| high-frequency oscillations and circadian rhythm of the membrane potential in spinach leaves. | the microelectrode technique was used to follow oscillations in membrane potential in mesophyll cells of spinach (spinacia oleracea l.) during exposure do different photoperiodic conditions. both high-frequency oscillations and circadian variations were observed. the circadian rhythm was imposed on the period of high-frequency oscillation during short days as well as in continuous light: the free-running period was 25.2 h. the average period of high-frequency oscillation increased from 7.64 min ... | 1979 | 24407253 |
| chloroplast phenylalanine ammonia-lyase from spinach leaves : evidence for light-mediated regulation via the ferredoxin/thioredoxin system. | phenylalanine ammonia-lyase (pal) from spinach (spinacia oleracea l.) leaves was resolved into three forms by diethyl-aminoethyl(deae)-cellulose chromatography. two forms were found in isolated chloroplasts, and the third form (the major component) was located outside of the chloroplasts. one of the chloroplast forms of the enzyme (designated the regulatory form) was activated by reduced thioredoxin. neither the other chloroplast form nor the extra-chloroplast form showed a response to thioredox ... | 1979 | 24317559 |
| light-dark regulation of starch metabolism in chloroplasts: ii. effect of chloroplastic metabolite levels on the formation of adp-glucose by chloroplast extracts. | the rate of adp-glucose formation from [(14)c]glucose 6-phosphate and atp by the soluble fraction of lysed chloroplasts is studied as a function of the levels of metabolites (3-phosphoglycerate, orthophosphate, hexose monophosphate, and atp) as determined in whole chloroplasts of spinacia oleracea in light and dark.a change in 3-phosphoglycerate concentration (from 4 to 1.4 millimolar, as in whole chloroplasts during light-dark transition) decreases the rate of adp-glucose formation 6- to 7-fold ... | 1979 | 16660658 |
| light-dark regulation of starch metabolism in chloroplasts: i. levels of metabolites in chloroplasts and medium during light-dark transition. | in spinacia oleracea the kinetics of co(2) fixation, of starch formation, and of changes in the levels of metabolites in chloroplasts and the surrounding medium has been investigated during light-dark and dark-light transitions with isolated intact chloroplasts.the internal level of orthophosphate stays constant throughout a light-dark-light cycle. the concentration of 3-phosphoglycerate in the chloroplasts is about 4 millimolar in the light and decreases in the dark within 3 minutes to about 1. ... | 1979 | 16660657 |
| [sulfate transport across the limiting double membrane or envelope, of spinach chloroplasts]. | evidence is presented for low rates of carrier-mediated uptake of sulphate, thiosulphate and sulphite into the stroma of the c3 plant spinacia oleracea. uptake of sulphate in the dark was followed using two techniques (1) uptake of sulphate [35s] as determined by silicon oil centrifugal filtration and (2) uptake as indicated by inhibition of co2-dependent o2 evolution rates after addition of sulphate. sulphate, thiosulphate and sulphite were transported across the envelope leading to an accumula ... | 1979 | 540107 |
| effect of high cation concentrations on photosystem ii activities. | the effects of wide concentration ranges of nacl, kcl, and mgcl(2) on ferricyanide reduction and the fluorescence induction curve of isolated spinach (spinacia oleracea) chloroplasts were investigated. concentrations of the monovalent salts above 100 mm and mgcl(2) above 25 mm produced a decrease in the rate of ferricyanide reduction by thylakoids uncoupled with 2.5 mm nh(4)cl which cannot be attributed to changes in the primary photochemical capacity of photosystem ii. salt-induced decreases in ... | 1978 | 16660632 |
| studies on cation-induced thylakoid membrane stacking, fluorescence yield, and photochemical efficiency. | trypsin digestion of photosynthetic membranes isolated from spinach (spinacia oleracea l.) leaves eliminates the cation stimulation of chlorophyll fluorescence. high concentrations of cations protect the fluorescence yield against trypsin digestion, and the cation specificity for this protection closely resembles that required for the stimulation of fluorescence by cations. trypsin digestion reverses cation-induced thylakoid stacking, and the time course of this effect seems to parallel that of ... | 1978 | 16660630 |
| the accumulation of neutral red in illuminated thylakoids. | thylakoids isolated from spinach (spinacia oleracea l.) bind only a small fraction of neutral red in the dark whereas they accumulate large amounts of the protonated dye in their inner space under light. light-induced neutral red uptake depends on the size of the proton gradient across the thylakoid membrane but does not follow the mechanism established for amines. instead, the correlation between ph gradient and neutral red uptake can be predicted quantitatively assuming that protonated neutral ... | 1978 | 718876 |
| freeze-thaw injury to isolated spinach protoplasts and its simulation at above freezing temperatures. | possibilities to account for the mechanism of freeze-thaw injury to isolated protoplasts of spinacia oleracea l. cv. winter bloomsdale were investigated. a freeze-thaw cycle to -3.9 c resulted in 80% lysis of the protoplasts. at -3.9 c, protoplasts are exposed to the equivalent of a 2.1 osmolal solution. isolated protoplasts behave as ideal osmometers in the range of concentrations tested (0.35 to 2.75 osmolal), arguing against a minimum critical volume as a mechanism of injury. average protopla ... | 1978 | 16660588 |
| diurnal oscillation of amylolytic activity in spinach chloroplasts. | chloroplasts isolated from spinach (spinacia oleracea l., cv. vital(r)) plants grown under controlled light/dark and temperature regimes, contained the phosphorolytic and amylolytic pathways for starch breakdown. the latter consists at least of alpha- and beta-amylase and maltase. only low amylolytic activity was observed in chloroplasts isolated during the light phase. in chloroplasts prepared during the dark phase, this activity was almost twice as high. these diurnal oscillations of the amylo ... | 1978 | 16660584 |
| chemical cross-linking of neighboring thylakoid membrane polypeptides. | cross-linking between protein components of whole spinach (spinacia oleracea var. nobel) thylakoids and of photosystem i- and ii-enriched thylakoid fractions has been produced by reaction with the bifunctional imidoester dimethyl-3,3'-dithiobispropionimidate dihydrochloride as well as by the oxidation of intrinsic sulfydryl groups with an orthophenanthrolinecupric ion complex. the mixture of membrane proteins and their cross-linked products has been analyzed by two-dimensional sodium dodecyl sul ... | 1978 | 16660519 |
| identification of an acyl donor in steryl ester biosynthesis by enzyme preparations from spinach leaves. | a pathway for steryl ester biosynthesis in acetone powder preparations from spinach (spinacia oleracea l.) leaves has been elucidated; free sterol and 1,2-diglyceride were the substrates. although animals synthesize cholesteryl esters by three distinct biosynthetic pathways, none of these pathways utilizes 1,2-diglyceride as an acyl donor. phosphatidylcholine, phosphatidic acid, triglyceride, 1,3-diglyceride, 1-monoglyceride, free fatty acid, and fatty acyl-coa were not acyl donors for spinach l ... | 1978 | 16660515 |
