Somatic embryogenesis in conifers
This thesis reports a series of experiments carried out to investigate the process of somatic embryogenesis in conifers, with emphasis on the spruces Picea abies (L.) Karst and P.sitchensis (Bong.) Carr. as experimental material. Successful regeneration of Sitka spruce plants from somatic embryos is reported. Experiments covered a number of aspects of the processes of embryo initiation, maturation and germination. Experiments on embryo initiation and proliferation covered the influence of plant growth regulators, temperature, interval between transfers to fresh medium, medium formulation and suspension culture. Preliminary experiments were also made on Pinus sylvestris and Larix leptolepis. Maturation experiments looked at the use of abscisic acid and other growth regulators and the effect of light. Germination experiments concentrated on the dilution and sucrose level of the medium, and preliminary attempts to remove plantlets from in vitro conditions to the greenhouse. To explore further the influences governing the initiation of somatic embryogenesis, an experiment was carried out using mature somatic embryos as the explant for initiation of embryogenic material, in comparison with excised zygotic embryos. In the discussion sections, an attempt was made to place somatic embryogenesis into context within the use of biotechnology as a technique for the improvement of forest tree species.