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  • Auxin  (30)
  • Springer  (30)
  • Wiley
  • 1975-1979  (30)
  • 1950-1954
  • 1978  (19)
  • 1977  (11)
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  • Springer  (30)
  • Wiley
Years
  • 1975-1979  (30)
  • 1950-1954
Year
  • 1978  (19)
  • 1977  (11)
  • 1979  (12)
  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Planta 134 (1977), S. 145-149 
    ISSN: 1432-2048
    Keywords: Affinity labels ; Auxin ; Cell membranes ; Hormone Receptors ; Receptors ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Two auxin analogues have been tested as affinity labels for auxin binding sites in coleoptile membranes of Zea mays L. Reacting the membranes at pH 8–9 with the diazonium salt of CAPA (2-chloro-4-aminophenoxyacetic acid) reduces their subsequent ability to bind NAA(1-naphthylacetic acid). Diazo-Chloramben (2,5-dichloro-3-aminobenzoic acid) is also effective in inhibiting NAA binding capacity and this inhibition is largely independent of reaction pH over the range pH 6–9. Similar experiments with sulphydryl reagents have shown that reaction of the membranes with p-mercuribenzoate (PMB) strongly inhibits subsequent auxin binding activity. Prior addition of NAA protects the binding sites against the action of diazo-Chloramben or PMB when the reactions are carried out at pH 6. From these results and from other considerations, several of the amino acid residues in the binding site environment have been tentatively assigned.
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  • 2
    ISSN: 1432-2048
    Keywords: Auxin ; Avena ; Helianthus ; pH drop ; Pisum ; Protoplast suspension
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Several indoleacetic acids, substituted in the benzene ring, were compared in the Avena straight growth bioassay. 4-Chloroindoleacetic acid, a naturally occurring plant hormone, is one of the strongest hormones in this bioassay. With an optimum at 10-6 mol l-1, it is more active than indoleacetic acid, 2,4-dichlorphenoxyacetic acid and naphthaleneacetic acid. 5-Chloro- and 6-chloroindoleacetic acids are very strong auxins as well. Other derivatives tested have a lower activity. 5,7-Dichloro- and 5-hydroxyindoleacetic acids have very low auxin activity at 10-4 mol l-1 and may be anti-auxins. Some of the derivatives were compared for their effect on pH decline in stem protoplast suspensions of Helianthus annuus L. and Pisum sativum L. The change of pH occurs without a lag period or with only a very short one. Derivatives which are very active in the Avena straight growth assay cause a larger pH decline than indoleacetic acid, while inactive derivatives cause effectively no pH decline.
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  • 3
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    Springer
    Planta 140 (1978), S. 107-109 
    ISSN: 1432-2048
    Keywords: Auxin ; Leaf movement ; Phaseolus ; Pulvinus ; Turgor movement
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Auxin application to the upper side of the pulvinus of primary leaves of Phaseolus vulgaris L. promoted bending away from the place of application. The effect had a latency of less than 20 min and was specifically induced by substances known as active auxins in growth tests (indoleacetic and 1-naphthaleneacetic acid) but not by inactive auxin analogs (2-naphthaleneacetic, 3-indolepropionic and benzoic acid); 2,4-dichlorophenoxyacetic acid, and L-(-)-2,4-dichlorophenoxyisopropionic acid were of intermediate activity. Auxin-promoted bending was reversible and presumably caused by turgor increase in the treated cells.
