Floral bud dormancy is responsible for the different flowering times of six Pleione species

Abstract

Flowering time is central to plant reproductive success and is significantly influenced by the time of floral bud differentiation and development. Pleione species flower in either spring or autumn; however, the mechanisms underlying floral bud differentiation and development are yet to be fully elucidated. In the present study, we investigated the floral bud development of three spring-flowering species and three autumn-flowering species using continuous anatomical observations. The renewed shoots grew on the side of the old pseudobulb after the fade of a previous flower, after which a new pseudobulb with 1–3 buds slowly formed at the base of the renewed shoot. For both spring-flowering and autumn-flowering species, the transition from vegetative to reproductive growth occurred in June, and flower differentiation was completed in August. The autumn-flowering species bloomed immediately after the completion of flower bud development, while the spring-flowering species went through six months of dormancy; thus, the time requirement from floral bud initiation to flowering was longer in the spring-flowering species than in the autumn-flowering species (∼ 270 days vs. ∼ 90 days, respectively). The dormancy time of the spring-flowering species, rather than the initiation or duration of floral bud development, was the reason for their differing flowering times. Shift of flowering from autumn to spring probably related to the evolution of Pleione from subtropical areas to higher elevations. These findings will be helpful in breeding new varieties and for the regulation of flowering time in horticultural production, and will enhance our understanding of the evolution of flowering time for closely related species.

Keywords

• Dormancy
• Floral bud differentiation
• Floral bud initiation
• Flowering time
• Regulation of flowering
• Orchid