• Nsangou, Mama
  The Graduate School, University of Maine
  

Somatic embryogenesis is a micropropagation method where embryonic or juvenile plant t.issue can be cultured in vitro to produce somatic embryos (embryoids). The first attempt (Tremblay 1991) to propagate red spruce via this method resulted in complete failure of somatic plantlets (emblings) to survive transfer to soil. In hybrid larch, only immature zygotic embryos exhibit embryogenic competence, while mature red spruce embryos readily form embryoids.

To understand and/or improve the embryogenic response of zygotic embryos of both species, mature zygotic and somatic embryos were explanted on an auxin and cytokinin-containing medium following pretreatment with various abscisic acid (ABA) concentrations. The embryogenic response of red spruce embryoids was increased. with increasing ABA concentration supplied during embryoid maturation. partial desiccation pretreatment following maturation enhanced this response. Mature hybrid larch embryoids displayed a 2 - fold increase in embryogenic potential following serial reinduction. In contrast, partial desiccation of embryoids significantly reduced this potential, suggesting that the loss of embryogenic competence of hybrid larch zygotic embryos may be associated with moisture loss occurring in late embryogenesis.