Effect Of Indole-3-acetic Acid Research Articles

The molecular organization of bimolecular lipid membranes. The effect of KCl on the location of indoleacetic acid in the membrane

The effect of indoleacetic acid on the individual dielectric and conductance parameters of the polar-head, hydrocarbon and unstirred surface-layer regions of bimolecular lipid membranes was studied using low frequency (0.1–100 Hz) impedance dispersion measurements. It was found that the effect of 10 −6 M indoleacetic acid on these parameters was dependent on the concentration of KCl in the external solution. Thus in 1 M KCl the conductance of the hydrocarbon region increased from 2 to 26 μΩ −1/ cm 2 in the presence of indoleacetic acid while the surface layer conductance was largely unaltered. In 1 mM KCl, however, the hydrocarbon region conductance was virtually unchanged by indoleacetic acid whereas the surface layer conductance decreased from 3000 μΩ −1/ cm 2 to 1100 μΩ −1/ cm 2 . The average value of the polar-head capacitance, which was not dependent on the KCl concentration decreased by a factor of 2 in the presence of 10 −6 M indoleacetic acid. A similar reduction in the conductance of this region was also observed. The hydrocarbon capacitance was insensitive to the presence of indoleacetic acid at all KCl concentrations. It is concluded that at low KCl concentrations indoleacetic acid is located only on the surface and in the polar-head regions of the membrane while at high concentrations of KCl indoleacetic acid is absorbed into the hydrocarbon region, leaving the surface largely in its unmodified state. These results correlate with the known salt dependence of the action of the hormone in plant cells.

Effetto dell'acido ascorbico sulla espressione del sesso in fiori di Cucumis sativus L.

Abstract Ascorbic acid effect on sex expression in Cucumis sativus L. – Ascorbic acid affects the sexual gradient of flowers of Cucumis sativus L.; it induces a remarkable production of male flowers (sometimes increases the number of male flowers for each female flower, in respect of control). Indoleacetic acid, instead, induces a femaleness, particularly by reducing the number of male flowers. The maleness induced by ascorbic acid, the earlier the treatment were performed, was the more evident. In groups of plants treated contemporaneously with ascorbic acid and indoleacetic acid, ascorbic acid could prevent the female effect of indoleacetic acid, particularly increasing the number of male flowers produced (almost three times) and of male flowers for each female flower. Also in determining the sexual gradient of flowers of Cucumis sativus L. ascorbic acid shows an action opposite to that of auxin.

The Effect of Indoleacetic Acid on pH in Mesophyll Protoplast Suspensions of Vicia faba: I. Direct and Continuous Measurements

pH changes in protoplast suspensions of Vicia faba could be measured directly during auxin tratment. The change in pH occurs without a lag period, immediately after IAA treatment of the cell suspension.

Gibberellic acid and indole acetic acid compete in ethylene promoted abscission

Abscission of cotton cotyledonary explant petioles is promoted by gibberellic acid (GA) in room air and, to a lesser extent, in 1 μl ethylene liter(-1) air. GA3 consistently reduced the abscission-retarding effect of indole-acetic acid (IAA) (promoted abscission in the presence of IAA), and exogenous ethylene further promoted abscission. It is proposed that GA's promotion of ethylene-induced abscission is achieved by reducing the abscission retarding action of auxin.

Effect of Indoleacetic Acid on the Abscisic Acid Level in Stem Tissue

AbstractExcised stem sections from growing plants of Populus tremula L. and Pisum sativum L. including lateral buds were treated with indole‐3‐acetic acid in a phosphate buffer solution. In control sections the level of the abscisic acid‐like inhibitor decreased strongly during 24 h as did the level of the endogenous auxin. Exogenous indoleacetic acid counteracted the decrease in the inhibitor level to a considerable extent. Implications of this auxin effect in relation to apical dominance are discussed.

