Does Auxin Inhibit the Abscission of Coleus Leaves by Acting as a Growth Hormone

Jacobs, W. P.; Kaushik, M. P.; Rochmis, P. G.

doi:10.2307/2439897

Cited by 12 publications

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“…Debladed petioles to which auxin had been applied did not abscise and showed no decline in PE on the distal side (locus 22, fig 1) (18)] than younger ones (7). Also, applications of 1 % IAA in lanolin result in higher than normal auxin levels in the older petioles as evidenced by their greater elongation (8) and the increased phloem regeneration in stem tisstues subjacent to them (10) even thouigh this treatment results in petiole longevity equivalent to that of intact, expanded leaves of all ages (8,22). Therefore, the higher PE activities observed in IAA-treated plants resulted from levels of auxin higher than usual in the older parts of these plants.…”

Section: Resultsmentioning

confidence: 99%

Pectin Esterase in Relation to Leaf Abscission in Coleus and Phaseolus

LaMotte¹,

Gochnauer²,

LaMotte³

et al. 1969

Plant Physiol.

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Section: Resultsmentioning

confidence: 99%

Pectin Esterase in Relation to Leaf Abscission in Coleus and Phaseolus

LaMotte¹,

Gochnauer²,

LaMotte³

et al. 1969

Plant Physiol.

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“…The broader questioni of the relationi between grow,th and longevity has been recently reviewx ed (13), and close parallels were shown between petiolar elongation and longevity, in both intact Coleuis plants and debladed but I AA-treated petioles ( 16,18). The results in general supportedl the hypothesis that IAA increased longevity through its growth effects.…”

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Effect of Gibberellic Acid on Elongation and Longevity of Coleus Petioles

Jacobs

Kirk

1966

Plant Physiol.

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The effects of gibberellic acid on the longevity and elongation of variously aged, debladed petioles of Coleus blumei were studied, with particular reference to the hypotheses 1) that auxin increases longevity by increasing growth, and 2) that gibberellic acid acts by increasing the endogenous levels of auxin.Gibberellic acid, substituted for the leaf blades, significantly decreased longevity of younger petioles, as measured by days or hours to abscission. Gibberellic acid also decreased the longevity resulting from 0.1% indoleacetic acid. This is the opposite of the effect expected if it is increasing auxin levels in the petiole.In its effect on elongation of younger petioles, however, gibberellic acid did act in the direction expected if it were increasing effective levels of auxin in the petiole. The elongation rate from 0.1% gibberellic acid plus 0.1% indoleacetic acid in lanolin was as large or larger than that for 1.0% indoleacetic acid.Petioles which were 10 or more weeks old (i.e., at positions 5+ below the apical bud were not affected by 0.1% gibberellic acid in either longevity or rate of elongation, with or without 0.1% indoleacetic acid. Since 1.0% indoleacetic acid increases both longevity and elongation rate of these petioles over 0.1% indoleacetic acid, gibberellic acid is clearly not acting on older petioles as if it were increasing effective auxin levels).

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“…In view of the role of nucleic acid and protein metabolism in aulxini iutilization ( The reqlluirements for establishing synergistic interactions have been eluicidated by Lockhart (10) aind are ftulfilled in these experiments. Repressioln of abscission of explanlts of the puilvinuiis zonie of primary bean-leaf petioles is (lepeii(lnent ulpoll auxinl and growth (5). Puilvinuis explanits (2) were incubated in agar containiing 10 MM IAA at 200; uinder these conditions, 50 % of the explanits absciss in 72 hoturs (9).…”

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Modification of abscission by UV-induced alteration in RNA and protein metabolism.

Klein¹,

Edsall²

1967

Plant Physiol.

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Low irra(liances of 254 nm UV photoreversibly interfere with the capacity of plant cells properly to tutilize auixin for cell division, enlargement and (lifferentiationi (3,8,17). This UV-induced auixinrecalcitrance does not seem to be caused by activation of aulxin oxidase or by alteration of auxin metal)olism, penetration, or translocation. The reqlluirements for establishing synergistic interactions have been eluicidated by Lockhart (10) aind are ftulfilled in these experiments. Repressioln of abscission of explanlts of the puilvinuiis zonie of primary bean-leaf petioles is (lepeii(lnent ulpoll auxinl and growth (5). Puilvinuis explanits (2) were incubated in agar containiing 10 MM IAA at 200; uinder these conditions, 50 % of the explanits absciss in 72 hoturs (9). Irradiation of explanits at zero time with 5 mJ/cm2 UV had no effect on abscission with this concentration of auxin, althouigh higher irradiances increased the percentage abscission (8).Concentration-response experiments with selectedI anitimetabolites and antibiotics presente(d at zero time were conducted to select a concentration which had little or no effect on abscission; higher concentrationis invariably increased abscission. The abscissioni-inicreasing effect of at least 1 antimetabolite from each group was reversible by the appropriate metabolite. All experiments were repeated 3 times with abouit 25 explants per variable: resuilts are presented as the averaged percent abscission.There was no interaction between UV andl any tested anti-thymine (table I) (7), and mytomycini C, which interferes with DNA-dependent RNA and ribosome synthesis (4, 15), all interacted synergistically with UV in increasin-g abscissioni, but chloramphenicol w-as inactive (11).The failure of alnti-thymines to interact withl UV in abscission, anid the synergistic initeractions nioted with anti-uracils, RNA antibiotics, an(ld attimetabolites of proteill syniithesis all ind(licate that UV serves to modify the RNA and(I proteini metabolism niecessary for aulxin actioni in the maintenalnce of the initegrity of the abscission zonie (12). It is possilble that the lack of interaction betweeni antithymines and UV may be duie to a proportional increase in resistance of DNA to UV as inicreasing numbers of thymine sites are occupied by anitithymines, btut the lack of UV-anti-thymine synergism arguies against this possibility.Since UV radiation can cauise dimer fornation in uiracil and uiridine (14) and can directly inlactivate RNA (13, 16) oulr results give presumtnptive evidence (bIlt nlot proof) that UV-induiced aulxinl recalcitrance is caused by a modification i.i that RNA (and hence protein) synthesis involved in atlxin utilization. This conclusion serves as a basis for more (letailed stuldies of the phenomelnon. Acknowledgments

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Does Auxin Inhibit the Abscission of Coleus Leaves by Acting as a Growth Hormone

Cited by 12 publications

References 0 publications

Pectin Esterase in Relation to Leaf Abscission in Coleus and Phaseolus

Pectin Esterase in Relation to Leaf Abscission in Coleus and Phaseolus

Effect of Gibberellic Acid on Elongation and Longevity of Coleus Petioles

Modification of abscission by UV-induced alteration in RNA and protein metabolism.

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