Distribution of Indoleacetic Acid Oxidase and Inhibitors in Light-Grown Cotton

Morgan, Page W.

doi:10.1104/pp.39.5.741

Cited by 29 publications

(19 citation statements)

References 11 publications

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“…These findings do not agree with the results of previous research, which showed that extractable IAA oxidase activity (7) and in vivo decarboxylation (6) both increase with the age of the tissue. Age-dependent increases in IAA oxidase activity (assayed by 02 uptake) have been reported in extracts from the leaves, stems, and floral parts of cotton, as well as from the leaves of peach, rhubarb, and pea (7).…”

Section: Methodscontrasting

confidence: 99%

“…This concept was supported by several subsequent papers which showed higher rates of IAA oxidase (7), peroxidase (12), and decarboxylating (6) activities in older tissues of cotton, cherry, and tobacco, respectively. However, most of these findings were based on work done in vitro using tissue homogenates or partially purified enzymes, and caution must be used in attempting to extrapolate these results to the situation in the intact plant, where additional enzymes, cofactors, inhibitors, and nonenzymic processes may be involved.…”

mentioning

confidence: 65%

“…Age-dependent increases in IAA oxidase activity (assayed by 02 uptake) have been reported in extracts from the leaves, stems, and floral parts of cotton, as well as from the leaves of peach, rhubarb, and pea (7). This was inversely correlated with the concentration of IAA oxidase inhibitors, which was greatest in extracts made from younger tissue.…”

Section: Methodsmentioning

confidence: 93%

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In Vivo Measurement of Indole-3-acetic Acid Decarboxylation in Aging Coleus Petiole Sections

Brennan¹,

Jacobs²

1983

Plant Physiol.

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The concentration of indoleacetic acid (IAA) in plant tissues is regulated, in part, by its rate of decarboxylation. However, the commonly used in vitro assays for IAA oxidase may not accurately reflect total in vivo decarboxylation rates. A method for measuring in vivo decarboxylation was utilized in which '4CO2 is collected following uptake of IAA is usually found in highest concentration in the juvenile parts of the plant, and at lower levels in regions removed from the growing points (10) and in the older leaves (4). In some cases, the senescence process may, in fact, be regulated by the changing levels of this hormone. This is perhaps best illustrated by the process of leaf abscission in Coleus (5). Based upon current evidence, it appears that under natural conditions a depletion of IAA in the older petioles is a prerequisite for abscission to occur, although some interaction with other hormones may be involved as well (5) It was first proposed by Galston and Dalberg (3) that IAA oxidase activity increases with the age of the tissue, and thereby reduces the IAA concentration. This concept was supported by several subsequent papers which showed higher rates of IAA oxidase (7), peroxidase (12), and decarboxylating (6) activities in older tissues of cotton, cherry, and tobacco, respectively. However, most of these findings were based on work done in vitro using tissue homogenates or partially purified enzymes, and caution must be used in attempting to extrapolate these results to the situation in the intact plant, where additional enzymes, cofactors, inhibitors, and nonenzymic processes may be involved.In the experiments reported here, we have attempted to devise a method which will enable us to accurately measure total IAA decarboxylation rates in vivo. This paper describes the procedure using excised Coleus petiole sections, and presents data which indicate that in this system the IAA decarboxylating activity of the tissue decreases with age. Benth. were grown in the greenhouse under natural day lengths that were supplemented by continuous light from incandescent bulbs. All plants in a given experiment were of identical age, as measured by the time since the cuttings were started. The petioles were numbered in a basipetal direction, with the No. 2 petioles defined as the youngest ones whose leaf blades were between 60 and 100 mm long. MATERIALS AND METHODS Plants of the Princeton clone of Coleus blumeiIn the decarboxylation experiments, 10-mm segments were cut from the center of the petioles being tested. The petiole segments were weighed and the cut ends dipped in collodion (Mallinckrodt Chemical Co., St. Louis) in order to minimize cut surface effects (13). For ease of handling, the segments within each group were then strung together into a loop using a needle and thread. The segments were then rinsed with sterile distilled H20 (surface sterilization had no effect) and placed in a 25-ml Erlenmeyer flask containing 5 ml 0.05 M sodium acetate buffer (pH 5.0) and 0.2 ,Ci [1-'4C]IAA (57 mCi/mmol), t...

