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Bull-Herenu, K. & Cla13en-Bockhoff, R.: Developmental conditions for terminal flower production in apioid umbellets. - Plant Div. Evol. 128: 221 232. 2010. - ISSN 1869-6155. Quantitative ontogenetic studies in DallclIs carola inflorescences illustrate that terminal flower p ro ducing umbellets ('closed ' umbell ets) have larger apical meristems than umbellets that lack terminal flowers ('open' umbell ets) . This structural differen ce is achieved through ontogeny by a different shaping of the apical meristem: in open umbellets it remains flat until it is completely consumed by flower primordia fr actionation, while it becomes dome shaped in the closed umbellets. The convex meristem is finally transformed into a terminal flower that is la rger than its direct neighbours. Since weaker and smaller individuals use to bear open umbellets, it is assumed that the relative nourishment conditions of the plants have an effect on the apical meristems geometry, that in turn would be capable or not to merge into a terminal flower.
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Bull–Hereñu et al. (2010) studied this question.
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