Different day and night temperature responses in Lilium hansonii in relation to growth and flower development

Temperature is one of the most important factors that directly affect the possibility and the rate of flower differentiation in many geophytes such as Lilium. In this experiment, different day and night temperatures were used to determine the required day and night temperature for flower bud development in Lilium hansonii. After low temperature exposure for breaking bulb dormancy, the bulbs were planted in pots, and placed in designated growth chambers each with a specific temperature. The plants were exposed to different temperatures for 30 days, and 15 days after planting sample plants were collected in each treatment for observation of flower bud development using the scanning electron microscope (SEM). Responses of plant height, number of leaves, and stem diameter were also measured as affected by difference between day and night temperature (DIF) and average daily temperature (ADT). The results showed that average daily temperature and high day temperature had a direct effect on the quality, quantity, and time required for flower bud development. They also affected the stem elongation, number of leaves, and stem diameter. Higher ADT and DT (25°C) promoted stem elongation and increased leaf unfolding rate (LUR), but with less number of leaves produced. As ADT and DT increased, stem diameter decreases. In lower ADT and DT (15°C) treatment, greater stem diameter and higher number of flower buds (2-7 buds) were produced. Higher ADT and DT promoted early flower bud initiation, but lower number of flower buds with higher possibilities of flower bud abortion, while lower ADT and DT showed slower flower bud initiation and development with higher flower bud formation.