Morphological development of normal and phyllody expressing Rosa hybrida cv. Motrea flowers

Anatomical and morphological development of a homeotic malformation known as phyllody has been investigated in rose flowers (Rosa hybrida cv. Motrea). The anatomical examination revealed that the phyllody of rose flowers is ensured from pistil transformation into leaf-like organs (phylloids). The study showed that the formation of leaf-like organs in place of the pistils results from the cessation of normal pistil development expressed by absence of marginal cell fusion of the style-tube primordia. The unfolded style-tube develops transformed to a green leaf-like organ containing chlorophyll and stomata. On the other hand, the ovary-sack although containing stomata as well as remained chlorophyll, only partially malformed. Transverse section SEM showed that the anatomical structure of the leaf-like organs was similar to that of cauline leaves rather than to sepals. Following the results of the present study demonstrating the evolutionary association of floral organs with leaves a hypothesis describing phyllody formation as an evolutionary regression is proposed.