Soluble sugar content of white spruce (Picea glauca) seeds during and after germination

In white spruce (Picea glauca [Moench.] Voss.) seeds, the raffinose family oligosaccharides (RFOs) provide carbon reserves for the early stages of ger mination prior to radicle protrusion. Some seedlots contain seeds that are dormant, failing to complete germination under optimal conditions. Since do rmancy may be imposed through a metabolic block in reserve mobilization, th e goal of this project was to identify any impediment to RFO mobilization i n dormant relative to nondormant seeds. Desiccated seeds contain primarily, and in order of abundance on a molar basis, sucrose and the first 3 member s of the RFOs, raffinose, stachyose and verbascose. Upon radicle protrusion at 25 degrees C, the contents of RFOs decreased to low amounts in all seed parts, regardless of prior dormancy status and sucrose was metabolized to glucose and fructose, which increased in seed parts. During moist chilling at 4 degrees C, RFO content initially decreased before stabilizing and then increasing. In seeds that did not complete germination, the synthesis of R FOs at 4 degrees C favored verbascose, so that at the end of 14 (nondormant ) or 35 (dormant) weeks, verbascose contents in megagametophytes exceeded t he amount initially present in the desiccated seed. This was also true in t he embryos of the dormant seedlot. In seed parts from both seedlots after m onths of moist chilling, stachyose amounts exceeded raffinose amounts. Upon radicle protrusion at 4 degrees C, RFO contents decreased to amounts most similar to those present in seeds that completed germination at 25 degrees C. Hence, the RFOs are utilized as a source of energy, regardless of the te mperature at which white spruce seeds complete germination. Based on the si milarity of sugar contents in seed parts between dormant and nondormant see ds that did not complete germination, differences in sugar metabolism are p robably not the basis of dormancy in white spruce seeds.