Acceleration and Retardation of Abscission by Indoleacetic Acid

Addicott, Fredrick T.; Lynch, Ruth Stocking

doi:10.1126/science.114.2974.688

Cited by 63 publications

(32 citation statements)

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“…The onset of abscission was found to be correlated with the gradient, or balance, of auxin across the abscission zone, auxin distal to the abscission zone tending to retard abscission, and auxin proximal to the zone tending to accelerate abscission. This general concept is supported by the results of a number of workers with a variety of plant materials from experiments involving extraction, diffusion, applications, and metabolism of auxin (6,14,15,19,21,(26)(27)(28). However, a few experiments have been reported in which proximal applications of auxin have retarded abscission (24), and in some cases distal applications have accelerated abscission (10,12,32 …”

mentioning

confidence: 51%

Applied Auxin Gradients and Abscission in Explants

Louie

Addicott

1970

Plant Physiol.

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The influence of applied auxin on abscission in explants (excised cotyledonary nodes) of cotton was investigated.Proximal applications to the stem stump accelerated abscission with all concentrations applied. Distal applications to the petiole stumps retarded abscission with all concentrations applied.Simultaneous applications to petiole and stem stumps accelerated, retarded, or were without effect on abscission depending on the relative amounts applied. Relatively high concentrations proximal on stem stumps accelerated abscission whereas relatively high concentrations distal on petiole stumps retarded abscission. The abscission rates from various combinations resulted in a multiphasic abscission response curve as the amounts applied were increased.Consideration of these and related data in the literature indicates that many factors can have profound effects on the nature of abscission responses to auxin.Interest in auxin as a controlling factor in abscission developed rapidly after Laibach (18) found that abscission can be retarded by the application of auxin to debladed petioles. His discovery led to a number of important agricultural practices (1,30,31) and stimulated basic researches on the influence of auxin in the control of abscission. All but the most recent literature has been described in reviews (1,5,16). A comprehensive article describing the physiological factors in abscission, including other hormones as well as auxin, has recently appeared (2).The early investigations established that auxin commonly functions to retard abscission. Further investigations disclosed other influences of auxin. The onset of abscission was found to be correlated with the gradient, or balance, of auxin across the abscission zone, auxin distal to the abscission zone tending to retard abscission, and auxin proximal to the zone tending to accelerate abscission. This general concept is supported by the results of a number of workers with a variety of plant materials from experiments involving extraction, diffusion, applications, and metabolism of auxin (6,14,15,19,21,(26)(27)(28). However, a few experiments have been reported in which proximal applications of auxin have retarded abscission (24), and in some cases distal applications have accelerated abscission (10,12,32 MATERIALS AND METHODSExcised abscission zones (explants) were used in this investigation following a method similar to that described by Addicott et al. (4). Explants were cut from the cotyledonary nodes of cotton seedlings (Gossypium hirsutum L. cultivar Acala 4-42) grown in perlite in galvanized flats in the greenhouse. Seedlings were used when their first internodes had attained a length of 2 cm (21-25 days after planting). Cotyledons were debladed 24 hr before the nodes were excised as this led to more rapid abscission, reducing the time required for an experiment. After excision each explant consisted of two 5-mm petiole stumps, a 5-mm stem stump (first internode), and a 10-mm hypocotyl stump, and thus each contained two abscission zones. The ...

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confidence: 51%

Applied Auxin Gradients and Abscission in Explants

Louie

Addicott

1970

Plant Physiol.

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“…Auxin levels declined with leaf age and senescence occurred when auxin levels between the leaf and stalk were approximately equal (Shoji et al, 1951). Application of IAA to the distal end of abscission zone explants delayed abscission, while addition to the proximal end promoted abscission (Addicott and Lynch, 1951). This suggests that changes in auxin gradients may signal the onset of or enhance senescence and may explain the observation that treating whole plants with auxin had little effect on abscission (Addicott et al, 1955).…”

