Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Hedera”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 91 records · Page 5Linked to original sources
PubMed2003

Ecophysiological relevance of cuticular transpiration of deciduous and evergreen plants in relation to stomatal closure and leaf water potential.

The water permeability of the leaves of three deciduous plants (Acer campestre, Fagus sylvatica, Quercus petraea) and two evergreen plants (Hedera helix, Ilex aquifolium) was analysed in order to assess its role as a mechanism of drought resistance. Cuticular permeances were determined by measurement of the water loss through adaxial, astomatous leaf surfaces. Minimum conductances after complete stomatal closure were obtained by leaf drying curves. The comparison of the water permeabilities determined with these two experimental systems revealed good agreement in the case of Acer, Fagus, Quercus, and Ilex. For Hedera the minimum conductance was 3-fold higher than the cuticular permeance indicating a significant contribution of residual stomatal transpiration. The leaf water potential was measured as a function of water content and analysed by pressure-volume curves. The influence of water potential as a component of the driving force for transpirational water loss was assessed in order to identify modifications of the cuticular barrier by the leaf water content. The ecophysiological meaning of the water relations parameters describing transpiration under drought conditions (cuticular transpiration, minimum transpiration, residual stomatal transpiration, effect of leaf water content on transpiration) and the water relations parameters derived from pressure-volume curves (osmotic potential at full saturation, turgor loss point, bulk modulus of elasticity) are discussed with regard to adaptations for drought resistance.

Disasters↗
PubMed2006

Cooccurring plants forming distinct arbuscular mycorrhizal morphologies harbor similar AM fungal species.

Arbuscular mycorrhizal (AM) fungal spores were isolated from field transplants and rhizosphere soil of Hedera rhombea (Miq) Bean and Rubus parvifolius L., which form Paris-type and Arum-type AM, respectively. DNA from the spore isolates was used to generate molecular markers based on partial large subunit (LSU) ribosomal RNA (rDNA) sequences to determine AM fungi colonizing field-collected roots of the two plant species. Species that were isolated as spores and identified morphologically and molecularly were Gigaspora rosea and Scutellospora erythropa from H. rhombea, Acaulospora longula and Glomus etunicatum from R. parvifolius, and Glomus claroideum from both plants. The composition of the AM fungal communities with respect to plant trap cultures was highly divergent between plant species. Analysis of partial LSU rDNA sequences amplified from field-collected roots of the two plant species with PCR primers designed for the AM fungi indicated that both plants were colonized by G. claroideum, G. etunicatum, A. longula, and S. erythropa. G. rosea was not detected in the field-collected roots of either plant species. Four other AM fungal genotypes, which were not isolated as spores in trap cultures from the two plant species, were also found in the roots of both plant species; two were closely related to Glomus intraradices and Glomus clarum. One genotype, which was most closely related to Glomus microaggregatum, was confined to R. parvifolius, whereas an uncultured Glomeromycotan fungus occurred only in roots of H. rhombea. S. erythropa was the most dominant fungus found in the roots of H. rhombea. The detection of the same AM fungal species in field-collected roots of H. rhombea and R. parvifolius, which form Paris- and Arum-type AM, respectively, shows that AM morphology in these plants is strongly influenced by the host plant genotypes as appears to be the case in many plant species in natural ecosystems, although there are preferential associations between the hosts and colonizing AM fungi in this study.

Ecosystem↗
PubMed2005

Acute anti-inflammatory activity of four saponins isolated from ivy: alpha-hederin, hederasaponin-C, hederacolchiside-E and hederacolchiside-F in carrageenan-induced rat paw edema.