| malate and dihydroxyacetone phosphate-dependent nitrate reduction in spinach leaf protoplasts. | isolated spinach (spinacia oleracea l. var. bloomsdale) leaf protoplasts reduced nitrate at rates of 9 micromoles per milligram chlorophyll per hour in light with a 3- to 4-fold stimulation in the presence of hco(3) (-). a similar stimulation of nitrate reduction in the absence of co(2) fixation was obtained by the addition of malate, oxaloacetate (oaa), phospho-3-glyceric acid (pga), or dihydroxyacetone phosphate (dhap). stimulation by malate and dhap was light-independent, while the pga and oa ... | 1978 | 16660489 |
| comparison of photosynthetic activities of spinach chloroplasts with those of corn mesophyll and corn bundle sheath tissue. | bundle sheath and mesophyll chloroplasts from zea mays showed comparable rates of o(2) evolution, which amounted to about half of the rate observed in spinach (spinacia oleracea) chloroplasts.ratios of 4.5, 4.6, and 6.2 mn(2+) atoms per 400 chlorophylls were observed in mesophyll, bundle sheath, and spinach chloroplasts, respectively. these ratios roughly correspond to the observed o(2) evolution rates.rates of electron transport from water to methylviologen (photosystem i and ii) in both types ... | 1978 | 16660469 |
| effects of inhibitors of catalase on photosynthesis and on catalase activity in unwashed preparations of intact chloroplasts. | the catalase activity of unwashed preparations containing intact spinach (spinacia oleracea l.) chloroplasts is inhibited both by cyanide and by azide at concentrations which also cause inhibition of photosynthetic co(2)- dependent o(2) evolution.aminotriazole can also be used to inhibit this contaminant catalase, and in this case inhibition of catalase can be achieved at aminotriazole concentrations which have little effect on the rate of photosynthetic co(2) fixation. aminotriazole may be used ... | 1978 | 16660434 |
| activation of chloroplast nadp-linked glyceraldehyde-3-phosphate dehydrogenase by the ferredoxin/thioredoxin system. | nadp-glyceraldehyde-3-p dehydrogenase of spinach (spinacia oleracea) chloroplasts was activated by thioredoxin that was reduced either photochemically with ferredoxin and ferredoxin-thioredoxin reductase or chemically with dithiothreitol. the activation process that was observed with the soluble protein fraction from chloroplasts and with the purified regulatory form of the enzyme was slow relative to the rate of catalysis. the nad-linked glyceraldehyde-3-p dehydrogenase activity that is also pr ... | 1978 | 16660360 |
| light-induced changes of the carotenoid levels in chloroplast envelopes. | the carotenoid content of thylakoids and envelopes isolated from dark-or light-treated spinach (spinacia oleracea l.) chloroplasts was compared. in thylakoids, light induced a decrease of violaxanthin parallel with a stoichiometric increase of zeaxanthin due to violaxanthin deepoxidation. in envelopes, violaxanthin was also decreased and the relative decrease was similar to thylakoids, but zeaxanthin increase was small resulting in an over-all decrease of the amount of envelope carotenoids. when ... | 1978 | 16660330 |
| free flow electrophoresis of chloroplasts. | highly purified intact chloroplasts were isolated from spinach (spinacia oleracea l.) leaves by free flow electrophoresis. morphological and biochemical studies showed that the fraction enriched in intact chloroplasts has a higher protein to chlorophyll ratio and a higher linolenic acid content than the broken organelles of the other fraction. the intact chloroplasts prepared by electrophoresis retained their capacity for co(2) fixation. sodium dodecyl sulfate polyacrylamide gel electrophoresis ... | 1978 | 16660315 |
| low temperature spectral properties of subchloroplast fractions purified from spinach. | spinach (spinacia oleracea l.) chloroplasts solubilized by digitonin were separated into five fractions by sucrose density gradient centrifugation. three of the fractions, f(i), f(ii), and f(iii), corresponding to photosystem i, photosystem ii, and the chlorophyll a/b complex, were purified further by two steps of diethylaminoethyl-cellulose chromatography followed by electrofocusing on an ampholine column. the polypeptide patterns of the fractions were examined by sodium dodecyl sulfate-polyacr ... | 1978 | 16660296 |
| partial characterization of steryl ester biosynthesis in spinach leaves. | acetone powders of a 20,000g pellet fraction from spinach leaves (spinacia oleracea l.) synthesized [4-(14)c]cholesteryl esters when incubated with [4-(14)c]cholesterol. the reaction was inhibited by digitonin. there was a reciprocal relationship between the decline of label in cholesterol and its incorporation into cholesteryl ester, indicating that free cholesterol was the direct precursor for cholesteryl ester biosynthesis. the hydrolysis of cholesteryl [1-(14)c]palmitate into free cholestero ... | 1978 | 16660291 |
| cytokinins in trna obtained from spinacia oleracea l. leaves and isolated chloroplasts. | cytokinin-active ribonucleosides have been isolated from trna of whole spinach (spinacia oleracea l.) leaves and isolated spinach chloroplasts. the trna from spinach leaf blades contained: 6-(4-hydroxy-3-methyl-2-butenylamino)-9-beta-d-ribofuranosylpurine (cis and trans isomers), 6-(3-methyl-2-butenylamino)-9-beta-d-ribofuranosylpurine, and 6-(4-hydroxy-3-methyl-2-butenylamino)-2-methylthio-9-beta-d -ribofuranosylpurine (cis and trans isomers). a method for isolation of large amounts of intact c ... | 1978 | 16660279 |
| effect of phosphon-d on photosynthetic light reactions and on reactions of the oxidative and reductive pentose phosphate cycle in a reconstituted spinach (spinacia oleracea l.) chloroplast system. | phosphon-d (tributyl-2, 4-dichlorobenzylphosphonium chloride), known as an inhibitor of gibberellin biosynthesis, enhances photosynthetic electron transport by up to 200%, with fe(cn) 6 (3-) and nadp(+) being the electron acceptors. maximum stimulation is reached at phosphon-d concentrations around 2-5 μm. at the same time photosynthetic atp formation is gradually inhibited. phosphon-d concentrations over 0.1 mm inhibit electron transport. the uncoupling activity of phosphon-d is manifested by i ... | 1978 | 24414777 |
| properties and intracellular distribution of two phosphoglucomutases from spinach leaves. | two isoenzymes of phosphoglucomutase from spinach (spinacia oleracea l.) leaves can be separated by ammonium-sulfate gradient solubilization or deae-cellulose ion exchange chromatography. they were designated as phosphoglucomutase 1 and 2, according to decreasing electrophoretic mobility towards the anode at ph 8.9. phosphoglucomutase 1 is localized in the stroma of the chloroplasts, phosphoglucomutase 2 is a cytosolic enzyme as judged from aqueous cell fractionation studies. both isoenzymes hav ... | 1978 | 24414634 |
