Quantitation of endogenous levels of IAA, IAAsp and IBA in micro-propagated shoots of hybrid chestnut pre-treated with IBA

Abstract

Endogenous levels of indole-3-acetic acid (IAA), indole-3-acetylaspartic acid (IAAsp) and indole-3-butyric acid (IBA) were measured during the first 8 d of in vitro rooting of rootstock from the chestnut 'M3' hybrid by high performance liquid chromatography (HPLC). Rooting was induced either by dipping the basal ends of the shoots into a 4.92-mM IBA solution for 1 min or by sub-culturing the shoots on solid rooting medium supplemented with 14.8-μM IBA for 5 d. For root development, the induced shoots were transferred to auxin-free solid medium. Auxins were measured in the apical and basal parts of the shoots by means of HPLC. Endogenous levels of IAA and IAAsp were found to be greater in IBA-treated shoots than in control shoots. In extracts of the basal parts of the shoots, the concentration of free IAA showed a significant peak 2 d after either root inductive method and a subsequent gradual decrease for the remainder of the time course. The concentration of IAAsp peaked at day 6 in extracts of the basal parts of shoots induced with 14.8-μM IBA for 5 d, whereas shoots induced by dipping showed an initial increase until day 2 and then remained stable. In extracts from basal shoot portions induced by dipping, IBA concentration showed a transient peak at day 1 and a plateau between day 2 and 4, in contrast to the profile of shoots induced on auxin-containing medium, which showed a significant reduction between 4 and 6 d after transferred to auxin-free medium. All quantified auxins remained at a relatively low level, virtually constant, in extracts from apical shoot portions, as well as in extracts from control non-rooting shoots. In conclusion, the natural auxin IAA is the signal responsible for root induction, although it is driven by exogenous IBA independently of the adding conditions.

Effects of in vitro subculture on the physiological characteristics of adventitious root formation in microshoots of Castanea mollissima cv. ‘yanshanhong’

“…We suggest that endogenous IAA is an important promotive factor of rooting and it could accumulate after subcultures. The accumulation of endogenous IAA driven by exogenous IBA is the signal responsible for root induction (Gonçalves et al 2008). However, the reverse results appeared in some researches.…”

The Use of Auxin Quantification for Understanding Clonal Tree Propagation

“…× C. crenata Siebold and Zucc. cuttings treated with IBA than in control cuttings, with the peak IAA concentration at the base of cuttings occurring on the second day after treatment, after which there is a gradual decrease [164]. Similarly, application of IBA to rootstock of 'Gisela 5' cherry increases endogenous IAA levels within the first day after application [27].…”

Differences in endo/exogenous auxin profile in cuttings of different physiological ages

“…Auxins were extracted following the methods ofŠtefančič et al (2007), Kovač et al (2003) and Goncalves et al (2008). Samples were ground into powder using a mortar and pestle with liquid nitrogen.…”

“…Excitation of the fluorescence detector was set at 292 nm and emission at 360 nm. The UV-VIS detector was adjusted to measure absorption at 280 nm (Goncalves et al, 2008). IAA, IBA and IAA-Asp were quantified by fluorimetry, comparing peak areas with those of corresponding standards.…”