This study was performed to depict the anatomical changes in apical meristems in order to determine the flower initiation and development of Iranian lily (Lilium ledebourii). Observations carried out by scanning electron microscope (SEM) on groups of bulbs with different age and size showed that only large (≥55 g and ≥6 cm in diameter) 9-year-old and older bulbs expressed flowering transition, abandoning the juvenile condition. The switch from vegetative to reproductive in the apical meristem was characterized by flattening its dome. Flower initiation started between 10 and 20 days after planting, once the bulbs have passed a period of vernalization of two months at 3°C. The first hint of floral organ definition was noted 30 to 50 days after planting when the outer perianths started to grow followed by inner perianths in a pattern of 3−3. After complementation of flower formation by stamen and pistil appearance and development, flower abortion occurred in some bulbs 30 days after flower initiation. Flower bud abortion could not be linked to the bulb size. Identification of the exact time of flower initiation will be useful to provide proper management of Iranian lily in the process of domestication of this endemic endangered lily.

105-113