| sources of reducing power for nitrate reduction in spinach leaves. | the possible source of nadh, the energy donor for nitrate reductase (ec 1.6.6.1), has been studied using an in vivo assay involving freezing the material (leaves of spinacea oleracea l.) in liquid nitrogen in order to render the tissue permeable to added substrates. glycolysis and the pentose phosphate pathway were capable of generating nadh through glyceraldehyde-3-phosphate dehydrogenase. malate and isocitrate were also capable of generating nadh white other organic acids tested were not, incl ... | 1978 | 24414563 |
| properties and physiological function of a glutathione reductase purified from spinach leaves by affinity chromatography. | glutathione reductase (ec 1.6.4.2) was purified from spinach (spinacia oleracea l.) leaves by affinity chromatography on adp-sepharose. the purified enzyme has a specific activity of 246 enzyme units/mg protein and is homogeneous by the criterion of polyacrylamide gel electrophoresis on native and sds-gels. the enzyme has a molecular weight of 145,000 and consists of two subunits of similar size. the ph optimum of spinach glutathione reductase is 8.5-9.0, which is related to the function it perf ... | 1978 | 24414099 |
| localization of adenosine 5'-phosphosulfate sulfotransferase in spinach leaves. | roots of spinach (spinacia oleracea l.) seedlings contained only a very low activity of adenosine 5'-phosphosulfate sulfotransferase compared to the cotyledons. adenosine 5'-phosphosulfate sulfotransferase activity increased about tenfold in cotyledons during greening. preparation of organelle fractions from spinach leaves by a combination of differential and isopycnic density gradient centrifugation showed that adenosine 5'-phosphosulfate sulfotransferase banded with nadp-glyceraldehyde-3-phosp ... | 1978 | 24408467 |
| cell organelles from crassulacean-acid-metabolism (cam) plants : i. enzymes in isolated peroxisomes. | cell organelles were isolated from the cam plants crassula lycopodioides lam., bryophyllum calycinum salisb. and sedum rubrotinctum r.t. clausen by isopycnic centrifugation in sucrose gradients. the inclusion of 2.5% ficoll in the grinding medium proved to be essential for a satisfactory separation of cell organelles during the subsequent centrifugation. peroxisomes, mitochondria, and whole and broken chloroplasts were at least partially resolved as judged by marker-enzyme-activity profiles. the ... | 1978 | 24408466 |
| regulation of photosynthetic electron transport and photophosphorylation in intact chloroplasts and leaves of spinacia oleracea l. | oxygen ist reduced by the electron transport chain of chloroplasts during co2 reduction. the rate of electron flow to oxygen is low. since antimycin a inhibited co2-dependent oxygen evolution, it is concluded that cyclic photophosphorylation contributes atp to photosynthesis in chloroplasts which cannot satisfy the atp requirement of co2 reduction by electron flow to nadp and to oxygen. inhibition of photosynthesis by antimycin a was more significant at high than at low light intensities suggest ... | 1978 | 24408259 |
| o2-dependent inhibition of photosynthetic capacity in intact isolated chloroplasts and isolated cells from spinach leaves illuminated in the absence of co2. | when isolated intact chloroplasts or cells from spinach (spinacia oleracea l.) leaves are incubated in the light in the absence of co2, their capacity for subsequent co2-dependent photosynthetic oxygen evolution is drastically decreased. this inhibition is light and oxygen-dependent and can be prevented by addition of bicarbonate. it is concluded that the normal dissipation of photosynthetic energy by carbon assimilation and in processes related to photorespiration is an essential condition for ... | 1978 | 24408108 |
| effect of growth regulators and role of roots in sex expression in spinach. | when 7-d-old plantlets of spinach (spinacia oleracea l.) were immersed with their roots for 24 h in 25 mg/l gibberellic acid (ga3), or 15 mg/l 6-benzylaminopurine (6-bap), or 15 mg/l indole-3-acetic acid (iaa), or 10 mg/l abscisic acid (aba) and subsequently grown on long (18-h) days, the ratio of plants with male and female flowers, which in the controls was almost 1:1 (48 and 52%, respectively), was greatly altered. the treatments with 6-bap, iaa and aba raised the percentage of female plants ... | 1978 | 24408104 |
| oxygen concentration in isolated chloroplasts during photosynthesis. | the o(2) concentration in intact and osmotically disrupted isolated spinach (spinacia oleracea, l.) chloroplasts during photosynthesis was estimated. the chloroplasts were allowed to reduce 3-phosphoglycerate, co(2), or ferricyanide in light until the rate of o(2) production was linear. when the light was turned off o(2) evolution from the chloroplasts continued for a few seconds. this prolonged o(2) evolution is due to an o(2) surplus inside the chloroplasts which equilibrates with that in the ... | 1977 | 16660210 |
| inhibition of chloroplast electron transport reactions by trifluralin and diallate. | the herbicides trifluralin (alpha,alpha,alpha-trifluoro-2,6-dinitro-n, n-dipropyl-p-toluidine) and diallate (s-[2,3-dichloroallyl] diisopropylthiocarbamate) inhibit electron transport, atp synthesis, and cytochrome f reduction by isolated spinach (spinacia oleracea l.) chloroplasts. both compounds inhibit noncyclic electron transport from h(2)o to ferricyanide more than 90% in coupled chloroplasts at concentrations less than 50 mum. neither herbicide inhibits electron transport in assays utilizi ... | 1977 | 16660197 |
| nitrate reductase from spinacea oleracea. fad and the reactivation of the enzyme treated with p-hydroxymercuribenzoate. | spinach nitrate reductase complex previously inactivated by treatment with mercurials p-hydroxymercuribenzoate or p-hydroxymercuriphenyl sulphonate can be reactivated by incubation with dithioerythritol. the reactivation of nadh-diaphorase seems to be fad-dependent, whereas that of fnh2-nitrate reductase is not. the requirement of fad for nadh-inactivation of nitrate reductase treated with p-hydroxymercuribenzoate disappears after treatment with dithioerythritol. | 1977 | 594486 |
| isolation and oxidative properties of intact mitochondria isolated from spinach leaves. | a procedure was described for preparing intact mitochondria from spinach (spinacia oleracea l.) leaves. these mitochondria oxidized succinate, malate, pyruvate, alpha-ketoglutarate, and nadh with good respiratory control and adp/o ratios comparable to those observed with mitochondria from other plant tissues. glycine was oxidized by the preparations. this oxidation linked to the mitochondrial electron transport chain, was coupled to three phosphorylation sites and was sensitive to electron trans ... | 1977 | 16660151 |
| photophosphorylation associated with photosystem ii: iii. characterization of uncoupling, energy transfer inhibition, and proton uptake reactions associated with photosystem ii cyclic photophosphorylation. | a number of uncouplers and energy transfer inhibitors suppress photosystem ii cyclic photophosphorylation catalyzed by either a proton/electron or electron donor. valinomycin and 2,4-dinitrophenol also inhibit photosystem ii cyclic photophosphorylation, but these compounds appear to act as electron transport inhibitors rather than as uncouplers. only when valinomycin, kcl, and 2,4-dinitrophenol were added simultaneously to phosphorylation reaction mixtures was substantial uncoupling observed. ph ... | 1977 | 16660145 |
