Plants offer exciting opportunities to understand major biological questions, i.e. the regulation of development and morphogenesis. How are changes of the environment, developmental cues, and other signals perceived and transduced in physiological responses? What are the elements of plant signalling pathways and what is their organization? The panoply of molecular tools and techniques as well as the blossoming field of plant genetics are providing an exciting ground for major breakthroughs in unravelling the fundamental mechanisms of plant signalling. The present book establishes a state-of-the-art framework spanning the wide spectrum of perception, signal transduction events and transport processes, including cell proliferation and cell cycle regulation, embryogenesis, and flowering. Moreover, the volume emphasizes the role of the major plant signalling substances known to date (the phytohormones and more recently studied substances) and summarizes what we know on their molecular mechanisms of action. The book emphasizes how the use of molecular technology has made plant signalling processes accessible to experimental test.