photosynthesis, growth, and ultraviolet irradiance absorbance of cucurbita pepo l. leaves exposed to ultraviolet-b radiation (280-315 nm).net photosynthesis, growth, and ultraviolet (uv) radiation absorbance were determined for the first leaf of cucurbita pepo l. exposed to two levels of uv-b irradiation and a uv-b radiation-free control treatment. absorbance by extracted flavonoid pigments and other uv-b radiation-absorbing compounds from the first leaves increased with time and level of uv-b radiation impinging on leaf surfaces. although absorbance of uv-b radiation by extracted pigments increased substantially, uv-b radiation a ...198116661610
third-harmonic detection of electron-paramagnetic-resonance spectra: resolution of the hyperfine splitting in nitrosylated nitrite reductase from vegetable marrow (cucurbita pepo). 19806256243
mavicyanin, a blue copper protein from cucurbita pepo medullosa. purification and characterization.1. the copper protein mavicyanin has been isolated and purified from the green squash cucurbita pepo medullosa. 2. mavicyanin contains one type-1 copper/18000 mr, which can be characterized by: intense absorption maximum at 600 nm (epsilon = 5000 m-1 cm-1/cu, a280/a600 = 8.0 +/- 0.5, a600/a403 = 7.0 +/- 0.25, maximum of fluorescence emission at 335 nm. 3. in the oxidized state the copper of mavicyanin is 100% detectable by electron paramagnetic resonance (epr). computer simulation of the rhombic ...1979228939
regulation of pyrimidine biosynthesis in intact cells of cucurbita pepo.the occurrence of the complete orotic acid pathway for the biosynthesis de novo of pyrimidine nucleotides was demonstrated in the intact cells of roots excised from summer squash (cucurbita pepo l. cv. early prolific straightneck). evidence that the biosynthesis of pyrimidine nucleotides proceeds via the orotate pathway in c. pepo included: (a) demonstration of the incorporation of [(14)c]nahco(3), [(14)c]carbamylaspartate, and [(14)c]orotic acid into uridine nucleotides; (b) the isolation of [( ...197916661010
affinity chromatography of a lectin from robinia pseudoacacia l. and demonstration of lectins in sieve-tube sap from other tree species.a carbohydrate-binding protein in the sievetube sap of robinia pseudoacacia l. was isolated by affinity chromatography on d-galactosamine coupled to ch-sepharose 4b. the yield of the purified protein was 41,3 μg/ml of sieve-tube sap or 5,7% of the total protein. in disk electrophoresis at an alkaline and acidic ph the lectin appeared to be homogenous. it has a molecular weight of about 100,000 and consists of four types of subunits (mol wt. 70,000, 60,000, 32,500, 25,000). the complex formation ...197924407326
distribution of alpha-galactosidase in cucurbita pepo.the distribution of alpha-galactosidase (alpha-d-galactoside galactohydrolase [ec]) in cucurbita pepo has been determined in an attempt to assess its involvement in hydrolysis of transport sugars of the raffinose oligosaccharide series ([alpha-1-6-0-galactopyranosyl](n) sucrose). extracts prepared from leaves and petioles at different stages of development, roots, flowers, dry and germinating seeds, all contained appreciable levels of alpha-galactosidase activity. chromatography of thes ...197816660591
electron-paramagnetic-resonance studies of the mechanism of leaf nitrite reductase. signals from the iron-sulphur centre and haem under turnover conditions.low-temperature e.p.r. spectra are presented of nitrite reductase purified from leaves of vegetable marrow (cucurbita pepo). the oxidized enzyme showed a spectrum at g=6.86, 4.98 and 1.95 corresponding to high-spin fe(3+) in sirohaem, which disappeared slowly on treatment with nitrite. the midpoint potential of the sirohaem was estimated to be -120mv. on reduction with na(2)s(2)o(4) or na(2)s(2)o(4)+methyl viologen a spectrum at g=2.038, 1.944 and 1.922 was observed, due to a reduced iron-sulphu ...1978208505
phosphoenolpyruvate carboxykinase and gluconeogenesis in cotyledons of cucurbita pepo.1. the aim of this work was to investigate the role of phosphoenolpyruvate carboxykinase (atp:oxaloacetate carboxy-lyase (transphosphorylating) ec in the conversion of fat to sugar by the cotyledons of seedlings of cucurbita pepo. 2. the enzyme was partially purified from the cotyledons of 5-day-old seedlings. the michaelis constants for oxaloacetate and atp were 56 and 119 micron, respectively. the decarboxylation reaction was optimum at ph 7.4. a range of intermediary metabolites did ...1978656445