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Section: Methodscontrasting

confidence: 99%

mentioning

confidence: 65%

Section: Methodsmentioning

confidence: 93%

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In Vivo Measurement of Indole-3-acetic Acid Decarboxylation in Aging Coleus Petiole Sections

Brennan¹,

Jacobs²

1983

Plant Physiol.

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“…Such a gradient of inhibitors of auxin destruction has also been reported by other workers, e.g., again recently in cotton by Morgan (1,2). However, only Phipps' (3,4) observations in tobacco appear to involve inhibitory substances with relatively high molecular weights.…”

Section: Discussionmentioning

confidence: 51%

Distribution of Three Auxin Protector Substances in Seeds and Shoots of the Japanese Morning Glory (Pharbitis nil)

Yoneda

Stonier

1967

Plant Physiol.

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“…It has been suggested that the distribution of peroxidase activity and IAA oxidase content can be correlated with the processes of natural abscission (10,11,13,17 (Fig. 1).…”

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confidence: 99%

Peroxidases in Tobacco Abscission Zone Tissue

Henry

Valdovinos²,

Jensen³

1974

Plant Physiol.

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Ethylene-induced abscission in flower pedicels of Nicotiana tabacum L. cv. Little Turkish causes a progressive increase in peroxidase activity during the first 4 hours of a 5-hour time course ethylene treatment period, with decrease in peroxidase activity occurring between 4 hours and 5 hours, when the supernatant extracts of abscission zone segments are tested spectrophotometrically for peroxidase activity, using guaiacol and hydrogen peroxide. Nonethylene-treated tissue has a much lower level of peroxidase activity over the same time course period. In ethylene-treated tissue the decline in break-strength correlates with the beginning of increase in peroxidase activity (3 hours). When the abscission zone area of the pedicel is further divided into proximal, abscission zone, and distal portions, respectively, the ethylene-treated tissue has the highest peroxidase activity in the abscission zone portion, with the maximum peak occurring at 4 hours and decreasing between 4 hours and 5 hours. Acrylamide gel electrophoresis of enzyme breis from ethylene-treated aand nonethylene-treated plants reveals that no new peroxidase isozymes are formed in response to ethylene, indicating an increase in the amount of one or in both of the two already existing isozyme banding patterns. The measurement of protein in the proximal, abscission zone, and distal segments, over a 5-hour ethylene treatment period, indicates that it is being translocated in a distal to proximal direction in the abscission zone pedicel. The possible participatory role for peroxidase in ethylene-induced tobacco flower pedicel abscission are discussed.Ethylene can stimulate peroxidase activity in petiole, stem, and leaf blade tissue of cotton plants (6, 12); in the pulvinus and separation layer of bean explants (3,14); in etiolated peas (1); and in sweet potato root discs (3). It has been suggested that the distribution of peroxidase activity and IAA oxidase content can be correlated with the processes of natural abscission (10,11,13,17 (Fig. 1).Groups of 10 segments (each segment 6 mm in length) from the flower pedicels were used for the spectrophotometric assay to determine peroxidase activity. A separate group of 10 segments was collected, and the 6-mm portion of the flower pedicel was further divided into distal (2 mm), abscission zone (2 mm), and proximal (2 mm) segments. Peroxidase activity in enzyme breis prepared from tissue segments was determined where the tissue had been previously exposed to ethylene for periods up to 5 hr.After excision from the flower pedicel the tissue segments (6-and 2-mm sections) were weighed and immediately put into prechilled mortars at 4 C. The tissue samples were ground with a mortar and pestle at 4 C for 5 min in 4 ml of 0.01 M phosphate buffer, pH 6.0. The tissue homogenates were centrifuged for 10 min at 4 C at 2.000g to remove cellular debris.The supernatant fraction was used for the peroxidase assays (15).Spectrophotometric determinations were measured at a wavelength of 460 nm, using a Beckman model DU s...

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Distribution of Indoleacetic Acid Oxidase and Inhibitors in Light-Grown Cotton

Cited by 29 publications

References 11 publications

In Vivo Measurement of Indole-3-acetic Acid Decarboxylation in Aging Coleus Petiole Sections

In Vivo Measurement of Indole-3-acetic Acid Decarboxylation in Aging Coleus Petiole Sections

Distribution of Three Auxin Protector Substances in Seeds and Shoots of the Japanese Morning Glory (Pharbitis nil)

Peroxidases in Tobacco Abscission Zone Tissue

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