Experimental system used for analysis. A, B) Embryogenic masses of Pinus radiata after 7 (P7) and 14 (P14) days of proliferation. Embryogenic tissue (in red) was stained with 1% acetocarmine. Bar: 2 mm. C) Early-maturation embryo at polarization stage (M1). Bar: 0.5 mm. D) Late-maturation embryo at tissue differentiation stage (M3). Bar: 0.8 mm. E) Hypocotyls from 21-day-old seedlings treated with 10 μM indole-3-butyric acid (IBA) after 28 days of culture. F, G) Hypocotyls (F) and epicotyls (G) from 90-day-old seedlings treated with 10 μM IBA.