Fig. 1.

Development of the monosymmetric corolla in I. amara. Different stages of Iberis flower development are shown. (A–C) Developmental stages before anthesis were monitored under the SEM; sepals were removed to reveal inner organs. (A) After simultaneous initiation, adaxial (aD) and abaxial (aB) petal (p) primordia are of equal size. Central stamen primordia arise slightly before the lateral stamen primorida, developing between the adaxial and abaxial petals. The gynoecium appears as a central dome. (B) At the onset of stamen differentiation, when filament and anther become distinguishable, adaxial and abaxial petals start to differ in size, with the abaxial petals being slightly larger. (C) Petal size difference slowly increases until anthesis of the flower. A lateral stamen is removed in B and C. (D) After flower opening, the petal size difference strongly increases from the young stage A1 to the fully mature stage A2 (E). (F) The young inflorescence of Iberis shows a corymboid architecture that gives it the appearance of one single, large flower. (Scale bars: A–C, 50 μm; D and E, 5 mm.)