Cytokinin-Induced Ethylene Biosynthesis in Nonsenescing Cotton Leaves

Suttle, Jeffrey C.

doi:10.1104/pp.82.4.930

Cited by 43 publications

(37 citation statements)

References 16 publications

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“…However, ACC was increased by the compounds with nearly the same order of activity as ethylene (Table I). This supports previous results of a cytokinin-induced, ACC-dependent ethylene formation (17). With the exception of Kn, which was comparatively more effective in increasing ethylene than in defoliating, a close correlation between both cytokinin-stimulated activities was observed (r = 0.88, P < 0.01; calculated from data presented in Fig.…”

Section: Ethylene Formation and Acc And Macc Levels In Leaf Discssupporting

confidence: 79%

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Induction of Leaf Abscission in Cotton Is a Common Effect of Urea- and Adenine-Type Cytokinins

Großmann¹

1991

Plant Physiol.

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Cytokinins of the urea and adenine type induced leaf abscission in young cotton (Gossypium hirsutum) plants in the following order of activity: N-phenyl-N'-1,2,3-thiadiazol-5-ylurea (thidiazuron) >> N-phenyl-N'-(2-chloro-4-pyridyl)urea > isopentenyladenine > 6-benzyladenine > zeatin = dihydrozeatin > kinetin. It is suggested that ethylene production is implicated in this response because it was stimulated by the compounds in cotton leaf discs with nearly the same effectiveness. Moreover, similar to thidiazuron (JC Suttle [1985] Plant Physiol 78: 272-276), isopentenyladenine-induced defoliation was inhibited by aminoethoxyvinylglycine, and the effect was restored by 1-aminocyclopropane-1-carboxylic acid.The phytohormonal cytokinins are N6-substituted adenine compounds that have been implicated in the regulation of many physiological processes including cell division and expansion, seed germination, flowering, and senescence (e.g. ref. 7). In addition to these natural cytokinins, synthetic compounds of different chemical classes demonstrated cytokinin-like activities (5, 9). Among them the N6-substituted adenine derivatives, e.g. Kn' and BA, and the heterocyclic ureas, e.g. TDZ and 4 PU-30, are the most effective substances known (9,10,19). In particular, TDZ and its derivatives displayed qualitatively similar biological properties to purine cytokinins in a range of bioassays including cytokinin-dependent ethylene production systems (19,23). The question is still open as to whether the biosynthesis and/or metabolism of cytokinins are influenced or a common site of action with endogenous cytokinins exists (1 1).As an additional physiological effect, TDZ induced abscission of young, nonsenescing, and mature cotton leaves (2). In this function, the compound is used in agriculture as a cotton defoliant to facilitate mechanical and manual harvesting (13). Results indicated that the effect was mediated by an increase in endogenous ethylene (16). This phytohormone is currently regarded as an important regulator of leaf abscission (6,13,15). However, TDZ-induced defoliation seems to be restricted to plants of the Malvaceae (1 1).Abbreviations: Kn, 6-furfurylaminopurine (kinetin); ACC, l-aminocyclopropane-l-carboxylic acid; MACC, N-malonyl-l-aminocyclopropane-l-carboxylic acid; AVG, aminoethoxyvinylglycine; DZ, DL-dihydrozeatin; IP, N6-(A2-isopentenyl)adenine; 4 PU-30, Nphenyl-N'-(2-chloro-4-pyridyl)urea; TDZ, N-phenyl-N'-1,2,3-thiadiazole-5-ylurea (thidiazuron); Z, zeatin. 234In contrast, purine-type cytokinins usually delay leaf senescence and abscission (e.g. Ref. 21). However, in exceptional cases such as in explants of Phaseolus (14) and leaves of Streptocarpus (20), promotion of the abscission process probably caused by stimulated ethylene (1) has been observed also.In cotton, ethylene production was increased by thidiazuron as well as by natural and synthetic cytokinins of adenine type (17). However, little information has been given in the literature on the potency of adenine-type cytokinins in defoliatin...

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Section: Ethylene Formation and Acc And Macc Levels In Leaf Discssupporting

confidence: 79%

“…In cotton, ethylene production was increased by thidiazuron as well as by natural and synthetic cytokinins of adenine type (17). However, little information has been given in the literature on the potency of adenine-type cytokinins in defoliating cotton.…”

mentioning

confidence: 99%

Induction of Leaf Abscission in Cotton Is a Common Effect of Urea- and Adenine-Type Cytokinins

Großmann¹

1991

Plant Physiol.

