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 [M oench.] Voss.) seeds and liquid-nitrogendecoated (LN(2)), unchilled se eds is significantly more than of intact, unchilled seeds and intact, unchilled seeds exposed to LN(2). The testa is largely responsible for imposition of dormancy in these seeds, although the megagametophyte a nd/or nucellus also play a role. One or both of these tissues undergoe s significant weakening during moist chilling. Excised embryos from do rmant 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 m edium without sugar. They are not killed by rapid imbibition on unsupp lemented media. Thus, embryos of white spruce do not exhibit innate do rmancy, but are dependent on a carbon source for elongation, and have dormancy imposed on them by their surrounding structures.