Trithuria is the sole genus of Hydatellaceae, a family of the early-divergent angiosperm lineage Nymphaeales. In order to help determine the early evolution of angiosperm cell-wall structures, Costa et al. use immunocytochemical techniques to examine arabinogalactan protein (AGP) epitopes in T. submersa and find intense labelling in the anthers and in the intine wall, the latter associated with pollen tube emergence. The results agree with labellings obtained for Arabidopsis and confirms the importance of AGPs in angiosperm reproductive structures as essential structural components and probably important signalling molecules.
Early-diverging angiosperms are important for studies of the origin and early evolution of the flower. Vialette-Guiraud et al. discuss the potential of the water lily Cabomba (Nymphaeales) as a model basal angiosperm, as it combines simplicity of floral structure, numerous pleisiomorphic angiosperm characters, and practical features that make it amenable to study using a broad range of molecular biological techniques. They also provide protocols for the growth and molecular analysis of Cabomba, a Cabomba flower EST database, and a genome size measurement of C. caroliniana.
The three earliest extant lineages of flowering plants are represented by only some 16 genera. Despite low species’ diversity, these genera are highly diverse in their morphology, so inferring ancestral features in angiosperms is problematic. Using SEM, TEM and immunocytochemistry , Prychid et al. investigate the reporoductive structures of a relatively newly discovered early angiosperm, Trithuria (Hydatellaceae). The presence of a dry-type stigma in Trithuria supports the hypothesis that this condition is ancestral in angiosperms.