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“…Previous studies have shown that treatment of intact cotton seedlings with TDZ results in an increase in ethylene production within 8 h while leaf abscission commences within 72 h (16,17). These responses were most apparent in the younger, recently expanded leaves.…”

Section: Resultsmentioning

confidence: 84%

“…Cotton (Gossypium hirsutum L. cv LG 102) seedlings were grown in a growth chamber as described previously (17). In Auxin Transport Assay.…”

Section: Methodsmentioning

confidence: 99%

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Disruption of the Polar Auxin Transport System in Cotton Seedlings following Treatment with the Defoliant Thidiazuron

Suttle¹

1988

Plant Physiol.

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The effect of the defoliant thidiazuron (TDZ) on basipetal auxin transport in petiole segments isolated from cotton (Gossypium hirsutum L. cv LG102) seedlings was examined using the donor/receiver agar block technique. Treatment of intact seedlings with TDZ at concentrations of 1 micromolar or greater resulted in a dose-dependent inhibition of 14C-IAA transport in petiole segments isolated 1 or 2 days after treatment. Using 100 micromolar TDZ, the inhibition was detectable 19 hours after treatment and was complete by 27 hours. Both leaves and petiole segments exhibited a marked increase in ethylene production following treatment with TDZ at concentrations of 0.1 micromolar or greater. The involvement of ethylene in this TDZ response was evaluated by examining the effects of two inhibitors of ethylene action: silver thiosulfate, 2,5-norbornadiene. One day after treatment, both inhibitors effectively antagonized the TDZ-induced inhibition of auxin transport. Two days after TDZ treatment both inhibitors were ineffective. The decrease in IAA transport in TDZ treated tissues was associated with increased metabolism of IAA. The transport of '4C-2,4-dichlorophenoxyacetic acid was also inhibited by TDZ treatment. This inhibition was not accompanied by increased metabolism. Incorporation of TDZ into the receiver blocks had no effect on auxin transport. The ability of the phytotropin N-1-naphthylphthalamic acid to stimulate IAA uptake from a bathing medium was reduced in TDZ-treated tissues. This reduction is thought to reflect a decline in the auxin efflux system following TDZ treatment.The timing and extent of leaf abscission is largely determined by the physiological interplay between the leafand the subtending abscission zone. To a large extent, this interplay involves alterations in the levels and activities of endogenous growth substances (1, 6, 9).The manipulation of leaf and other organ abscission continues to be an important aspect of modern agricultural and horticultural practice. Although many chemical treatments have been devised to alter abscission to suit individual needs, all suffer from inherent problems, chief of which is inconsistent performance. It can reasonably be expected that future improvements in the deliberate manipulation of abscission will depend on increased fundamental knowledge of the physiology of the abscission process itself.To this end, a series of investigations has been initiated in this laboratory with the goal of developing a more thorough understanding of the physiology of leaf abscission through the systematic study of the action of a registered defoliant. TDZ' 2 is a recently introduced cotton defoliant. It is unique among defoliants in that it stimulates the premature shedding of seemingly healthy, turgid leaves (so-called 'green-drop'). It has been shown that TDZ treatment of cotton results in a massive and sustained increase in ethylene production and that ethylene is, at least partially, responsible for the subsequent leaf fall (16, 17).It is generally thought (1, 9) t...

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Regulatory Mechanisms Underlying Activation of Organ Abscission

Jiang

Gao

2021

Annual Plant Reviews Online

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Abscission is a tightly regulated developmental process that initiates in response to endogenous and environmental cues. In an agricultural context, regulation of abscission has substantial effects on crop productivity and quality. Crop domestication often selected against abscission of the fruit, allowing easier harvesting. A better understanding of the mechanisms underlying abscission will, therefore, inform efforts to improve crop breeding and harvesting practices. In this article, we summarize our current knowledge of the various regulatory mechanisms involved in abscission. We first review the regulation of abscission zone cells as they acquire competence in response to abscission signals. We then summarize the regulation of abscission initiation, exploring the phytohormone signals, developmental factors, and environmental cues regulating the initiation of abscission.

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Cytokinin-Induced Ethylene Biosynthesis in Nonsenescing Cotton Leaves

Cited by 43 publications

References 16 publications

Induction of Leaf Abscission in Cotton Is a Common Effect of Urea- and Adenine-Type Cytokinins

Induction of Leaf Abscission in Cotton Is a Common Effect of Urea- and Adenine-Type Cytokinins

Disruption of the Polar Auxin Transport System in Cotton Seedlings following Treatment with the Defoliant Thidiazuron

Regulatory Mechanisms Underlying Activation of Organ Abscission

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