of leaf age. a simil ... | 1988 | 24226692 |
| chalcone synthases from spinach (spinacia oleracea l.) : i. purification, peptide patterns, and immunological properties of different forms. | the two chalcone-synthase forms from leaves ofspinacia oleracea l. were purified to apparent homogeneity. antibodies were raised against both proteins in rabbits. the specificity of the antibodies was tested using immunotitration, immunoblotting, and immunoelectrophoresis techniques. the antibodies exhibited exclusive specificity for chalcone synthase and did not discriminate between the two antigens. the homodimeric chalcone synthases had the same subunit molecular weight but differed in their ... | 1988 | 24226691 |
| effect of high light intensities on oxygen evolution and the light activation of nadp-malate dehydrogenase in intact spinach chloroplasts. | the factors limiting the photosynthetic carbon metabolism of intact spinach (spinacia oleracea l.) chloroplasts after a high-light pretreatment have been studied. photosynthetic co2 fixation was decreased and became more sensitive to the inhibitory effect of the cyclic-electron-flow inhibitor, antimycin a. depending on the extent of photoinhibition, changing the balance of linear to cyclic electron flow by adding oxaloacetate and antimycin a either did not relieve, or partially relieved the phot ... | 1988 | 24226683 |
| characterization of elemental sulfur in isolated intact spinach chloroplasts. | incubation of intact spinach (spinacia oleracea l.) chloroplasts in the presence of (35)so(4) (2-) resulted in the light-dependent formation of a chloroform-soluble sulfur-containing compound distinct from sulfolipid. we have identified this compound as the most stable form (s(8)) of elemental sulfur (s(0), valence state for s = o) by mass spectrometry. it is possible that elemental sulfur (s(0)) was formed by oxidation of bound sulfide, i.e. after the photoreduction of sulfate to sulfide by int ... | 1988 | 16666485 |
| carbon dioxide-induced oscillations in fluorescence and photosynthesis: role of thylakoid membrane energization in regulation of photosystem ii activity. | the response of co(2) fixation to a sudden increase in ambient co(2) concentration has been investigated in intact leaf tissue from spinach (spinacia oleracea) using a dual channel infrared gas analyzer. simultaneous with these measurements, changes in fluorescence emission associated with a weak, modulated measuring beam were recorded. application of brief (2-3 seconds) dark intervals enabled estimation of the dark fluorescence level (f(o)) under both steady state and transient conditions. the ... | 1988 | 16666432 |
| purification and assay of rubisco activase from leaves. | ribulose 1,5-bisphosphate carboxylase/oxygenase (rubisco) activase protein was purified from spinach leaves by ammonium sulfate precipitation and ion exchange fast protein liquid chromatography. this resulted in 48-fold purification with 70% recovery of activity and yielded up to 18 milligrams of rubisco activase protein from 100 grams of leaves. based on these figures, the protein comprised approximately 2% by weight of soluble protein in spinach (spinacia oleracea l.) leaves. the preparations ... | 1988 | 16666412 |
| phosphate sequestration by glycerol and its effects on photosynthetic carbon assimilation by leaves. | glycerol induced a limitation on photosynthetic carbon assimilation by phosphate when supplied to leaves of barley (hordeum vulgare l.) and spinach (spinacia oleracea l.). this limitation by phosphate was evidenced by (i) reversibility of the inhibition of photosynthesis by glycerol by feeding orthophosphate (ii) a decrease in light-saturated rates of photosynthesis and saturation at a lower irradiance, (iii) the promotion of oscillations in photosynthetic co2 assimilation and in chlorophyll flu ... | 1988 | 24220742 |
| effects of irradiance and methyl viologen treatment on atp, adp, and activation of ribulose bisphosphate carboxylase in spinach leaves. | since activation of ribulose bisphosphate carboxylase (rubisco) by rubisco activase is sensitive to atp and adp in vitro, we aimed to test the correlation between atp level and rubisco activation state in intact leaves of spinacia oleracea l. in response to changes in irradiance and after feeding the electron acceptor methyl viologen. leaves were exposed to various irradiances for 45 minutes at atmospheric partial pressures of co(2) and o(2). after measuring the rate of co(2) assimilation, leave ... | 1988 | 16666396 |
| ferredoxin cross-links to a 22 kd subunit of photosystem i. | we have used a cross-linking approach to study the interaction of ferredoxin (fd) with photosystem i (psi). the cross-linking reagent n-ethyl-3-(3-dimethylaminopropyl) carbodiimide was found to cross-link spinach fd to a 22 kilodalton subunit of psi in both isolated spinach (spinacia oleracea) psi complexes and spinach thylakoid membranes. the product had an apparent molecular weight of 38 kilodaltons on sodium dodecyl sulfate-polyacrylamide gel electrophoresis and was identified as a cross-link ... | 1988 | 16666389 |
| hydrophobic-cluster analysis of plant protein sequences. a domain homology between storage and lipid-transfer proteins. | hydrophobic-cluster analysis was used to characterize a conserved domain located near the c-terminal amino acid sequence of wheat (triticum aestivum) storage proteins. this domain was transformed into a linear template for a global search for similarities in over 5200 protein sequences. in addition to proteins that had already been found to exhibit homology to wheat storage proteins, a previously unreported homology was found with non-specific lipid-transfer proteins from castor bean (ricinus co ... | 1988 | 3214430 |
| detection of polypeptides associated with the cold acclimation process in spinach. | exposure of spinach (spinacia oleracea) seedlings to 5 degrees c for several days has previously been shown to induce a greater tolerance to the stresses of extracellular freezing. associated with this response to low temperature, termed cold acclimation, was a subtle shift in protein synthesis and altered polypeptide composition. two-dimensional gel electrophoresis was used to study the changes in spinach leaf tissue protein synthesis in an effort to identify polypeptides that may play a centra ... | 1988 | 2471636 |
| effects of temperature pretreatment in the dark on photosynthesis of the intact spinach chloroplast. | isolated, intact spinach (spinacia oleracea l. var. "long standing bloomsdale") chloroplasts were heated in the dark and the effect of this treatment on photosynthetic activities was determined at 25 degrees c. dark incubation of the chloroplasts for 10 minutes at 35 degrees c and ph 8.1 resulted in a 50% decline in co(2) photoassimilation. this decline in photosynthetic performance was dependent upon time, temperature, and medium ph with the optimum effect at acidic ph values. photosynthetic de ... | 1988 | 16666267 |