| photophosphorylation associated with photosystem ii: ii. effects of electron donors, catalyst oxidation, and electron transport inhibitors on photosystem ii cyclic photophosphorylation. | incubation of kcn-hg-nh(2)oh-inhibited spinach (spinacia oleracea l.) chloroplasts with p-phenylenediamine for 10 minutes in the dark prior to illumination produced rates of photosystem ii cyclic photophosphorylation up to 2-fold greater than the rates obtained without incubation. partial oxidation of p-phenylenediaine with ferricyanide produced a similar stimulation of atp synthesis; addition of dithiothreitol suppressed the stimulation observed with incubation. addition of ferricyanide in amou ... | 1977 | 16660144 |
| influence of antimycin a and uncouplers on anaerobic photosynthesis in isolated chloroplasts. | anaerobiosis depresses the light- and bicarbonate-saturated rates of o(2) evolution in intact spinach (spinacia oleracea) chloroplasts by as much as 3-fold from those observed under aerobic conditions. these lower rates are accelerated 2-fold or more by the addition of 1 mum antimycin a or by low concentrations of the uncouplers 0.3 mm nh(4)cl or 0.25 mum carbonyl cyanide m-chlorophenylhydrazone. oxaloacetate and glycerate 3-phosphate reduction rates are also increased by antimycin a or an uncou ... | 1977 | 16660133 |
| influence of ph upon the warburg effect in isolated intact spinach chloroplasts: ii. interdependency of glycolate synthesis upon ph and calvin cycle intermediate concentration in the absence of carbon dioxide photoassimilation. | the light-dependent synthesis of glycolate derived from fructose 1,6-diphosphate, ribose 5-phosphate, or glycerate 3-phosphate was studied in the intact spinach (spinacia oleracea) chloroplasts in the absence of co(2). glycolate yield increased with an elevation of o(2), ph, and the concentration of the phosphorylated compound supplied. no ph optimum was observed as the ph was increased from 7.4 to 8.5. the average maximal rate of glycolate synthesis was 50 mumoles per milligram chlorophyll per ... | 1977 | 16660122 |
| characterization of starch breakdown in the intact spinach chloroplast. | starch degradation with a rate of 1 to 2 microgram-atom carbon per milligram chlorophyll per hour was monitored in the isolated intact spinach (spinacia oleracea) chloroplast which had been preloaded with (14)c-starch photosynthetically from (14)co(2). starch breakdown was dependent upon inorganic phosphate and the (14)c-labeled intermediates formed were principally those of the embden-meyerhof pathway from glucose phosphate to glycerate 3-phosphate. in addition, isotope was found in ribose 5-ph ... | 1977 | 16660081 |
| chloroplast phosphofructokinase: ii. partial purification, kinetic and regulatory properties. | chloroplast phosphofructokinase from spinach (spinacia oleracea l.) was purified approximately 40-fold by a combination of fractionations with ammonium sulfate and acetone followed by chromatography on deae-sephadex a-50. positive cooperative kinetics was observed for the interaction between the enzyme and the substrate fructose 6-phosphate. the optimum ph shifted from 7.7 toward 7.0 as the fructose 6-phosphate concentration was taken below 0.5 mm. the second substrate was mgatp(2-) (michaelis c ... | 1977 | 16660079 |
| glucose transport into spinach chloroplasts. | the uptake of radioactively labeled hexoses and pentoses into the sorbitol-impermeable (3)h(2)o space (the space surrounded by the inner envelope membrane) of spinach (spinacia oleracea l.) chloroplasts has been studied using silicone layer filtering centrifugation. of the compounds tested, d-xylose, d-mannose, l-arabinose, and d-glucose are transported most rapidly, followed by d-fructose and l-arabinose. the rate of l-glucose uptake is only about 5% of that of d-glucose.the transport of d-gluc ... | 1977 | 16660077 |
| reversal of 3-(3,4-dichlorophenyl)-1,1-dimethylurea inhibition of carbon dioxide fixation in spinach chloroplasts and protoplasts by dicarboxylic acids. | 3-(3,4-dichlorophenyl)-1,1-dimethylurea (dcmu) inhibition of (14)co(2) fixation in isolated intact spinach (spinacia oleracea l.) chloroplasts was reversed (by about 34%) by l-malate but not by oxaloacetate (oaa). however, oaa reversed the dcmu inhibition in spinach protoplasts indicating an extrachloroplastic enzyme requirement. extrachloroplastic oaa reduction was coupled with external dihydroxyacetone phosphate (dhap) oxidation, and the malate formed from such coupling might then enter the ch ... | 1977 | 16660042 |
| effect of light and chilling temperatures on chilling-sensitive and chilling-resistant plants. pretreatment of cucumber and spinach thylakoids in vivo and in vitro. | 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 th ... | 1977 | 16659980 |
| inhibition of photosynthesis by azide and cyanide and the role of oxygen in photosynthesis. | cyanide and azide inhibit photosynthesis and catalase activity of isolated, intact spinach (spinacia oleracea) chloroplasts. when chloroplasts are illuminated in the presence of cn(-) or n(3) (-), accumulation of h(2)o(2) is observed, parallel to inhibition of photosynthesis. photosynthetic o(2) evolution is inhibited to the same extent, under saturating light, whether co(2) or phosphoglycerate is present as electron acceptor.the illumination of chloroplasts with cn(-) or n(3) (-) inactivates th ... | 1977 | 16659956 |
| chloroplast glutathione reductase. | glutathione reductase (ec 1.6.4.2) activity is present in spinach (spinacia oleracea l.) chloroplasts. the ph dependence and substrate concentration for half-maximal rate are reported and a possible role in chloroplasts is proposed. | 1977 | 16659940 |
| influence of ph upon the warburg effect in isolated intact spinach chloroplasts: i. carbon dioxide photoassimilation and glycolate synthesis. | the influence of ph upon the o(2) inhibition of (14)co(2) photoassimilation (warburg effect) was examined in intact spinach (spinacia oleracea) chloroplasts. with conditions which favored the warburg effect, i.e. rate-limiting co(2) and 100% o(2), o(2) inhibition was greater at ph 8.4 to 8.5 than at ph 7.5 to 7.8. at ph 8.5, as compared with 7.8, there was an enhanced (14)c-labeling of glycolate, and a decrease of isotope in some phosphorylated calvin cycle intermediates, particularly triose-pho ... | 1977 | 16659887 |
| evidence for alpha-tocopherol function in the electron transport chain of chloroplasts. | the effect of three different stable radicals-2,2-diphenyl-1-picrylhydrazyl, 1,3,5-triphenyl-verdazyl, and galvinoxyl-was studied in photosystem ii of spinach (spinacia oleracea) chloroplasts. inhibition by the three was noted on dimethylbenzoquinone reduction in presence of 2,5-dibromo-3-methyl-6-isopropyl-p-benzoquinone (dbmib) and on silicomolybdate reduction in presence of 3-(3,4-dichlorophenyl)-1,1-dimethylurea (dcmu) in photosystem ii and on the h(2)o --> methylviologen reaction encompassi ... | 1977 | 16659867 |
