Plant Hormones in the Control of Abscission

Addicott, Fredrick T.

doi:10.1111/j.1469-185x.1970.tb01175.x

Cited by 118 publications

(36 citation statements)

References 138 publications

(90 reference statements)

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“…The existence of different sites of ETH action in distinct subcellular compartments is another possibility. Substantial evidence, indicating different concentration dependencies for ETH effects within the same tissue, has recently been discussed (15), and it has been suggested that ETH may have more than one role in abscission (3,6,10).…”

Section: Resultsmentioning

confidence: 99%

Patterns of Ethylene and Carbon Dioxide Evolution during Cotton Explant Abscission

Marynick¹

1977

Plant Physiol.

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The relationship between abscission and the evolution of ethylene and CO2 was examined in explants and explant segments of cotton seedlings (Gossypium hirsutum L. cv. Acala SJ-1) under both static and flow system conditions, and in the presence and absence of mercuric perchlorate. Explant excision was immediately followed by increased ethylene evolution (wound ethylene); senescence was also accompanied by increased ethylene evolution (senescence ethylene Cotton plants have provided the materials for extensive abscission research, and ETH2 has been implicated in the regulation of this abscission many times over (1,8,9,19,21,24,26 In a flow system specifically designed for this work, the patterns of ETH and CO2 evolution accompanying abscission in control explants were established and then compared with those patterns in explants treated with IAA and ABA. Abscission of hormone-treated and untreated explants was compared in the presence and absence of MP. Patterns of ETH and CO2 evolution were also studied in segments of cotton explants and in individual explants. MATERIALS AND METHODSGeneral Explant Techniques. All experiments were performed with excised cotyledonary nodes of 14-day-old cotton seedlings (Gossypium hirsutum L. cv. Acala SJ-1) or with further subdivisions of this explant. Subdivision of a standard explant consisted of excising the petiole stumps and dividing them each into two segments 2 to 2.5 mm in length. The proximal segments contained the abscission zones with their surrounding tissues and were called abscission zone segments. The distal segments and the axes were referred to, respectively, as petiole stump segments and axial segments. On subdivision, each standard explant yielded two abscission zone segments, two petiole stump segments, and one axial segment. The standard growth regime and cotton explant procedures were followed with minor modifications (7,12,28). Briefly, the explants were supported in an upright position by a shallow layer (5 mm) of 1.5% agar covering the base of the explant chamber, approximately 10 g of pressure was applied to the petioles in testing for abscission, and abscised petioles were not removed from the explant chambers until all gas production data had been obtained. Agar droplets were omitted on all stem and petiole stumps unless otherwise indicated.Flow System, Chromatography, and Sampling. Most experiments were conducted in a flow system. Rates of ETH and CO2 evolution were determined from chromatographic analysis of gas samples withdrawn from the explant chambers (22,23). Instantaneous rates of gas evolution were calculated using the appropriate formula (22), and total amounts produced were estimated by cutting and weighing Xerox copies of the individual rate versus time graphs.The atmosphere of the flow system was Purafil-filtered ETHfree air. The flow system was similar to that described by Claypool and Keefer (14) for respiration studies.

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Section: Resultsmentioning

confidence: 99%

Patterns of Ethylene and Carbon Dioxide Evolution during Cotton Explant Abscission

Marynick¹

1977

Plant Physiol.

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“…The data presented here support this view and further lend support to the hypothesis that auxin transport in petioles is a controlling factor in stress-induced abscission. That the level of endogenous auxin arriving at the abscission zone from the leaf blade determines the fate of the cells adjacent to the separation layer has been clearly demonstrated in numerous studies (1)(2)(3)(4). The petiole is the crucial link between this specialized area of cells and the sites of auxin synthesis in the lamina.…”

Section: Discussionmentioning

confidence: 99%

“…Since the work of Laibach (14) on debladed petioles, numerous workers have demonstrated the requirement of a constant auxin supply from the leaf blade to the abscission zone for maintenance of the cellular integrity of that zone (2)(3)(4) …”