| chloroplast osmotic adjustment and water stress effects on photosynthesis. | previous studies have suggested that chloroplast stromal volume reduction may mediate the inhibition of photosynthesis under water stress. in this study, the effects of spinach (spinacia oleracea, var ;winter bloomsdale') plant water deficits on chloroplast photosynthetic capacity, solute concentrations in chloroplasts, and chloroplast volume were studied. in situ (gas exchange) and in vitro measurements indicated that chloroplast photosynthetic capacity was maintained during initial leaf water ... | 1988 | 16666266 |
| ion homeostasis in chloroplasts under salinity and mineral deficiency: ii. solute distribution between chloroplasts and extrachloroplastic space under excess or deficiency of sulfate, phosphate, or magnesium. | spinach (spinacia oleracea var "yates") plants grown hydroponically were exposed to an excess or deficiency of various mineral ions. solutes were measured in leaf extracts and in isolated intact chloroplasts. under phosphate (120 millimoles per liter nah(2) po(4)), sulfate (200 millimolar per liter (na(2) so(4)), or magnesium excess (150 millimolar per liter mgcl(2)), concentrations of these ions in leaf extracts increased, but in chloroplasts, concentrations of all ions remained constant. conce ... | 1988 | 16666233 |
| nucleotide sequence of cdna clones encoding the complete precursor for the "10-kda" polypeptide of photosystem ii from spinach. | by screening lambda gt11 cdna expression libraries prepared from poly(a+) rna of illuminated (4 and 16 h) spinach seedlings (spinacia oleracea var. monatol), we have recovered phage containing inserts corresponding to the complete "10-kda" precursor polypeptide associated with the water oxidizing photosystem ii. the amino acid sequence deduced from the nucleotide sequence indicates a polypeptide of 140 amino acid residues (15.0 kda). the mature protein is predicted to consist of 99 amino acid re ... | 1988 | 2839473 |
| regulation of ribulose-1,5-bisphosphate carboxylase activity by the activase system in lysed spinach chloroplasts. | ribulose-1,5-bisphosphate (rubp) carboxylase in lysed spinach (spinacia oleracea l. cv virtuosa) chloroplasts that had been partly inactivated at low co(2) and mg(2+) by incubating in darkness with 4 millimolar partially purified rubp was reactivated by light. if purified rubp was used to inhibit dark activation of the enzyme, reactivation by light was not observed unless fructose-1,6-bisphosphate, atp, or adp plus inorganic phosphate were also added. presumably, adp plus inorganic phosphate act ... | 1988 | 16666184 |
| ph and kinetic studies of chloroplast sedoheptulose-1,7-bisphosphatase from spinach (spinacia oleracea). | the aim of this paper is to study some steady-state kinetic properties of sedoheptulose-1,7-bisphosphatase, its ph-dependence and the effect of a substrate analogue, fructose 2,6-bisphosphate. studies were carried out with sedoheptulose 1,7-bisphosphate and with fructose 1,6-bisphosphate, an alternative substrate. the pk values are identical for both substrates, and fructose 2,6-bisphosphate behaves like a competitive inhibitor. these results suggest that there exists a unique active site for ei ... | 1988 | 2844169 |
| differential inhibition and activation of two leaf dihydroxyacetone phosphate reductases : role of fructose 2,6-bisphosphate. | the chloroplastic and cytosolic forms of spinach (spinacia oleracea cv long standing bloomsdale) leaf nadh:dihydroxyacetone phosphate (dhap) reductase were separated and partially purified. the chloroplastic form was stimulated by dithiothreitol, reduced thioredoxin, dihydrolipoic acid, 6-phosphogluconate, and phosphate; the cytosolic isozyme was stimulated by fructose 2,6-bisphosphate but not by reduced thioredoxin. end product components that severely inhibited both forms of the reductase incl ... | 1988 | 16666150 |
| spectral, photophysical, and stability properties of isolated photosystem ii reaction center. | photosystem ii reaction center (rc) preparations isolated from spinach (spinacea oleracea) by the nanba-satoh procedure (o nanba, k satoh 1987 proc natl acad sci usa 84: 109-112) are quite labile, even at 4 degrees c in the dark. simple spectroscopic criteria were developed to characterize the native state of the material. degradation of the rc results in (a) blue-shifting of the red-most absorption maximum, (b) a shift of the 77 k fluorescence maximum from approximately 682 nm to approximately ... | 1988 | 16666138 |
| dodecyl maltoside-sodium dodecyl sulfate two-dimensional polyacrylamide gel electrophoresis of chloroplast thylakoid membrane proteins. | a two-dimensional electrophoretic system has been developed for the separation of chloroplast thylakoid membrane proteins. this system incorporates nondenaturing polyacrylamide gel electrophoresis in the presence of the nonionic detergent dodecyl-beta-d-maltoside in the first dimension and sodium dodecyl sulfate-polyacrylamide gel electrophoresis in the second dimension. thylakoid membranes isolated from spinacia oleracea were solubilized in 1.0% dodecyl-beta-d-maltoside and separated in 4-7% li ... | 1988 | 3407930 |
| coarse control of sucrose-phosphate synthase in leaves: alterations of the kinetic properties in response to the rate of photosynthesis and the accumulation of sucrose. | it has been investigated whether diurnal rhythms of sucrose-phosphate synthase (sps) are involved in controlling the rate of photosynthetic sucrose synthesis. extracts were prepared from spinach (spinacia oleracea l.) and barley (hordeum vulgare l.) leaves and assayed for enzyme activity. the activity of sps increased in parallel with a rising rate of photosynthesis, and was increased by feeding mannose and decreased by supplying inorganic phosphate. in leaf material where sucrose had accumulate ... | 1988 | 24221478 |
| synthesis of mono- and digalactosyldiacylglycerol in isolated spinach chloroplasts. | purified, intact chloroplasts of spinacia oleracea l. synthesize galactose-labeled mono- and digalactosyldiacylglycerol (mgdg and dgdg) from udp-[u-(14)c]galactose. in the presence of high concentrations of unchelated divalent cations they also synthesize tri- and tetra-galactosyldiacylglycerol. the acyl chains of galactose-labeled mgdg are strongly desaturated and such mgdg is a good precursor for dgdg and higher oligogalactolipids. the synthesis of mgdg is catalyzed by udp-gal:sn-1,2-diacylgly ... | 1988 | 16666019 |
| fractional control of photosynthesis by the qb protein, the cytochrome f/b 6 complex and other components of the photosynthesic apparatus. | in order to obtain information on fractional control of photosynthesis by individual catalysts, catalytic activities in photosynthetic electron transport and carbon metabolism were modified by the addition of inhibitors, and the effect on photosynthetic flux was measured using chloroplasts of spinacia oleracea l. in thylakoids with coupled electron transport, light-limited electron flow to ferricyanide was largely controlled by the qb protein of the electron-transport chain. fractional control b ... | 1988 | 24226408 |
| stromal free calcium concentration and light-mediated activation of chloroplast fructose-1,6-bisphosphatase. | light-mediated activation of fructose-1,6-bisphosphatase (ec 3.1.3.11) in intact spinach chloroplasts (spinacia oleracea l.) is enhanced in the presence of 10(-5) molar external free ca(2+). the most pronounced effect is observed during the first minutes of illumination. ruthenium red, an inhibitor of light-induced ca(2+) influx, inhibits this ca(2+) stimulated activation. in isolated stromal preparations, the activation of fructose-1,6-bisphosphatase is already enhanced by 2 minutes of exposure ... | 1988 | 16665924 |
