ASPECTS OF SOMATIC EMBRYOGENESIS IN LARCH

Success on somatic embryogenesis has been reported for conifer species since few years. We have initiated and established embryogenic callis from Larix decidua. Two embryogenic calli lines were obtained on a medium supplemented with 2,4-D (10 mg.l-1), BA and kinetine (5 mg.l-1). These two lines were coming from characteristic calli with both small-dense and elongated vacuoled cells. They could be maintened during several months by subculture on the same medium without PGRs. Proembryos appeared at the surface of the callus at the end of a bundle of elongated cells which looks like a suspensor structure. Globular at first, embryos elongate progressively and hypocotyl and cotyledons turn green. Continuous light increases the number of embryos, like gelrite (4 g.l-1) instead of agar (6 g.l-1). In the same way, adding of 100 to 200 g.l-1 of PEG to the liquid medium increases the number of embryos starting their maturation. By this way, the embryos were able to complete their development process and to start their germination.