Levels of endogenous indole-3-acetic acid and indole-3-acetyl-aspartic acid during adventitious rooting in avocado microcuttings

Quantification of endogenous IAA and lAAsp was carried out duringadventitious root formation in avocado microcuttings. Both auxinand conjugate were monitored in control cuttings (rooted inthe absence of auxin) as well as in cuttings treated with arooting promotor (IBA) or an auxin transport inhibitor (TIBA).Additionally, a histological study to follow root differentiationwas carried out. In control cuttings IAA levels remained constantthroughout the rooting process, however, in IB A-treated cuttingsIAA levels increased 2-fold during the first 6 d. Addition of200 µM TIBA induced a slight decrease of IAA levels andinhibited root formation. As for IAAsp levels, both control and IBA-treated cuttings showeda big increase before root differentiation occurred and as theprocess went on, a progressive decrease took place. However,in TIBA-treated cuttings IAAsp levels not only did not increasebut diminished progressively during the process. The role ofauxin conjugates during the rooting process of avocado is discussed. Key words: Avocado, IAA, IAAsp, rooting