| choline oxidation by intact spinach chloroplasts. | 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 (ad hanson et al. 1985 proc natl acad sci usa 82: 3678-3682). 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 nano ... | 1988 | 16665893 |
| pathways of fatty acid hydroperoxide metabolism in spinach leaf chloroplasts. | the metabolism of 13-hydroperoxylinolenic acid was examined in protoplasts and homogenates prepared from mature leaves of spinach (spinacia oleracea l.). chloroplast membranes were the principal site for metabolism of the compound by at least two highly hydrophobic enzyme systems, hydroperoxide lyase and hydroperoxide dehydrase, the new name for an enzyme system formerly known as hydroperoxide isomerase and hydroperoxide cyclase. hydroperoxide lyase was most active above ph 7 and could be separa ... | 1987 | 16665806 |
| n-ammonia assimilation, 2-oxoglutarate transport, and glutamate export in spinach chloroplasts in the presence of dicarboxylates in the light. | the direct incorporation of (15)nh(4)cl into amino acids in illuminated spinach (spinacia oleracea l.) chloroplasts in the presence of 2-oxoglutarate plus malate was determined. the amido-n of glutamine was the most highly labeled n-atom during (15)nh(4) assimilation in the presence of malate. in 4 minutes the (15)n-label of the amido-n of glutamine was 37% enriched. in contrast, values obtained for both the n-atom of glutamate and the amino-n of glutamine were only about 20% while that of the n ... | 1987 | 16665749 |
| atp-dependent activation of a new form of spinach leaf 6-phosphofructo-2-kinase/fructose 2,6-bisphosphatase. | a novel form of 6-phosphofructo-2-kinase/fructose 2,6-bisphosphatase that possesses little 2-kinase or bisphosphatase activity as isolated has been partially purified from spinach (spinacia oleracea l.) leaves. however, the new form can be activated by pretreatment with mg x atp at room temperature. after atp activation, the fructose 2,6-bisphosphatase activity has a michaelis constant for fructose 2,6-bisphosphate of about 1 mm, and is inhibited by high substrate concentrations (greater than 2 ... | 1987 | 2821921 |
| partial purification of gibberellin oxidases from spinach leaves. | 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(12) --> ga(53) --> ga(44) --> ga(19) --> ga(20). two of these, ga(53) oxidase and ga(19) oxidase, were separable from the other two, ga(44) oxidase and ga(12) 13-hydroxylase, by anion exchange high performance liquid chromatography (hplc). apparent molecular weights of the four enzymes as dete ... | 1987 | 16665690 |
| induction of freezing tolerance in spinach is associated with the synthesis of cold acclimation induced proteins. | spinach (spinacia oleracea l. cv bloomsdale) seedlings cultured in vitro were used to study changes in protein synthesis during cold acclimation. seedlings grown for 3 weeks postsowing on an inorganic-nutrient-agar medium were able to increase their freezing tolerance when grown at 5 degrees c. during cold acclimation at 5 degrees c and deacclimation at 25 degrees c, the kinetics of freezing tolerance induction and loss were similar to that of soil-grown plants. freezing tolerance increased afte ... | 1987 | 16665536 |
| induction of freezing tolerance in spinach during cold acclimation. | spinach (spinacia oleracea l.) seedlings, grown in soil or on an agar medium in vitro, became cold acclimated when exposed to a constant 5 degrees c. plants subjected to cold acclimation, beginning 1 week postgermination, attained freezing tolerance levels similar to that achieved by seedlings that were cold acclimated beginning 3 weeks after sowing. seedlings at 1 week of age had only cotyledonary leaves, while 3-week-old seedlings had developed true leaves. plants grown in vitro were able to i ... | 1987 | 16665535 |
| inhibition of spinach leaf nadph(nadh)-glyoxylate reductase by acetohydroxamate, aminooxyacetate, and glycidate. | acetohydroxamate (aha) and aminooxyacetate (aoa) were found to be potent inhibitors of purified nadph(nadh)-dependent glyoxylate reductase from spinach (spinacia oleracea) leaves. aha was a noncompetitive (ro mixed) inhibitor of the nadph-dependent activity of the reductase with a k(i) of 0.33 millimolar. with nadh serving as a cofactor, aha preferentially bound to the same form of the enzyme as glyoxylate, exhibiting a k(i) of 0.31 millimolar. glycine hydroxamate and l-glutamic acid-gamma-hydro ... | 1987 | 16665491 |
| calcium binding by spinach stromal proteins. | calcium binding to spinach (spinacia oleracea l.) stromal proteins was examined by dual-wavelength spectrophotometry using the metallochromic indicator tetramethylmurexide. the data are consistent with the existence of at least two, probably independent, classes of binding sites. the total number of binding sites varied between 90-155 nmol·mg(-1) protein with "average" binding constants of 1.1-2.7·mm(-1). both mg(2+) and la(3+) inhibited calcium binding competitively, with "average" inhibitor co ... | 1987 | 24227335 |
| non-photochemical quenching of chlorophyll a fluorescence in isolated chloroplasts under conditions of stressed photosynthesis. | non-photochemical quenching of chlorophyll a fluorescence after short-time light, heat and osmotic stress was investigated with intact chloroplasts from spinacia oleracea l. the proportions of non-photochemical fluorescence quenching (q n ) which are related (q e ) and unrelated (q i ) to the transthylakoid proton gradient (δph) were determined. light stress resulted in an increasing contribution of q ito total q n.the linear dependence of q. eand δph, as seen in controls, was maintained. the me ... | 1987 | 24227329 |
| phospholipid and fatty acid composition in mitochondria from spinach (spinacia oleracea) leaves and petioles. a comparative study. | essentially chlorophyll-free mitochondria from photosynthetic (leaf) and non-photosynthetic tissue (petiole) were isolated from spinach (spinacia oleracea). leaf mitochondria were found to contain more phosphatidylcholine than phosphatidylethanolamine compared with petiole mitochondria. galactolipids were found in small and equal amounts (5 mol of galactolipids/100 mol of galactolipids and phospholipids) in both leaf and petiole mitochondria. fatty acid composition showed a significant differenc ... | 1987 | 3632635 |
| oxidation-reduction midpoint potentials of the molybdenum center in spinach nadh:nitrate reductase. | oxidation-reduction midpoint potentials for the molybdenum center in assimilatory nadh:nitrate reductase isolated from spinach (spinacia oleracea) have been determined at ph 7.0 in the presence of dye mediators using epr spectroscopy to monitor formation of mo(v). values for the mo(vi)/mo(v) and mo(v)/mo(iv) couples were determined to be -8 and -42 mv, respectively. | 1987 | 3030817 |
