Endogenous levels of abscisic acid, indole-3-acetic acid, zeatin and zeatin-riboside during the course of adventitious root formation in cuttings of Craigella and Craigella lateral suppressor tomatoes

Indole acetic acid (IAA). abscisic acid (ABA), and zeatin plus zeatin riboside (Z + ZR) were determined daily in cuttings of Lycopersicon esculentum Mill. cv. Craigella (C) and the Craigella Lateral Suppressor (CLS) mutant during the first 5 days of the root-forming process. A solid-phase enzyme immunoassay using specific anti-hormone antibodies was used following a one-step HPLC purification procedure. The hormone measurements were made in cuttings divided into 4 parts. The main variations occurred in the terminal bud and in the basal part of the hypocotyl of the two tomato varieties, i.e. significant IAA and ABA increases during the first 2 days followed by a more or less fast return to the initial values at day 4 or 5. This is probably due to the ablation of the root system. Z + ZR levels dramatically decreased in the basal part of the Craigella hypocotyl 1 day after cutting. Contrary to CLS, C hypocotyls recovered the initial high levels when roots regenerated (day 5). This is probably linked to the greater ability of roots to produce cytokinins in C plants than in CLS ones. The first step of root formation (reactivation of the pericyclic cells and formation of root primordia) corresponded to a high IAA/Z + ZR ratio in the root-forming tissue, whereas the second step (elongation of young roots) was characterized by a low ratio with low levels of hormones.