Diversity and evolutionary trends of the ovary and ovule in Bromeliaceae

Abstract Members of the bromeliads exhibit a great morphological diversity of reproductive organs. In this study, we comparatively analyzed the ovule and ovary anatomy of 23 species, including all Bromeliaceae subfamilies; additionally, the ancestral character optimization for six traits of the ovule was performed. In species with superior ovaries, the carpel displays a homogeneous mesophyll and species with inferior ovaries have a gynoecial hypanthium, which possibly features specific characters such as trichomes in the ovary epidermis, collenchymatous thickening and aerenchyma in the ovary mesophyll. Concerning the ovule, different patterns were recorded for the integument thickness. The inner integument presents little variation in the number of cell layers among the subfamilies, whereas the outer integument shows significant variations in specific taxa. Ancestrally elongated and acuminated, the chalazal appendage displayed distinct morphologies in Catopsis and Puyoideae, while it was reduced in various genera of Bromelioideae. This study demonstrated that many structures in the ovule and ovary of different Bromeliad lineages are more stable than had previously been thought and suggests potentially useful features in the Bromeliaceae taxonomy like collenchymatous thickening and aerenchyma in the gynoecial hypanthium, number of integument cell layers, chalazal appendage type and nucellar epidermal cells. Moreover, unique features observed in ovules of specific lineages are consistent with the form and function of seed and fruit that develop subsequently and play a specific role in diaspore dispersion.