Figure 1.

Embryo initiation, development and seed germination in mono-embryonic and poly-embryonic citrus. (A–F) Paraffin sections of ovules and seeds from mono-embryonic Clementine mandarin illustrating sexual embryo development. (G–I) Mature mono-embryonic seed of Clementine mandarin with the seed coat removed and the single plantlet germinated from one seed. (J–O) Paraffin sections of ovules and seeds from poly-embryonic Valencia sweet orange. The emergence of the nucellar embryo initial (NEI) cells and the development of nucellar embryos are apparent. (P–R) Mature poly-embryonic seed of Valencia sweet orange with the seed coat removed and multiple plantlets germinated from one seed. The red arrows point to NEI cells. The green arrows point to nucellar poly-embryos. The green dotted lines enclose the sexual embryo sac. Scale bars 20 μm.