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Results for “INDOLEACETIC ACID”

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PubMed1974

Morphogenesis in Selaginella: II. Auxin Transport in the Root (Rhizophore).

The rhizophore of Selaginella willdenovii Baker develops from the ventral angle meristem. The morphological nature of this organ has been in dispute. The purpose of this investigation was to obtain physiological evidence to support the contention that the rhizophore is a root and not a shoot. This was accomplished by studying the movement of (3)H-indoleacetic acid and (14)C-indoleacetic acid in Selaginella rhizophores. In 6-millimeter tissue segments, twice as much radioactivity accumulated in acropetal receivers as in basipetal. During 1 hour of transport in intact roots auxin traveled twice as far in the acropetal direction as basipetal. A significant amount of radioactivity transported in the tissue was found to co-chromatograph with cold indoleacetic acid. Decarboxylation accounted for 10% loss of activity from donors. The data provide sufficient physiological evidence that this organ is morphogenetically a root.

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PubMed1986

Effects of Dimethyl Sulfoxide and pH on Indoleacetic Acid-Induced Lateral Root Formation in the Radish Seedling Root.

Segments (2.5 cm) cut from 3-day-old seedling roots of radish (Raphanus sativus L. ;Scarlet Globe') were cultured in medium with or without indoleacetic acid (IAA). Lateral root primordia frequency, determined for the central centimeter of segments, was dependent on IAA concentration and on conditions affecting IAA uptake. Dimethyl sulfoxide treatment, or a relatively low medium pH, greatly enhanced the response to exogenous IAA. It was concluded that a permeation barrier exists between the external medium and the hormone responsive sites within the radish seedling root.

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PubMed1973

Mechanism of a Synergistic Effect of Kinetin on Auxin-induced Ethylene Production: Suppression of Auxin Conjugation.

In hypocotyl segments of mung bean (Phaseolus mungo L.) seedlings, exogenously supplied indoleacetic acid was rapidly conjugated mainly into indoleacetylaspartic acid, which was inactive in inducing ethylene production. Kinetin is known to stimulate indoleacetic acid-induced ethylene production. The mechanism of kinetin action on indoleacetic acid-induced ethylene production by hypocotyl segments of mung bean seedlings was studied in relation to indoleacetic acid uptake and indoleacetic acid metabolism. Kinetin enhanced indoleacetic acid uptake during the initial 2-hour incubation and markedly suppressed the conversion of indoleacetic acid to indoleacetic acid conjugates throughout the whole 7-hour incubation. As a result, there was more free indoleacetic acid and less conjugated indoleacetic acid in the segments treated with kinetin than in those receiving no kinetin. A close relationship was demonstrated between the rate of ethylene production and the level of free indoleacetic acid, which was regulated by kinetin.

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PubMed1974

Auxin Does Not Alter the Permeability of Pea Segments to Tritium-labeled Water.

The possibility of an auxin effect on the permeability of pea (Pisum sativum L. ev. Alaska) segments to tritium-labeled water has been investigated by three separate laboratories, and the combined results are presented. We were unable to obtain any indication of a rapid effect of indoleacetic acid on the efflux of (3)HHO when pea segments previously "loaded" for 90 minutes with (3)HHO were transferred to unlabeled aqueous medium with indoleacetic acid. We were able to confirm that segments pretreated with (3)HHO plus indoleacetic acid for 60 to 90 minutes can show an enhanced (3)HHO release as compared with minus indoleacetic acid controls. However, this phenomenon appears to be due to an increased uptake of (3)HHO during the prolonged indoleacetic acid pretreatment, and therefore we conclude that auxin does not alter the permeability of pea segments to (3)HHO in either short term or long term tests. We confirm previous reports that the uptake of (3)HHO in pea segments proceeds largely through the cut surfaces, and that the cuticle is a potent barrier to (3)HHO flux.

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PubMed1974

Effect of pH and Auxin on Chloride Uptake into Avena Coleoptile Cells.