| membrane rupture is the common cause of damage to chloroplast membranes in leaves injured by freezing or excessive wilting. | the effects of freezing and desiccation of spinach leaves (spinacia oleracea l. cv yates) on the thylakoid membranes were assessed using antibodies specific for thylakoid membrane proteins. the peripheral part of the chloroplast coupling factor atpase (cf1) was used as a molecular marker for chemical membrane damage by chaotropic solutes. plastocyanin, a soluble protein localized inside the closed thylakoid membrane system, was a marker for damage by mechanical membrane rupture. after freezing a ... | 1987 | 16665230 |
| the relationship between the activities of the pentose phosphate pathway and glycolysis during early stages of floral induction in spinach. | a quantitative cytochemical study was made of fructokinase, glucokinase, and fructokinase (both pfk-atp and pfk-pp + f-2:6-p) activities in shoot apices of 4-week old spinacia oleracea. the rates of activity of these enzymes in the central zone of the shoot apex of plants kept on a short day regime were compared with those from plants transferred from a range of timing up to 24 h to a continuous light regime when floral induction occurred. a mechanism is suggested explaining how no measurable ch ... | 1987 | 3654278 |
| effects of the sesquiterpene lactone tetraesters thapsigargicin and thapsigargin, from roots of thapsia garganica l., on isolated spinach chloroplasts. | the effect of thapsigargicin and thapsigargin, extracted from the roots of thapsia garganica l., on isolated photosynthetic membranes (thylakoids) and intact chloroplasts from spinach leaves (spinacia oleracea l.) was investigated. both sesquiterpene lactone tetraesters impair membranes and organelles in an identical, chlorophyll-dependent manner. in thylakoids these compounds primarily act as inhibitors of photophosphorylation. at lower sesquiterpene lactone tetraester/chlorophyll ratios, cycli ... | 1987 | 3617076 |
| isolation and purification of chloroplastic spinach (spinacia oleracea) sedoheptulose-1,7-bisphosphatase. | higher-plant sedoheptulose-1,7-bisphosphatase was isolated and purified over 200-fold from spinach (spinacia oleracea) chloroplast stromal extracts to apparent electrophoretic homogeneity by deae-fractogel, molecular sieving on sephadex g-200 and blue b dye-matrix affinity chromatography. it is a protein of mr 66,000, made up of two apparently identical subunits (mr 35,000). the enzyme is activated by reduced thioredoxin fb in the presence of dithiothreitol. its specificity towards sedoheptulose ... | 1987 | 3032163 |
| characterization and properties of the spinach chloroplast transcriptionally active chromosome isolated at high ionic strength. | the transcriptionally active chromosome (tac) of spinach (spinacia oleracea l.) chloroplasts has been isolated at a high ionic strength, with low mechanical shearing, by glycerol gradient centrifugation. the properties of the tac differ from those previously reported for the tac isolated either from euglena chloroplasts or from spinach using a low-ionic-strength solubilization medium and gel filtration. the high-salt-isolated tac is homogenous in density but not in size and contains fewer weakly ... | 1986 | 24232757 |
| spinacia oleracea chloroplast dna sequence homology with ars and arc elements within the inverted repeat, upstream of the rdna operon. | | 1986 | 3774557 |
| gibberellin metabolism in cell-free extracts from spinach leaves in relation to photoperiod. | cell-free extracts capable of converting [(14)c]-labeled gibberellins (gas) were prepared from spinach (spinacia oleracea l.) leaves. [(14)c]-labeled gas, prepared enzymically from [(14)c]mevalonic acid, were incubated with these extracts, and products were identified by gas chromatography-mass spectrometry. the following pathway was found to operate in extracts from spinach leaves grown under long day (ld) conditions: ga(12) --> ga(53) --> ga(44) --> ga(19) --> ga(20). the ph optima for the enz ... | 1986 | 16664991 |
| limitation of photosynthesis by carbon metabolism : ii. o(2)-insensitive co(2) uptake results from limitation of triose phosphate utilization. | the occurrence of o(2)-insensitive photosynthesis at high quantum flux and moderate temperature in spinacia oleracea was characterized by analytical gas exchange measurements on intact leaves. in addition photosynthetic metabolite pools were measured in leaves which had been rapidly frozen under defined gas conditions. upon switching to low o(2) in o(2)-insensitive conditions the atp/adp ratio fell dramatically within one minute. the p-glycerate pool increased over the same time. ribulose bispho ... | 1986 | 16664954 |
| purification and characterization of leu-proteinase, the leucine specific serine proteinase from spinach (spinacia oleracea l.) leaves. | the leucine specific serine proteinase present in the soluble fraction of leaves from spinacia oleracea l. (called leu-proteinase) has been purified by acetone precipitation and a combination of gel-filtration, ion exchange, and adsorption chromatography. this enzyme shows a molecular weight of 60,000 +/- 3,000 daltons, an isoelectric point of 4.8 +/- 0.1, and a relative electrophoretic mobility of 0.58 +/- 0.03. the leu-proteinase catalyzed hydrolysis of p-nitroanilides of n-alpha-substituted(- ... | 1986 | 16664908 |
| freezing of isolated thylakoid membranes in complex media : iii. differences in the pattern of inactivation of photosynthetic reactions. | chloroplast thylakoid membranes isolated from spinach leaves (spinacia oleracea l. cv. monatol) were subjected to a freeze-thaw treatment in a buffered medium containing 70 mm kcl, 30 mm nano3 and 20 mm k2so4 in different combinations. in the presence of the three predominant inorganic electrolytes, inactivation of photophosphorylation was mainly caused by a decrease in the capacity of the photosynthetic electron transport; release of proteins from the membranes was not manifest and light-induce ... | 1986 | 24232033 |
| α-1,4-glucan phosphorylase forms from leaves of spinach (spinacia oleracea l.) : ii. peptide patterns and immunological properties. a comparison with other phosphorylase forms. | peptide patterns and immunological properties of the cytoplasmic and chloroplastic α-1,4-glucan phosphorylase (ec 2.4.1.1) from spinach leaves have been studied and were compared with those of phosphorylases from other sources. the two spinach leaf phosphorylases were immunologically different; a limited cross-reactivity was observed only at high antigen or antibody concentrations. peptide mapping of the two enzymes resulted in complex patterns composed of more than 20 fragments; but no peptide ... | 1986 | 24232025 |
| stimulation of photosynthesis by 2% oxygen at low temperatures is restored by phosphate. | the effect of phosphate feeding on the influence of low (2%) oxygen on photosynthetic carbon assimilation has been investigated in leaf discs of spinach (spinacia oleracea l.) at 12°c. the following observations were made. first, after the transition from 20% o2 to 2% o2, the rate of co2 uptake was inhibited at co2 concentrations between about 250 and about 800 μl co2·l(-1). second, phosphate feeding stimulated the rate of co2 uptake in 20% o2 at higher concentrations of co2 (500-900 μl·l(-1)). ... | 1986 | 24233739 |
