Organogenesis of Reproductive Structures inBetula alnoides(Betulaceae)

Abstract

In order to scrutinize the floral development of the unisexual Betula alnoides and to discuss the organogenesis throughout other members of Betulaceae, the inflorescences, cymules, and flowers of B. alnoides were examined using scanning electron microscopy. In staminate flowers, there is no vestige of the carpel, and a 90°change in the orientation of two stamen primordia was noted during the developmental process. Tepals are usually laminar but vary in number and morphology. Secondary bracts are laminar, similar to the tepals. Pistillate flowers lack stamen primordia; tepals are arrested in early development, and the secondary bracts are more reduced than bracts in the male flowers. Despite this contrasting morphology, the organogenesis pattern of male and female cymules and flowers is similar. Bracts and tepals keep the same arrangements in both genders. The orientation of stamens and carpels is also consistent. Phylogenetic relationships within the family are discussed. The division of Betulaceae into Coryleae and Betuleae and the sister group relationship between Betula and Alnus are reinforced in the aspect of floral ontogeny.

Comparative flower development ofJuglans regia,Cyclocarya paliurusandEngelhardia spicata: homology of floral envelopes in Juglandaceae

“…These include bisexual to unisexual flower, loss of tepals and tricarpellary to bicarpellary ovaries. The floral organogenesis data in Juglandaceae and Betulaceae revealed different degrees of reduction of staminate flower tepals and stamens among genera in the two families (Li et al ., ; Zhu & Lu, ; Lin, Zeng & Chen, ; Zhu et al ., ; this study).…”

Desenvolvimento floral e expressão sexual em espécies de Ficus L. (Moraceae)

“…Heslop- Harrison 1957, Tucker 1988, Dellaporta & Calderón-Urrea 1993, Ainsworth 2000, de acordo com seu processo de formação: por supressão, denominada tipo I e por perda do verticilo reprodutivo, denominada tipo II (Mitchell & Diggle 2005). Embora essa tipologia mascare a diversidade de mecanismos reprodutivos encontrada nas angiospermas (Mitchell & Diggle 2005), ela é bastante útil para o reconhecimento de padrões morfológicos que permitam estudos posteriores sobre expressão gênica (Caporali et al 2000, Adam et al 2007, Sather et al 2010, reconstruções filogenéticas (Tucker et al 1993, Lin et al 2010) e mecanismos fisiológicos (Chailakhan 1979, Maier et al 1997, Talamali et al 2003 envolvendo flores imperfeitas (Perl-Treves & Rajagopalan 2006).…”