Leaf Morphogenesis in Dicotyledons: Current Issues

The last decade of the twentieth century has witnessed a period of renewed interest, redefinition of questions, and some dramatic advances toward resolving some of the long-standing issues related to the developmental regulation of leaf morphogenesis. New interest has been sparked by the application of developmental genetics, molecular biology, and mosaic analysis to the study of genetic model species. The integration of knowledge gained from these newer approaches with that derived from more than a century of comparative developmental morphology is crucial for advancing understanding of leaf morphogenesis. This link is particularly important for the interpretation of mutant phenotypes and gene expression patterns. In this brief review article, we provide a general framework for the study of leaf morphogenesis and identify areas where we believe that important issues remain unresolved.