| simulation of in situ freezing damage of the photosynthetic apparatus by freezing in vitro of thylakoids suspended in complex media. | chloroplast thylakoid membranes were isolated from leaves of unhardened and cold-acclimated spinach (spinacia oleracea l.). for freezethaw treatment, the membranes were suspended in complex media composed to simulate the solute concentrations in the chloroplast stroma in the unhardened and hardened states of the leaves. in particular, high concentrations of amino acids were applied for simulating the hardened state. after frost treatment, photosynthetic activities and chlorophyll fluorescence pa ... | 1986 | 24233737 |
| salt treatment induces frost hardiness in leaves and isolated thylakoids from spinach. | frost hardiness of spinach (spinacia oleracea l.) leaves was increased by high concentrations of nacl in the hydroponic culture medium. freezing damage was determined by measurement of slow chlorophyll fluorescence quenching after freezing of leaves. both the osmolality of the leaf sap and forst hardiness of the leaves were linearly correlated with the salt concentration in the hydroponic culture medium. freezing damage occurred, irrespective of the extent of frost hardening, when dehydration of ... | 1986 | 24233734 |
| polypeptides of the chloroplast envelope membranes as visualized by immunochemical techniques. | the polypeptides of relative molecular masses (mr) 22,000, 29,000, and 36,000 represent three major constituents of the chloroplast envelope of spinach (spinacia oleracea l.) leaves. the mr 22,000 polypeptide has been localized in the outer membrane, whereas the two other peptides have been attributed to the inner envelope membrane (joyard et al., 1983). the mr 29,000 polypeptide has been identified as the "phosphate translocator" (flügge and heldt, 1979). in this investigation, we studied the t ... | 1986 | 3517143 |
| α-1,4-glucan phosphorylase forms from leaves of spinach (spinacia oleracea l.) i. in situ localization by indirect immunofluorescence. | antisera were raised against two forms of α-1,4-glucan phosphorylase (ec 2.4.1.1) which had been purified from leaves of spinacia oleracea l. immunoglobulin g preparations were isolated from the antisera, and their specificity was ensured by immunoplobulin g preparations were used for in situ localization of the two phosphorylase forms in spinach leaf thin sections by indirect immuno-fluorescence. both enzyme forms were present in the palisade and spongy parenchyma and in the guard cells, but th ... | 1986 | 24240359 |
| effects of light and spermine on senescence of hydrilla and spinach leaves. | light treatment markedly accelerated chlorophyll loss in hydrilla (hydrilla verticillata [l.f.] royle) over dark treatment whereas such acceleration could not be observed in spinach (spinacia oleracea l.) leaf segments. spermine, a polyamine, retarded the loss of chlorophyll in the dark but markedly accelerated this loss in the light during senescence of hydrilla leaves. however, such effect of spermine in the dark was not so pronounced in spinach. the loss of protein was slower in the light tha ... | 1986 | 16664713 |
| partial niche separation in spinacia oleracea l.: an examination of reproductive allocation. | | 1986 | 28556030 |
| the influence of a decrease in irradiance on photosynthetic carbon assimilation in leaves of spinacia oleracea l. | when leaves of spinacia oleracea l. were subjected to a decrease from a saturating to a limiting irradiance, photosynthetic carbon assimilation exhibited a pronounced lag. this comprised a postlower-illumination co2 burst (vines et al. 1982, plant physiol. 70, 629-631) and a slow increase in the rate of carbon assimilation to the new lower steady-state rate. the latter phenomenon was distinguishable from the former because it was present in leaves when photorespiration was inhibited by high conc ... | 1986 | 24240313 |
| the relationship between phosphate status and photosynthesis in leaves : reversibility of the effects of phosphate deficiency on photosynthesis. | spinach (spinacia oleracea l.) and barley (hordeum vulgare l.) were grown in hydroponic culture with varying levels of orthophosphate (pi). when leaves were fed with 20 mmol·l(-1) pi at low co2 concentrations, a temporary increase of co2 uptake was observed in pi-deficient leaves but not in those from plants grown at 1 mmol·l(-1) pi. at high concentrations of co2 (at 21% or 2% o2) the pi-induced stimulation of co2 uptake was pronounced in the pi-deficient leaves. the contents of phosphorylated m ... | 1986 | 24240307 |
| copy numbers of chloroplast and nuclear genomes are proportional in mature mesophyll cells of triticum and aegilops species. | the possibility of estimating the proportion of chloroplast dna (ctdna) and nuclear dna (ndna) in nucleic-acid extracts by selective digestion with the methylation-sensitive restriction enzyme psti, was tested using leaf extracts from spinacia oleracea and triticum aestivum. values of ctdna as percentage ndna were estimated to be 14.58%±0.56 (se) in s. oleracea leaves and 4.97%±0.36 (se) in t. aestivum leaves. these estimates agree well with those already reported for the same type of leaf mater ... | 1986 | 24241861 |
| bicarbonate, not co2, is the species required for the stimulation of photosystem ii electron transport. | evidence is presented that the bicarbonate ion (hco3-), not co2, h2co3 or co32-, is the species that stimulates electron transport in photosystem ii from spinach (spinacia oleracea). advantage was taken of the ph dependence of the ratio of hco3- to co2 at equilibrium in order to vary effectively the concentration of one species while holding the other constant. the hill reaction was stimulated in direct proportion with the equilibrium hco3- concentration, but it was independent of the equilibriu ... | 1986 | 3942713 |
| chlorophyll-protein complexes from euglena gracilis and mutants deficient in chlorophyll b: ii. polypeptide composition. | chlorophyll-protein complexes (cps) obtained from thylakoids of euglena gracilis klebs var bacillaris cori contain the following polypeptides (listed in parentheses in order of prominence after coomassie r-250 staining of polyacrylamide gels): cp ia (66, 18, 22, 22.5, 27.5, 21, 28, 24, 25.5, and 26 kilodaltons [kd]); cp i (66 kd); cpx (41 kd); lhcp(2) (an oligomer of lhcp) (26.5, 28, and 26 kd); cpy (27 and 19 kd); cpa (54 kd); and lhcp (26.5, 28, and 26 kd). mutants of bacillaris low in chlorop ... | 1986 | 16664588 |
| enzyme regulation in c4 photosynthesis: purification, properties, and activities of thioredoxins from c4 and c3 plants. | procedures are described for the purification to homogeneity of chloroplast thioredoxins f and m from leaves of corn (zea mays, a c4 plant) and spinach (spinacea oleracea, a c3 plant). the c3 and c4f thioredoxins were similar immunologically and biochemically, but differed in certain of their physiochemical properties. the f thioredoxins from the two species were capable of activating both nadp-malate dehydrogenase (ec 1.1.1.37) and fructose-1,6-bisphosphatase (ec 3.1.3.11) when tested in standa ... | 1986 | 3004333 |
