In vitro flowering of Lilium rubellum Baker

Scales excised from in vitro cultured bulblets of Lilium rubellum were cultured on MS medium supplemented with 0.044 or 4.4 μM BA in the dark for 300 days, the culture period of which was divided into three stages, with temperatures in each stage as follows: 25 °C in stage 1 (days 0–60); 25 °C or 8 °C in stage 2 (days 61–210); 20 °C in stage 3 (days 211–300). Numbers of bulblets per scale and bulblets with elongated stem (the transition from juvenile to vegetative adult phase) depended on the culture condition. The highest number of bulblets and the percentage of bulblets with elongated stems were obtained in scales cultured in medium with 4.4 μM BA at 25 °C in stage 2. On the other hand, BA concentration (0.044 and 4.4 μM) and/or temperatures (25 and 8 °C) in stage 2 influenced flowering in the bulblets with elongated stems (the transition from vegetative adult to flowering phase). Flowering occurred in bulblets with elongated stems when bulblets on scale were cultured in medium with 4.4 μM BA at 8 °C in stage 2, whereas no flowering occurred in bulblets cultured in any other culture conditions. In conclusion, the concentration of BA affects the transition from juvenile to vegetative adult phase, and the exposure of in vitro developed bulblets to low temperature is indispensable to initiate the flowering process.