The effect of pH on (36)Cl(-) movement into coleoptile cells (Avena sativa L. cv. Garry) was investigated and compared with effects of indoleacetic acid. (36)Cl(-) uptake, but not efflux, is stimulated when coleoptile sections are placed in media adjusted to pH levels from 5 to 3 after a preincubation period at pH 6.5. The enhancement is seen within 2 minutes, is not correlated with growth, and is completely erased by respiratory inhibitors. In comparison to the acid-induced stimulation, the stimulatory effect of indoleacetic acid on (36)Cl(-) uptake is also not accompanied by accelerated efflux, and indoleacetic acid does not further stimulate (36)Cl(-) uptake into 1-millimeter sections beyond that seen at pH 3.5 without auxin.

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PubMed1978

Role of Indole-3-acetic Acid and Gibberellin in the Control of Internodal Elongation in Avena Stem Segments: Long Term Growth Kinetics.

Exogenous application of indoleacetic acid results in a significant suppression of the linear growth that is promoted by exogenous gibberellic acid in Avena stem segments in a fashion similar to that previously noted in Avena leaf base segments (van Overbeek and Dowding, 1961, Fourth International Conference Plant Growth Regulation). Treatment with the auxin transport inhibitors, methyl-2-chloro-9-hydroxyfluorene-(9)-carboxylate (CFM) or 2,3,5-triiodobenzoic acid (TIBA), alone promotes elongation growth of the stem segments over that of control growth. This effect is interpreted as being due to the interference in the transport of native indoleacetic acid by CFM and TIBA, thus removing the inhibitory effect of native indoleacetic acid on gibberellin-promoted growth in the internodal intercalary meristem. This results in a greater promotion of internodal growth by native gibberellins. In the presence of (2-chloroethyl) trimethylammonium chloride (CCC), the growth-promoting effects of CFM and TIBA are decreased, and the antiauxin, PCIB (4-chloro-phenoxyisobutyric acid), has no growth-promoting effects whatsoever. These results indicate that the CFM and TIBA-promoted growth require the continuous presence of gibberellins. They further support the view that native indoleacetic acid acts as a growth suppressor hormone in its regulation of gibberellin-promoted internodal extension in Avena shoots.

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PubMed1980

An Examination of Centrifugation as a Method of Extracting an Extracellular Solution from Peas, and Its Use for the Study of Indoleacetic Acid-induced Growth.

A technique of centrifuging pea epicotyl sections which extracts water-soluble cell wall polysaccharides with less than 1.5% cytoplasmic contamination as revealed by malate dehydrogenase activity determinations was developed. Tests for protein, hexose, pentose, and malate dehydrogenase indicate that significant damage to the cells occurs above 3,000g. Below this force, there is little damage, as evidenced by the similar growth rates of centrifuged and noncentrifuged sections. Centrifugation at 1,000g extracts polysaccharides containing rhamnose, fucose, arabinose, xylose, mannose, galactose, and glucose. An increase in xylose and glucose, presumably xyloglucan, is induced by treating sections with indoleacetic acid. Much of the alcohol-insoluble, water-soluble polysaccharide within the wall is extractable by centrifugation, since nearly as much arabinose and xylose are extractable by centrifugation as by homogenization. The utility of this method for the study of cell wall metabolism is discussed.

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PubMed2003

Degradation of tryptophan and related indolic compounds by ruminal bacteria, protozoa and their mixture in vitro.

In vitro experiments were conducted to examine the degradation of d- and l-isomers of tryptophan (Trp) and 10 related indolic compounds by mixed rumen bacteria (B), protozoa (P) and a combination of the two (BP). The analyses were carried out by HPLC. d-Trp (1.0 mM) was not degraded by rumen microorganisms during the 24-h incubation period. The net degradation of 1 mM l-Trp was 46.5%, 8.7% and 80.0% by B, P and BP suspensions, respectively. Trp was degraded into indoleacetic acid, indolelactic acid and indole by rumen bacteria and protozoa, and into skatole, p-cresol and indolepropionic acid by rumen bacteria only. Of them, indoleacetic acid was the major product of Trp found in B (15.4%) and P (3.1%), and skatole in BP (43.2%). This is the first report of the production of indolelactic acid and p-cresol from Trp by rumen microbes. Starch, d-glucose, salinomycin and monensin inhibited the production of skatole and indole from Trp, and skatole from indoleacetic acid by rumen bacteria.

