Effects of Temperature on Flowering of Crinum × powellii Hort. ex Bak. cv. Album

Abstract

In this study, the growth periodicity of Crinum × powellii Hort. ex Bak. cv. Album grown outdoors was clarified and the effect of temperature on the initiation and development of flower buds was investigated.
1. The crinum bulb develops a sympodial branching system. Each unit has a membranous scale and 23 foliage leaves in a spiral arrangement from the base upwards, terminating in an inflorescence that bears 710 florets. During the growing period from spring to autumn, repeated sympodial branching results in 56 inflorescences being initiated.
2. In July after the flowering season, 56 inflorescences existed in each bulb. The first florets in the 1st, 2nd, and 3rd inflorescences were already at the stage when carpel margins fuse to form the ovary. The pollen mother cell of these florets reached the tetrad stage and the pollen grains matured and became functional between April and May of the following year. They bloomed in late May through June. Differentiation of the 4th and 5th inflorescences proceeded after the 3rd inflorescence, but they aborted at the stage when carpel margins fuse between June and July of the following year. Floral parts of the 6th inflorescence developed gradually reaching the stage of carpel fusion by June which is essentially the same as that described for the 1st inflorescence.
3. Plants did not flower when they were moved from the outdoors to a glasshouse kept above 20°C on or before 2 November. This suggests that the plants have a chilling requirement for flowering.
4. When plants with inflorescences at carpel formation stage were exposed to chilling at 15°/12°C (day/night) for 30 days or at 6°Cfor 45 days and then shifted to a glasshouse kept above 20°C, they flowered normally.
5. After the chilling requirement was fully satisfied, exposure to higher temperatures resulted in earlier flowering without a reduction in the length of scapes or number of florets.