| nitrite reduction in reconstituted and whole spinach chloroplasts during carbon dioxide reduction. | nitrite reduction in either whole, isolated spinach chloroplasts (spinacia oleracea l.) or in reconstituted spinach chloroplasts is stimulated by a short period of photosynthetic co(2) fixation in the light prior to nitrite addition. with reconstituted chloroplasts, a similar stimulation can be obtained in nitrite reduction without co(2) fixation by the addition of dihydroxyacetone phosphate or fructose 6-phosphate. specific intermediate metabolites of the photosynthetic carbon reduction cycle m ... | 1977 | 16659813 |
| sulfate and sulfite translocation via the phosphate translocator of the inner envelope membrane of chloroplasts. | the permeability of the inner envelope membranes of spinach (spinacia oleracea) chloroplasts to sulfite and sulfate was investigated in vitro, using the technique of silicone oil centrifugal filtration. the results show that there is a permeability towards both ions, resulting in rates of uptake of about 1.0 (so 3 (2-) ) and 0.7 (so 4 (2-) ) μmol mg chlorophyll(-1) h(-1) respectively (external concentration 2 mmol l(-1)). the rates depend on the external concentration of the anions. anion exchan ... | 1977 | 24420671 |
| subcellular distribution of (35)s-sulfur in spinach leaves after application of (35)so 4 (2-) , (35)so 3 (2-) , and (35)so 2. | (35)so2, (35)so 3 (2-) , and (35)so 4 (2-) , respectively, were applied to leaves of spinacia oleracea l. for 60 min in the light. thereafter, the specific activity was determined in the organelles separated by means of sucrose density gradient centrifugation. in mitochondria and peroxisomes, the specific activity was equally distributed in their protein moieties. after application of (35)so2 or (35)so 3 (2-) , the chloroplast lamellae are characterized by elevated specific activity, which is no ... | 1977 | 24419888 |
| in-vitro interaction between chloroplasts and peroxisomes as controlled by inorganic phosphate. | peroxisomes, whole chloroplasts, mitochondria, and broken chloroplasts of spinach (spinacia oleracea l.), each form 1 band at its typical density, when isolated in sucrose gradients by isopycnic centrifugation in glycylglycine buffer. in potassium-phosphate buffer peroxisomes form a 2nd band at the density of whole chloroplasts. the phosphate effect is half-saturated at a concentration of 10-20 mm. if whole chloroplasts are removed by differential centrifugation before isopycnic centrifugation n ... | 1977 | 24419687 |
| cyclic nucleotide phosphodiesterase from spinacea oleracea l: subcellular distribution and properties [proceedings]. | | 1977 | 199507 |
| subcellular localization of o-acetylserine sulfhydrylase in spinach leaves. | a combination of differential centrifugation and isopycnic sucrose density gradient centrifugation of extracts from spinach leaves (spinacia oleracea l.) shows that about 20% of the o-acetylserine sulfhydrylase are associated with chloroplasts. no appreciable amounts of o-acetylserine sulfhydrylase band with mitochondrial and peroxisomal marker enzymes. | 1976 | 1021428 |
| enzymic reconstitution of photosynthetic carbon assimilation. pentose phosphate-dependent o evolution by illuminated envelope-free chloroplasts from spinacia oleracea. | | 1976 | 183119 |
| organelle-specific isozymes of aspartate-alpha-ketoglutarate transaminase in spinach leaves. | four distinct isozymes of aspartate-alpha-ketoglutarate transaminase in a spinach (spinacia oleracea l.) leaf extract were separated by starch gel electrophoresis. of the total aspartate-alpha-ketoglutarate transaminase activity, approximately 45% was represented by the chloroplast isozyme, 26% by the cytosol isozyme, 19% by the mitochondrial isozyme, and 3 to 10% by the peroxisomal isozyme. the aspartate-alpha-ketoglutarate transamination activity in the four subcellular compartments behaved si ... | 1976 | 16659609 |
| the role of the gas phase in the greening and growth of illuminated cell suspension cultures of spinach (spinacia oleracea, l.). | the gas phase developed above spinach suspension cultures critically affected their growth and greening. ethylene accumulation inhibited greening; this effect of ethylene was antagonised when the culture gas phase was enriched with carbon dioxide. greening was enhanced by reducing the partial pressure of oxygen below the air level; this effect was observed when oxygen supply did not restrict growth. | 1976 | 965016 |
| starch degradation in isolated spinach chloroplasts. | a method for loading isolated intact spinach (spinacia oleracea l.) chloroplasts with (14)c-starch is described. these intact chloroplasts were incubated aerobically in the dark for 30 minutes. radioactivity in starch declined and glyceric acid 3-phosphate and maltose were the major radioactive products. it is proposed that starch is degraded within the chloroplast to glyceric acid 3-phosphate and to maltose. | 1976 | 16659602 |
| photoreduction of sulfur dioxide by spinach leaves and isolated spinach chloroplasts. | labeled sulfur dioxide was found to be extensively absorbed by spinach (spinacea oleracea l.) leaves. labeled sulfides detected in leaf blades following fumigations with sulfur dioxide in light indicated that photoreduction of sulfur dioxide had occurred. measurable proportions of this labeled sulfur was localized within the chloroplast fraction. suspensions of isolated chloroplasts supplied with labeled sulfur dioxide contained labeled sulfides following a 30-minute illumination period in water ... | 1976 | 16659572 |
| alterations in chloroplast thylakoids during an in vitro freeze-thaw cycle. | plastocyanin and chloroplast coupling factor 1 (cf(1)) are released from spinach (spinacia oleracea l.) thylakoids during a slow freezethaw cycle. cf(1) addition increases the proton uptake of thylakoids previously frozen in sucrose concentrations of 15 mm to 100 mm. addition of cf(1) and plastocyanin restores the proton uptake of thylakoids frozen in 100 mm sucrose. plastocyanin and cf(1) release is a manifestation, not the cause, of freeze-thaw damage.frozen-thawed thylakoids appear to exhibit ... | 1976 | 16659550 |
| nitrate reductase from spinacea oleracea. fad and the inactivation by nad (p) h. | | 1976 | 5082 |
| organization of electron transport in photosystem ii of spinach chloroplasts according to chelator inhibition sites. | the organization of electron transport in photosystem ii of spinach (spinacia oleracea) chloroplasts was studied by means of various chelators and uncouplers. the partial reactions used included h(2)o-->methyl viologen, h(2)o-->silicomolybdic acid h(2)o-->ferricyanide, and h(2)o-->dimethylbenzoquinone. three types of chelator inhibition were found (a) inhibition common to all pathways and presumably affecting the mn or water oxidation site in photosystem ii (salicylaldoxime, dithizone, acridine, ... | 1976 | 16659501 |
