Fig. 1.

Pods of Medicago collected for analysis and corresponding stages of embryogenesis. a–h Images of flowers and pods (with petals removed) used to isolate RNA for qRT-PCR. a Stage 0: flower bud at 2 days before anthesis. b Stage 1: flower at anthesis. c Stage 2: early pod with one complete spiral. d Stage 3: pod with three complete spirals corresponding to early embryo development. e Stage 4: pod with five complete spirals and spine initials corresponding to early globular embryos. f Stage 5: pod with six spirals and immature spines corresponding to late globular embryos. g Stage 6: pod with six spirals and elongated, maturing spines corresponding to heart-stage embryos. h Stage 7: Pod with six spirals, mature spines and increased girth corresponding to torpedo-stage embryos. i–m Zygotic embryos as visualised in ovules isolated from the middle portion of pods corresponding to stages S3–S7. i 8–16 cell-stage embryo. j Early globular-stage embryo. k Late globular-stage embryo. l Heart-stage embryo. m Torpedo-stage embryo. Bars 2 mm (a–h) and 25 μm (i–m)