Abscission: Role of Abscisic Acid

Abstract

Abstract. Th2 effect of abscisic acid on cotton (Gossypium hirsutuin L. cv. Acala 4-42) and bean (Phaseolus vulgaris L. cv. Red Kidney) explants was 2-fold. It increased ethylene producticn from the explants, which was found to account for some of its ability to accelerate abscission. Absci ic acd also increased the activity of cellulase. Increased synthesis of cellulaso was not du to an increase in aging of the explants but rather was an effect of abscisic acid on the processes that lead to cellulase synthesis or activity. Earlier papers from this laboratory have described Lhe trea:mncnt of explants with e.hylene anid CO., in desiccators and gas collection bottles (4), the measurement of ethylene by gas chromatography (8), the injection of actinomycin D (1 1 g//,l water) into the separation layers of explants (6), the determination of celluilase ac.ivity by the lo s of viscosity of sodiuim carboxymethyl cellulose (CMC) (4), and break strength measurements by a recording abscissor ( 14). ResultsThe effect of abscisic acid on break strength and ethylene production from explants is summmarized in

Abscission

“…The data in Figure 1 agree with previous work from this (10) and other laboratories (15,17), that there is a fixed period of time in which IAA can be added to an explant and inhibit abscission.…”

“…Indole-3-acetic acid, the conjugates and derivatives of IAA (indoleacetyl aspartate, indoleacetamide, and ethyl indoleacetate), and 2,4-D were applied by placing a 50-Al drop of 1.5% agar containing the compound on the distal cut surface of the explant. In instances where the agar was subsequently removed, the explant was wiped with a moist tissue (10). The concentration of growth substance supplied in the agar was 50 M for IAA and its derivatives and 500 AM for 2,4-D.…”

“…These concentrations of IAA and 2,4-D were selected as being effective for inhibition of abscission (1,8,10 Ethylene Treatnent. Earlier papers from this laboratory have described the treatment of explants with ethylene in gas collection bottles and the measurement of ethylene by gas chromatography (3,6).…”

“…Indoleacetic acid has been demonstrated to effectively inhibit abscission in many plant systems if it is applied to the distal cut surface of petioles (10,14,15,17). The applied auxin has been supposed to replace the continuous auxin supply from the leaf (14,20).…”

“…2,4-Dichlorophenoxyacetic acid, which is not destroyed or conjugated by this system, did not lose its ability to inhibit abscission. It was concluded that indole-3-acetic acid destruction is one of the processes involved in the aging stage of abscission in explants.Indoleacetic acid has been demonstrated to effectively inhibit abscission in many plant systems if it is applied to the distal cut surface of petioles (10,14,15,17). The applied auxin has been supposed to replace the continuous auxin supply from the leaf (14,20).…”