Carbohydrate status during somatic embryo maturation in Norway spruce

The development of Norway spruce (Picea abies (L.) Karst.) somatic embryos on a maturation medium was accompanied by changes in nonstructural carbohyd rate status. During embryo maturation, the content of total soluble sugars in the embryonal suspensor mass decreased and the partitioning between sucr ose and hexoses changed considerably in favor of sucrose. Developing somati c embryos were mainly responsible for these changes. Osmotic stress caused by the presence of 3.75% polyethylene glycol (PEG) in the maturation medium (decrease in osmotic potential by 52.5 kPa) resulted in dramatic changes i n the content of endogenous saccharides. There was a lower total carbohydra te content in the embryonal suspensor mass grown on the medium containing P EG in comparison with the untreated control. isolated embryos from later st ages of embryo development contained mainly sucrose with a small amount (20 %) of fructose and nearly no glucose. A further increase in PEG concentrati on in the medium (7.5%; decrease in osmotic potential by 112.5 kPa compared to the maturation medium) led to a large increase in the total endogenous sugar content. This increase in sugars was a result of the enhanced content of sucrose, fructose, and glucose. The increased glucose content was in co ntrast to embryos grown on the medium with lower or no PEG content.