Effect of Growth Regulators and Herbicides on Photosynthetic Partial Reactions in Isolated Leaf Cells

AbstractThe effect of indoleacetic acid, gibberellic acid, 2,4‐dichloro‐phenoxyacetic acid and amitrole at various concentration levels ranging from 0.05 to 1.0 mM on the photosynthetic evolution of O2 and 14CO2 fixation by isolated leaf cells was studied. The plant growth regulators enhanced O2 evolution and 14CO2 fixation at low concentrations and were inhibitory beyond a critical level. The amitrole had an inhibitory effect at all the concentration levels used. All the substances exhibited similar patterns of effect on the ferricyanide reduction by isolated chloroplasts and on the electron transport rates of sub‐chloro‐plast particles containing PS‐I and PS‐II independently, under non‐phosphorylating conditions. As was seen from the response in all the three electron transport systems of the chloroplast studied, the electron transport chain connecting PS‐II and PS‐I could be considered as a possible site of action at least for the growth regulating substances as it is the only part that is common to all the three reactions. The phosphorylation associated with this part of the electron transport was “inhibited” by the substances even at the lowest concentration used. The stimulation of non‐phosphorylating electron flow, with a simultaneous reduction in the rate of ATP synthesis, at low concentration levels indicated that these substances played a possible uncoupling role. The amitrole on the other hand appeared to have a generalized non‐specific inhibitory action on all the partial reactions of photosynthesis.

Indoleacetic Acid Effect on the Distribution of Photosynthetically Fixed Carbon in the Bean Plant ) )

Summary Indoleacetic acid (IAA) was applied to leaves or stem tips of bean plant. One or two leaves on the plant were then allowed to fix I4CO2 and the distribution of photoassimilated 14C throughout the plant was measured after a 2–3h period of translocation. IAA applied to a primary leaf did not increase photosynthesis of the opposite leaf or increase translocation to the treated leaf. However, translocation to the stem tip was significantly enhanced. IAA applied to the decapitated stem tip greatly enhanced translocation upwards and to the roots, but not to primary leaves. IAA applied to a developing trifoliate leaf doubled the rate of photosynthesis of a nearby mature leaf and increased by six-fold the translocation of recent photosynthate to the treated leaf. Translocation to other parts of the plant was stimulated to a lesser extent. The results show that IAA from outside to a leaf affects the translocation of recent photosynthate from the leaf, both the amount exported and the direction in which it moves. The data are related to the concept of a “sink signal” affecting photosynthesis and translocation.

Effects of Indoleacetic Acid on Dictyosomes of Apical and Expanding Cells of Oat Coleoptiles

We found that the auxin-induced growth is mediated through the activation of the dictyosomes (collectively, the Golgi apparatus). Incubation of oat (Avena sativa) coleoptile segments in indoleacetic acid-sucrose-phosphate buffer changes significantly the number of dictyosomes in the expanding cells. A further indication of auxin enhancement of dictyosome activity is a decrease in dictyosomal cisternae (flattened membranous sacs) number. This decrease occurred after 6 minutes of incubation in auxin, and then was followed by a reduction in the organelle number per se. These times are in keeping with the rapid action of auxin-induced cell elongaton, and the latent period of geotropism. In the apical cells, the effect of indoleacetic acid is more subtle and complex. The periods of increased dictyosome utilization and of increased dictyosome synthesis in auxin-treated segments alter with those of the control. These observations indicate that dictyosomes not only have a function in cell elongation, but also may participate in processes such as auxin transport and stimuli perception. The expanding cells have five times as many dictyosomes as the cells in the apex. Dictyosome number within a cell appears to be directly proportional to the length of the cell. The fluctuation of dictyosome number and the effect of auxin on the rate of elongation of individual outer epidermis are discussed.

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.

