The invention is a method for reproducing coniferous trees by somatic embryogenesis using plant tissue culture techniques. It comprises a multistage culturing process. A suitable explant, typically the fertilized embryo excised from a mature or immature seed, is first cultured on a medium that induces multiple early stage proembryos. Preferably these proembryos are further multiplied in a second culture having reduced growth hormones. The early stage proembryos may then be placed in or on a late stage proembryo development culture which may have a significantly higher osmotic potential than the previous stage or stages to develop very robust late stage proembryos having at least about 100 cells and multiple suspensor cells. Culturing from this point continues in an embryo development medium very low in or lacking cytokinins and auxins but containing a relatively high concentration of exogenous abscisic acid and an adsorbent material, such as activated charcoal. The combination of abscisic acid and activated charcoal appears to increase the absolute number of embryos produced for most genotypes studied. Further, the vigor and morphology of the embryos is improved. After a period of several weeks cotyledonary embryos will have formed. These have a well defined bipolar structure with cotyledonary primordia at one end and a latent radicle at the other. If desired these embryos may be stored at about 4 DEG C. for extended periods while still on the development medium.
