Figure 1

Cell reactivation and somatic embryogenesis in leaf explants from two chicory genotypes. A: Sections of K59 leaf explants from in vitro plantlets at d0. B: Early reactivating cells. C: Late reactivating cells. D: The second phase of the cell reactivation (d4). E: Cell divisions (d4). Daughter-cells (1, 2, 3) derived from mitosis of a single FRC. F: Morphogenesis (d11). Somatic embryos (SE) are detected as compact, rectangular-shaped and are composed of dense-embryonary cells. G: Sections of C15 leaf explants from in vitro plantlets at d0. The first phase of cell reactivation in C15 leaf explants proceeds in as similar way to that observed in K59: increase of nuclear volume (H), relocation of plastids around the voluminous nucleus and occurrence of a partial plastid crown (I). Neither fully reactivated cells nor cell division events can be observed. J: Evolution of nuclear- and nucleolar-volumes during cell reactivation in the K59 genotype. The first phase of cell reactivation is characterised by a significant increase in both nuclear volume (white bar, × 40 volume increase) and nucleolar volume (black triangle, × 67) volume increase) as compared to those of differentiated mesophyll cells. The second phase of cell reactivation is characterised by a slight increase of nuclear volume (white bar, × 1.5) and nucleolar volume (black triangle, × 1.9) as compared to the first phase of cell reactivation. Fully reactivated-cell status is given to those dedifferentiated cells able to re-enter the cell cycle in only K59. mc: differentiated mesophyll cells; mv: minor veins; RC: reactivating cells; nu: nucleus; chlp-p: chloroplasts in parietal position; chlp-n: perinuclear crown of chloroplasts; n = 10 semi-thin sections from K59 leaf explants. Bars represent standard error. A-L: Three micrometer-semi-thin sections stained with TBO. Bar = 20 μm.