IN VITRO EFFECTS OF SOME GROWTH REGULATORS ON RHIZOBIUM

The effect of indoleacetic acid (IAA), gibberellic acid (GA), kinetin, 2, 4, 5- trichlorophenoxyacetic acid (2, 4, 5-T) (1-10ppm) and morphactin (25- 250ppm) on growth of rhizobia was studied in vitro. IAA and Morphactin were inhibitory at all concentrations tried, whereas 2, 4, 5-T and kinetin showed inhibition only at higher concentrations. Gibberellic acid stimulated the growth of Rhizobium up to 8ppm level.

Effect of indole acetic acid and gibberellic acid on histone composition in the nucleoprotein of dark grown pea epicotyls

Summary Histones from gibberellic acid and indole acetic acid treated etiolated pea epicotyls have been compared with histones from untreated epicotyls by Polyacrylamide gel electrophoresis. The histone components were found to be altered in relative quantity of individual fractions by both gibberellic acid and indole acetic acid treatment. Gibberellic acid specially increased the relative quantity of the 3 fastest moving fractions, indole acetic acid specially increased the quantity of the 2 fastest moving fractions, by comparison with the samples of untreated epicotyls.

Studies on Roots. V. Effects of Indoleacetic Acid on the Standard Root Growth Pattern of Phleum pratense

The effects of indoleacetic acid (IAA) on the elongation of Phleum pratense roots have been analyzed using photomicrographic records of the epidermal cells taken during growth. Concentrations applied to the root ranged from 10-5 to 10-11 M; the duration of the experimental period was about 5 hr. Effects can be separated into two categories Cells in their accelerating phase of growth and located close to the meristem (Phase I of Burstrom) were immediately inhibited by the higher concentrations (10-5-10-7 M) but after 1 hr began to recover their relative elemental growth rate, the extent of the recovery depending upon the strength of the application At lower concentrations (e g, 10-9 M) there may be a stimulation of the relative elemental growth rate Cells in their decelerating phase of growth and located in the basal portion of the elongating zone (Phase II of Burstrom) were irreversibly inhibited at all concentrations employed.

Indoleacetic acid inhibition of a phenylalanine ammonia-lyase preparation from suspension cultures of WR-132 tobacco

The effect of indoleacetic acid, 2,4-dichlorophenoxyacetic acid, tryptophan, scopoletin, scopolin, and related compounds on the activity of a phenylalanine ammonia-lyase preparation from tobacco tissue WR-132 grown in suspension culture has been investigated. Under the experimental conditions used, IAA and its probable plant precursor trytophan, were found to inhibit the enzyme strongly. Scopoletin showed slightly lesser inhibition. The synthetic auxin, 2,4-D, produced little effect on the enzyme except at the higher concentration used. Scopolin, kinetin, gibberellic acid, and β-indole-3-propionic acid showed no effect. The concentration of β-mercaptoethanol used in each assay was found to affect the values obtained for the percentage inhibition of phenylalanine ammonia-lyase by IAA. The possible physiological significance of these inhibitions is discussed.

Effect of indoleacetic acid on the growth of Rhizobium in culture.

After inoculation ofRhizobium lupini strain A98 andR. leguminosarum strain PRE into a medium containing IAA, growth was initially suppressed. However, when IAA was added in the course of the logarithmic phase, growth was not inhibited. Apparently, IAA affects primarily the lag phase cells.

Effect of Indoleacetic Acid and Hydroxyproline on Isoenzymes of Peroxidase in Wheat Coleoptiles

Indoleacetic acid at 0.017 millimolar inhibited the formation of three peroxidase isoenzymes in both soluble and wall-bound enzyme fractions of wheat coleoptile (Triticum vulgare) tissue. Hydroxyproline at 1 millimolar prevented the indoleacetic acid-induced inhibition. Indoleacetic acid oxidase activity in the soluble fraction was decreased by indoleacetic acid and was restored by hydroxyproline. Most of the indoleacetic acid oxidase activity was located in the electrophoretic zones occupied by two of the peroxidase isoenzymes influenced by indoleacetic acid and hydroxyproline. At least part of the effect of hydroxyproline on auxin-induced elongation of coleoptile tissue may be through control of auxin levels by indoleacetic acid oxidase.

