Dormancy in white spruce (Picea glauca [Moench.] Voss.) seeds is imposed by tissues surrounding the embryo

The germination of intact, moist-chilled white spruce (Picea glauca [Moench.] Voss.) seeds and liquid-nitrogendecoated (LN₂), unchilled seeds is significantly more than of intact, unchilled seeds and intact, unchilled seeds exposed to LN₂. The testa is largely responsible for imposition of dormancy in these seeds, although the megagametophyte and/or nucellus also play a role. One or both of these tissues undergoes significant weakening during moist chilling. Excised embryos from dormant and nondormant white spruce seeds elongate when placed on solid Murashige and Skoog minimal organics medium supplemented with a carbon source (sucrose, glucose or galactose), but elongate very little on medium without sugar. They are not killed by rapid imbibition on unsupplemented media. Thus, embryos of white spruce do not exhibit innate dormancy, but are dependent on a carbon source for elongation, and have dormancy imposed on them by their surrounding structures.