purification and kinetics of higher plant nadh:nitrate reductase.squash cotyledon (cucurbita pepo l.) nadh:nitrate reductase (nr) was purified 150-fold with 50% recovery by a single step procedure based on the affinity of the nr for blue-sepharose. blue-sepharose, which is prepared by direct coupling of cibacron blue to sepharose, appears to bind squash nr at the nadh site. the nr can be purified in 2 to 3 hours to a specific activity of 2 mumol of nadh oxidized/minute * milligram of protein. corn (zea mays l.) leaf nr was also purified to a specific activity ...197816660347
dark fixation of co2 during gluconeogenesis by the cotyledons of cucurbita pepo l.we did this work to discover the pathway of co2 fixation into sugars in the dark during gluconeogenesis by the cotyledons of 5-day-old seedlings of cucurbita pepo l. we paid particular attention to the possibility of a contribution from ribulosebisphosphate carboxylase. the detailed distribution of (14)c after exposure of excised cotyledons to (14)co2 in the dark was determined in a series of pulse and chase experiments. after 4s in (14)co2, 89% of the (14)c fixed was in malate and aspartate. in ...197824414566
auxin binding to subcellular fractions from cucurbita hypocotyls: in vitro evidence for an auxin transport auxin binding sive, with characteristics different from the previously described auxin binding sites i and ii in maize coleoptiles, is reported in homogenates of zucchini (cucurbita pepo l. cv. black beauty) hypocotyls. evidence from differential centrifugation and sucrose and metrizamide density gradients indicates that the site is localized on the plasma membrane. the site has a kd of 1-2×10(-6) m for indole acetic acid and has a ph optimum of 5.0. binding specificity measured with several ...197824407991
evidence about the catecholoxidase activity of the enzyme ascorbate oxidase extracted from cucurbita pepo medullosa.pure ascorbate oxidase (l-ascorbate:oxygen oxidoreductase, ec isolated from cucurbita pepo medullosa, which is known to be specific for ascorbic acid, shows a secondary catecholoxidase activity at approx. ph 6.7. this activity was tested against natural and synthetic compounds possessing a catechol-like structure. among natural compounds (+)-catechin furnishes the same complex oxidation mixture obtained with other oxidases. among synthetic compounds, 3,5-di-t-butylcatechol and 4-t-buty ...197720960
phloem loading in squash.squash (cucurbita pepo l. var. melopepo torticalis, bailey) leaves were supplied with (14)c-sucrose, then specific radioactivities of the glucose and galactose moieties of translocated stachyose were determined. in every case, the specific radioactivity of the galactose moiety was greater than that of the glucose moiety. it is concluded that the stachyose was not synthesized at either the phloem-loading site or subsequent to phloem loading, but rather in cells that were not a part of the translo ...197716660138
early effects of boron deficiency on indoleacetic acid oxidase levels of squash root tips.the indoleacetic acid (iaa) oxidase activity of root tips of boron-sufficient, -deficient, recovering, and iaa-treated boron-sufficient squash plants (cucurbita pepo l.) was determined. apical and subapical root sections displayed an increase in iaa oxidase activity between 6 and 9 hours after boron was withheld, and after 24 hours the activity of the apical sections showed a 20-fold increase over +b controls. root elongation of -b plants was inhibited before an increase in oxidase activity coul ...197716659990
effect of boron on cell elongation and division in squash roots.this work establishes that cessation of root elongation of intact squash (cucurbita pepo l.) plants is an early result of boron deficiency. root elongation is slowed by 6 hours and is virtually stopped as early as 24 hours after boron is first withheld from the nutrient solution. as root elongation ceased, cell elongation progressed distally into the region normally occupied by the apical meristem and eventually the meristem became indistinguishable. differentiation was determined by use of an e ...197716659961
