The control of leaf development

Summary The formation of a leaf is a basic aspect of plant development. This review provides an overview of our present understanding of the process from initiation to the final form of the leaf. Molecular genetic and cell biology approaches have yielded significant advances in this area, adding not only to our knowledge of leaf development but also to fundamental principles in plant biology. These principles will be highlighted, as well as areas where our understanding is still incomplete, in particular the problem of coordinating the multifaceted steps involved in the generation of the leaf structure. Contents Summary 9 I. Introduction 9 II. The shoot apical meristem: the creation of a field of cells from which leaves can be formed 10 III. Patterning: the selection of leaf initiation site 10 IV. Morphogenesis: the initial stages of leaf formation 12 V. Differentiation and determination: transcriptional networks controlling determinancy 14 VI. The elaboration of leaf form 14 VII. Early steps in leaf histogenesis 15 VIII. Later steps in leaf differentiation: epidermal cell fate 16 IX. Compound and simple leaves: variation on a theme? 17 X. Changes in leaf form: developmental and environmental influences 17 XI. A model of leaf formation 17 Acknowledgements 18 References 18