The anti-inflammatory potential of alpha-hederin (monodesmoside) and hederasaponin-C from Hedera helix, and hederacolchisides-E and -F (bidesmosides) from H. colchica was investigated in carrageenan-induced acute paw edema in rats. Saponins and indomethacin were given orally in concentrations of 0.02 and 20mg/kg body wt. For the first phase of acute inflammation, indomethacin was found as the most potent drug. Alpha-hederin and hederasaponin-C were found ineffective, while hederacolchisides-E and -F showed slight anti-inflammatory effects on the first phase. For the second phase of acute inflammation, indomethacin and hederacolchiside-F were determined as very potent compounds. alpha-hederin was found ineffective for the second phase, either. Despite hederasaponin-C and -E were found effective in the second phase of inflammation, they were not found as effective as indomethacin and hederacolchiside-F. As a conclusion, hederasaponin-C, -E and -F, may exert their anti-inflammatory effects by blocking bradykinin or other inflammation mediators. The latter affect may occur via affecting prostaglandin pathways. Regarding the structure activity relationship, it is likely that sugars at C3 position and Rha7-Glcl-6Glc moiety at C28 position are essential for the acute anti-inflammatory effect.

Animals↗
PubMed2003

Efficacy of dry extract of ivy leaves in children with bronchial asthma--a review of randomized controlled trials.

OBJECTIVES: To investigate if extracts from dried ivy leaves (Hedera helix L.) are effective in the treatment of chronic airway obstruction in children suffering from bronchial asthma. DESIGN: Systematic review of trials documented in the literature with re-analysis of original data. TRIALS: 5 randomized controlled trials investigating the efficacy of ivy leaf extract preparations in chronic bronchitis, 3 of which were conducted in children and met our selection criteria. One compared ivy leaf extract cough drops to placebo, one compared suppositories to drops and one tested syrup against drops. MAIN OUTCOME MEASURES: Body-plethysmographic and spirometric measures. RESULTS: Drops were significantly superior to placebo in reducing airway resistance (primary outcome measure; p = 0.04 two-sided) and descriptively superior in all other 'objective' measures. For syrup and suppositories, at least 54%, resp. 35% of the effect against placebo were preserved. CONCLUSIONS: The trials included in this review indicate that ivy leaf extract preparations have effects with respect to an improvement of respiratory functions of children with chronic bronchial asthma, but more far-reaching conclusions can hardly be drawn because of a meagre database, including the fact that only one primary trial included a placebo control. Further research, particularly into the long-term efficacy of the herbal extract, is needed.

Asthma↗
PubMed2004

Species-specific variation in the importance of the spectral quality gradient in canopies as a signal for photosynthetic resource partitioning.

BACKGROUND AND AIMS: Plants adjust the distribution of photosynthetic capacity and chlorophyll to canopy density. The importance of the gradient in the red : far-red ratio (R : FR) relative to the irradiance gradient was studied for its perception with respect to this partitioning of photosynthetic resources. Whether the relative importance of these two signals varied between six species of different growth habit (Phaseolus vulgaris, Lysimachia vulgaris, Hedera helix, Ficus benjamina, Carex acutiformis and Brachypodium pinnatum) was investigated further. METHODS: Single leaves of plants were shaded in daylight by a spectrally neutral filter or a leaf. In another experiment, leaves were treated with supplemental FR. In most cases, treatment effects were evaluated after 2 weeks. KEY RESULTS: Nitrogen and photosynthetic capacity (Amax) per leaf area, parameters pertaining to between-leaf resource partitioning, were strongly reduced in neutral shade but not additionally by spectral leaf shade. Supplemental FR reduced these parameters also, except in Carex. Acceleration of induction of senescence was observed in spectral leaf shade in primary bean leaves. Amax per unit chlorophyll, a parameter pertaining to within-leaf resource partitioning, was reduced in neutral shade, but not in spectral leaf shade or supplemental FR. CONCLUSIONS: Signalling mechanisms associated with perception of the R : FR gradient in canopies were less important than those associated with the irradiance gradient for between-leaf and within-leaf partitioning of photosynthetic resources. The relative importance of the signals differed between species because Carex was the only species for which no indications were found for an involvement of the spectral gradient in perception of canopy density.

Carex Plant↗
PubMed2002

The hydraulic conductance of the angiosperm leaf lamina: a comparison of three measurement methods.