differential effect of irradiance and nutrient nitrate on the relationship of in vivo and in vitro nitrate reductase assay in chlorophyllous tissues.growth at increasing continuous irradiance (at high nutrient nitrate) and nutrient nitrate concentrations (at high continuous irradiance) furnished increases in the in vivo and in vitro nitrate reductase activities of corn (zea mays l.), field peas (pisum arvense l.), wheat (triticum aestivum l.), barley (hordeum vulgare l.), and globe amaranth (gomphrena globosa l.) leaves and of marrow (cucurbita pepo l.) cotyledons. ratios of in vivo to in vitro activity declined exponentially in all species ...197716659888
phytochrome and phosphotungstate-chromate-positive vesicles from cucurbita pepo l.the phosphotungstic acid-chromic acid (pta-cro3) stain, putatively specific for the plasma membrane of plants, has been used in an attempt to monitor the distribution of this membrane in a 20,000 x g particulate fraction from cucurbita hypocotyl hooks. on discontinuous sucrose gradients, the relative distributions of the phytochrome and pta-cro3-positive vesicles present in this fraction appear to be correlated. when intact tissue is stained, however, other components, in addition to the plasma ...197724425221
gel filtration of particle-bound phytochrome.pelletable phytochrome from hypocotyl hooks of cucurbita pepo l. seedlings has been separated into two fractions by gel filtration on sepharose cl-2b. one fraction with a k av of 0.7 was detected only after red irradiation (in vivo or in vitro). this separated from a ribonucleoprotein fraction during gel filtration. the weak interaction with ribonucleo-protein which required magnesium (optimal at 10 mm) was overcome by high salt concentrations and prevented by ribonuclease treatment. the second ...197724419784
autoradiographic and ultrastructural study of cucurbita pepo root cells during their growth and differentiation.cortex cells of the root meristem of cucurbita pepo (0.0-0.5 mm from the cap junction), in the 3-4, 5-6 and 7-8 mm segments above the root tip, and the cells of the first three layers of lateral part of root cap were the object of the present study. the volume of cortex cells increases more than 20 times in the 7-8 mm segment as compared with meristematic cells, and the volume of cytoplasm about sevenfold. the largest increment of the cytoplasmic volume occurs between 0.5-6.0 mm. in consecutive ...1976993066
leaf development and phloem transport in cucurbita pepo: maturation of the minor veins.young leaves of cucurbita pepo l. were examined by whole-leaf autoradiography and serial paradermal sections were examined by light microscopy to determine whether commencement of sugar export depends upon the minor vein phloem achieving structural maturity. maturation of these veins develops progressively from the largest toward the smallest elements with the minor veins in the distal region of the leaf maturing before those in the proximal region. commencement of sugar export is coincident wit ...197624430968
[changes of glyco- and phospholipid contents during leaf senescence].the glyco- and phospholipid levels in green, green-yellow and yellow leaves of impatients balsamina l., daucus carota l. and cucurbita pepo l. were determined on a leaf area basis. in fagus silvatica l. leaves the kinetics of lipid breakdown during autumnal senescence was analysed. it was shown that yellow tissues still contain 40% to 50% of galactolipids and 50% to 60% of phospholipids present in green tissues. in the early stages of senescence of autumnal fagus leaves we found a more rapid dec ...197624430693
location of gluconeogenesis from phosphoenolpyruvate in cotyledons of cucurbita pepo.1. the aim of this work was to discover the location of the enzymes that convert phosphoenolpyruvate to fructose 6-phosphate during gluconeogenesis in fatty seeds. cotyledons of 5-day-old dark-grown seedlings of marrow (cucurbita pepo) were used as experimental material. 2. cotyledons were separated into palisade and mesophyll tissue. extracts of the two tissues had comparable activities of gluconeogenic enzymes. 3. extracts of cotyledons were fractionated by density gradient centrifugation to y ...1975164923
