Patent ID: 8216840

Claim:
A method for producing stratified cotyledonary conifer somatic embryos comprising: (a) incubating a culture comprising immature conifer somatic embryos in a culture vessel comprising a development medium comprising PEG at a concentration of from 1% to 15% and having an osmolality in the range of from 300 mM/Kg to 450 mM/Kg at a temperature of from 22° C. to 25° C. for a first incubation period sufficient in length for at least a portion of the embryos to reach anatomical maturity; and (b) subjecting the embryos in the culture vessel comprising the development medium comprisine PEG at a concentration of from 1% to 15% and having an osmolality in the range of from 300 mM/Kg to 450 mM/Kg, in accordance with step (a), to a temperature of from 0° C. to 10° C. for a second incubation period of at least one week to produce stratified cotyledonary somatic embryos.