INFLUENCE OF NITROGEN-BALANCE OF CULTURE-MEDIUM ON NORWAY SPRUCE [PICEA-ABIES(L) KARST] SOMATIC POLYEMBRYOGENESIS - HIGH-FREQUENCY ESTABLISHMENT OF EMBRYONAL-SUSPENSOR MASS LINES FROM MATURE ZYGOTIC EMBRYOS

Proliferating embryonal-suspensor masses (ESMs) were initiated from ma ture open-pollinated seeds of a northern Norway spruce (Picea abies (L .) Karst) family possessed a relatively low level of embryogenic activ ity. Different nitrogen content modifications of the half-strength von Arnold and Eriksson (1/2 LP) basal medium were tested for both the in duction of ESM formation and the establishment of ESM lines. Both orga nic and inorganic nitrogen strongly affected the ESM line establishmen t. Amide nitrogen (asparagine or glutamine) was an obligatory prerequi site for the ESM line establishment and prolonged maintenance. The opt imal ammonium/nitrate molar ratio in the presence of 3.0 mM glutamine was about 0.2. The highest frequency ESM line establishment (33 %) was obtained with 7.5 mM ammonium, 33.8 mM nitrate and 3.0 mM glutamine. Somatic embryo maturation was determined by the combined effects of th e nitrogen balances of maintenance and maturation media. After a two-s tep maturation procedure, mature somatic embryos were successfully ger minated and transferred ex vitrum.