Animals↗

PubMed1984

Application of modified Lineweaver-Burk plots to studies of kinetics and regulation of radish 3-hydroxy-3-methylglutaryl-CoA reductase.

We propose the use of modified Lineweaver-Burk plots for the correct evaluation of Michaelis-Menten parameters in radioactive enzyme assays. A correction factor X for the translation of 1/S0 into 1/S is directly derived from the integrated Michaelis-Menten equation without the need of complicated calculations. In practice, this approach is favorably combined with an isotope dilution method which enhances the reliability of measurements at low substrate concentrations. The usefulness of the theoretical and practical approach is demonstrated in investigations of HMG-CoA reductase present in membrane fractions isolated from radish seedlings. The enzyme in the two main membrane fractions obtained by centrifugation at 16000 X g ( P16000 ) and at 105000 X g ( P105000 ) appears to be independently regulated by phytochrome and by phytohormones. Whereas active phytochrome decreases the apparent V of HMG-CoA reductase in the P105000 without affecting the Km, it increases the apparent Km in the P16000 . Kinetin treatment also results in a higher apparent Km of the enzyme in the P16000 fraction. Gibberellic acid and indoleacetic acid did not exhibit such a clear effect.

Cell Membrane↗

PubMed2004

Determination of phytohormones of environmental impact by capillary zone electrophoresis.

A test mixture of five phytohormones [naphthaleneacetic acid (NAA), naphthoxyacetic acid (NOA), indoleacetic acid (IAA), indolebutyric acid (IBA), and indolepropionic acid (IPA)] was investigated. These compounds were cleanly separated with good resolution by capillary zone electrophoresis with a UV diode array detector using 20 mM sodium phosphate buffer (pH 7.25). The lowest detection limit was obtained for IPA (0.45 mg L(-)(1) or 0.005 mg kg(-)(1)) and the highest for NAA (1.04 mg L(-)(1) or 0.014 mg kg(-)(1)). The method has been applied for tomato samples fortified with the five phytohormones using a liquid-liquid extraction procedure, obtaining recovery percentages ranging from 91 to 109.0%.

Agriculture↗

PubMed1992

Enhancement of Naphthaleneacetic Acid-Induced Rhizogenesis in T(L)-DNA-Transformed Brassica napus without Significant Modification of Auxin Levels and Auxin Sensitivity.

Determination of the abscisic acid and indoleacetic acid (IAA) contents of floral stem segments of nontransformed and pRi A(4) T(L)-DNA-transformed rape (Brassica napus L. var oleifera, cv Brutor) using a high performance liquid chromatography-enzyme-linked immunosorbent assay procedure and mass spectrometry controls showed that IAA levels were not modified. The regeneration abilities of the in vitro cultured explants were compared on media supplemented with several plant growth regulator combinations. No regeneration occurred on hormone-free media, and shoot production was similar in both genotypes when supplemented with benzyladenine. In the presence of naphthaleneacetic acid (NAA), transformed explants were characterized by faster root regeneration and reduced shoot organogenesis. The optimum for root formation was the same in nontransformed and transformed plants, but the sensitivity threshold was slightly lower in the latter. The NAA inductive period was shorter (14 versus 22 h) with transformed tissue. Root neoformation occurred about 72 h earlier on transformed explants. Our results suggest mainly that there is an acceleration of the auxinic signal transduction and/or that the events preliminary to the formation of roots occur faster in the transformed tissues than in the normal ones.

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PubMed1996

Effect of Salt Stress on Germin Gene Expression in Barley Roots.

