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The general body plan of plants is established during embryogenesis, when the undifferentiated meristematic regions of root and shoot are set aside. However, much of plant development occurs postembryonically, through the reiterative production of organ primordia at the shoot apical meristem (SAM). In most species, the SAM initially gives rise to vegetative organs such as leaves, but at some point the SAM makes the transition to reproductive development and the production of flowers.

This change in the developmental fate of primordia initiated at the SAM is controlled by environmental and endogenous signals (Bernier, 1988; McDaniel et al., 1992). However, unlike many developmental transitions in animals, the SAM of plants is not irreversibly “committed” to reproductive development once flowering commences. In some species and genotypes under certain environmental conditions, leafy shoots are formed …