DEVELOPMENTAL ANATOMY AND ULTRASTRUCTURE OF EARLY SOMATIC EMBRYOS IN EUROPEAN BLACK PINE (PINUS-NIGRA ARN)

Embryogenic callus cultures of European black pine (Pinus nigra Am.) w ere established on megagametophytes containing zygotic embryos in earl y developmental stage. In addition to many elongated cells and disorga nized growing clumps they contained early somatic embryos at Various s tages of development. At all stages of embryogenesis the embryos were organized as bipolar structures. Cell pairs composed of one isodiametr ic cell with dense cytoplasm and a second large vacuolated cell were t he simplest bipolar system. The vacuolated cell underwent senescence. The cytoplasm-rich cell and its derivates divided transversally, resul ting in several cytoplasmic cells arranged in row. An early embryonal cylindrical mass was formed by longitudinal division of the cells in a filament. Proximally localized cells in the early embryonal mass beca me vacuolized and elongated gradually giving rise to the secondary sus pensor. Distal cells remained cytoplasmic in character and formed an e mbryonal mass along the axis of long early somatic embryos. Difference s in the proportion of organelles and heterochromatin clumps, thicknes s of cell walls and number of plasmodesmata between cells at various s tages of early somatic embryogenesis were described.