Ricerc@Sapienza

Adventitious roots (ARs) are post-embryonic roots formed in planta by tissues of the primary root in secondary vascular structure and by tissues of the aerial organs. Indole-3-acetic acid (IAA), and its natural precursor indole-3-butyric acid (IBA), control AR formation in planta and in vitro, however IBA roles have to be elucidated. Arabidopsis thin cell layers (TCL) consist of stem inflorescence tissue external to the vascular system and 10 microM IBA applied with 0.1microM Kinetin induce AR formation from stem TCL.

The role of indole-3-acetic acid (IAA) and indole-3-butyric acid (IBA) and of the auxin-interacting phytohormone ethylene on xylogenesis is still little known, even if a xylogenic promotion by auxins has been reported. In particular, auxin/ethylene-target tissue(s), modality of the de novo xylary process, and the kind of ectopic elements formed (metaxylem vs. protoxylem) are currently unknown. It is instead widely known that auxins positively affect adventitious root (AR) formation, e.g. in the model plant Arabidopsis thaliana and in in vitro cultured systems of numerous species.

Auxins induce adventitious roots (ARs) in numerous culture-systems, and indole-3-butyric acid (IBA) is frequently the best AR-inducer. Vitamin requirements vary according to species, explant, and culture-conditions. Arabidopsis thaliana thin cell layers (AtTCLs) are uncapable of AR-formation on hormone-free medium containing thiamine and myo-inositol, whereas ARs are induced when IBA (10 μM), with/without kinetin (Kin, 0.1 μM), is added. The research frst aim was to determine whether a synergism between IBA and myo-inositol and thiamine was necessary for AR-formation.