A central question in botany is "How do plants grow and develop?" Without a mechanistic answer, we will not be able to understand how plants interact with their environments, how they reproduce, or how they evolve. In the past decade there has been much learned from developmental genetics, starting with plants mutant in single genes, and from experiments with these plants to infer the role of individual gene products in developmental processes. Such studies have led to an outline of the mechanism of floral induction and some aspects of flower development, and of cell behavior in root and shoot apical meristems. This year we will complete the complete genomic sequence of a plant, the mustard Arabidopsis thaliana. From this sequence, we can roughly identify the complete list of genes necessary for all of the cellular and organismal processes of a plant. This list of parts gives us, for the first time, a view of the total complexity of a plant and its life processes. It also gives us, based on earlier work on single genes, a series of testable hypotheses for the mechanisms by which plant cells communicate with each other, and learn their positions in developing tissues. One conclusion is that plants have hundreds of receptor protein kinases of a type not found in animals, that appear to form a regulatory network for communication between plant cells that may act to control relative rates of cell division and differentiation. The Arabidopsis genome contains, in addition to many genes whose biochemical function can be inferred from comparison to known genes, over 10,000 genes that code for proteins that are completely unfamiliar. Thus the genomic sequence also allows us to quantitate our ignorance; the quantity is large.

Key words: Arabidopsis thaliana , development, developmental genetics, genomics, meristems