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  • 4
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    Springer
    Planta 140 (1978), S. 201-211 
    ISSN: 1432-2048
    Keywords: Auxin ; Cell elongation ; Coleoptiles ; Fusicoccin ; Zea
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract To analyze early effects of auxin application, an apparatus was developed which continuously and simultaneously registered the curvature of 10 individual maize (Zea mays L.) coleoptiles. Resolution was less than 5 μm over a range of ±0.5 mm. The data were evaluated and plotted via paper tape and Hewlett-Packard-computer. Unilateral application of 3×10-5 M indoleacetic acid (IAA) resulted in a transient inhibition of growth on the side of application for ca. 10 min (Phase I), followed by a strong stimulation (Phase II). The phytotoxin fusicoccin (FC) caused an immediate stimulation of elongation. The initial negative reaction of Phase I is auxin-specific. Only active auxins such as IAA and 1-naphtaleneacetic acid produced this initial inhibition; chemical analogs-inhibitory or neutral in long-term growth tests, e.g. phenylacetic acid-did not show any significant effects on Phase I. When the coleoptiles were symmetrically preloaded with different levels of auxin, only a large step-up of subsequent unilateral auxin application resulted in a negative phase I; a small step-up led to an immediate positive reaction. The results are discussed in context with the parallel kinetics for various other auxin-induced reactions of coleoptile cells which have already been published.
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  • 5
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    Planta 136 (1977), S. 97-102 
    ISSN: 1432-2048
    Keywords: Acid growth ; Auxin ; Ethylene ; Fusicoccin ; Growth inhibition ; Lens ; Root growth
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Both acid pH (4.0) and fusicoccin (FC) strongly stimulate root elongation in intact lentil (Lens culinaris Med.) seedlings. FC-induced elongation is apparently mediated by FC-enhanced H+ secretion since the toxin induces massive secretion of H+ in these roots after a latent period of less than 5 min. Auxin (indole-3-acetic acid) strongly inhibits elongation in control roots as well as acid-induced and FC-induced root elongation. Treatment of apical root segments with auxin causes only a slight apparent uptake of H+ and has no inhibitory effect on FC-induced H+ secretion, whether the hormone is given before or after the toxin. Auxin induces ethylene production in excised roots of lentil but the latent period is at least 30 min while inhibition of root elongation by IAA is maximal within 30 min. It is concluded that the inhibitory action of auxin on acid-and fusicoccin-induced root elongation is a direct effect, independent of auxin-induced ethylene production or auxin-mediated modification of cell-wall pH.
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  • 6
    ISSN: 1432-2048
    Keywords: Abelmoschus ; Auxin ; Gibberellin ; Root formation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Indole-3-acetic acid (IAA) and gibberellic acid (GA3) enhanced the formation of roots on the stem cuttings of Abelmoschus esculentus. The effect increased considerably when both IAA and GA3 were applied together.
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  • 7
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    Planta 138 (1978), S. 107-110 
    ISSN: 1432-2048
    Keywords: Auxin ; Nitrogen fixation (asymbiotic) ; Pisum ; Rhizobium
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Treatment of epicotyls of dark-grown pea (Pisum sativum L.) seedlings with indole-3-acetic acid causes swelling of the tissue. Application of Rhizobium to the cut surface of the swollen tissue results in the development of an “infection”. The infection spreads in the cortical cells and proceeds 2–3 mm deep into the stem within 3–4 days. An acetylene reduction assay used for detecting nitrogen-fixation capacity of the infected tissue was negative at 10% [O2]; however, if [O2] was reduced to below 1%, some activity could be detected. Ultrastructural observations indicate that the cytoplasmic contents of the infected cells are destroyed and no membrane structure around the bacteria is formed during this infection. Rhizobium does not appear to have developed any symbiotic relationship with the host. Failure to develop symbiosis appears to result in a parasitic or saprophytic association and the nitrogen fixed under such conditions may not be of any use to the plant.
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  • 8
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    Planta 138 (1978), S. 181-184 
    ISSN: 1432-2048
    Keywords: Abscisic acid ; Auxin ; Cannabis ; Cytokinin ; Flowers (sex) ; Gibberellin ; Sex expression
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Application, through the root system, of growth regulators to hemp (Cannabis sativa L.) plants having 2–3 pairs of visible leaves caused pronounced shifts of sex expression in the adult individuals. Treatment with gibberellic acid (25 mg/l) resulted in more than 80% of the plants being male, i.e. having staminate flowers (controls, ca. 30%). Treatment with 6-benzylaminopurine and with indole-3-acetic acid (in either case, 15 mg/l) resulted in all plants being either female (pistillate flowers) or intersexes (bisexual flowers); treatment with abscisic acid (10 mg/l) had a similar but somewhat less pronounced effect.