The hormonal regulation of bud outgrowth in Phaseolus vulgaris L.

Aqueous solutions of indole acetic acid, kinetin, gibberellic acid and abscisic acid were applied singly and in combination to the decapitated stem stump of Phaseolus seedlings. Application of indole acetic acid will not completely replace the intact stem apex with regard to the inhibition of lateral bud extension. The greatest inhibition of bud growth is obtained when indole acetic acid is applied in combination with both kinetin and abscisic acid. Treatment with gibberellic acid causes massive bud growth even in the presence of indole acetic acid, kinetin and abscisic acid. Although both abscisic acid and kinetin have only a slight promoting effect on bud outgrowth when applied singly, these hormones will modify the effects of indole acetic acid and gibberellic acid.

Effects of Indoleacetic Acid on Lignification In Wheat Internodes and In Vitro

The formation of lignin was determined in wheat internodes incubated with ferulic acid, hydrogen peroxide, and various concentrations of indoleacetic acid (IAA). lAA was found to markedly inhibit lignification in the lower two-thirds of the internode. Experiments which were carried out in vitro utilized the polymerization of free radicals, formed after eugenol had been oxidized by peroxidase and hydrogen peroxide, as a model system for lignification. The polymerization was inhibited considerably by IAA. A mechanism is postulated to explain the effects of lAA.

The Initiation of Vascular Cambium and Production of Secondary Xylem in Flower Bud Pedicels of Asclepias curassavica L. in Culture

Flower buds of Asclepias curassavica were cultured to determine the effects of indole3-acetic acid (IAA) and kinetin (6-furfurylaminopurine) on the secondary growth of the pedicels. Initiation and activity of the cambium were achieved on media containing both of these substances as well as on media containing 1 mg/l auxin and 10 mg/l autoclaved deoxyribonucleic acid (DNA). The highest cambial activity and secondary xylem production occurred in pedicels grown on the latter medium. This study suggests that the presence of IAA and kinetin together in the medium enhances the mobility of both, and that there is an interaction between auxin and kinetin in initiating vascular cambium and influencing its subsequent activity. Such an interaction may also take place in the pedicels of fruit of Asclepias curassavica undergoing secondary growth.

Effects of indoleacetic acid on intracellular distribution of β-glucanase activities in the pea epicotyl

β-1,4-Glucanase (cellulase) and β-1,3-glucanase activities were estimated in various subfractions of the growing region of decapitated Pisum sativum epicotyls. Treatment of the epicotyl apex with the hormone indoleacetic acid (IAA) caused total and specific cellulase activity to increase, first and most markedly, in a microsomal fraction containing membrane-bound ribosomes and eventually in fractions containing soluble enzyme and wall material. The responses did not occur in the presence of actinomycin D or during growth after treatment with other hormones. In the absence of IAA, cellulase activity disappeared within a few days from microsomal and wall fractions. It is concluded that cellulase is synthesized via an IAA-dependent mechanism and is inactivated extracellularly. In the same system, β-1,3-glucanase activity increased greatly with time but microsomes failed to show preferential enrichment at any stage of development and IAA treatment failed to affect the increase unilaterally.

Effect of Kinetin on the Phosphatase Enzymes of Acetabularia

THE effect of auxins on higher plants has been extensively studied1–3 but their action on algae is not clear. Thimann and Beth4 concluded that while various auxins promoted some aspects of algal growth, there was a wide variation in the effect and the specificity of action was uncertain. They also measured the effect of indole acetic acid and naphthalene acetic acid on the growth of nucleate and enucleate Acetabularia mediterranea. They found that these auxins increased the growth rate but did not affect cap formation in mature cells. Similar effects occurred to a smaller extent in enucleate cells.