Gibberellin and Inhibitor Content during Iris Bulb Development

Concentrations of gibberellin-like substances and inhibitors were determined in different organs from Iris hollandica cv. Prof. Blaauw during cold treatment and during growth in the greenhouse. Barley-aleurone, dwarf pea and Avena coleoptile straight growth bioassays were used to determine the activity. Developing bulblets contained the highest level of gibberellin activity followed by that in floral organs. During the development of the plants quantitative changes occurred both in the non-acidic, free, and bound pools of gibberellins. Two kinds of inhibitors, “acidic” and “non-acidic”, have been found in the extracts. Most of the non-acidic type were present in the roots. The acidic inhibitors were present in scales and sheath-leaves and disappeared with cold treatment.