Effect of Exogenous Indole-3-Acetic Acid and Indole-3-Butyric Acid on Internal Levels of the Respective Auxins and Their Conjugation with Aspartic Acid during Adventitious Root Formation in Pea Cuttings

Abstract

The influence of exogenous indole-3-acetic acid (IAA) and indole-3-butyric acid (IBA) on the internal levels of these auxins was studied during the first 4 days of adventitious root formation in cuttings of Pisum sativum L. The quantitations were done by high performance liquid chromatography with spectrofluorometric detection. IBA, identified by combined gas chromatography-mass spectrometry (GC-MS), was found to naturally occur in this plant material. The root inducing ability of exogenous IBA was superior to that of IAA. The IAA level in the tissue increased considerably on the first day after application of IAA, but rapidly decreased again, returning to a level twice the control by day 3. The predominant metabolic route was conjugation with aspartic acid, as reflected by the increase in the level of indole-3-acetylaspartic acid. The IBA treatment resulted in increases in the levels of IBA, IAA, and indole-3-acetylaspartic acid. The IAA content rapidly returned to control levels, whereas the IBA level remained high throughout the experimental period. High amounts of indole-3-butyrylaspartic acid were found in the tissue after feeding with IBA. The identity of the conjugate was confirmed by 'H-nuclear magnetic resonance and GC-MS. IBA was much more stable in solution than IAA. No IAA was detected after 48 hours, whereas 70% IBA was still recovered after this time. The relatively higher root inducing ability of IBA is ascribed to the fact that its level remained elevated longer than that of IAA, even though IBA was metabolized in the tissue. Adventitious root formation is discussed on the basis of these findings.Auxins and cytokinins appear to be the major endogenous factors regulating adventitious root formation. The cytokinins are considered inhibitory (6, 7), whereas the auxins are stimulatory (13, 21). Although IAA is probably the major auxin,

Conjugation of Indole-3-Acetic Acid (IAA) in Wild-Type and IAA-Overprodcing Transgenic Tobacco Plants, and Identification of the Main Conjugates by Frit-Fast Atom Bombardment Liquid Chromatography-Mass Spectrometry

“…The conversion of exogenous IAA to IAAsp appears to be a common process in plants. This process has been demonstrated in Pinus (Riov and Gottlieb, 1980), Dalbergia (Monterio et al, 1988), Vigna (Norcini and Heuser, 1988), Pisum (Nordstrom et al, 1991), and Lycopersicon (Catali et al, recently shown in Dalbergia (Ostin et al, 1992a), and based on cochromatography with an IAGlu standard in an HPLC system, it was tentatively identified in Cucumis both after IAA application (Purves and Hollenberg, 1982) and as an endogenous compound (Sonner and Purves, 1985). IAGluc formation after IAA addition has also been reported in Colchium (Zenk, 1961), Pinus (Riov and Gottlieb, 1980), and Lycopersicon (Catalá et al, 1992).…”

“…Identifications of IAA conjugates as endogenous substances in vegetative tissues include IAIns in Z. mays (Chisnell, 1984), indole-3-acetylalanine in Picea abies (Ostin et al, 1992b), and IAAsp in P. syluestris (Andersson and Sandberg, 1982), Glycine max (Cohen and Baldi, 1983), and Heracleum laciniatum (Cohen and Ernstsen, 1991). In addition, formation of IAA conjugates has also been demonstrated after exogenous IAA application, and IAAsp appears to be a common product in many species (Riov and Gottlieb, 1980;Monterio et al, 1988;Norcini and Heuser, 1988;Nordstrom et al, 1991). Formation of IAGluc has also been reported after exogenous IAA application (Zenk, 1961;Riov and Gottlieb, 1980;Catali et al, 1992), and recently, an enzyme catalyzing IAGluc synthesis was purified to homogeneity from maize (Komoszynski and Bandurski, 1991).…”

Adventitious rooting of conifers: influence of physical and chemical factors

“…Nordström et al (1991) attributed this preference, relative to IAA, to the higher stability of IBA. On the other hand, in many conifers the cuttings respond well to a pulse treatment with NAA.…”

Branching Out in Roots: Uncovering Form, Function, and Regulation

“…An ATP-binding cassette transporter mediating IAA efflux (ABCB19) has also been linked to adventitious root formation (Sukumar et al, 2013). Other members of the same family have been shown to transport the auxin precursor indole-3-butyric acid (Ruzicka et al, 2010;Strader and Bartel, 2011), which, among all tested auxin isoforms, has the highest competence to induce adventitious root formation (Nordström et al, 1991). Additional hormone signals regulate adventitious roots (Bellini et al, 2014; Fig.…”