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  • 9
    ISSN: 1432-2048
    Keywords: Auxin ; Ethylene ; Root formation ; Vigna
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Rooting responses and ethylene production by hypocotyl cuttings from etiolated mung-bean seedlings treated with the auxins α-naphthaleneacetic acid, γ-(indole-3)-n-butyric acid (IBA) and 2,4,5-trichloro-phenoxypropionic acid were determined. There was no relationship between the abilities of the auxins to induce root formation and their capacities for inducing ethylene production. Studies with mixtures of 3-indoleacetic acid, a poor stimulator of rooting but an effective inducer of ethylene production, and IBA, an effective rooting stimulator but a poor inducer of ethylene production, exposure of cuttings to ethylene or (2-chloroethyl) phosphonic acid (Ethephon), hypobaric storage (150 mb) of treated cuttings, and exposure of auxin-treated cuttings to 7% CO2 also indicated that ethylene is not directly involved in initiation of adventitious roots in this plant material.
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  • 10
    ISSN: 1432-2048
    Keywords: Auxin ; Fusicoccin ; Glucose transport ; Proton flux ; Roots ; Zea
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Auxin and fusicoccin (FC) stimulate the active uptake of 3-O-methyl glucose (3-O-MG) in those materials in which they have been shown to activate an electrogenic proton extrusion (Pisum sativum L. stems, Zea mays L. coleoptiles and roots). In maize roots the curve relating 3-O-MG influx to external concentrations indicated that the values of the apparent Km increase in the 3-O-MG concentration range between 2×10-5 mol l-1 and 2×10-2 mol l-1. FC did not alter the Km values and its stimulating effect was nearly constant at all 3-O-MG concentrations tested. Basal and FC-induced uptake of 3-O-MG appeared associated with a transient proton influx suggesting that also in maize roots a sugar-proton contransport occurs. Diethyl stilbestrol, which inhibits proton extrusion, inhibited also basal and FC-induced 3-O-MG uptake. The data support the view that the stimulation by FC of 3-O-MG uptake is closely related to that of proton extrusion. The stimulation by FC of 3-O-MG uptake cannot be replaced by increasing extracellular proton concentration, nor may be explained only by the FC-induced hyperpolarization of transmembrane potential difference. The hypothesis is proposed that the effect of FC on 3-O-MG uptake depends on an increase of cytoplasmic pH, following the activation of the proton extruding system.
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  • 11
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    Planta 141 (1978), S. 179-181 
    ISSN: 1432-2048
    Keywords: Auxin ; Maize ; Root tip ; Zea
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract [5-3H]Indol-3yl-acetic acid (IAA) applied to the shoot apices of intact 6-day-old maize (Zea mays L.) plants moved into the primary root and accumulated at the root apex. IAA from the shoot could partially satisfy the requirement of the primary root for IAA for growth.
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  • 12
    ISSN: 1432-2048
    Keywords: AMO-1618 ; Antiauxin ; Auxin ; Bromodeoxyuridine ; Cell (fiber) growth ; Gibberellin ; Gossypium ; Ovules (in-vitro culture)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The effects of 5-bromo-2-deoxyuridine (BUdR, thymidine analogue), AMO-1618 (2-isopropyl-4-dimethylamino-5-methylphenyl-1-piperidine carboxylate methyl chloride), a growth retardant, and p-chlorophenoxyisobutyric acid (PCIB, an antiauxin) on growth (dry weight increase) and fiber development in unfertilized cotton (Gossypium hirsutum L.) ovules grown in vitro have been studied. BUdR (5 μM) causes about 70% inhibition of fiber production, with little effect on ovule growth, if applied during the first 6 d of culture in the presence of GA3 and IAA. AMO-1618, when used with GA3 alone, causes only a small reduction in both dry weight and fiber production, but when used with IAA alone reduces both fiber production and dry weight, the effect on the latter being predominant. In the presence of both IAA and GA3, AMO-1618 causes a small decrease in fiber production but a major decrease in dry weight. PCIB completely inhibits fiber growth but has little effect on dry weight, especially when GA3 is present. These results indicate that GA3 mainly promotes ovule growth while IAA is largerly responsible for fiber growth.