l-ornithine:2-oxoacid aminotransferase from squash (cucurbita pepo, l.) cotyledons: purification and properties.ornithine: 2-oxoacid aminotransferase (ec has been purified over 400-fold with a total recovery of 14% from acetone powders of cotyledons of germinating squash (cucurbita pepo, l.) seedlings. the ph optimum of the transamination between l-ornithine and alpha-ketoglutarate is 8 and the michaelis constants are 4.7 mm and 6.3 mm, respectively. the enzyme has a molecular weight of 48,000 as determined by gel filtration. the reaction is essentially specific for alpha-ketoglutarate as the am ...197516659110
leaf development and phloem transport in cucurbita pepo: carbon photosynthesis, dark respiration and growth for leaf 5 of cucurbita pepo l. plants grown under controlled conditions were measured and the data used for an assessment of the changes in carbon balance during growth of the leaf through expansion to maturity. the blade is first capable of net co2 fixation when ca. 8% expanded but the initial rapid growth during this period is sustained almost entirely through imported nutrients. when the growth rate starts to decline rapidly the net photosynthe ...197524436024
particle-bound phytochrome: the nature of the interaction between pigment and particulate fractions.particle-bound phytochrome from hypocotyl hooks of cucurbita pepo l. seedlings is associated with either a "heavy" membrane fraction or a 31s ribonucleoprotein (rnp) component on sucrose gradients. those amounts of phytochrome and rnp which co-pellet in response to added mg(2+) are primarily localised in the 31s fraction. the phytochrome-rnp association itself, however, is not dependent on the added cation. this indicates that mg(2+)-enhanced phytochrome pelletability results indirectly from agg ...197524435123
particle-bound phytochrome: association with a ribonucleoprotein fraction from cucurbita pepo the absence of ethylenediaminetetraacetic acid (edta) and added mg(2+), the phytochrome, rna, protein, cytochrome c oxidase and nadph-cytochrome c reductase in 20000 x g pellets from hypocotyl hooks of red-irradiated cucurbita seedlings are more or less coincident in a single, broad band on linear sucrose gradients. the inclusion of 3 mm edta in the extraction, resuspension and gradient media has three major effects: (a) the phytochrome profile splits into two main bands; (b) the main rna pop ...197524435122
[response of flowering plant seedlings to the action of n-nitroso-n-methylurea].the influence of n-nitroso-n-methylurea on seedlings of two species of plants--cucurbita pepo l., helianthus annuus l.--was investigated. nmu was added in agar-agar, on which seedlings were growing. 0.02% concentration of nmu was used. in addition to the delay in growth and appearance of necrotic regions, also local overgrowth of cotyledons of c. pepo and overgrowth of hypocotyl and the base of cotyledons of h. annuus were observed. a histological analysis has shown that these swellings arise du ...19751210149
[reaction of the seedlings of flowering plants to the effects of imino-di-(paradimethylaminophenyl)-methane-aurine-00].the influence of auramine-00 on seedlings of three species of plants - cucurbita pepo l., helianthus annuus l., zea mays l.-was investigated. auramine was added in agar-agar, on which the seedlings were growing. two concentrations of auramine were used--0.001%. besides the delay in growth, also the formation of local overgrowth of cotyledons and hypocotyl of c. pepo, the base of cotyledons of h. annuus and mezocotyl of z. mays were observed. the histological analysis has shown these swellings to ...19751166654
in-vitro binding of phytochrome to a particulate fraction: a function of light dose and steady-state p fr level.the binding of phytochrome to a particulate fraction in extracts from hypocotyl hooks of etiolated cucurbita pepo l. seedlings has been examined as a function of the light dose and p fr level established in vitro. as the steady-state level of p fr transiently established in the 500×g supernatant is increased, so the level of p r subsequently pelletable at 20 000×g increases up to a saturation level. increasing both the time and irradiance parameters of the light dose while holding the steady-sta ...197424442379