A comparison was made of three methods for measuring the leaf lamina hydraulic conductance (K(lamina)) for detached mature leaves of six woody temperate angiosperm species. The high-pressure method, the evaporative flux method and the vacuum pump method involve, respectively, pushing, evaporating and pulling water out of the lamina while determining the flow rate into the petiole and the water potential drop across the leaf. Tests were made of whether the high-pressure method and vacuum pump method measurements of K(lamina) on single leaves were affected by irradiance. In Quercus rubra, the high pressure method was sensitive to irradiance; K(lamina) measured under high irradiance (>1200 micro mol m(-2) s(-1 )photosynthetically active radiation) was 4.6-8.8 times larger than under ambient laboratory lighting (approximately 6 micro mol m(-2) s(-1 )photosynthetically active radiation). By constrast, the vacuum pump method was theoretically expected to be insensitive to irradiance, and this expectation was confirmed in experiments on Hedera helix. When used in the ways recommended here, the three methods produced measurements that agreed typically within 10%. There were significant differences in species' K(lamina); values ranged from 1.24x10(-4) kg s(-1) m(-2) MPa(-1) for Acer saccharum to 2.89x10(-4) kg s(-1) m(-2) MPa(-1) for Vitis labrusca. Accurate, rapid determination of K(lamina) will allow testing of the links between K(lamina), water-use, drought tolerance, and the enormous diversity of leaf form, structure and composition.

Acer↗
PubMed2003

In situ localization associates biologically active plant natriuretic peptide immuno-analogues with conductive tissue and stomata.

Plant natriuretic peptide immuno-analogues (irPNP) have previously been shown to affect a number of biological processes including stomatal guard cell movements, ion fluxes and osmoticum-dependent water transport. Tissue printing and immunofluorescent labelling techniques have been used here to study the tissue and cellular localization of irPNP in ivy (Hedera helix L.) and potato (Solanum tuberosum L.). Polyclonal antibodies active against human atrial natriuretic peptide (anti-hANP) and antibodies against irPNP from potato (anti-StPNP) were used for immunolabelling. Tissue prints revealed that immunoreactants are concentrated in vascular tissues of leaves, petioles and stems. Phloem-associated cells, xylem cells and parenchymatic xylem cells showed the strongest immunoreaction. Immunofluorescent microscopy with fluorescein isothiocyanate (FITC)-conjugated goat anti-rabbit IgG supported this finding and, furthermore, revealed strong labelling to stomatal guard cells and the adjacent apoplastic space as well. Biologically active immunoreactants were also detected in xylem exudates of a soft South African perennial forest sage (Plectranthus ciliatus E. Mey ex Benth.) thus strengthening the evidence for a systemic role of the protein. In summary, in situ cellular localization is consistent with physiological responses elicited by irPNPs reported previously and is indicative of a systemic role in plant homeostasis.

Amino Acid Sequence↗
PubMed1997

Isolation and immunoaffinity purification of biologically active plant natriuretic peptide.

It has recently been demonstrated that antibodies against atrial natriuretic peptides (ANP) recognise analogues in plants and that rat ANP binds specifically to isolated plant membranes and promotes stomatal guard cell opening in a concentration dependent manner. Here we report the isolation and immunoaffinity purification of plant natriuretic peptide (PNP) from ivy (Hedera helix) with rabbit anti-alpha-ANP (1-28) (human, canine) antiserum. We also demonstrate that immunoaffinity purified plant peptide induces stomatal opening in a concentration dependent manner. This is therefore the first report of an active indigenous peptide hormone in plants. We propose that PNPs are part of a signalling system that has evolved early in evolution and is involved in the regulation of ion transport and transpiration in plants.

Animals↗
PubMed2004

Inhibition of HUVEC tubulogenesis by hederacolchiside-A1 is associated with plasma membrane cholesterol sequestration and activation of the Ha-Ras/MEK/ERK cascade.