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  • 13
    ISSN: 1432-2048
    Keywords: Auxin ; Chlorophyll content ; Chloroplast ; Photosynthetic rate ; Raphanus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Dark-grown radish seedlings (Raphanus sativus L.) were sprayed with 10-3 mol·l-1 2,4-dichlorophenoxyacetic acid and then were exposed to a 14:10 light: dark cycle. Cotyledon samples from these seedlings and unsprayed controls were taken for electron microscopy, chlorophyll determinations, and photosynthetic rate measurements at regular intervals for 72 h. A normal development of etioplasts to chloroplasts with formation of typical grana-fret work system was observed in the control cotyledons. The chloroplasts in the 2,4-D-treated cotyledons showed changes in the organization of the grana thylakoids; these thylakoids being more appressed to each other than in the controls. The chlorophyll content of treated plants was less than that of controls but the rate of chlorophyll biosynthesis was unaffected. The photosynthetic rate/mg chlorophyll was considerably higher for treated plants suggesting that 2,4-D treatment resulted in decreased size of the photosynthetic unit.
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  • 14
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    Planta 144 (1978), S. 39-47 
    ISSN: 1432-2048
    Keywords: Aquatic plants ; Auxin ; Cell elongation ; Ethylene ; Ethylene biosynthesis ; Silverions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Elongation of the shoots of three aquatic plants (Hydrocharis morsus-ranae, Regnellidium diphyllum and Ranunculus sceleratus) is stimulated by treatment with ethylene or IAA. The effects of the two hormones are additive, and experiments with an ethylene biosynthesis inhibitor and silver ions indicate that the mechanisms by which ethylene and IAA stimulate growth may be different. Hydrocharis and Ranunculus leaf discs synthesize [14C]ethylene from [14C]methionine, but no [14C]ethylene is formed by Regnellidium, suggesting the existence of an alternative pathway of ethylene biosynthesis in the fern.
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  • 15
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    Planta 136 (1977), S. 173-180 
    ISSN: 1432-2048
    Keywords: Auxin ; Immunoassay ; Nicotiana ; Radioimmunoassay
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We have developed a specific radioimmunoassay [RIA] for indole-3-acetic acid (IAA) in the 0.2 ng to 12 ng range which, in principle, can be extended to other indole auxins as well. Methods are presented for obtaining suitable antibody, for the RIA procedure, and for measuring IAA in methanolic extracts of plant tissues. Antibody specific for IAA was obtained from rabbits immunized with IAA bound to bovine serum albumin by formaldehyde treatment. In assays with this antibody, 2,4-dichlorophenoxyacetic acid and indoles structurally related to IAA reacted from 300- to 3000-fold less than did IAA itself. However, α-and β-naphthaleneacetic acid reacted significantly and hence interfered with the assay. Extracts of tobacco (Nicotiana tabacum L.) tissue were immunoassayed after partial purification by buffer-ether partition. Crown-gall tumor tissue, which is auxin-autotrophic, and pith tissue depleted of auxin by the diffusion method contained, respectively, 26.7 ng and 〈0.5 ng extractable IAA per gram fresh weight.
