Document Type



In the past twenty years a number of morphologists and physiologists have studied the organization and behavior of shoot apices during the vegetative and flowering phases of development. Changes in size and shape as well as alterations in stratification have been reported to occur during each plastochron or interval between the production of leaf primordia (Foster 1939). A number of authors have noted differences in size and shape between vegetative and flowering apices in the same species. Although the literature contains numerous references to studies on vegetative and flowering apices, only casual observations have been made on the possible permanent changes that occur in the apex at the onset of flowering. In most of the literature the terminal meristem is considered to be unchangeable in position and to produce foliar or floral primordia in an opposite or spiral order on the flanks. Petunia hybrida Vilm. in the Solanaceae shows unique developmental changes in the shoot apex at flowering. These changes in apical configuration and method of producing floral primordia are constant and of sufficient difference in pattern of development to seem worthy of report. The present paper contains a detailed description of the size, shape and zonation of the vegetative and inflorescence apices of Petunia hybrida. The dynamics of apical behavior during the production of individual flower primordia is contrasted with apical activity during leaf primordia production. Apical criteria that indicate the onset of flowering are discussed.

Publication Date


Journal Title

Proceedings of the Iowa Academy of Science





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©1957 Iowa Academy of Science, Inc.



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