PURPOSE: Neoangiogenesis is critical to cancer proliferation and metastasis and constitutes an attractive target for cancer therapy. It has previously been demonstrated that hederacolchiside-A1 (HCol-A1), a triterpenoid saponin from Hedera colchica Koch, has antimelanoma potential. The goal of this study was to evaluate, in vitro, if in addition to its tumoricidal effect on melanoma cells, HCol-A1 might affect endothelial cell network formation. METHODS: We investigated whether HCol-A1 affects matrigel-induced tubulogenesis and inhibits the viability (WST-1 assay) of human umbilical vein endothelial cells (HUVECs). To provide structure-activity relationships (SAR), studies were conducted on HCol-A1, oleanolic acid and hederacolchiside A (HCol-A), a triterpenoid saponin which possess the same sugar sequence as Hcol-A1. Plasma membrane cholesterol sequestration was studied by labelling with [3H]cholesterol and assayed with HCol-A1-cholesterol complexes. HCol-A1 signalling was investigated using immunoassays. RESULTS: In contrast to HCol-A and oleanolic acid, HCol-A1 inhibited matrigel-induced angiogenesis at micromolar concentration. Plasma membrane cholesterol sequestration was found to be critical for this activity. Activation of the Ras/MEK/ERK cascade appears to be one of the mechanisms by which Hcol-A1 affects HUVEC network formation. The predominant activation of the Ha-Ras isoform, which decreases HUVEC-tolerance to apoptosis, might contribute to the high susceptibility of this cell line to HCol-A1. CONCLUSION: Since cholesterol sequestration affects cell confluence-dependent remodelling of endothelial membranes and vascular endothelial growth factor receptor-2 activity, these results raise the possibility that Hcol-A1 might slow-down cancer proliferation and metastasis in vivo by inhibiting critical aspects of neoangiogenesis. Further in vivo studies are needed to verify this hypothesis.

Cell Survival↗
PubMed2001

Effect of humidity on cuticular water permeability of isolated cuticular membranes and leaf disks.

The effects of humidity on water permeability of astomatous, isolated cuticular membranes and leaf disks of Citrus aurantium L., Vinca major L., Prunus laurocerasus L., Hedera helix L. and Forsythia intermedia (Thunb.) Vahl. were investigated by a new method using 3H2O. With isolated cuticular membranes of P. laurocerasus the isotope method resulted in values similar to those obtained by a well-established gravimetric method. Cuticular water permeability significantly increased by factors of 2 to 3 when air humidities increased from 2 to 100%. Plots of permeances vs. air humidity were non-linear and the slope increased with increasing air humidity. Permeances of intact leaf disks showed a response to increasing humidity similar to those of isolated cuticular membranes. When cuticular water permeability was measured using wax-free, isolated polymer matrix membranes that had been methylated, the effect of air humidity was significantly suppressed compared to non-methylated polymer matrix membranes. From this observation it is concluded that non-esterified, free carboxyl groups present in the cutin polymer matrix significantly contribute to the effect of humidity on cuticular water permeability. These and other polar groups sorb water, which in turn increases the water permeability of polar domains of the cuticle. This humidity-sensitive, polar path of cuticular water permeability is arranged in parallel with the major, dominating and humidity-independent, non-polar path of cuticular water permeability formed by the lipophilic wax components of the cuticle. This conclusion is supported by the fact that cuticular transpiration can be increased by orders of magnitude upon (i) wax extraction, (ii) increase in temperature or (iii) the action of plasticizers, none of which influenced or only marginally influenced the permeability of inorganic ions penetrating plant cuticles across humidity-sensitive polar pores.

Biological Transport↗
PubMed1984

Accumulation and transport of (2,4-dichlorophenoxy)acetic acid in plant cuticles: I. Sorption in the cuticular membrane and its components.