| plastocyanin is encoded by an uninterrupted nuclear gene in spinach. | plastocyanin is a member of photosynthetic electron transport chains that transfers electrons from cytochrome f to the oxidized p700 chlorophyll a pigment of the photosystem i reaction center. we have isolated and characterized cdna- and genomic clones from spinach (spinacia oleracea) encoding the complete plastocyanin-precursor polypeptide. the amino acid sequence derived from the nucleotide sequence shows that the precursor consists of 168 amino acid residues including a transit sequence of 69 ... | 1986 | 2834087 |
| characterization of calcium fluxes across the envelope of intact spinach chloroplasts. | calcium fluxes across the envelope of intact spinach chloroplasts (spinacia oleracea l.) in the light and in the dark were investigated using the metallochromic indicator arsenazo iii. light induces ca(2+) influx into chloroplasts. the action spectrum of light-induced ca(2+) influx and the inhibitory effect of 3-(3',4'-dichlorophenyl)-1,1-dimethylurea (dcmu) indicate an involement of photosynthetic electron transport in this process. the driving force for light-induced ca(2+) influx is most like ... | 1985 | 24241617 |
| the effect of low osmotic potential on nitrite reduction in intact spinach chloroplasts. | the effect of water stress (reduced osmotic potential) on photosynthetic nitrite reduction was investigated using intact, isolated spinach (spinacia oleracea) chloroplasts. nitrite-dependent o(2) evolution was inhibited 39% at -29.5 bars osmotic potential, relative to a control at -11 bars. in the presence of an uncoupler of photophosphorylation this inhibition was not seen. reduced osmotic potential did not inhibit either methyl viologen reduction or photosynthetic o(2) reduction. these results ... | 1985 | 16664429 |
| effect of triacontanol on chlamydomonas: ii. specific activity of ribulose-bisphosphate carboxylase/oxygenase, ribulose-bisphosphate concentration, and characteristics of photorespiration. | increased photosynthetic co(2) assimilation by chlamydomonas reinhardtii cells treated with triacontanol (tria) was not due to changes in glycolate excretion, co(2) compensation point, or the sensitivity of photosynthetic co(2) assimilation to o(2). kinetic analysis of tria-treated cells showed that the increase in photosynthetic co(2) assimilation was a result of an increase in the apparent v(max) for intact cells. the total activity of ribulose-p(2) carboxylase/oxygenase was higher in cell lys ... | 1985 | 16664415 |
| stromal protein phosphorylation in spinach (spinacia oleracea) chloroplasts. | when intact spinach chloroplasts were supplied with [32p]pi, stromal protein phosphorylation was found to occur in the dark. on illumination the thylakoid protein kinase was activated and the amount of label found in thylakoid proteins quickly exceeded that incorporated into stromal protein, such that the latter was found to account for only 10-15% of the total radioactivity bound to chloroplast proteins after 5 min illumination. the rate of phosphorylation of stromal polypeptides was unchanged ... | 1985 | 4062895 |
| photoinhibition of photosynthesis under anaerobic conditions studied with leaves and chloroplasts of spinacia oleracea l. | the role of oxygen in the photoinactivation of the photosynthetic apparatus of spinacia oleracea l. was investigated. moderate irradiation (1200 μmol photons m(-2)s(-1)) of spinach leaves in an atmosphere of pure nitrogen caused strong inhibition of subsequently measured net co2 assimilation, whereas considerably less photoinhibition was observed in the presence of low partial pressures (10-20 mbar) of o2. the decrease in activity caused by anaerobiosis in the light was not based on stomatal clo ... | 1985 | 24241150 |
| metabolite levels in the stroma of spinach chloroplasts exposed to osmotic stress: effects of the ph of the medium and exogenous dihydroxyacetone phosphate. | the levels of stromal photosynthetic intermediates were measured in isolated intact spinach (spinacia oleracea l.) chloroplasts exposed to reduced osmotic potentials. stressed chloroplasts showed slower rates of metabolite accumulation upon illumination than controls. relative to other metabolites sedoheptulose-1,7-bisphosphate (sbp) and fructose-1,6-bisphosphate (fbp) accumulated in the stroma in the stressed treatments. under these conditions 3-phosphoglycerate (3-pga) efflux to the medium was ... | 1985 | 24241148 |
| effect of temperature on the co2/o 2 specificity of ribulose-1,5-bisphosphate carboxylase/oxygenase and the rate of respiration in the light : estimates from gas-exchange measurements on spinach. | responses of the rate of net co2 assimilation (a) to the intercellular partial pressure of co2 (p i ) were measured on intact spinach (spinacia oleracea l.) leaves at different irradiances. these responses were analysed to find the value of p i at which the rate of photosynthetic co2 uptake equalled that of photorespiratory co2 evolution. at this co2 partial pressure (denoted г), net rate of co2 assimilation was negative, indicating that there was non-photorespiratory co2 evolution in the light. ... | 1985 | 24241146 |
| photoinhibition of photosynthesis in broken chloroplasts as a function of electron transfer rates during light treatment. | photoinhibition was studied in osmotically broken chloroplasts isolated from spinach leaves (spinacia oleracea l.). both whole chain electron transport (measured as ferricyanide-dependent o(2) evolution in the presence of nh(4)cl) and photosystem ii activity (measured as o(2) evolution in the presence of either silicomolybdate plus 3-(3,4-diphenyl)-1,1 dimethylurea or parabenzoquinone) showed similar decreases in activity in response to a photoinhibitory treatment (8 minutes of high light given ... | 1985 | 16664315 |
| monoclonal antibodies to a higher-plant nitrate reductase: differential inhibition of enzyme activities. | a set of monoclonal antibodies has been raised against nadh-nitrate reductase (nr; ec 1.6.6.1) from spinach (spinacea oleracea l.) leaves. antibodies were screened by enzyme-linked immunosorbent assay and by their ability to inhibit various activities of the enzyme. the six monoclonals selected (afrc mac 74 to 79) are all gamma globulins; four (mac 74 to 77) inhibit all terminal donating activities (nadh-nr; flavin mononucleotide, reduced form (fmnh2)-nr; and methyl viologen, reduced form (mv)-n ... | 1985 | 24240965 |
| isolation of photosystem i complexes from octyl glucoside/sodium dodecyl sulfate solubilized spinach thylakoids : characterization and reconstitution into liposomes. | we have used the nonionic detergent octyl-beta-d-glucopyranoside in combination with sodium dodecyl sulfate to isolate two novel photosystem i (psi) complexes from spinach (spinacea oleracea l.) thylakoid membranes. these complexes have been characterized as to their spectral properties, content of psi reaction center chlorophyll p(700), and protein composition. psi-b, purified from solubilized membranes by sucrose density gradient centrifugation, is a putative native psi complex. psi-b contains ... | 1985 | 16664291 |
| association of fe-s center(s) with the large subunit(s) of photosystem i particles. | treatment of photosystem i particles from spinach (spinacia oleracea) with dodecyl sulfate destroyed the protein-bound fe-s centers and converted some of the acid-labile sulfide to zero-valence sulfur which remained covalently bound to the proteins. when the proteins were resolved by gel-permeation chromatography or by polyacrylamide gel electrophoresis in the presence of dodecyl sulfate, a considerable amount of zero-valence sulfur was associated with the large molecular weight polypeptide(s) ( ... | 1985 | 2995329 |
