Is seasonal flowering time of Paphiopedilum species caused by differences in initial time of floral bud differentiation?

Abstract

Members of the genus Paphiopedilum are world-famous for their large, colourful flowers, unique floral morphology and long floral lifespan. Most Paphiopedilum species bloom in spring or autumn. The control of flowering time is of great significance to the commercial production of floral crops, because it affects the sales and prices of flowers. However, the mechanism that regulates when Paphiopedilum species bloom is unclear. In the present study, floral bud initiation and development of P. micranthum (spring-flowering species with one flower per stalk), P. dianthum (autumn-flowering species with multiple flowers per stalk) and P. henryanum (autumn-flowering species with one flower per stalk) were investigated by morphological and anatomical methods. We divided Paphiopedilum floral bud differentiation into six phases: the initiation of differentiation, inflorescence primordium differentiation, flower primordium differentiation, sepal primordium differentiation, petal primordium differentiation and column primordium differentiation. We found that the timing of floral bud differentiation for the three species was synchronized when experiencing the same environment, while the period from initiation to flowering largely differed. In addition, initiation of floral bud differentiation in P. dianthum was earlier at a warmer environment. The difference in flowering time of three species was mainly caused by the duration of floral bud development, rather than the initiation time. The findings were of great significance for the cultivation and flowering regulation of Paphiopedilum species.

Genome Size and Labellum Epidermal Cell Size Are Evolutionarily Correlated With Floral Longevity in Paphiopedilum Species

“…Therefore, a trade-off should exist between investment and return in flowering plants. Time taken for DNA synthesis, and developmental duration in organs, is longer with larger genomes (Finch, 1990 ; Monaghan and Metcalfe, 2000 ; Feng et al, 2021 ). Within the angiosperms, the genome size of the orchids is relatively large (Leitch et al, 2009 ), and the reason for this is not clear.…”

“…micrantum and P . henryanum with shorter floral longevity (Feng et al, 2021 ). In this study, the strong positive correlation is between floral longevity and genome size in 13 Paphiopedilum species.…”

“…We speculated that genome size may be related to floral longevity through cell size effect on physiological function within floral organs. Species with larger genome and longer floral longevity might need longer developmental duration (Feng et al, 2021 ).…”

Floral Initiation, Organogenesis, and Flowering of Mature Paphiopedilum Clair de Lune ‘Edgard Van Belle’ Award of Merit/American Orchid Society Plants Derived from Divisions

“…Furthermore, flower bud differentiation in a spring-flowering species [Paphiopedilum micranthum (Parvisepalum subgen.)] and in two autumn-flowering species [i.e., Paphiopedilum dianthum (the section Pardalopetalum) and Paphiopedilum henryanum (the section Paphiopedilum)] all started in April and May (Feng et al 2021). These results indicate that the variation in flowering time among some Paphiopedilum species could be the duration of floral bud development, as opposed to floral bud differentiation timing (Feng et al 2021).…”

“…Similarly, relatively high temperatures may be disadvantageous to floral induction in Dendrobium nobile and potted Miltoniopsis (Lopez and Runkle 2006;Yen et al 2008). To the best of our knowledge, there few studies on the growth and flower development of Paphiopedilum orchids (Feng et al 2021;Pi et al 2009;Yin et al 2022).…”