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  • 16
    ISSN: 1432-2048
    Keywords: Auxin ; Calcium ions ; Cell growth ; Gibberellin ; Membrane permeability ; Membrane potential ; Zea
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The membrane potential difference of dwarf maize coleoptile cells is increased by both 10-5moll-1 gibberellic acid (GA3) and indoleacetic acid (IAA) a few minutes after application. A final level is reached after 10–20 min. The membrane permeability ratio P Na:P K is altered by both hormones during the first 15 min after application, indicating a rapid effect on the membrane. Elongation growth of coleoptile segments, however, is only stimulated by IAA. The auxin-induced growth as well as the auxin effect on membrane permeability depends on the calcium ion concentration of the medium. It is concluded that IAA acts via a proton extrusion pump that is electrically balanced by a potassium ion uptake, driven by the electromotive force of the pump. The mode of action of GA3 on elongation growth is assumed to involve a process that depends on the physiologic state of the tissue and/or metabolic energy.
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  • 17
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    Planta 140 (1978), S. 31-35 
    ISSN: 1432-2048
    Keywords: Auxin ; Coleoptiles ; Electrical Potential ; Zea
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Following asymmetric application of indoleacetic acid to maize (Zea mays L.) coleoptiles the early time course of changes in lateral electrical potential was externally monitored with static-drop electrodes. First, an early negative potential change of ca.-1 mV was measured at the surface on the side of a strong auxin application. This negative auxin effect ended after ca. 15 min and was followed by a strong and lasting auxin stimulation of a positive lateral potential up to +12 mV at the auxin-treated side. The initial auxin effect appeared to depend on the size of the step-up in auxin concentration.
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  • 18
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    Planta 140 (1978), S. 137-142 
    ISSN: 1432-2048
    Keywords: Auxin ; Cell elongation ; Proton secretion ; Triticum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Growth of Triticum aestivum L. cv. Cappelle Desprez coleoptiles is promoted by 5.7×10−5 M indole acetic acid (IAA) as effectively in pH 3.4 buffer as in water, but IAA is not effective in the presence of buffer at pH 3.0 or 3.2 A combination of 5.7×10−5 M IAA and pH 3.4 buffer promotes growth to a greater extent than pH 3.2 buffer alone, which is optimal for acid-induced growth. IAA employed at 10−7 M is still effective at promoting growth in the presence of pH 3.4 buffer, moreover, IAA at 10−7 M interacts synergistically with the acidic buffer to promote growth. It is concluded that IAA and acid promote growth via separate mechanisms, and that IAA does not promote cell wall loosening by rendering the cell wall more acid.
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  • 19
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    Planta 144 (1978), S. 79-84 
    ISSN: 1432-2048
    Keywords: Auxin ; Cell elongation ; Lead ; Triticum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In vitro studies of IAA-induced cell elongation in Triticum aestivum have demonstrated that lead causes a large reduction in elongation. Inhibition of elongation can be reduced by increasing the concentration of IAA, or by the addition of calcium. The inhibitory effect appears to be linked with changes in the properties of the cell walls. Experiments are described which show that lead becomes bound strongly to certain chemical substances involved in cell wall architecture.
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  • 20
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    Planta 142 (1978), S. 207-210 
    ISSN: 1432-2048
    Keywords: Abscisic acid ; Auxin ; Cytokinin ; Flowers (sex) ; Gibberellin ; Sex expression ; Spinacia
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract 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 to 88, 76 and 71%, respectively; the GA3 treatment increased the percent of male plants to 79%. When young, vegetative spinach plants (3 visible leaves) grown in 18-h days were cut a the root neck, and the shoots grown with their bases in nutrient solution, with adventitious roots either being allowed to develop or being systematically removed, 85% of the plants without roots became males, 85% of those with roots became females. But if the cut shoots were first, for 28 h, placed in a 15-mg/l 6-BAP solution and then grown in the absence of roots, the percent of female plants was restored to 84. These results fully agree with those obtained previously with hemp, namely, that plant growth regulators exert a regulating effect on the sex expression of dioecious plants when applied through the roots in early stages of development; that the root system plays an important role in determining the sex of these plants, that this role of the roots is associated with the synthesis of cytokinins in them. Dioecious short- and long-day plants do not differ in these respects.
