Iberis amara petal development. (A) SEM image of adaxial stage A1 petal. Adaxial and abaxial stage A1 (B) and stage A2 (C) petals. (D-F): In situ hybridization with IaH4 of longitudinal sections through Iberis amara flower buds before anthesis. (D) In young flowers, IaH4 is expressed throughout emerging petal buds. (E) Later, in differentiating petals, IaH4 localizes to the upper, distal petal part that forms the blade and decreases in the proximal part, developing into the claw. (F) IaH4 transcript accumulates before anthesis at petal tips in older flowers. A few cells scattered throughout the entire petal lengths still express IaH4. aD, adaxial; aB, abaxial; b, blade; c, claw; p, petal; se, sepal; lst, lateral stamen; st, stamen; g, gynoecium. Scale bars: A, D-F, 100 μm; B and C, 5 mm.