Flower meristems have the capacity to expand throughout their development, generating space for new structures.
Claßen-Bockhoff and Meyer demonstrated this by the example of corona formation in passionflowers. The conspicuous corona elements arise as ‘de novo’ structures with ongoing receptacle expansion. Open space obviously induces their formation as a self-regulating process. Considering spatio-temporal conditions widens our view on flower meristems, clarifies homology and allows new interpretations in combination with molecular, phylogenetic and morphogenetic data.