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  • 21
    ISSN: 1432-2048
    Keywords: Auxin ; Benzoxazolinones ; Receptors ; Supernatant factor ; Zea
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A naturally-occurring material termed ‘supernatant factor’ [Ray, P.R., Dohrmann, U., Hertel, R.: Plant Physiol. 59. 357–364 (1977)], which has the property of modifying the binding affinity of auxins to receptor sites, has been isolated from corn (Zea mays L.) and characterised as a mixture of 6-methoxy-2-benzoxazolinone (MBOA) and 6,7-dimethoxy-2-benzoxazolinone (DMBOA). DMBOA is about 50 times more active than MBOA in inhibiting binding of the auxin 1-naphthylacetic acid to membrane-bound or solubilised receptors. The activity of these compounds and the parent analogue in inhibiting auxin binding is correlated with their ability to inhibit auxin-induced growth.
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  • 22
    ISSN: 1432-2048
    Keywords: Auxin ; Compartmental analysis ; Ion fluxes ; Petroselinum ; Suspension culture
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Transport of 86Rb+/K+, 22Na+, 36Cl−, and [3H]indole acetic acid (IAA) has been studied on suspension-cultured cells of the parsley, Petroselinum crispum (Mill) Nym. By compartmental analysis two intracellular compartments of K+, Na+, and Cl− have been identified and ascribed to the cytoplasm and vacuole; half-times of exchange were around 200 s and 5 h, respectively. According to the Ussing-Teorell flux equation, active transport is required for the influx into the cytoplasm at the plasmalemma (K+, Cl−) and the tonoplast (K+, Na+, Cl−). The plasmalemma permeability pattern, PK:PNa:PCl=1.00:0.24:0.38, features an increased chloride permeability compared with cells from higher plant tissues. IAA uptake showed an exponential timecourse, was half-maximal after 10 min, and a linear function of the IAA concentration from 10−9 to 10−5 M. IAA and 2,4-dichlorophenoxy acetic acid reduce the apparent influx of K+, Na+, Cl− during the initial 30 min after addition and subsequently accelerate both in- and efflux of these ions. We discuss that auxins could affect the ion fluxes in a complex way, e.g. by protonophorous activity and by control of the hypothetical proton pump.
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  • 23
    ISSN: 1432-2048
    Keywords: Auxin ; Cytokinin ; 5-Fluorouracil ; Helianthus ; Ribosome synthesis and activity ; Tuber
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In order to examine the relation of protein synthesis to the onset of growth, changes in ribosome content and activity were compared in aged, metabolically active Jerusalem artichoke (Helianthus tuberosus L.) slices incubated in water or 2,4-dichlorophenoxyacetic acid+kinetin. In water, cells do not grow or divide and rRNA and protein levels remain constant. The percentage membrane-bound (mb) ribosomes drops from 25% to 16% during 24h. At the same time the proportion of ribosomes active in protein synthesis in both free and mb populations declines from about 69% to 54%. In auxin+kinetin, cell expansion occurs and is accompanied by a 3-fold increase in rRNA and a 50% increase in total protein content. The percentage mb ribosomes remains at 25% throughout 48 h of growth. During the first 24h of growth 70% of ribosomes in both free and mb populations are active; this value declines to near water levels at 48 h. Considering the large increase in total ribosomes the number of synthetically active ribosomes is substantially increased during growth. 5-Fluorouracil (5-FU) does not inhibit hormone induced growth but does depress total rRNA content by about one-third. It also reduces [3H]uridine incorporation into ribosomes by 70% and the newly made ribosomes are mostly inactive in protein synthesis. On the other hand, the inhibitor does not significantly affect the proportion of total ribosomes active in protein synthesis and only partially reduces protein accumulation during the second 24 h of growth. It is suggested that while ribosome production is reduced in 5-FU, ribosome turnover is also retarded resulting in retention of near normal capacity for protein synthesis and growth.
