One Upward, Two Steps Down: Order of Floral Organ Initiation

Abstract

In most angiosperms, floral organs are acropetally initiated, i.e., from the perianth upwards to the gynoecium. The review surveys examples of deviation from this typical pattern that takes place in both oligomerous and polymerous whorled flowers. The plants displaying the same non-acropetal pattern of floral development are not necessarily closely related and thus similarities in their floral structure and development should be regarded as convergences. Vice versa, representatives of the same family often show different patterns of initiation of floral organs. Flowers with the same groundplan can demonstrate either typical acropetal or non-acropetal developmental pattern. In other words, evolution of patterns of floral development is relatively homoplastic. Presumably, the repeated transitions from acropetal to non-acropetal developmental patterns (and back) readily occurred in evolution and were of a saltational nature.