Partition coefficients (K) of (2,4-dichlorophenoxy)acetic acid (2,4-D) have been determined for the system plant cuticle/aqueous buffer. Cuticles isolated enzymatically from leaves (Clivia miniata, Ficus elastica, Citrus aurantium, Hedera helix, Pyrus communis cv. Conférence and cv. Williams, Olea europaea) and fruits (Lycopersicon esculentum, Capsicum annuum, Solanum melongena, Cucumis sativus) were utilized. Only the nondissociated species of 2,4-D was sorbed by cuticles and their lipophilic components. The average partition coefficient for leaf cuticles was 316 (range, 240-470) and for fruit cuticles 476 (range, 424-579). The dependence of sorption upon 2,4-D concentration was tested using tomato fruit cuticle. The sorption isotherm was linear from 2.0 to 5.0 X 10(-4) mol m-3. With increasing 2,4-D concentrations partition coefficients decreased slightly. Extraction of soluble cuticular lipids (SCL) increased the partition coefficients and these relative increases were correlated to relative amounts of SCL. In most species the hydrolytic removal of polar cuticular components resulted in a further increase of partition coefficients. No single cuticle was found to be representative for the sorption characteristics of all plant species investigated. The amounts of cuticle present in plant communities can be estimated from the data presented in conjunction with leaf area indices.

2,4-Dichlorophenoxyacetic Acid↗
PubMed1994

Relative sensitivity of greenhouse pot plants to long-term exposures of NO- and NO2-containing air.

Thirty-five cultivars of pot plants of 20 families were exposed for 50-64 days in a greenhouse facility to either 1 microl litre(-1) NO with 0.5 microl litre(-1) NO2, or 1 microl litre(-1) NO2 with 0.1 microl litre(-1) NO for 15 h each day, with air which was free from these gases as the reference. A sensitivity ranking of the pot plants was compiled, with the highest priority on visible injuries, followed by growth reductions, primarily as a response to the NO-dominated exposures, simulating the NOx-polluted environment in direct-fired, CO2-enriched greenhouses. This treatment reduced the leaf dry weight more than the number and area of the leaves. Twenty-two cultivars were significantly injured, while two (Hibicus sp, Epipremnum pinnatum, green) were significantly improved. The NOx-sensitivity of pot plants was highest in cultivars with variegated, small or narrow leaves, and in the Moraceae family. Nine cultivars (Ficus elastica 'Robusta', F. benjamina, F. pumila 'Sonny', Dieffenbachia maculata 'Camilla', F. elastica 'Tineke', Epipremnum pinnatum 'Marble Queen', Begonia elatior 'Nelson', Cyclamen persica, Poinsettia 'Mini') were specifically sensitive to the NO-containing exposure; six were specifically sensitive to the NO2-containing exposure (F. elastica 'Robusta', Asparagus den. 'Sprengeri', Hedera helix 'Shamrock', Aspledium nidus, Aster novo-belgii, Hypoestes phyl. 'Betina'); and 12 (Soleirolia soleirolii, Asparagus den. 'Sprengeri', H. helix 'Ester', Codiaeum 'Pictum', Rosa 'Minimo Red', F. benjamina 'Starlight', Saintpaulia ionantha 'light blue', F. pumila, Rhododendron simsii, H. helix 'Shamrock', Hibiscus sp., E. pinnatum) were equally sensitive to mixtures dominated by either gas, as measured by at least one response parameter.

Journal Article↗
PubMed2001

Automated dynamic sampling system for the on-line monitoring of biogenic emissions from living organisms.

An automated system for continuous on-line monitoring of biogenic emissions is presented. The system is designed in such a way that volatiles, emitted as reaction to biotic or abiotic stress, can be unequivocally elucidated. Two identical sampling units, named target and reference bulb, are therefore incorporated into the system and consecutively analyzed in monitoring experiments. A number of precautions were considered during these experiments to avoid the application of unwanted stress onto both organisms. Firstly, the system is constructed in such a way that both bulbs are continuously flushed, i.e. before, during and after analysis, with high purity air to avoid any accumulation of emitted volatiles. Moreover, the air is pre-humidified by bubbling it through water to sustain the biological samples for longer periods in the in vitro environment. Sorptive enrichment on polydimethylsiloxane (PDMS) was used to trap the headspace volatiles. The hydrophobic nature of this material permitted easy removal of trapped moisture by direct flushing of the sampling cartridge with dry air before desorption. The system was used to monitor the emissions from in vitro mechanically wounded ivy (Hedera helix) and of in vitro grown tomato plants (Lycopersicon esculentum Mill.) upon cotton leafworm (Spodoptera littoralis) feeding. Differences in light and dark floral emissions of jasmine (Jasminum polyanthum) were also studied.