Section: Auxin and Senescencementioning

confidence: 70%

AUXIN RESPONSE FACTOR1andAUXIN RESPONSE FACTOR2regulate senescence and floral organ abscission inArabidopsis thaliana

et al. 2005

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In plants, both endogenous mechanisms and environmental signals regulate developmental transitions such as seed germination, induction of flowering,leaf senescence and shedding of senescent organs. Auxin response factors(ARFs) are transcription factors that mediate responses to the plant hormone auxin. We have examined Arabidopsis lines carrying T-DNA insertions in AUXIN RESPONSE FACTOR1 (ARF1) and ARF2 genes. We found that ARF2 promotes transitions between multiple stages of Arabidopsis development. arf2 mutant plants exhibited delays in several processes related to plant aging, including initiation of flowering, rosette leaf senescence, floral organ abscission and silique ripening. ARF2 expression was induced in senescing leaves. ARF2 regulated leaf senescence and floral organ abscission independently of the ethylene and cytokinin response pathways. arf1 mutations enhanced many arf2 phenotypes, indicating that ARF1 acts in a partially redundant manner with ARF2. However, unlike arf2mutations, an arf1 mutation increased transcription of Aux/IAA genes in Arabidopsis flowers, supporting previous biochemical studies that indicated that ARF1 is a transcriptional repressor. Two other ARF genes, NPH4/ARF7 and ARF19, were also induced by senescence,and mutations in these genes enhanced arf2 phenotypes. NPH4/ARF7 and ARF19 function as transcriptional activators, suggesting that auxin may control senescence in part by activating gene expression.

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“…Since that time, numerous reports have added substantial support to the idea that auxins control abscission through an inhibitory influence (1,10,19, 25). More recently the concept of hormonal control has been extended to include auxin promotion of abscission as well (1,11).A useful tool for studying the effects of various substances on abscission has been the petiole explant test described by Addicott et al (4). This test with modification has been used subsequently by a number of workers: by Livingston (18) to study the effects of ethylene, sucrose, and auxins on abscission; by Carns (6) to study the influence of metabolic inhibitors; by Osborne (21) to seek a natural factor which promotes abscission; and by Gaur and Leopold (11) to study the quantitative effects of auxin on abscission.…”

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Factors Influencing Abscission.

Biggs¹,

Leopold²

1957

Plant Physiol.

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The hormonal concept of abscission control was spearheaded by the suggestive experiments of Laibach in 1933 (15) and then more specifically established by the experiments of La Rue (17) in which he found that indoleacetic acid, pollen extracts, or urine could delay the abscission of debladed petioles. Since that time, numerous reports have added substantial support to the idea that auxins control abscission through an inhibitory influence (1,10,19, 25). More recently the concept of hormonal control has been extended to include auxin promotion of abscission as well (1,11).A useful tool for studying the effects of various substances on abscission has been the petiole explant test described by Addicott et al (4). This test with modification has been used subsequently by a number of workers: by Livingston (18) to study the effects of ethylene, sucrose, and auxins on abscission; by Carns (6) to study the influence of metabolic inhibitors; by Osborne (21) to seek a natural factor which promotes abscission; and by Gaur and Leopold (11) to study the quantitative effects of auxin on abscission.It has been observed in this laboratory that explant tests performed under similar conditions but at different times showed a considerable degree of variation and in fact in some tests no abscission occurred at all. The following experiments were undertaken to establish a more reliable explant test and to clarify some of the factors influencing abscission. Interactions between leaf age, substrates, light and auxin are described.MATERIAL AND METHODS Seedlings of Phaseolus vulgaris L. var. Red Kidney, were grown in flats in the greenhouse on a 16-hour-day. Daylength was extended with incandescent lamps giving approximately 70 ft-c at plant level.Explants 1 cm in length were taken from the primary leaves to include 5 mm of petiole and 5 mm of pulvinus tissue. These explants were placed in 5-cm Petri dishes, basal end down, to a 4-mm depth in 1 % agar with or without addenda. There were 20 explants per treatment. Each experiment reported here was repeated in its entirety at least 3 times and the results are consistent with 35 other experiments encompassing variations on these reported ones. Napthaleneacetic acid (NAA) was incorporated into the agar as its ammonium salt. No organic solvent was used to dissolve the auxin.Light treatments given to the explants involved a 12-hr day w ith 300 ft-c light intensity supplied by

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Acceleration and Retardation of Abscission by Indoleacetic Acid

Cited by 63 publications

References 4 publications

Applied Auxin Gradients and Abscission in Explants

Applied Auxin Gradients and Abscission in Explants

AUXIN RESPONSE FACTOR1andAUXIN RESPONSE FACTOR2regulate senescence and floral organ abscission inArabidopsis thaliana

Factors Influencing Abscission.

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