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At least 343 records · Page 19Linked to original sources
PubMed1966

Differentiation between indoleacetic Acid and the citrus auxin by column chromatography.

A gradient elution column chromatography technique and a step-wise technique succeeded in differentiating between IAA and the citrus auxin. IAA was eluted ahead of the citrus auxin in both systems. The highest Avena curvature ever obtained from the citrus auxin occurred after the auxin had passed through the 2 purification techniques and a paper chromatography step. This is probably due to the elimination of inhibitors. Fluorometric assay, Ehrlich's reaction, thin-layer chromatography, and biological assay were used for the detection of IAA or citrus auxin in the column eluates.

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PubMed1966

Auxin Transport in Zea mays L. Coleoptiles I. Influence of Gravity on the Transport of Indoleacetic Acid-2-C.

(14)C-methylene labeled IAA was used to determine the influence of reorientation with respect to gravity on auxin transport in Zea mays L. coleoptile segments. It was observed that inversion of the segments leads to a decrease in the capacity to transport (14)C-IAA basipetally, as well as, in certain instances, the linear velocity of that transport. Segments were also reoriented horizontally, and the transport velocity and capacity of the upper and lower tissue halves compared with vertical halves. There was no significant change in the velocity, but the transport capacity of lower halves was higher than that of the vertical halves, which in turn was higher than the capacity of the horizontal upper halves. It is suggested that the geocurvature of horizontally placed coleoptiles may be caused primarily by the effect of reorientation on auxin transport.

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PubMed1969

Radioautographic analysis of the distribution of label from h-indoleacetic Acid supplied to isolated coleus internodes.

Isolated fifth internodes of Coleus blumei Benth. were supplied with (3)H-IAA at their apical ends. Microradioautography, using thin sections (0.25-0.5 microns) of Epon embedded tissue and liquid emulsion techniques, revealed extremely specific localization of the acetone-insoluble derivatives of IAA. Changes in the patterns of labeling were followed over periods of 3, 24, and 48 hr at various distances from the source of applied auxin. Progressively basipetal labeling of the cell walls of the youngest xylem elements was evident with time. At the end of 24 hr the label was detected also within the cytoplasm or slime of phloem elements. After 24 to 48 hr, labeling of plastids was evident. The results suggest a continued incorporation of IAA derivatives into cell wall precursors.

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PubMed1970

Effects of iron and copper ions in promotion of selective abscission and ethylene production by citrus fruit and the inactivation of indoleacetic Acid.

Application of Cu(2+) (<10(-2) M) and Fe(3+) ions as aqueous solutions of chloride salts promoted fruit abscission, erratic rind damage, and ethylene production of various citrus species with little to no defoliation. Mixing of 10(-5) M Cu(2+) or Fe(3+) ions with equimolar indole-3-acetic acid resulted in a reduction of the ultraviolet absorption at 220 nanometers, and an increase at 245 nanometers. Ultraviolet irradiation accelerated the change by Fe(3+) and Cu(2+) ions in the absorption of indole-3-acetic acid. Pretreatment of indole-3-acetic acid with Fe(3+) and Cu(2+) ions for 6 hours resulted in more than 90% reduction in its growth-promoting activity in the Avena bioassay, even when cations were removed by chromatography. Acceleration of abscission by Fe(3+) and Cu(2+) ions could be related to both promotion of ethylene production and direct inactivation of auxin.

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PubMed1971

Effects of Seselin and Coumarin on Growth, Indoleacetic Acid Oxidase, and Peroxidase, with Special Reference to Cucumber (Cucumis sativa L.) Radicles.

Seselin, a natural coumarin derivative isolated from citrus roots, inhibited radicle growth in seedlings of cucumber (Cucumis sativa), lettuce (Lactuca sativum), radish (Raphanus sativus), and wheat (Triticum aestivum) grown in the dark. Coumarin similarly inhibited radicle growth of cucumber seedlings. Growth retardation of the cucumber radicles was accompanied by an increased activity of peroxidase and indole-3-acetic acid oxidase. Both compounds antagonized indole-3-acetic acid-induced growth of wheat coleoptiles, whereas coumarin was much less effective than seselin in antagonizing gibberellic acid-induced release of reducing sugars from barley endosperm. It is suggested that seselin plays an important role in the regulation of root growth, and that it is the indole-3-acetic acid oxidase cofactor previously detected in citrus roots.

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PubMed1971

Indoleacetic Acid biosynthesis in Avena coleoptile tips and excised bean shoots.

Avena coleoptiles did not elongate when incubated with tryptophan under sterile conditions. Indole, anthranilic acid, and tryptamine promoted elongation. Under the same conditions, the tissue converted tryptophan-(14)C to IAA-(14)C. More IAA-(14)C was produced from indole-(14)C than from tryptophan-(14)C; however, the free tryptophan content of the tissue was also greatly increased by the indole treatment. Tryptophan-(14)C was readily taken up by the tissue but was mainly incorporated into protein and did not increase the free tryptophan level. When bean shoots were labeled with tryptophan-(14)C or indole-(14)C, the label incorporation into IAA-(14)C was very nearly the same. In this tissue the free tryptophan level in the tryptophan-(14)C and indole-(14)C treatments was also about equal. These results suggest that failure of exogenously supplied tryptophan to promote the elongation of Avena coleoptiles is a result of its predominant incorporation into protein and consequent unavailability for conversion to IAA.

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