particle-bound phytochrome: spectral properties of bound and unbound irradiation of extracts of maize (zea mays l.) coleoptiles with red light enhances phytochrome pelletability as was previously reported for cucurbita pepo l. in neither case is this the result of an irradiation-induced increase in the level of total pelletable protein. the transformation difference spectra of bound and unbound phytochrome fractions obtained after both in-vivo and in-vitro irradiations are not significantly different. the data, therefore, do not indicate that irradiation ...197424442378
fractionation of the proteins of plant microbodies.1. glyoxysomes and peroxisomes have been isolated from dark- and light-grown seedlings of pumpkin (cucurbita pepo) by sucrose-density-gradient centrifugation. 2. pumpkin microbodies and castor-bean (ricinus communis) glyoxysomes may be fractionated, by a combination of osmotic shock and treatment with kcl, into three distinct groups of proteins: readily soluble (matrix enzymes), solubilized in the presence of kcl (membrane-bound enzymes) and relatively insoluble (membrane ;ghost' proteins). 3. s ...19744468822
autoradiographic examination of meristems of intact boron-deficient squash roots treated with tritiated thymidine.intact roots of boron-sufficient squash (cucurbita pepo l.) plants, plants entering boron deficiency, and plants recovering from boron deficiency were exposed to tritiated thymidine at the end of the treatment period to label the replicating dna of root tip cells. using histological sections, autoradiographs of intact root meristems were prepared. the labeling pattern in +b root tips revealed the presence of a well defined quiescent center. the ability of root tip cells to incorporate label is c ...197416658968
the amino acid sequence of plastocyanin from cucurbita pepo l. (vegetable marrow).the amino acid sequence of plastocyanin from marrow was determined. it consists of a single polypeptide chain of mol.wt. 10284 containing 99 amino acid residues. the sequence was determined by using a beckman 890c automatic sequencer and by dansyl-phenyl isothiocyanate analysis of peptides obtained by the enzymic digestion of purified cnbr fragments. the sequence is in good agreement with the amino acid composition, except that fewer residues of glutamic acid were found in the sequence than were ...19744462555
dependence of phytochrome dark reactions on the initial photostationary state.under conditions of continuous irradiation, the p jr destruction rate constants (k d ) of phytochrome in hooks and cotyledons of squash (cucurbita pepo l.) seedlings do not depend on the photostationary state ϕλ and are the same in both organs. on the other hand, the rate constants of the dark reversion and the first destruction step, plotted as a function of ϕ λ (0) , show optimum curves with maxima between ϕ λ (0) and 0.5. similar results were obtained for dark reactions of mustard (sinapis al ...197424458195
temperature dependence of phytochrome dark reactions.the dark reversion and the destruction reaction of the phytochrome of squash (cucurbita pepo l.) cotyledons show different temperature behaviour in the temperature range 15-35°. the arrhenius activation energy of the destruction reaction is temperature independent whereas that of the reversion reaction shows a jump at 20°. this indicates an interaction of phytochrome molecules with membranes. a reaction scheme is discussed which can explain the differences of the dark kinetics in a quantitative ...197424458194
in vivo properties of membrane-bound phytochrome.after a 3-minute irradiation with red light, which saturates the phototransformation from the red light-absorbing form of phytochrome to the far red light absorbing form of phytochrome, about 40% of the phytochrome extractable from hooks of etiolated squash seedlings (cucurbita pepo l. cv. black beauty) can be pelleted as pfr at 17,000g after 30 minutes. dark controls yield only 2 to 4% pelletable phytochrome in the form pr. if a dark period intervenes between red irradiation and extraction, the ...197416658872
the isolation and partial characterization of a membrane fraction containing phytochrome.if 4-day-old dark-grown zucchini squash seedlings (cucurbita pepo l. cv. black beauty) are exposed briefly to red light, subsequent cell fractionation yields about 40% of the total extractable phytochrome in the far red-absorbing form bound to a particulate fraction. the amount of far red-absorbing phytochrome in the pellet is strongly dependent on the mg concentration in the extraction medium. the apparent density of the pfr-containing particles following sedimentation on sucrose gradients corr ...197416658871