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confidence: 99%

Auxin Transport as Related to Leaf Abscission during Water Stress in Cotton

1977

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Plant water deficits reduced the basipetni transport of auxin in cotyledonary petiole sections taken from cotton (Gossypium hirsutum L.) seedlings. A pulse-labeling technique was employed to eliminate complications of uptake or exit of "4C-indoleacetic acid from the tissue. The transport capacity or the relative amount of radioactivity in a 30-minute pulse which was basipetaUly translocated was approximately 30% per hour in petioles excised from well watered seedlings (plant water potentials of approximately -4 to -8 bars). No cotyledonary leaf abscission took place in weUl watered seedlings. Plant water potentials from -8 to -12 bars reduced the transport capacity from 30 to 15% per hour, and although the leaves were wilted, cotyledonary abscission did not increase appreciably at these levels of stress. The threshold water potential suffcient to induce leaf abscission was approximately -13 bars and abscission increased with increasing stress while the auxin transport capacity of the petioles remained relatively constant (15% per hour). The basipetal transport capacity of weU watered petioles tested under anaerobic conditions and acropetal transport tested under aUl conditions were typically less than basipetal transport under the most severe stress conditions. Cotyledonary abscission took place during and 24 hours after relief of stress with little or no abscission taking place 48 hours after relief of stress. Although the water potential returned to -4 bars within hours after rewatering the stressed plants, partial recovery of the basipetal transport capacity of the petioles was not apparent until 48 hours after rewatering, and at least 72 hours was required to return the transport capacity to near normal values. These data support the view that decreased levels of auxin reaching the abscission zone from the leaf blade influence the abscission process and further suggest that the length of time that the auxin supply is maxmally reduced is more critical than the degree of reduction.Various lines of indirect evidence suggest that foliar abscission resulting from water deficits may be at least partly mediated by a decrease in the availability of auxin reaching the abscission zone from the leaf blade. Since the work of Laibach (14) [PAR, nm] with a 15-hr photoperiod). Following emergence, the plants were watered with modified Hoagland solution (12). After 12 days from planting, those trays of seedlings destined for stress studies were transferred to a similar growth chamber programed for identical conditions but which supplied only 30% constant relative humidity. Four days in this low relative humidity chamber (without additional water) was sufficient to impose severe water stress (c -20 bars) on the seedlings. However, by removing trays for the transport experiments at the appropriate time, a range of 4, was obtained. Those plants destined to be controls remained in the high humidity growth chamber a total of 14 days from planting and were watered daily. Thus, all transport experiments were conducted on...

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“…The concentration of IAA remained low until 4 d postanthesis and then increased (Table I). Because IAA inhibits abscission (1,2), the high concentration of IAA in flower buds could be an important factor in their resistance to abscission, although not necessarily the only factor. An increase in ethylene production at anthesis (12) is another likely cause of an increase in abscission after anthesis.…”

Section: Resultsmentioning

confidence: 99%

Changes in Abscisic Acid and Indoleacetic Acid before and after Anthesis Relative to Changes in Abscission Rates of Cotton Fruiting Forms

Guinn¹,

Brummett²

1988

Plant Physiol.

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Cotton (Gossypium hirsutum L.) fruiting forms exhibit pronounced changes, with age, in their probability of abscission. Large floral buds rarely abscise, but after anthesis the young fruits (boils) have a high probability of abscising. Abscission rate reaches a peak about 5 to 6 days after anthesis and then gradually decreases. An experiment was conducted to try to determine the reason for the rapid and pronounced increase in probability of abscission just after anthesis. Cotton was grown in the field and fruiting forms of various ages from 9 days before to 9 days after anthesis were all harvested the same day and subsequently analyzed for ABA and UIA. The concentration of ABA decreased slightly at anthesis and increased gradually thereafter. In contrast, the concentration of IAA was high before anthesis and then decreased at anthesis to about onefifth the previous concentration. IAA remained low for at least 4 days after anthesis and then increased rapidly between 7 and 9 days after anthesis. The high concentration of IAA in floral buds before anthesis is probably a major factor in their resistance to abscission. Likewise, the low concentration of IAA at anthesis and for about 4 days thereafter may promote fruit abscission during the young boll stage.

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Plant Hormones in the Control of Abscission

Cited by 118 publications

References 138 publications

Patterns of Ethylene and Carbon Dioxide Evolution during Cotton Explant Abscission

Patterns of Ethylene and Carbon Dioxide Evolution during Cotton Explant Abscission

Auxin Transport as Related to Leaf Abscission during Water Stress in Cotton

Changes in Abscisic Acid and Indoleacetic Acid before and after Anthesis Relative to Changes in Abscission Rates of Cotton Fruiting Forms

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