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ШАГ ВВЕРХ, ДВА ШАГА ВНИЗ: ПОРЯДОК ЗАЛОЖЕНИЯ ОРГАНОВ ЦВЕТКА
In the majority of angiosperms, the floral organs are initiated acropetally – the first organs to be initiated are the perianth members and the last organs are the carpels. The relatively rare examples of non-acropetal patterns of organ initiation can be found in oligomerous as well as in polymerous flowers. Taxa sharing the same non-acropetal developmental patterns are not necessarily closely related to each other and thus similarities in their floral structure and development should be regarded as convergences. And 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, the floral developmental patterns are rather homoplastic. Non-acropetal patterns (and reversals to the acropetal condition) appeared many times in angiosperm evolution. Such labile and apparently saltational transitions are probably due to special features of floral meristems and modular organisation of angiosperm flowers.