Maturation,germination, and conversion of norway spruce (Picea abies L.) somatic embryos to plants

Summary Quantitative data are presented on the efficiency of three stages of plant regeneration from somatic embryos of Norway spruce (Picea abies L.): 1) Maturation, the development of immature embryos to the cotyledonary stage; 2) Germination, primary root growth; and 3) Conversion, plantlet survival and continued growth in nonaxenic conditions. Maturation frequency was calculated relative to the number of immature somatic embryos induced to develop on the basal medium of von Arnold and Eriksson (1981). The average number of immature somatic embryos was 700 per gram of embryogenic callus, on medium supplemented with ABA and IBA (1 μM each). Maturation was the least efficient stage of regeneration; an average of 3% of the embryos induced to develop reached the cotyledonary stage. Mean germination frequencies were improved on treatments which avoided immersion of the radicle in medium solidified with agar. Whereas, 27% of the somatic embryos germinated when radicles were immersed in agar medium, 45% germinated when placed on the surface of the medium, and 56% germinated when cotyledons were immersed in agar medium and the culture vessel inverted. Twenty-nine percent of the somatic embryos germinatedin vitro were converted to plants. Under greenhouse conditions these plants set dormant buds, subsequently survived overwintering (to −5°C), and renewed vegetative growth synchronously with seedlings grown under the same conditions. Our results verified long-term (2 year) growth and development potential of conifer somatic embryo plants.