| an electron transport system in maize roots for reactions of glutamate synthase and nitrite reductase : physiological and immunochemical properties of the electron carrier and pyridine nucleotide reductase. | a non-heme iron containing protein which bears an antigenic similarity to ferredoxin from spinach leaves (spinacia oleracea l.) has been identified in extracts prepared from young roots of maize (zea mays l., hybrid w64a x w182e). the ferredoxin-like root electron carrier could substitute for ferredoxin in a cytochrome c reduction system in which pyridine nucleotide (nadph) reduces the root electron carrier in a reaction catalyzed by ferredoxin-nadp(+) reductase (ec 1.6.7.1) from spinach leaves. ... | 1985 | 16664248 |
| altered gene expression during cold acclimation of spinach. | exposure of spinach (spinacia oleracea l.) plants to a constant 5 degrees c induced a greater tolerance to extracellular freezing. the metabolic basis of this cold acclimation response in plants is not understood. in this study we tested the hypothesis that cold acclimation derives from altered gene transcription. we found that exposure of plants to low temperature resulted in a rapid and stable change in the translatable poly(a)+ rna populations extracted from leaves, as determined by a cell-fr ... | 1985 | 3858842 |
| development of cytosol and chloroplast aldolases during germination of spinach seeds. | the total activity of aldolase (ec 4.1.2.13) and the activities of cytosol and chloroplast aldolase were determined in seeds, cotyledons, primary leaves and secondary leaves of spinach (spinacia oleracea l., cv. monopa) during germination. total aldolase activity in cotyledons increased from low levels to a low maximum in the dark after one week and to a high maximum in white light after three to four weeks and declined thereafter. the activity in primary and secondary leaves started to rise str ... | 1985 | 24249508 |
| potentiel intracellulaire du mésophylle d'épinard (spinacia oleracea l. cv. nobel) en relation avec la lumière et l'induction florale. | using glass microelectrodes we studied (in spinach, a long-day plant) the characteristics of the intracellular potential of mesophyll cells as well as its response towards light, in particular during the transfer of the plant to an inductive photoperiod (transfer from short day to continuous photoperiod). when 20 minutes treatments of alternating white light (2 minutes) and darkness (2 minutes) are provided every 2 hours (during the photo-or nyctoperiod), the amplitude of the bioelectrical respo ... | 1985 | 23196180 |
| inhibition of photosynthetic reactions by light : a study with isolated spinach chloroplasts. | illumination of isolated intact chloroplasts of spinacia oleracea l. for 10 min with 850 w m(-2) red light in the absence of substrate levels of bicarbonate caused severe inhibition of subsequently measured photosynthetic activities. the capacity of co2-dependent o2 evolution and of non-cyclic electron transport were impaired to similar degrees. this photoinactivation was prevented by addition of bicarbonate which allowed normal carbon metabolism to proceed during preillumination. photoinhibitio ... | 1985 | 24249342 |
| abscisic acid accumulation in spinach leaf slices in the presence of penetrating and nonpenetrating solutes. | abscisic acid (aba) accumulated in detached, wilted leaves of spinach (spinacia oleracea l. cv savoy hybrid 612) and reached a maximum level within 3 to 4 hours. the increase in aba over that found in detached turgid leaves was approximately 10-fold. the effects of water stress could be mimicked by the use of thin slices of spinach leaves incubated in the presence of 0.6 molar mannitol, a compound which causes plasmolysis (loss of turgor). about equal amounts of aba were found both in the leaf s ... | 1985 | 16664022 |
| pyruvate-derived amino acids in spinach chloroplasts : synthesis and regulation during photosynthetic carbon metabolism. | a probable carbon flow from the calvin cycle to branched chain amino acids and lipids via phosphoenolpyruvate (pep) and pyruvate was examined in spinach (spinacia oleracea) chloroplasts. the interpendence of metabolic pathways in and outside chloroplasts as well as product and feedback inhibition were studied. it was shown that alanine, aromatic, and small amounts of branched chain amino acids were formed from bicarbonate in purified intact chloroplasts. addition of pep only favored formation of ... | 1984 | 16663866 |
| conversion of glycerate to serine in intact spinach leaf peroxisomes. | intact spinach (spinacia oleracea l.) leaf peroxisomes converted glycerate to serine in the presence of nad and alanine. the reaction proceeded optimally at ph9. addition of oxaloacetate or alpha-ketoglutarate plus aspartate enhanced the conversion about three-fold. alteration of the concentration of one of the reaction components, consisting of 2 mm glycerate, 0.2 mm nad, 0.5 mm oxaloacetate, and 2 mm alanine, revealed half-saturation constants of 0.45 mm for glycerate, 0.06 mm for nad, 0.02 mm ... | 1984 | 6435526 |
| control of photosynthetic sucrose synthesis by fructose 2,6-bisphosphate : iii. properties of the cytosolic fructose 1,6-bisphosphatase. | the cytosolic fructose 1,6-bisphosphatase from spinach (spinacia oleracea u.s. hybrid 424) leaves has been partially purified and its response to fructose 2,6-bisphosphate, amp, and fructose 1,6-bisphosphate studied, using concentrations present in the cytosol during photosynthesis. in the presence of fructose 2,6-bisphosphate, the substrate saturation kinetics for fructose 1,6-bisphosphate are sigmoidal, with half-maximal activity being attained in 0.1 to 1 millimolar concentration range. the i ... | 1984 | 16663666 |
| control of photosynthetic sucrose synthesis by fructose 2,6-bisphosphate : ii. partitioning between sucrose and starch. | the role of fructose 2,6 bisphosphate in partitioning of photosynthate between sucrose and starch has been studied in spinach (spinacia oleracea u.s. hybrid 424). spinach leaf material was pretreated to alter the sucrose content, so that the rate of starch synthesis could be varied. the level of fructose 2,6-bisphosphate and other metabolites was then related to the accumulation of sucrose and the rate of starch synthesis. the results show that fructose 2,6-bisphosphate is involved in a sequence ... | 1984 | 16663665 |
| control of photosynthetic sucrose synthesis by fructose 2,6-bisphosphate : i. coordination of co(2) fixation and sucrose synthesis. | a mechanism is proposed for a feed-forward control of photosynthetic sucrose synthesis, which allows withdrawal of carbon from the chloroplast for sucrose synthesis to be coordinated with the rate of carbon fixation. (a) decreasing the rate of photosynthesis of spinach (spinacia oleracea, u.s. hybrid 424) leaf discs by limiting light intensities or co(2) concentrations leads to a 2-to 4-fold increase in fructose 2,6-bisphosphate. (b) this increase can be accounted for by lower concentrations of ... | 1984 | 16663664 |