Automation↗
PubMed2000

Antithrombin activity of medicinal plants of the Azores.

A chromogenic bioassay was utilized to determine the antithrombin activity of methylene chloride and methanol extracts prepared from 50 plants of Azores. Extracts of the six plants Hedychium gardneranum, Tropaeolum majus, Gunnera tinctoria, Hedera helix, Festuca jubata and Laurus azorica demonstrated activity of 78% or higher in this bioassay system.

Azores↗
PubMed1998

Separation, identification and quantitative determination of free amino acids from plant extracts.

This research presents the results obtained from the separation, identification and quantitative determination of free amino acids from Gingko biloba and Hedera helix leaf extracts, using three modern techniques: thin layer chromatography (TLC), high performance liquid chromatography (HPLC), and gas chromatography-mass spectrometry. The presence of the determined amino acids explains the utilisation of G. biloba and H. helix leaf extracts in cosmetic and pharmaceutical products.

Amino Acids↗
PubMed2001

An unusual seed-specific 3-ketoacyl-ACP synthase associated with the biosynthesis of petroselinic acid in coriander.

Petroselinic acid (18:1 delta6) is the major component of the seed oil of Umbelliferae species such as coriander (Coriandrum sativum) as well as Araliaceae and Garryaceae species. This unusual fatty acid is synthesized in plastids by the delta4 desaturation of palmitoyl-acyl carrier protein (16:0-ACP) and subsequent elongation of delta4-hexadecenoyl (16:1 delta4)-ACP. To characterize the enzymatic nature of the elongation reaction, an in vitro assay was developed with 16:1 delta4-ACP and 16:0-ACP as substrates. Extracts from developing coriander seeds elongated 16:1 delta4-ACP in a competitive assay at rates ten-fold greater than that with 16:0-ACP. In contrast, extracts from castor seeds, which do not synthesize petroselinic acid, displayed a strong preference for the elongation of 16:0-ACP rather than 16:1 A4-ACP. In addition, the elongation of 16:1 A4-ACP and 16:0-ACP by coriander seed extracts was strongly inhibited by cerulenin at concentrations as low as 10 microM. This finding suggested that the elongation of 16:1 A4-ACP and 16:0-ACP in coriander seed is catalyzed by a 3-ketoacyl-ACP synthase (KAS) 1-type enzyme(s), rather than a KAS II-type activity that is typically associated with 16:0-ACP elongation. Consistent with this, a cDNA for a diverged form of KAS I was isolated from a cDNA library prepared from developing coriander seed. Using a variety of heterologous probing techniques, no KAS II-type cDNAs could be identified in this library. Multiple alignment of KAS amino acid sequences indicated that, although the polypeptide corresponding to the coriander cDNA is more closely related to KAS I. its active site motif deviates from those found in both KAS I and KAS II enzymes. Also suggestive of a possible role in petroselinic acid synthesis, antibodies raised to the recombinant protein recognize an abundant 45 kDa polypeptide in coriander endosperm that is not detected in coriander leaves. These antibodies also recognize a major band of similar size in developing seeds of English ivy (Hedera helix), an Araliaceae species that also accumulates petroselinic acid in a seed-specific manner.

3-Oxoacyl-(Acyl-Carrier-Protein) Synthase↗
PubMed1968

Biosynthesis of phytoquinones. Biosynthetic origins of the nuclei and satellite methyl groups of plastoquinone, tocopherols and tocopherolquinones in maize shoots, bean shoots and ivy leaves.