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  • 24
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    Planta 135 (1977), S. 289-295 
    ISSN: 1432-2048
    Keywords: Antiauxin ; Auxin ; Meristem differentiation ; Riella
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract During the development of the unistratose gemmae of Riella helicophylla, the single intercalary meristem of the very young gemmae is subdivided into two lateral meristems. The duration of the cell reproduction cycle increases from the margin to the median part of the gemmae. This polarization within the meristem disappears after addition of the antiauxin PCIB to the culture medium. PCIB leads to a retardation or blockage of the cell cycle during the light period of the culture. Under the influence of PCIB the amount of starch in the chloroplasts is strikingly increased, probably because of a reduction of starch degradation. Addition of sugars compensates the effect of PCIB on the cell cycle. The effects of PCIB are counteracted by auxin. The results are taken as evidence that auxin plays a role in directing the transport of substances needed for the continuation of the cell reproduction cycle between adjacent cells of the meristem.
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  • 25
    ISSN: 1432-2048
    Keywords: Auxin ; Cambium ; Gibberellin ; Picea ; Tracheids-wood production
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The diameter and wall thickness of tracheids produced after indoleacetic acid treatment were not significantly different from those of the intact controls, for the first few weeks after treatment of disbudded shoots of Picea abies Karst. and Picea sitchensis (Bong.) Carr. However, lateral application of indoleacetic acid (IAA) to intact shoots increased both tracheid diameter and wall thickness; it is suggested that IAA acted synergistically with another endogenous growth regulator, which was also removed by disbudding. Increase in wall thickness after exogenous IAA was associated with increase in duration of the wall thickening phase of tracheid differentiation; this is discussed in relation to the seasonal change from early to latewood. Cambial dormancy was induced by disbudding during active wood production. Since this occurred with or without the presence of current leaves, it is concluded that in Picea continued cambial activity depends upon supply of auxin from the buds, and cannot be supplied from expanded leaves or from the internode itself. Neither indoleacetic acid nor gibberellic acid stimulated renewed cambial activity when applied after the cessation of wood production. With both disbudded and intact shoots, the effectiveness of exogenous IAA declined with time, probably due to decreasing penetration through callus developing at the wounded surface. It is suggested that this apparent change in IAA effectiveness may explain some discrepancies between the results of previous observers.
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  • 26
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    Planta 134 (1977), S. 295-299 
    ISSN: 1432-2048
    Keywords: Abscisic acid ; Apical dominance ; Auxin ; Gibberellin ; Hormone transport ; Phaseolus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Abscisic acid (ABA) in lanolin, applied to the internode of decapitated runner bean plants enhances the outgrowth of lateral buds. The optimum concentration of the paste is 10-5 M. The effect of ABA is counteracted by indoleacetic acid (IAA) but not by gibberellic acid (GA3). There is no effect when ABA is applied to the apical bud or lateral buds of intact plants. However, 13.2 ng given to the lateral buds of decapitated plants stimulate their growth, whereas higher concentrations are inhibitory. Consequently, ABA enhances growth of lateral buds directly, but only when apical dominance is already weakened. The growth of the decapitated 2nd internode was not affected by ABA. Radioactivity from [2-14C] ABA, applied to nonelongating 2nd internode stumps of decapitated runner bean plants moves to the lateral buds, whereas [1-14C]IAA-and [3H]GA1-translocation is much weaker. ABA transport is inhibited if IAA or [3H]GA1 is applied simultaneously. In elongating internodes [14C]ABA is almost completely immobile. [14C]IAA-and [3H]GA1-translocation is not affected by ABA. The amount of radioactivity from labelled ABA, translocated to the lateral buds, is highest during the early stages of bud outgrowth.