| chlorophyll and peptide compositions in the two photosystems of marine green algae. | the molar ratios of chlorophyll a to b in the thalli of marine green algae were between 1.5 and 2.2, being appreciably lower than the ratio between 2.8 and 3.4 found for the leaves of higher plants and the cells of fresh-water green algae. the ratio of chlorophylls to p-700 in these marine algae was also lower than that in higher plants. the a/b ratios in the pigment proteins of photosystems 1 and 2 separated by polyacrylamide-gel electrophoresis from sodium dodecyl sulfate-solubilized chloropla ... | 1976 | 1247608 |
| effects of ph and oxygen on photosynthetic reactions of intact chloroplasts. | oxygen inhibition of photosynthesis was studied with intact spinach (spinacia oleracea l.) chloroplasts which exhibited very high rates of photosynthetic co(2) reduction and were insensitive to additions of photosynthetic intermediates when co(2) was available at saturating concentrations. photosynthetic rates were measured polarographically as o(2) evolution, and the extent of the reduction of substrate was estimated from the amount of o(2) evolved. with co(2) as substrate, inhibition of photos ... | 1976 | 16659466 |
| the presence of glutathione and glutathione reductase in chloroplasts: a proposed role in ascorbic acid metabolism. | both glutathione and an nadph-dependent glutathione reductase are present in spinach (spinacia oleracea l.) chloroplasts. it is proposed that glutathione functions to stabilise enzymes of the calvin cycle, and it may also act to keep ascorbic acid in chloroplasts in the reduced form. | 1976 | 24425174 |
| the adenosine-5'-phosphosulfate sulfotransferase from spinach (spinacea oleracea l.). stabilization, partial purification, and properties. | adenosine-5'-phosphosulfate (aps) sulfotransferase was purified 25-fold from spinach (spinacea oleracea l.) leaves by sephadex-g-200 gel filtration and chromatography on deae-cellulose. enzyme activity was stabilized with 0.05 m tris-hcl ph 8.0 containing 10 mm mercaptoethanol (me), 10 mm mgcl2, and 30% glycerol. the molecular weight of the aps-sulfotransferase was estimated by gel filtration to be about 110,000 daltons. the enzyme is specific for the sulfonucleotide aps; paps is not a sulfur do ... | 1976 | 24424637 |
| chloroplast growth and replication in germinating spinach cotyledons following massive gamma-irradiation of the seed. | spinach seeds (spinacia oleracea l.) given massive doses of gamma-irradiation (500 krad) germinate and form a seedling with two green cotyledons and a radicle, but develop no further. irradiated cotyledons show no increase in cell number or total dna over a 7-day period in the light, while in control cotyledons there is a small increase in cell number and large increases in total dna and chloroplast number. the chloroplasts of irradiated cotyledons are delayed in their division, become greatly e ... | 1976 | 16659421 |
| effect of oxygen on photosynthesis by spinach leaf protoplasts. | the photosynthetic co(2) fixation by spinach leaf (spinacia oleracea l. var. kyoho) protoplasts was inhibited by substituting an atmosphere of n(2) with one of either air (21% o(2)) or 100% o(2). the inhibitory effect of 100% o(2) was greater than that of air. the mode of inhibition by 100% o(2) and air was competitive with respect to co(2); ki(o(2)) value was 0.32 mm at ph 7 and 0.28 mm at ph 8.5 the labeling patterns of compounds in protoplasts exposed to (14)co(2) in light after transferring ... | 1975 | 16659379 |
| ph dependence of the km(co(2)) of ribulose 1,5-diphosphate carboxylase. | the km(co(2)) values of ribulose 1,5-diphosphate carboxylase in freshly ruptured spinach (spinacia oleracea l.) chloroplasts and in the purified form isolated from spinach leaves were found to be ph dependent. raising the ph of the assay solution produced a substantial decrease in the km(co(2)) of both enzyme systems. in freshly ruptured chloroplasts at ph 7.2 the km(co(2)) was 25 mum, at ph 8 it decreased to 19 mum, and at ph 8.8 a further decrease to 7 mum was found. with the purified enzyme a ... | 1975 | 16659359 |
| sulfur dioxide inhibition of photosynthesis in isolated spinach chloroplasts. | 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 ... | 1975 | 16659319 |
| biosynthesis of hydroxyfatty acid polymers. enzymatic epoxidation of 18-hydroxyoleic acid to 18-hydroxy-cis-9,10-epoxystearic acid by a particulate preparation from spinach (spinacia oleracea). | | 1975 | 240325 |
| metabolic conversion of l-ascorbic acid to oxalic acid in oxalate-accumulating plants. | l-ascorbic acid-1-(14)c and its oxidation product, dehydro-l-ascorbic acid, produced labeled oxalic acid in oxalate-accumulating plants such as spinach seedlings (spinacia oleracea) and the detached leaves of woodsorrel (oxalis stricta and o. oregana), shamrock (oxalis adenopylla), and begonia (begonia evansiana). in o. oregana, conversion occurred equally well in the presence or absence of light. this relationship between l-ascorbic acid metabolism and oxalic acid formation must be given carefu ... | 1975 | 16659288 |
| carbon dioxide assimilation by leaves, isolated chloroplasts, and ribulose bisphosphate carboxylase from spinach. | the relationship between rate of photosynthesis and co(2) concentration has been reinvestigated using isolated spinach (spinacia oleracea) chloroplasts. the apparently low co(2) concentration required for half-maximal photosynthesis is shown to result partly from a ceiling imposed by electron transport. in double reciprocal plots of rate against co(2) concentration, this ceiling results in departures from linearity at high co(2) concentrations. if these rate limitations are disregarded in extrap ... | 1975 | 16659216 |
| the glyceraldehyde 3-phosphate and glycerate 3-phosphate shuttle and carbon dioxide assimilation in intact spinach chloroplasts. | the regulation of co(2) assimilation by intact spinach (spinacia oleracea) chloroplasts by exogenous nadp-linked nonreversible d-glyceraldehyde-3-phosphate dehydrogenase (ec 1.2.1.9) was investigated. this dehydrogenase mediated a glyceraldehyde 3-phosphate/glycerate 3-phosphate shuttle for the indirect transfer of nadph from chloroplast to the external medium. the rate of nadph formation in the medium reflected glyceraldehyde 3-phosphate efflux from the chloroplast. increasing enzyme concentrat ... | 1975 | 16659203 |
| nitrate reductase from spinacea oleracea. effects of sulfhydryl-group reagents on the activities of the complex and the inactivation by nadh. | | 1975 | 167749 |
| transport of metabolites across isolated envelope membranes of spinach chloroplasts. | isolated envelope membranes of spinach chloroplasts (spinacia oleracea l. var. viroflay) exhibited selective permeability. metabolites such as 3-phosphoglycerate, bicarbonate, glyoxylate, and acetate were transported rapidly; 6-phosphogluconate, glycolate, glycine, l-malate, and succinate were intermediate; whereas glucose 6-phosphate, fructose 1,6-diphosphate, and sucrose were hardly transported. transport rates, metabolite accumulations within the membrane vesicles, and the internal water volu ... | 1975 | 16659179 |
