XVI International Botanical Congess

While it is clear from the fossil record that gymnosperms predate angiosperms, the gymnosperm group from which angiosperms arose is not clear. In an effort to better understand the phylogenetic relationship between angiosperms and gymnosperms, our lab studies ovule development in Arabidopsis thaliana (an angiosperm) and Ephedra viridis (a gymnosperm). We present here a detailed, morphological characterization of ovule development in the gymnosperm, Ephedra viridis. The data presented here provide a framework of well-defined developmental stages based upon morphological benchmarks. This framework will enable comprehensive comparison of angiosperm and gymnosperm ovule ontogeny. In concert with analysis of Ephedra genes identified through homology to cloned Arabidopsis genes, the scheme presented here will provide a useful tool in the analysis of gymnosperm ovule development.