Anatomy and ontogeny of unisexual flowers in dioecious Woonyoungia septentrionalis (Dandy) Law (Magnoliaceae)

Abstract

Woonyoungia septentrionalis (Dandy) Law is a dioecious species with unisexual flowers in Magnoliaceae. The floral morphology and structure of the species are conspicuously different from other species and are important to the study of floral phylogeny in this family. The floral anatomy and ontogeny were investigated to evaluate the systematic position of W. septentrionalis, using scanning electron microscopy and light microscopy. All of the floral organs are initiated acropetally and spirally. The carpels are of conduplicated type without the differentiation of stigma and style. The degenerated stamens in the female flowers have the same structures as the normal stamens at the earlier developmental stages, but they do not undergo successive development and eventually degenerate. The male floral apex was observed to have the remnants of carpels in a few investigated samples. As the bisexual flower features could be traced both in the male and female flowers in W. septentrionalis, it suggests that the flower sex in Magnoliaceae tends toward unisexual. As well as the unisexual flowers, the reduced tepals and carpels and concrescence of carpels conform to the specialized tendency in Magnoliaceae, which confirms the derived position of W. septentrionalis in this family. As the initiation pattern of floral parts of W. septentrionalis is very similar to other species in this family, it needs further investigation and especially comparison with species in Kmeria to evaluate the separation of Woonyoungia.

Floral ontogeny of Knema and Horsfieldia (Myristicaceae): evidence for a complex androecial evolution

“…In the staminate flowers of Knema examined, we found that the central area of the floral apex, where a gynoecium normally develops, remains undifferentiated. However, in the species of Magnoliaceae with unisexual flowers, there is a carpel residuum in the staminate flowers, which indicates the sex change (Fu et al ., 2009). In unisexual Annonaceae (e.g.…”

From leaf and branch into a flower: Magnolia tells the story

“…Eames ( 1931 ) once stated that the primitiveness of this kind of carpel is unequivocal. Detailed studies on the gynoecia in the Magnoliaceae have demonstrated that this oversimplification cannot be corroborated (Tucker 1961 ; Eyde 1975 ; Tucker 1975 ; Ueda 1982 ; Endress et al 2000 ; Xu and Rudall 2006 ; Fu et al 2009 ; Deroin 2010 ). Furthermore, the traditional phylogenetic position of the Magnoliaceae as sister to remaining angiosperms (Cronquist Magnolialean hypothesis; Cronquist 1988 ;) is no longer tenable and has been replaced by the APG system (Qiu et al 1999 ; Hilu et al 2003 ; APG 2009 ; Chase and Reveal 2009 ; Vialette-Guiraud and Scutt 2009 ; Soltis et al 2011 ).…”

Genetic diversity and population structure of an insect‐pollinated and bird‐dispersed dioecious tree Magnolia kwangsiensis in a fragmented karst forest landscape

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