Development in plants refers to the formation of shape and pattern in the multicellular organism. While development can be influenced by environmental factors such as light or temperature, the major factor controlling development of any plant is, of course, its genes. Genes determine the overall shape and size of the mature plant, its branching pattern and leaf type, the extent and arrangement of vascular tissue in root and shoot, and the timing of flowering and the form of flowers produced.

In plants the genetic mechanisms that control developmental events are best understood in the case of flower development. A normal (wild type) flower of most angiosperms (flowering plants) has four distinct types of organs that are arranged in four concentric rings (whorls). The outermost whorl has green, leaflike organs called sepals. The second whorl from outside consists of brightly colored organs called...