| photosynthetic enhancement studied in intact spinach chloroplasts. | the emerson enhancement effect was evaluated in the intact spinach (spinacia oleracea var. long standing bloomsdale) chloroplast by monitoring the uptake of (14)co(2) during illumination by 640 nm and 720 nm lights. low levels (about 10 mum) of fructose 1,6-diphosphate, ribose 5-phosphate, and glycerate 3-phosphate stimulated the rate of photosynthesis and abolished enhancement values observed in their absence. concentrations of the two sugar phosphates at levels of 1 mm responded similarly. in ... | 1975 | 16659171 |
| the amino acid sequence of plastocyanin from spinach. (spinacia oleracea l.). | the amino acid sequence of spinach (spinacia oleracea l.) plastocyanin was determined. it consists of a single polypeptide chain of 99 residues and has a sequence molecular weight of 10415. the sequence was determined by using a beckman 890c automatic sequencer and by the dansyl--phenyl isothiocyanate analysis of peptides obtained by the enzymic digestion of purified cnbr fragments. overlap through the two methionine residues was not shown. sedimentation equilibrium in the ultracentrifuge gave a ... | 1975 | 1180895 |
| [a ferredoxin-linked sulfite reductase from spinacia oleracea (author's transl)]. | a sulfite reductase from spinach has been purified 125 fold. throughout all stages of purification the reduction of sulfite has been found dependent on ferredoxin. reduced ferredoxin has been provided either by photosynthetic reduction in isolated, broken chloroplasts or by nadph via the ferredoxin-nadp-oxidoreductase. during the purification procedure ferredoxin as electrondonor has been replaced by reduced methylviologen. | 2016 | 241168 |
| photosynthetic activities of spinach leaf protoplasts. | photosynthetic activities of protoplasts isolated from spinach leaf (spinacia oleracea l.) were investigated. the protoplasts were stable up to 9 hr, without loss of the original activity of co(2) fixation (33-75 mumoles co(2)/mg chl.hr) and light-dependent o(2) evolution (33-40 mumoles o(2)/mg chl.hr), when stored in 0.8 m mannitol-0.05 m n-tris (hydroxymethyl)-methylglycine-naoh buffer, ph 7, at 4 c in dark. the optimum ph of 8.5 for co(2) fixation reaction carried out in the present experimen ... | 1975 | 16659152 |
| carbonic anhydrase of spinach: studies on its location, inhibition, and physiological function. | carbonic anhydrase activity was determined in spinach (spinacia oleracea) leaf organelles isolated on sucrose density gradients and was found to be predominantly in the intact chloroplast fraction. the small amount of activity associated with the mitochondrial fractions was probably due to intact chloroplast contamination. no activity could be associated with the broken chloroplast or microbody fractions. based upon inhibitor studies, carbonic anhydrase was found to be around 2 mm in the chlorop ... | 1975 | 16659104 |
| localization and properties of ribulose diphosphate carboxylase from castor bean endosperm. | a substantial portion of the ribulose 1,5-diphosphate carboxylase activity in the endosperm of germinating castor beans (ricinus communis var. hale) is recovered in the proplastid fraction. the partially purified enzyme shows homology with the enzyme from spinach (spinacia oleracea) leaves, as evidenced by its reaction against antibodies to the native spinach enzyme and to its catalytic subunit. the enzyme from the endosperm of castor beans has a molecular weight of about 500,000 and, with the e ... | 1975 | 16659056 |
| formation of c-4 dicarboxylic acids by intact spinach chloroplasts. | it is concluded from (14)c labelling kinetics as well as from enzyme analysis that formation of malate and aspartate from glycerate-3p via carboxylation of p-enolpyruvate occurs in isolated photosynthesizing spinach (spinacia oleracea l.) chloroplasts. carbon incorporation into both dicarboxylic acids was about 1% of the total co2 fixation. both acids are suggested to act as substrates for counter exchange for glutamate and α-ketoglutarate. | 1975 | 24435300 |
| a sulfotransferase from spinach leaves using adenosine-5'-phosphosulfate. | active sulfotransferase can be extracted from spinach (spinacea oleracea l.) leaves (and other higher plants) using a buffer system containing 0.1 m kcl and thiol reagents. this sulfotransferase is labile, it can, however, be stabilized by storage in 70% ammonium sulfate containing 10 mm mercaptoethanol. this extract will reduce labelled adenosine-5'-phosphosulfate (aps) and 3'-phosphoadenosine-5'-phosphosulfate (paps) to acid-volatile radioactivity when dithioerythrol is added. the reduction fr ... | 1975 | 24435265 |
| dark starvation and plant metabolism : iii. co2 fixation and the distribution of radioactive intermediates in leaf discs from spinach plants. | when leaf discs from spinach plants (spinacia oleracea l.) maintained in the dark for several days were subsequently illuminated, the decrease of incorporated (14)co2 measured under steady state conditions was found to be accompanied by an altered fixation pattern. substances found to contain a significantly lower label, were malate and aspartate. in contrast, an enhanced incorporation of radioactivity was observed for those substances known to be formed during light respiration. since the same ... | 1975 | 24435231 |
| dark starvation and plant metabolism : ii. co2 fixation in isolated chloroplasts. | the fixation pattern of radioactive labelled photosynthetic intermediates was followed under steady state conditions during prolonged dark starvation of spinach plants (spinacia oleracea l.). it is suggested that the considerable increase of radioactive dihydroxyacetonephosphate is correlated with a specific leakage of the outer chloroplast envelope induced by dark starvation. the primary fixation product, phosphoglyceric acid, followed the same decreasing tendency as observed for the net co2 fi ... | 1975 | 24435230 |
| relative thermostability of the chloroplast envelope. | intact isolated chloroplasts from leaves of spinacia oleracea l. were subjected to heat treatment. after heating, the integrity of the chloroplast envelopes and the activities of various light-dependent chloroplast reactions were tested. the integrity of the chloroplast envelopes, as judged from rates of ferricyanide reduction, enzyme compartmentation and visual appearance of the chloroplasts in the light microscope with phase optics, was affected much less by heat stress than the photochemical ... | 1975 | 24430479 |
| inhibition of the adenosine-5'-phosphosulfate-sulfotransferase activity from spinach, maize, and chlorella by adenosine-5'-monophosphate. | adenosin-5'-phosphosulfate (aps) sulfotransferase from higher plants and algae seems to be regulated by adenosine-5'-monophosphate, an endproduct of the aps-sulfotransferase reaction. this was found in crude extracts of spinacea oleracea l. and zea mays l. and with partially purified aps-sulfotransferase fractions from chlorella pyrenoidosa. half-maximal inhibition with adenosine-5'-monophosphate, was found to be (a) 1.3 mm for spinacea; (b) 1.3 mm for zea; and (c) 1.6 mm for chlorella. this inh ... | 1975 | 24430289 |
