The effect of cold, anoxia and ethylene on the flowering ability of buds of Cichorium intybus

The apical bud and the axillary buds of Witloof chicory ( Cichorium intybus L. cv. Tardive d'Anvers) remain in the vegetative state if they are left on the root and maintained at 18°C. Flowering occurs in long days of 16 h after a pretreatment of either 8 weeks at 3°C, 3 days in complete anoxia at 15°C, or 4 days in the presence of ethylene (1000 ppm) at 15°C. In contrast, the adventitious buds which spread out on the root after ablation of the collar flower in a photoperiod of 16 h without particular pretreatment. The grafting of apical buds onto roots after different treatments shows that cold and ethylene act on the root, whereas anoxia acts directly at the level of the bud. It seems that the inhibition of the flowering of preformed buds (apical and axillary) stems from the collar. A hypothesis is proposed to explain this inhibition and why it is broken by cold, anoxia and ethylene.