Figure 2.

Different stages during P. polyphylla germination and plantlet regeneration from zygotic embryos (top panel) and somatic embryos (bottom panel). Plantlets and seedlings refer to the plants derived from tissue culture and seeds, respectively. (A) Dehisced capsule and seeds of P. polyphylla. (B) Seeds wholly covered with red, fresh, and juicy sarcotesta. (C) Umbilici borne at the seed base. (D) The undifferentiated embryo within the endosperm occupies a small area of the seed. (E) The embryo grows gradually and the radicle first protrudes from the micropyle. The asterisk signifies that some of the dwarf accessions would germinate within three months of planting, but most would not germinate until eight months later. (F) The cotyledon breaks away from the seed coat and spreads out to form the first heart-shaped leaf. (G) Single-leaf seedlings become sterile plants, which bear a whorl of leaves (three to five) at the stem apex. (H) Translucent yellow embryogenic callus. (I) Initiation of a large number of somatic embryos from the embryogenic callus. (J) The apex of the globular embryos is further differentiated. (K) Cotyledonary embryos are formed. (L) The cotyledonary embryo and radicle become elongated to generate a complete plantlet with well-developed roots and shoots. (M) The base of the hypocotyl connecting the root of the plant to the stem segment is enlarged and oval. (N) Axillary buds are formed in the rhizome, and the scales (leaf sheaths) on the surface of the rhizome are raised in the shape of a spire. (O) The plant enters dormancy and the somatic embryo-derived complete plantlet is ready for acclimatization. (P) Sterile plants derived from somatic embryos. Ste, seed testa; umbilici, um; em, embryo; en, endosperm; co, cotyledon; ra, radicle; sc, embryogenic callus; rh, rhizome; sc, scales; ab, axillary buds; le, leaf; st, stem; m, month.