PRODUCTION OF VIGOROUS, DESICCATION TOLERANT WHITE SPRUCE (PICEA-GLAUCA [MOENCH] VOSS) SYNTHETIC SEEDS IN A BIOREACTOR

This report describes a low-cost method for generating large numbers o f high quality mature white spruce (Picea glauca [Moench.] Voss) somat ic embryos which survived desiccation and grew to plantlets more vigor ously than excised zygotic embryos cultured in vitro. Somatic embryos from suspension culture were supported within a culture chamber on a f lat absorbent pad above the surface of a liquid culture medium contain ing 20-50 mu M abscisic acid and 7.5% polyethylene glycol. Throughout a 7 week culture period 3 L of fresh medium was pumped into one end of the chamber, while the spent medium exited by gravity from the opposi te end. Over 6,300 cotyledonary stage white spruce somatic embryos wer e recovered after this time from a single culture chamber without manu al manipulation. The somatic embryos were of excellent appearance with well developed cotyledons, and possessed high levels of storage lipid s. They survived drying to about 8% moisture content following treatme nt for 4 weeks at 63% relative humidity, and following imbibition conv erted to normal plantlets at a frequency of 92%, compared to 80% for e mbryos grown in Petri dishes. Somatic embryos cultured within the bior eactor developed to plantlets that were 20% longer than zygotic embryo s excised from mature seed and grown in vitro, and were 38% longer tha n somatic embryos cultured upon agar medium in Petri dishes.