Flower ontogeny in Capparis spinosa (Capparaceae) with special emphasis on symmetry expression

Abstract

The flower ontogeny of Capparis spinosa L. was studied using scanning electron microscopy (SEM) in order to shed light on the early expression of symmetry in a representative member of Capparaceae. Sepals start decussately with the abaxial and adaxial sepals, followed by the lateral ones. Petal appearance proceeds uni‐directionally from the abaxial to the adaxial side. Stamens develop centrifugally on an androecial ring. Five to seven carpel lobes arise on a gynoecial ring. Monosymmetry is established in early development by the uni‐directional petal appearance and is further enhanced by the acquisition of an abaxial nectary appendage and differential development of perianth organs at anthesis. The early monosymmetric pattern found in C. spinosa differs from the early monosymmetric and early disymmetric pathways of Cleomoideae. Our findings are consistent with the hypothesis that the late establishment of monosymmetry is a reflective of symmetry in early development.