Germin gene expression in barley (Hordeum vulgare L.) seedlings responds to developmental and environmental cues. During seed germination, germin mRNA levels were maximal 2 d after the start of imbibition in control seedlings and declined to low levels by 6 d. When seeds were sown in the presence of 200 mM NaCl, germin mRNA levels were also maximal after 2 d, but NaCl treatment, which slowed seedling growth, prolonged germin gene expression for an additional 1 d. In 4-d-old seedlings, germin mRNA levels were highest in roots and higher in the vascular transition region than in shoots. In roots of 6-d-old seedlings, germin gene expression was regulated by salt shock and plant growth regulators. Induced germin mRNA levels were maximal 8 h after treatment with NaCl, salicylate, methyl salicylate, or methyl jasmonate and 4 h after treatment with abscisic acid and indoleacetic acid. Like germin mRNA, dehydrin mRNA levels were maximal 8 h after NaCl treatment. In contrast, peroxidase mRNA levels declined to less than control levels within 30 min of treatment. Germin gene expression is regulated developmentally by salt stress and by treatments with plant hormones. Since germin is an oxalate oxidase, these result imply that oxalate has important roles in plant development and homeostasis.

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PubMed1981

In vitro auxin binding to cellular membranes of cucumber fruits.

Specific binding of 1-naphthaleneacetic acid (NAA) to crude membrane preparations from cucumber (Cucumis sativus L.) was demonstrated. This in vitro binding had a pH optimum of 3.75 and an equilibrium dissociation constant of 10 to 20 micromolar with 1250 picomoles binding sites per gram fresh weight. The NAA-binding sites were pronase sensitive. The supernatant from the fruit partially inhibited the in vitro NAA binding to fruit membranes. NAA, 2-naphthoxyacetic acid, 3-indoleacetic acid, 2-4-dichlorophenoxyacetic acid, and 2,3,5-triiodobenzoic acid, which are reported to be very good inducers of parthenocarpy in cucumber, showed a high degree of specific binding to cucumber fruit membranes. In comparison, 2-naphthaleneacetic acid and indolepropionic acid, which are reported to be very weak auxins in corn coleoptile, pea stem, and strawberry fruit growth bioassays, did not bind efficiently to cucumber fruit membranes. In vitro binding studies with fruit membranes suggest that auxin stimulated fruit growth may be mediated by membrane-associated, auxin-binding protein(s).

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PubMed1991

Effects of exogenous auxins on expression of lipoxygenases in cultured soybean embryos.

The expression of lipoxygenases (LOXs) is known to be developmentally regulated in soybeans (Glycine max. [L.] Merr.). Hormones have been firmly established as being involved in the growth and developmental processes of a number of plant species. Correlation between the expression of LOXs and the development and germination of soybean embryos suggests that plant hormones may affect the expression of LOXs. The present studies were conducted to investigate the effects of exogenous auxins on the expression of LOX isozymes and LOX activities in cultured cotyledon tissues of immature soybean seeds. The results revealed that at least one of the more acidic nonembryo LOX isozymes was induced by either alpha-naphthaleneacetic acid or indoleacetic acid but not by 2,4-dichlorophenoxyacetic acid after 4 days' exposure. Levels of LOX-1, -2, and -3 proteins and activities were significantly decreased by 2,4-dichlorophenoxyacetic acid 10 days after explanting. S1 analysis showed that embryo LOX messenger RNAs were detectable in the tissues treated with each of the auxins. The reduced levels of the embryo LOX proteins may, therefore, be regulated at the levels of translation, posttranslational modification, or degradation. The more acidic isozymes induced by alpha-naphthaleneacetic acid showed enzymatic activity and shared the same molecular mass and isoelectric point values as the germination-associated LOX isozymes found in hypocotyls and radicles, suggesting that those LOXs are involved in germination competency of soybean embryos.

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PubMedDate not supplied

Kynurenic acid and xanthurenic acid excretion after tryptophan loading in actinic reticuloid.

The metabolism of L-tryptophan (TRP) before and after an oral loading dose of 20 mg/kg body weight was studied in three patients with actinic reticuloid (AR) and four healthy male volunteers. The preload mean plasma TRP concentrations and mean 24-hour urinary excretions of TRP in the AR group were significantly lower than in the control group. After oral TRP administration, plasma TRP concentrations increased normally in AR, thereby excluding defective intestinal absorption. The mean preload and postload excretions of kynurenic acid (KA), xanthurenic acid (XA), 5-hydroxyindoleacetic acid (5HIAA), and 3-indoleacetic acid (3IAA) were not significantly different between the two groups. We conclude that KA, which has been shown to have phototoxic properties in vitro, is not altered primarily in AR, and that the reported abnormalities of TRP metabolism are most likely the consequence of the severe photosensitivity in this disorder.