translocation of sucrose by squash plants.sucrose-(14)c was fed to the leaf blades of squash plants (cucurbita pepo l. var. melopepo torticallis bailey) for 30 or 60 minutes. petioles of treated plants were cut into sections and extracted. the majority of the (14)c within the petiole was in sucrose rather than stachyose, the sugar that is transported by the squash plants when (14)co(2) is supplied. this indicates that the phloem loading system of squash plants is not the system that specifies which sugar is transported.197316658634
[localization of dehydrogenases of energy metabolism in the pholoem of cucurbita pepo l].in the stem phloem of cucurbita pepo the enzymes gapdh, adh, mdh, nadp-idh, nad-idh, g6pdh and sdh were localized histochemically with the aid of tetrazolium salt (nbt). when the stems were deep-frozen the most intense formation of formazan was found in companion cells, less in phloem parenchyma cells, and very little in sieve tubes.the distribution of enzymes in phloem markedly changes when stems were cut 2 minutes before freezing: 2,5 cm behind the sectional area little formazan was found. com ...197324469572
turnover of phytochrome in pumpkin using density labeling, it was found that the protein moiety of phytochrome is synthesized de novo in the red-absorbing form in cotyledons of dark-grown pumpkin (cucurbita pepo l.) seedlings, as well as those irradiated with red light and returned to the dark. the rate of synthesis appears to be unaffected by the light treatment. turnover of the red-absorbing form was also detected in dark grown seedlings using density labeling, while turnover of the far red-absorbing form is already implied ...197316658512
de novo synthesis of phytochrome in pumpkin hooks.phytochrome becomes density labeled in the hook of pumpkin (cucurbita pepo l.) seedlings grown in the dark on d(2)o, indicating that the protein moiety of the pigment is synthesized de novo during development. red light causes a rapid decline of the total phytochrome level in the hook of etiolated seedlings but upon return to the dark, phytochrome again accumulates. these newly appearing molecules are also synthesized de novo. newly synthesized phytochrome in both dark-grown and red-irradiated s ...197316658511
characteristics of the rapidly reassociating deoxyribonucleic acid of cucurbita pepo l. and the sequences complementary to ribosomal and transfer ribonucleic acids. 19734711479
[studies on the phloem exudate of cucurbita pepo l. : ii. enzyme activities of gluconeogenesis and of the synthesis and degradation of di- and polysaccharides].tests for enzymes of gluconeogenesis and of the synthesis and degradation of sucrose and polysaccharides have been carried out in the phloem exudate of cucurbita pepo. all the enzymes which are necessary for the synthesis of sucrose and polysaccharides from metabolites of the citric acid cycle were found to be present in the exudate, except phosphoenolpyruvate carboxykinase. the polysaccharide synthetase was found to exhibit higher activity with glycogen (which is an unnatural polysaccharide in ...197324458664
[studies on the phloem exudate of cucurbita pepo l. : i. enzyme activities of aerobic and anaerobic glycolysis and of the citric acid cycle].in the phloem exudate of cucurbita pepo enzyme activities of aerobic and anaerobic glycolysis as well as of citric acid cycle were tested. all enzymes of the aerobic glycolysis and the alcoholic fermentation were present. in the phloem these metabolic pathways should be functioning as well. since the lactate dehydrogenase could not be detected all the time, lactate fermentation is probably not an obligatory constituent of phloem metabolism. of the citric acid cycle the enzymes malate dehydrogena ...197324458663
relationships between structural development and the absorption of ions by the root system of cucurbita both the seminal axis and lateral roots of cucurbita pepo l. the formation of large central xylem elements and the commencement of secondary cambial activity occur 10-20 cm from the root tip. concomitant with or slightly preceding these developments there are changes in the structure of the walls of endodermal cells where the lignified casparian band spreads along the radial wall and substances staining with sudan iv are deposited in both radial and tangential walls. at distances more than 30 ...197324458660
