Table 1 Developmental landmarks for each stage identified during flower and fruit development

Stage 1

The floral meristem can first be distinguished (Fig. 5a)

Stage 2

The two sepal primordia initiate (Fig. 5a)

Stage 3

Initiation of the first whorl of homeotic stamens (Fig. 5b, c)

Stage 4

Formation of the next two to three staminal whorls (Fig. 5d, e)

Stage 5

Initiation of the bicarpellate gynoecium closing the floral meristem (Fig. 5f, g)

Stage 6

Overtopping of the two carpels around the single ovule (Fig. 5h, i)

Stage 7

Differentiation of the style and the stigma (Fig. 5i, k)

Stage 8

Medial–lateral plane differentiation in the carpel. Two valves are distinguished, each with a central midvein, separated by a persistent commissural ring-like tissue, also irrigated by two massive vascular traces (Fig. 5l–n)

Differentiation of the proximo-distal zones including a gynophore, an ovary and a short style with two massive vascularized stigmas (Fig. 5l–n)

Stage 9

Anthesis. Formation of up to 12 layers in the ovary wall including both the outer and inner epidermis

Stage 10

Young fruits. Expansion of the valves by both anticlinal and limited periclinal cell division reaching up to 15 layers in the fruit wall (Fig. 5o, p)

Expansion of the commissural ring outwards developing a larger central vascular bundle surrounded abaxially and adaxially by collenchyma (Fig. 5o, p)

Stage 11

Mature fruits. Radial elongation of the outer epidermis accompanied by tangential elongation of the hypodermal cell layers in the mesoderm (Fig. 5q–s)

Flattening of the two inner-most cell layers in the endoderm in the periphery of the dehiscence zone where they expand and become sclerenchymatic (Fig. 5q–s)

Formation of the dehiscence zone by 2–3 layers of smaller cells in the limits between the commissural ring and the fruit valves (Fig. 5q–s)

Stage 12

Opercular dehiscence, which occurs between the valves and the persistent ring-like tissue and the single seed remains attached to the base of the ring through the funicle, exposing a fleshy red aril that may be a bird attractant tissue for seed dispersal (Fig. 1c, d)