| an improved method for the isolation of spinach chloroplast envelope membranes. | a three-phase, discontinuous sucrose gradient yielded two distinct fractions of envelope membranes from spinach (spinacia oleracea l.) chloroplasts. their buoyant densities were 1.08 g cm(-3) and 1.11 g cm(-3). electron micrographs showed the lighter and heavier fractions to consist primarily of single and double membranes, respectively. the milligrams of lipid-milligrams of protein ratio for the complete envelope membrane (double membrane fraction) was 1.74. thin layer chromatograms showed that ... | 1974 | 16658971 |
| properties of glucosyltransferase and glucan transferase from spinach. | a glucosyl and a glucosyl-glucan transferase activity from spinach (spinacia oleracea l. var. matador) leaves have been partially purified and characterized. the latter activity (fraction 1 after diethylaminoethylcellulose chromatography) is responsible for the transfer of glucosyl as well as of maltosyl, maltotriosyl, and higher homologous residues to glucose giving rise to maltose and the correspondingly larger molecules. this fraction also shows beta-amylase activity. the transfer takes place ... | 1974 | 16658965 |
| photosynthetic activity of spinach chloroplasts after isopycnic centrifugation in gradients of silica. | chloroplast suspensions from spinach (spinacia oleracea l.) were clearly resolved into intact and stripped chloroplasts by isopycnic centrifugation in density gradients of silica sol ("ludox") and polyethlene glycol. the intact chloroplasts fixed co(2) and evolved o(2) more rapidly than the crude suspensions; the stripped chloroplasts were inactive. during the photosynthetic fixation of (14)co(2) in the intact chloroplasts recovered from the gradient, the (14)c label was observed to spread throu ... | 1974 | 16658922 |
| uptake of bicarbonate ion in darkness by isolated chloroplast envelope membranes and intact chloroplasts of spinach. | bicarbonate uptake by isolated chloroplast envelope membranes and intact chloroplasts of spinach (spinacia oleracea l. var. viroflay) in darkness exhibited a similar dependency upon temperature, ph, time, and concentrations of isolated or attached envelope membranes. this similarity in uptake properties demonstrates the usefulness of the envelope membranes for the study of chloroplast permeability. maximal rates for dark hco(3) (-) uptake by isolated envelope membranes and intact chloroplasts we ... | 1974 | 16658920 |
| dependence of nitrite reduction on electron transport chloroplasts. | methyl viologen and phenazine methosulfate (photosystem i electron acceptors), 3-(3,4-dichlorophenyl)-1, 1-dimethylurea (dcmu, electron-transport inhibitor), and methylamine (photophosphorylation uncoupler) were used to study the dependence of nitrite reduction on electron transport in chloroplasts.dcmu, methyl viologen, and phenazine methosulfate markedly inhibited, whereas methylamine stimulated no(2) (-) reduction in isolated, intact spinach (spinacia oleracea l.) chloroplasts. the addition o ... | 1974 | 16658912 |
| relationship between the level of adenine nucleotides and the carboxylation activity of illuminated isolated spinach chloroplasts: a study with antimycin a. | the changes in the levels of intact spinach (spinacia oleracea l.) chloroplast adenine nucleotides during the time course of light-dependent co(2) fixation were determined with respect to the effect of antimycin a. this study demonstrated that antimycin a lowered the rate of atp formation during the induction period of carboxylation. while the steady state levels of atp and the energy-charge value also decreased in the presence of antimycin, the concomitant increase of the co(2) fixation activit ... | 1974 | 16658804 |
| phosphoenolpyruvate carboxylase from spinach leaf tissue: inhibition by sulfite ion. | phosphoenolpyruvate carboxylase (ec 4.1.1.31), partially purified from spinach (spinacia oleracea) leaves, is inhibited by so(3) (2-) ion. the inhibition is competitive or mixed type with respect to hco(3) (-) (ki = 17 mm), and noncompetitive with respect to phosphoenolpyruvic acid (ki = 11 mm), mg(2+) (ki = 10 mm), and mn(2+) (ki = 2.4 mm). the inhibitory effect of so(3) (2-) is more significant in the presence of mn(2+) than in the presence of mg(2+). l-malate, an inhibitor of phosphoenolpyruv ... | 1974 | 16658799 |
| nitrate reductase from spinacea oleracea. reversible inactivation by nad(p)h and by thiols. | | 1974 | 4151885 |
| levels of (+/-) abscisic acid and xanthoxin in spinach under different environmental conditions. | the levels of the growth inhibitors(+)-abscisic acid and xanthoxin were determined in the long day plant spinach (spinacia oleracea l. cv. savoy hybrid 612) grown under different environmental conditions. when plants were transferred from light to darkness, the (+)-abscisic acid level always decreased, whereas the xanthoxin content did not change. the (+)-abscisic acid content was higher in plants grown under low than under high relative humidity.xanthoxin levels were not affected by photoperiod ... | 1974 | 16658759 |
| [behavior of a mitochondrial population in the shoot apex of spinach]. | in spinach (spinacia oleracea) certain mitochondria of the sporogenic promeristem would appear to show lysosomal involvement. this occasional involvement occurs when the photoperiodic conditions do not favor flowering. the mitochondrial morphological changes indicate increase in the production of membrane. the acid phosphatase activity normally found in the neighbourhood of the dictyosomes is present. | 1974 | 24458994 |
| nitrite assimilation and amino nitrogen synthesis in isolated spinach chloroplasts. | the assimilation of nitrite leading to de novo synthesis of amino nitrogen in a chloroplast-enriched fraction isolated from freshly harvested young spinach (spinacia oleracea l.) leaves was demonstrated. the preparations showed approximately 55% intact chloroplasts as determined by light scattering properties and fixed co(2) at rates of approximately 100 mumoles hr(-1) mg chlorophyll(-1).the chloroplast-enriched fraction contained the enzymes, nitrite reductase and nadph-glutamate dehydrogenase, ... | 1974 | 16658715 |
| further studies on the bicarbonate stimulation of photophosphorylation in isolated chloroplasts. | the bicarbonate effect in stimulating the rate of photophosphorylation by isolated spinach (spinacia oleracea var. virginia blight-resistant savoy) chloroplasts at a ph below the optimum has been re-examined. its seasonal nature may be related to the hormonal status of the plants. bicarbonate anions stimulate adenosine 5'-triphosphate synthesis if added in the final, adenosine 5'-triphosphate-forming stage of either a postillumination or an acid-base experiment. they also stimulate the membrane- ... | 1974 | 16658679 |
| biosynthesis of phosphatidylethanolamine by enzyme preparations from plant tissues. | the enzymic utilization of cytidine diphosphoethanolamine in the synthesis of phosphatidylethanolamine is localized in the microsomal fraction of spinach (spinacia oleracea) leaves. the metal ion requirement can be satisfied by mn(2+) (saturation approximately 0.6 mm) or mg(2+) (saturation approximately 25 mm). the enzyme has a ph optimum of 8.0 in the presence of mn(2+) and 7.5 in the presence of mg(2+). a michaelis constant of 20 mum was determined for cytidinediphos-phoethanolamine. enzyme ac ... | 1974 | 16658671 |