Growing up green: cellular basis of plant development.

Plant development is a biphasic process. Pattern formation during embryogenesis generates a basic body organisation, including self-maintaining stem-cell systems called meristems at opposite ends of the main axis of polarity. During post-embryonic development, the meristems produce new organs with reference to the existing body, transforming the juvenile seedling into the species-specific adult plant. Studies in Arabidopsis indicate that patterning in plants involves not only cell surface interactions but also unique modes of communication such as movement of transcription factors between cells and directional transport of the signaling molecule auxin.