the conversion of mevalonic acid into gibberellin a12-aldehyde in a cell-free system from cucurbita pepo.a cell-free system prepared from immature seed of cucurbita pepo incorporates the label from mevalonate-2-(14)c into ent-kaur-16-en-19-oic acid (i), ent-7α-hydroxy-kaur-16-en-19-oic acid (ii), and ent-gibberell-16-en-7-al-19-oic acid (iii) (gibberellin a12-aldehyde). the products were identified by gas liquid chromatography and by combined gas chromatography-mass spectrometry of the methylated and trimethylsilylated fractions. the radioactivity of the compounds was established by recrystallisati ...197224482208
embryoid formation by fragments of cotyledons and hypocotyls in cucurbita pepo.after a prolonged culture on murashige-skoog medium the primary explants of hypocotyls and cotyledons of the pumpkin develop embryoid-producing callus tissue. ten separate strains of such tissue have been obtained and have now been in culture for more than one year, continuing to produce embryoids.197224481562
an investigation of the contractile protein hypothesis of phloem translocation.experiments are reported which were designed to test the hypothesis that the movement of the translocation stream is driven by the contractile activity of p-protein filaments. the different types of filament found after negative staining of phloem exudates from ricinus communis and cucurbita pepo are described. an approximate model is proposed for the quaternary structure of a 20 nm component in the r. communis exudate. none of the filaments showed any ability to bind heavy meromyosin subfragmen ...197224477956
[an in vivo study of detectable phytochrome in seeds of cucurbita pepo l. in the course of different phases of germination].in dry gourd seeds all the phytochrome is in the pfr form. the increase of phytochrome content from the beginning of hydration involves two phases, a and b, in the embryonic axis as well as in the cotyledons. cycloheximide does not prevent the appearance of pr during phase a. we assume that pr is gradually released from an inactive complex. on the other hand phase b is inhibited by cycloheximide; this could mean that a de novo synthesis of pr occurs.some experiments indicate that the phytochrome ...197224477896
the purification and some properties of a protein causing gelling in phloem sieve tube exudate from cucurbita pepo. 19725022434
incorporation of c-kaurene into the gibberellin of a higher plant (pharbitis nil chois).enzymic formation of (14)c-kaurene from 2-(14)c-mevalonate was carried out with a cell-free system of cucurbita pepo l. it was shown that either heating of the enzyme system or the addition of the growth retardants (2-chloroethyl)-trimethylammonium chloride and 2'-isopropyl-4' (trimethylammonium chloride)-5'-methylphenyl piperidine-1-carboxylate prevented the synthesis of (14)c-kaurene. experiments in which (14)c-kaurene was applied to seedlings of pharbitis nil revealed that the kaurene is conv ...197116657821
plastocyanin from cucurbita pepo l. 19715158501
the isolation and some properties of a factor causing gelling in the phloem sieve-tube exudate of the squash plant (cucurbita pepo). 19715127345
rate of freezing and integrity of vegetable tissues: iv: observations on summer squash (cucurbita pepo l.).this paper reports histological observations on blanched and unblanched summer squash tunnel frozen at different rates. the detected textural damage consisted of detached cell layers, cell tearings, cavities, and various changes in the cytoplasm, nucleous, and starch granules. the number and extent of these damages increased as the freezing rate decreased. blanching made the tissue more sensitive to freezing damage. with 5 mm thick slices, the critical freezing time is less than 15 min at - 35°c ...197128372011