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  • 27
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    Planta 135 (1977), S. 207-212 
    ISSN: 1432-2048
    Keywords: Auxin ; Cytokinin ; Explants ; Helianthus ; Tuber (explants) ; Xylem differentiation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract the culture of Jerusalem artichoke (Helianthus tuberosus L.) tuber explants on filter paper discs moistened with liquid medium resulted in rapid and consistent xylem differentiation. The number of tracheary elements increased in discrete steps, the first at 48 h with a second at 56–58 h, following partially synchronous mitoses at 20 and 30 h. Factors favouring xylem cell differentiation were optimum levels of both an auxin and a cytokinin, low medium nitrogen concentrations, small volumes of medium, and high culture temperatures. A cell counting method employing Feulgen-stained nuclei and suitable for quantifyings small numbers of immature tracheary elements is described.
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  • 28
    ISSN: 1432-2048
    Keywords: Auxin ; Avena ; Cell elongation ; Ion uptake ; Malate synthesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The short-term effects of auxin (indole-3-acetic acid) and fusicoccin (FC) on Rb+ uptake and malate accumulation in Avena sativa L. coleoptile sections have been investigated. FC stimulates 86Rb+ uptake within 1 min while auxin-enhanced uptake begins after a 15–20-min lag period. Auxin has little or no effect on 86Rb+ uptake at external pHs of 6.0 or less, but substantial auxin effects can be observed in the range of pH 6.5 to 7.5. Competition studies indicate that the uptake mechanism is specific for Rb+ and K+. After 3 h of auxin treatment the total amount of malate in the coleoptile sections is doubled compared to control sections. FC causes a doubling of malate levels within 60 min of treatment. Auxin-induced malate accumulation exhibits a sensitivity to inhibitors and pH which is similar to that observed for the H+-extrusion and Rb+-uptake responses. Both auxin- and FC-enhanced malate accumulation are stimulated by monovalent cations but this effect is not specific for K+.
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  • 29
    ISSN: 1432-2048
    Keywords: Abscisic acid ; Auxin ; Cambium ; Picea
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Indole-3-acetic acid (IAA) and abscisic acid (ABA) were identified by combined gas chromatography-mass spectrometry (GCMS) in fractions obtained by diffusion and extraction from bark peelings of Sitka spruce. A procedure is described for the quantitative analysis of IAA and ABA levels in the same extract using the GCMS technique of single-ion current monitoring. This procedure was used to measure the diffusible, free, and bound fractions of IAA and ABA in the cambial region of Sitka spruce throughout one year; the range in concentration for these fractions was 0.06–0.30, 0.46–3.85, and 0.04–0.20 μg/g oven-dry weight, respectively, for IAA, and 0–0.08, 0.03–2.21, and 0.13–0.66 μg/g oven-dry weight, respectively, for ABA. Movement in the cambial region was found to be polar for endogenous IAA and nonpolar for endogenous ABA. Recoveries of [14C]IAA internal standards showed that 73–99.5% of the IAA was lost during purification, and that there could be up to 5-fold differences in recovery between purifications, indicating that IAA loss shold be measured in quantitative analyses.
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  • 30
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    Planta 135 (1977), S. 1-5 
    ISSN: 1432-2048
    Keywords: Auxin ; Cell elongation ; Elongation ; Root growth ; Zea
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The effect of indole-3-acetic acid (IAA) on the elongation rates of 2 mm corn (Zea mays L.) root segments induced by citrate-phosphate buffer (or unbuffered) solutions of pH 4.0 and 7.0 was studied. At pH 7.0, auxin initially reduced the elongation rate in both buffered and unbuffered solutions. Only in buffer at pH 7.0 was auxin at a concentration of 0.1 μM found to promote the elongation rate though briefly. THis promoted rate represented only ca. 20% of the rate achieved with only buffer at pH 4.0. Auxin in pH 4.0 buffered and unbuffered solutions only served to reduce the elongation rates of root segments. Some comparative experiments were done using 2 mm corn coleoptile segments. Auxin (pH 6.8) promoted the elongation rate of coleoptile segments to a level equal or greater than the maximal H ion-induced rate. The two responses of root segments to auxin are compared to auxin action in coleoptile growth.
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