1. By using dl-[ring-(14)C]phenylalanine, dl-[beta-(14)C]phenylalanine, dl-[alpha-(14)C]-tyrosine and dl-[beta-(14)C]tyrosine it was shown that in maize shoots (Zea mays) the nucleus and one nuclear methyl group of each of the following compounds, plastoquinone, gamma-tocopherol (aromatic nucleus) and alpha-tocopherolquinone, are formed from the nuclear carbon atoms and beta-carbon atom respectively of either exogenous phenylalanine or exogenous tyrosine. With ubiquinone only the aromatic ring of the amino acid is used in the synthesis of the quinone nucleus. Chemical degradation of plastoquinone and gamma-tocopherol molecules labelled from l-[U-(14)C]tyrosine established that a C(6)-C(1) unit directly derived from the amino acid is involved in the synthesis of these compounds. Radioactivity from [beta-(14)C]cinnamic acid is not incorporated into plastoquinone, tocopherols or tocopherolquinones, demonstrating that the C(6)-C(1) unit is not formed from any of the C(6)-C(1) phenolic acids associated with the metabolism of this compound. 2. The incorporation of radioactivity from l-[U-(14)C]tyrosine, dl-[beta-(14)C]tyrosine and dl-[U-(14)C]phenylalanine into bean shoots (Phaseolus vulgaris) and dl-[beta-(14)C]tyrosine and l-[Me-(14)C]methionine into ivy leaves (Hedera helix) was also investigated. Similar results were obtained to those reported for maize, except that in beans phenylalanine is only used for ubiquinone biosynthesis. This is attributed to the absence of phenylalanine hydroxylase from these tissues. In ivy leaves it is found that the beta-carbon atom of tyrosine gives rise to the 8-methyl group of delta-tocopherol, and it is suggested that for all other compounds examined it will give rise to the nuclear methyl group meta to the polyprenyl unit. 3. Preliminary investigations with the alga Euglena gracilis showed that in this organism ring-opening of tyrosine occurs to such an extent that the incorporation data from radiochemical experiments are meaningless. 4. The above results, coupled with previous observations, are interpreted as showing that in higher plants the nucleus of ubiquinone can be formed from either phenylalanine or tyrosine by a pathway involving as intermediates p-coumaric acid and p-hydroxybenzoic acid. Plastoquinone, tocopherols and alpha-tocopherolquinone are formed from p-hydroxyphenylpyruvate by a pathway in which the aromatic ring and C-3 of the side chain give rise respectively to the nucleus and to one nuclear methyl group. 5. Dilution experiments provided evidence that in maize shoots p-hydroxyphenylpyruvic acid and homogentisic acid (produced from p-hydroxyphenylpyruvic acid) are involved in plastoquinone biosynthesis, and presumably the biosynthesis of related compounds: however, other possible intermediates in the conversion including toluquinol (the aglycone of the proposed key intermediate) showed no dilution effects. Further, radioactivity from [Me-(14)C]toluquinol is not incorporated into any of the compounds examined. 6. Dilution experiments with 3,4-dihydroxybenzaldehyde and radioactive-labelling experiments with 3,4-dihydroxy[U-(14)C]benzoic acid demonstrated that these compounds are not involved in the biosynthesis of either ubiquinone or phylloquinone in maize shoots. 7. Evidence is also presented to show that in maize shoots ring-opening of the aromatic amino acids takes place. The suggestion is offered that this may take place via homogentisic acid, as in animals and some micro-organisms.

Amino Acids↗
PubMed1997

Visualization of the cytoskeleton within the secondary vascular system of hardwood species.

A single fixation technique has been devised to demonstrate localization of alpha-tubulin (for microtubules) and F-actin (for microfilaments) within the secondary vascular system of hardwood trees by indirect immunofluorescence microscopy using butyl-methylmethacrylate-embedded material. Application of this technique to problems of cytomorphogenesis during secondary growth and its versatility are demonstrated with the hardwood species Aesculus hippocastanum L., Salix viminalis L., S. burjatica Nazarov x S. viminalis L., Hedera helix L., Acer platanoides L., Platanus sp., Quercus ilex L. and Liriodendron tulipifera L., and in the softwood Pinus pinea L. The methods employed have considerable scope for advancing knowledge of the role of the cytoskeleton in differentiation within the secondary vascular system of woody species.

Actins↗