nitrite and hydroxylamine reduction in higher plants. fractionation, electron donor and substrate specificity of leaf enzymes, principally from vegetable marrow (cucurbita pepo l.).nitrite reductase was purified between 760- and 1300-fold from vegetable marrow (cucurbita pepo l.) and residual hydroxylamine reductase activity was low or negligible by comparison. with ferredoxin as electron donor, nitrite loss and ammonia formation at ph7.5 were stoicheiometrically equivalent. crude nitrite reductase preparations showed negligible activity with nadph as electron donor maintained in the reduced state by glucose 6-phosphate, whereas by comparison, activity was high when either ...19704395427
possible sites in nitrite reductase and hydroxylamine reductases from vegetable marrow (cucurbita pepo l). 19705420040
cytokinins in seeds of pumpkin.extracts of seeds of pumpkin (cucurbita pepo linn.) contain three chromatographically distinguishable cytokinins which are held on dowex 50-w and are extractable by ethanol and n-butanol. two of the active factors are precipitable by silver nitrate at acidic ph. the chromatographic behavior and the spectral characteristics of one of these cytokinins are similar to those of zeatin. however, the r(f) values of the other two active compounds do not match with those of any of the known natural cytok ...197016657272
[localization of acid deoxyribonuclease in the radicular meristem of the pumpkin (cucurbita pepo l. cucurbitaceae)]. 19694989892
the enzymic preparation of (14)c-kaurene.endosperm from immature seeds of cucurbita pepo l. converts 2-(14)c-dl-mevalonate to (14)c-(-)-kaurene with a yield of nearly 40% of the active isomer. kaurene is the main product and the only diterpene hydrocarbon which is formed from mevalonate in the system and is therefore easily obtained radiochemically pure. the product was identified by thin-layer chromatography and recrystallization with authentic (-)-kaurene to constant specific radioactivity.196924515589
[localization of thiolacetic esterase in the radicular meristem of the pumpkin (cucurbita pepo l cucurbitaceae)]. 19694989954
[identification of tritiated assimilales within the sieve tubes of cucurbita pepo].after application of d-glucose-6-t to small areas of leaf surfaces of cucurbita, radioactivity - mainly sucrose-t - could exclusively be localized by histoautoradiography ("dry-technique") within single sieve tubes of exporting bundles. the centre of activity corresponded to the "slime"-plugs (in crosssection-autoradiograms) of the sieve tubes and to the sieve plates (in longitudinal sections). it is concluded that only the sieve tubes are the conducting channels for the long-distance transport ...196824519078
the reduction of nitrate, nitrite and hydroxylamine to ammonia by enzymes from cucurbita pepo l. in the presence of reduced benzyl viologen as electron donor.1. enzyme systems from cucurbita pepo have been shown to catalyse the reduction of nitrite and hydroxylamine to ammonia in yields about 90-100%. 2. reduced benzyl viologen serves as an efficient electron donor for both systems. activity of the nitrite-reductase system is directly related to degree of dye reduction when expressed in terms of the function for oxidation-reduction potentials, but appears to decrease to negligible activity below about 9% dye reduction. 3. nadh and nadph alone produce ...196514342247
[investigation of salt-soluble proteins of pumpkin seeds (cucurbita pepo l.) by a column gradient extraction method]. 20095870889
researches on milk-clotting enzymes from palestinian plant sources. v. a vegetal rennin from the pumpkin (cucurbita pepo). 196414228392
root hairs, cuticle, and pits.the filamentous roots of mustard (raphanus sativus), radish (brassica nigra), squash (cucurbita pepo), and wheat (triticum aestivum) are covered throughout their length with living nucleated root hairs which may measure 1600 micro or more. the outer walls of piliferous and nonpiliferous cells consist of successive layers of mucilage, cutin, and the cellulose-pectic framework of the cell. plasmodesmata and pits occur on all cell walls. under the electron microscope individual pores and pits in th ...196317746006
[lipoxidase in cucurbita pepo roots]. 200713628795
[anthelminthic action of cucurbita pepo seeds]. 195414380318
dimorphic female blossom and fruit types on the same plant in cucurbita pepo. 195015428628
significance of phloem exudate of cucurbita pepo with reference to translocation of organic materials. 194116653692
a study of the effects of cucurbita pepo seeds on kidney excretion. 192216576619
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