Towards a comprehensive integration of morphological and genetic studies of floral development.

Floral developmental genetics has exploded as a discipline. In addition to the rich genetic database for well-established models (Arabidopsis, Antirrhinum, Zea), numerous species have become the focus of floral genomic and genetic initiatives. Extensive documentation of the developmental morphology of Arabidopsis flowers has facilitated the linkage of genes and morphology. Complete developmental series also need to be assembled for emerging systems of molecular studies of floral genes. We address issues of homology assessment in floral structures, emphasize the need for assembling a complete floral developmental series for each species studied molecularly and genetically, stress the importance of a common set of terminology, and suggest a set of 'landmarks' to designate major events in floral development. We compare the floral developmental series of three species with different floral morphologies and propose a consensus of developmental stages to facilitate comparison of gene expression patterns. Taxa occupying key phylogenetic positions offer great potential for generating hypotheses about the regulation of floral development.