Effect of Gibberellic Acid on Elongation and Longevity of <i>Coleus</i> Petioles

Jacobs, William P.; Kirk, Susan C.

doi:10.1104/pp.41.3.487

Cited by 18 publications

(9 citation statements)

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“…GibbereUins and kinetin.-Although early investigations of the effect of GA on excised abscission zones were negative [Coleus (14), corollas of Papaver (49,50»). studies since then have firmly established the existence of a promo tive action (11,17,23,35,44,58). Carns et al (17), using explants prepared from the excised cotyledonary nodes of cotton, found that both distal and proximal applications of GA accelerated abscission when applied the day following blade excision.…”

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“…From their results, they concluded that GA accelerated stage I of the "two-stage" response; the first substance found to do so. Jacobs & Kirk (44) have studied the effects of GA and its interaction with IAA on abscission of de-bladed (two-sided) Coleus plants. GA promoted abscission in the presence or absence of inhibiting amounts of IAA when applied to petiole stumps.…”

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Abscission and its Control

Carns¹

1966

Annu. Rev. Plant. Physiol.

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The need to control abscission in order to increase the quality and yields of agriculturally useful plants has been recognized for centuries. Hand thin ning of fruits to minimize alternate bearing characteristics in some tree crops, and to improve the size and quality of fruits in others, has only within the past 20 years been replaced by the use of chemicals. The reduction in labor costs has been tremendous. Crane (27) has recently reviewed the current information on the chemical control of fruiting, and the reader is referred to this citation for further information on the subject. In the area of field crops there are numerous cases where the removal of leaves would greatly facilitate harvesting. Unfortunately, at the present stage of our knowledge, economi cally successful chemical methods have been evolved in only a few cases. In the most successful application, defoliation of cotton in preparation for mechanical harvesting, the chemicals and methods in use are often somewhat less effective than desired. In spite of this, over 7,000,000 acres of cotton are defoliated annually in the United States alone. Recognition of the need to apply chemical defoliation practices to other crops, to control patterns of fruit-set, and to improve quality and yields offer pressing needs for the con tinued intensive effort to understand the physiological and biochemical factors involved in the control of the abscission process.Four recent reviews (2, 3, 42, 83) have presented a comprehensive survey of the literature on abscission. This article wi!! be limited, insofar as possible, to recent reports and how they seem to have altered or changed our past concepts. The use of the term auxin will be restricted to endogenous growth promoting substances active in the Avena or similar bioassays. The abscission zone will be considered as the histologically distinct region at the base of an abscising organ and the term separation layer, the transverse layer of cells where separation is effected.Auxin and abscission.-Auxin has been recognized as playing a significant role in abscission since 1933 (48). In recent reviews, Addicott (3), Jacobs (42), and Rubinstein & Leopold (83) have each assigned to auxin a specific and differing regulator� role in the abscission process. The observed effects of auxin-like substances on abscission of explants (excised abscission zones) and the correlative effects demonstrated by mutilation experiments with whole plants form the major basis for the separate concepts.Addicott and co-workers based their interpretation of the role of auxin in control of abscission chiefly on the observations that 3-indoleacetic acid (IAA) applied to petiole stumps (distal) of explants retarded abscission and 1 The survey of literature perta ining to this review was completed in August 1965. 295 Annu. Rev. Plant. Physiol. 1966.17:295-314. Downloaded from www.annualreviews.org Access provided by University of California -San Francisco UCSF on 11/27/14. For personal use only. Quick links to online content Further ANNUAL REVIEWS

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Abscission and its Control

Carns¹

1966

Annu. Rev. Plant. Physiol.

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“…This slower rate was also typical of the effect observed when GA overcame the abscission retarding effect of IAA. The phenylurethane, Barban, blocked the GA acceleration of abscission, but it did not affect the rate of abscission of control or IAA treated midribs.Auxins and gibberellins have been shown to be involved in the control of leaf abscission of many plants (2,6,10,11,13,18), including citrus (14) 1D). Preliminary experiments showed no correlation between ithe position of the debladed midrib on the seed-ling and the order in which (they abscised.…”

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Interactions of Indoleacetic Acid and Gibberellic Acid in Leaf Abscission Control

Lewis

Bakhshi

1968

Plant Physiol.

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Abstract. Debladed midribs of citrus leaves showed the typical delay of abscission in response to indoleacetic acid (IAA), and the typical acceleration of abscission in response to gibberellic acid (GA). Interaction experiments with these 2 hormones indicated that the balance of the 2 hormones may be more important in regulating abscission than the quantity of either. The often reported acceleration of abscission with low quantities of IAA did not seem to exist in citrus. IAA did accelerate abscission in this tissue when its application was delayed for at least 24 hours after deblading, which suggests the 2-stage effect is also present in citrus.When abscission was first delayed with IAA and then allowed to continue, the rate of abscission proceeded at a slower rate than was typical for this tissue. This slower rate was also typical of the effect observed when GA overcame the abscission retarding effect of IAA. The phenylurethane, Barban, blocked the GA acceleration of abscission, but it did not affect the rate of abscission of control or IAA treated midribs.Auxins and gibberellins have been shown to be involved in the control of leaf abscission of many plants (2,6,10,11,13,18), including citrus (14) 1D). Preliminary experiments showed no correlation between ithe position of the debladed midrib on the seed-ling and the order in which (they abscised. The compounds to be tested were applied at the distal end of the midrib in a manner similar to that of the leaf explants. Treated seedlings were retained in the growth chamber in the dark at 250. In experiments where hormonal treatments were to be applied at different time intervals after leaf removal, the length of ithe miidrib was increased to 6 mm, of which 2 mm were removed just prior to 'application o'f compounds to facilitate uniform uptake through a freshly-cuit surface.

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“…Our plan was to add GA3 at a low, physiological concentration to young Coleus petioles, as a tissue whose strongly polar auxin transport properties we had thoroughly investigated already (23,27), and whose younger petioles we knew responded to physiological levels of GA3 (10). We selected barley endosperm as the bioassay for GA3 because of its requisite sensitivity and the histological simplicity of the reacting tissue.…”

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