| measurement of subcellular metabolite levels in leaves by fractionation of freeze-stopped material in nonaqueous media. | this paper describes a technique for measuring the in vivo metabolite levels in the chloroplast stroma, the cytosol, and the vacuole of spinach (spinacia oleracea u.s.a. hybrid 424) leaves. spinach leaves were freeze stopped and the frozen tissue was ground and lyophilized. the dry material was homogenized by sonication in a mixture of carbon tetrachloride and heptane, and fractionated by density gradient centrifugation. measurements of the activity of marker enzymes in various subcellular compa ... | 1984 | 16663663 |
| light-induced nuclear synthesis of spinach chloroplast fructose-1,6-bisphosphatase. | 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 (2)h(2)o and [(35)s]methionine. the rise of bisphosphatase activity under illumination is strongly inhibited by cycloheximide, but not by the 70s ribosome inhibitor lincocin, which shows t ... | 1984 | 16663662 |
| the co2/o 2 specificity of ribulose 1,5-bisphosphate carboxylase/oxygenase : dependence on ribulosebisphosphate concentration, ph and temperature. | the substrate specificity factor, v cko/vokc, of spinach (spinacia oleracea l.) ribulose 1,5-bisphosphate carboxylase/oxygenase was determined at ribulosebisphosphate concentrations between 0.63 and 200 μm, at ph values between 7.4 and 8.9, and at temperatures in the range of 5° c to 40° c. the co2/o2 specificity was the same at all ribulosebisphosphate concentrations and largely independent of ph. with increasing temperature, the specificity decreased from values of about 160 at 5° c to about 5 ... | 1984 | 24253719 |
| a rapid reverse phase evaporation method for the reconstitution of uncharged thylakoid membrane lipids that resist hydration. | comparison of several lipid reconstitution methods showed that they were not equally efficient at transferring the predominant thylakoid lipid, monogalactosyldiglyceride (mg), to the aqueous phase. we report a reverse phase evaporation method that employs freon 11 as a lipid solvent and is capable of successfully hydrating mg in spinach (spinacia oleracea l.) at room temperature within minutes. using this method it is possible to force an equal weight mixture of mg and digalactosyldiglyceride in ... | 1984 | 16663653 |
| photosynthetic carbon metabolism in leaves and isolated chloroplasts from spinach plants grown under short and intermediate photosynthetic periods. | responses of foliar and isolated intact chloroplast photosynthetic carbon metabolism observed in spinach (spinacia oleracea cv wisconsin bloomsdale) plants exposed to a shortened photosynthetic period (7-hour light/17-hour dark cycle), were used as probes to examine in vivo metabolic factors that exerted rate determination on photosynthesis (ps) and on starch synthesis. compared with control plants propagated continuously on a 12-hour light/12-hour dark cycle, 14 to 15 days were required, subseq ... | 1984 | 16663634 |
| the uptake of gibberellin a1 by suspension-cultured spinacia oleracea cells has a carrier-mediated component. | the kinetics of the uptake of [(3)h]gibberellin a1 (ga1) by light- and dark-grown suspension-cultured cells of spinacia oleracea (spinach) have been studied. use of nonradioactive ga1 and gibberellic acid (ga3) show that the uptake has a saturable and a nonsaturable component. the nonsaturable component increases as the ph is lowered at a fixed concentration of [(3)h]ga1 and is probably caused by non-mediated diffusion of the uncharged protonated species of ga1. the saturable component is not th ... | 1984 | 24258671 |
| characteristics of light-dependent inorganic carbon uptake by isolated spinach chloroplasts. | the light-dependent accumulation of radioactively labeled inorganic carbon in isolated spinach (spinacia oleracea l.) chloroplasts was determined by silicone oil filtering centrifugation. intact chloroplasts, dark-incubated 60 seconds at ph 7.6 and 23 degrees c with 0.5 millimolar sodium bicarbonate, contained 0.5 to 1.0 millimolar internal inorganic carbon. the stromal pool of inorganic carbon increased 5- to 7-fold after 2 to 3 minutes of light. the saturated internal bicarbonate concentration ... | 1984 | 16663542 |
| purification and properties of spinach leaf debranching enzyme. | starch debranching enzyme was purified from intact spinach (spinacia oleracea l. cv vital) chloroplasts and from a spinach leaf extract using affinity chromatography on sepharose 6b-bound cycloheptaamylose (schardinger beta-dextrin). the enzyme from both sources was homogeneous upon sodium dodecyl sulfate-polyacrylamide gel electrophoresis. spinach leaf debranching enzyme appears to consist of a single polypeptide chain, since the molecular weight of the native protein (110,000 daltons) was not ... | 1984 | 16663522 |
| de novo maltotriose biosynthesis from the reducing end by spinacia oleracea l. chloroplasts. | the distribution of (14)c in the various glucose residues of maltotriose was studied as a function of time of photosynthesis of isolated chloroplasts of spinach (spinacia oleracea l.) using (14)co(2). the distribution of label showed that the reducing-end glucose residue was labeled first and the label subsequently distributed to the second and third glucose residues at approximately equal rates.a mechanism for the distribution of label and the synthesis of maltotriose from the reducing end is p ... | 1984 | 16663512 |
| freeze-fracture ultrastructure of thylakoid membranes in chloroplasts from manganese-deficient plants. | leaves from spinach (spinacia oleracea l. cv hybrid 102) plants grown in mn-deficient nutrient solution were characterized by chlorosis, lowered chlorophyll a/b ratio and reduced electron transport. there were characteristic changes in room temperature fluorescence induction kinetics with increased initial yield (f(o)) and decreased variable fluorescence (f(v)). the fluorescence yield after the maximum fell rapidly to a level below f(o). the shape of the rise from f(o) to the maximum was altered ... | 1984 | 16663491 |
| subcellular localization of triacylglycerol synthesis in spinach leaves. | the subcellular location of diacylglycerol acyltransferase (ec 2.3.1.20) in spinach leaves (spinacia oleracea l. cv. longstanding bloomsdale) was determined after sucrose-gradient centrifugation of tissue homogenates. enzyme activity was associated primarily with gradient fractions containing oil bodies and intact chloroplasts. gradient fractions enriched with the endoplasmic reticulum contained insignificant levels of diacylglycerol acyltransferase activity. on the basis of chlorophyll, diacylg ... | 1984 | 27520324 |
| evidence for control of carbon partitioning by fructose 2,6-bisphosphate in spinach leaves. | excision of spinach (spinacia oleracea l.) leaves had no effect on photosynthetic rates, but altered normal carbon partitioning to favor increased formation of starch and decreased formation of sucrose. the changes were evident within 2 hours after excision. concurrently, leaf fructose-2,6-bisphosphate content increased about 5-fold (from 0.1 to 0.5 nanomoles per gram fresh weight). the activities of sucrose-p synthase and cytoplasmic fructose 1,6-bisphosphatase in leaf extracts remained constan ... | 1984 | 16663440 |