Figure 4. Longitudinal sections of floral meristems and flowers during floral organogenesis.

(A–J) Sections (stained with toluidine blue) of “Malmaison” (A–D,I) and “St Anne's” (E–H, J) were observed, from the floral meristem stage (stage 1; A, E) until carpel formation (stage 4, I, J). Scale bar equals 150 µm for A to H and 1 mm for I and J. (K) Analysis of floral organogenesis in “Malmaison” (top) and “St Anne's” (bottom). Sepals, petals, stamens and carpels are labeled in yellow, green, blue and red colors, respectively. The different whorls composition is displayed as follows: whorl 1 comprises 5 sepals; whorl 2 is composed of the first 10 petals; whorl 3 is composed of stamens in “St Anne's” and petals plus stamens in “Malmaison”; whorl 4 is composed of carpels. Numbers 1 to 5 at the bottom define the flower development stages. Note that “Malmaison” has an enlarged floral receptacle starting from stage 4 (I).