Aged↗

PubMed2006

Purification and characterization of phosphotriesterases from Pseudomonas aeruginosa F10B and Clavibacter michiganense subsp. insidiosum SBL11.

A microbial biodegradation of monocrotophos was studied in the present investigation. The monocrotophos-degrading enzyme was purified and characterized from two soil bacterial strains. The cells were disrupted and the membrane-bound fractions were studied for purification and characterization. Solubilization of the membrane-bound fractions released nearly 80% of the bound protein. Phase separation further enriched the enzyme fraction 34-41 times. The enzyme phosphotriesterase (PTE) from both the strains was purified to more than 1000-fold with 13%-16% yield. Purified PTE from Clavibacter michiganense subsp. insidiosum SBL11 is a monomeric enzyme with a molecular mass of 43.5 kDa (pI of 7.5), while PTE from Pseudomonas aeruginosa F10B is a heterodimeric enzyme with a molecular mass of 43 and 41 kDa (pI of 7.9 and 7.35). Both purified enzymes are stable enzymes with peak activity at pH 9.0. The enzyme from strain F10B was more thermostable (half-life=7.3 h) than that from SBL11 (half-life=6.4 h at 50 degrees C), while both showed the same temperature optimum of 37 degrees C. Inhibitors like dithiothreitol and EDTA inhibited the purified enzyme, while p-chloromercuribenzoic acid and indoleacetic acid had a very little effect.

Actinomycetales↗

PubMed2002

Manipulation of chloride flux affects histamine-induced contraction in rabbit basilar artery.

Cl(-) efflux induces depolarization and contraction of smooth muscle cells. This study was undertaken to explore the role of Cl(-) flux in histamine-induced contraction in the rabbit basilar artery. Male New Zealand White rabbits (n = 16) weighing 1.8-2.5 kg were euthanized by an overdose of pentobarbital sodium. The basilar arteries were removed for isometric tension recording. Histamine produced a concentration-dependent contraction that was attenuated by the H(1) receptor antagonist chlorpheniramine (10(-8) M) but not by the H(2) receptor antagonist cimetidine (3 x 10(-6) M) in normal Cl(-) Krebs-Henseleit bicarbonate solution (123 mM Cl(-)). The histamine-induced contraction was reduced by the following manipulations: 1) inhibition of Na(+)-K(+)-2Cl(-) cotransporter with bumetanide (3 x 10(-5) and 10(-4) M), 2) bicarbonate-free HEPES solution to disable Cl(-)/HCO exchanger, and 3) blockade of Cl(-) channels with the use of niflumic acid, 5-nitro-2-(3-phenylpropylamino) benzoic acid, and indoleacetic acid 94 R-(+)-methylindazone. In addition, substitution of extracellular Cl(-) (10 mM) with methanesulfonate acid (113 mM) transiently enhanced histamine-induced contraction. Manipulation of Cl(-) flux affects histamine-induced contraction in the rabbit basilar artery.

Animals↗

PubMed1973

Auxin inhibition of ripening in bartlett pears.

The effect of indoleacetic acid and 2,4-dichlorophenoxyacetic acid on the ripening of intact mature-green pears (Pyrus communis var. Bartlett) was investigated using a vacuum infiltration technique.The effects of indoleacetic acid and 2,4-dichlorophenoxyacetic acid at concentrations of 0.01, 0.1, and 1.0 mm each were studied on softening, degreening, and on ethylene and CO(2) evolution. Softening and degreening were inhibited increasingly in response to increased concentrations of indoleacetic acid. This inhibitory property was amplified by 2,4-dichlorophenoxyacetic acid at concentrations comparable to those of indoleacetic acid. Application of the auxins also prevented the climacteric rise in respiration, but stimulated ethylene synthesis. Despite the presence of elevated ethylene levels, the inhibitory auxin effect was predominant.It is proposed that endogenous auxins in fruit represent a resistance factor in ripening and must be inactivated before ripening can occur.

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