SCANNING ELECTRON-MICROSCOPY OF HYDRATED AND DESICCATED MATURE SOMATIC EMBRYOS AND ZYGOTIC EMBRYOS OF WHITE SPRUCE (PICEA-GLAUCA [MOENCH] VOSS)

Four scanning electron microscope techniques for preparing somatic and zygotic embryos of white spruce (Picea glauca [Moench] Voss.) were co mpared. Direct sputter coating without critical point drying worked we ll for desiccated embryos while conventional methods using chemical fi xation were appropriate for hydrated somatic embryos. Low temperature scanning electron microscopy and plastic replicas provided excellent s pecimens of all embryos studied. Plastic replicas were used to documen t cotyledon formation and growth during maturation of somatic embryos. Apart from some differences in embryo size, orientation of cotyledons and surface wrinkling, the general morphology of mature somatic embry os of white spruce was very similar to zygotic embyros at a similar st age of development.