DIFFERENCES IN THE INITIATION OF THE ZYGOTIC AND PARTHENOGENETIC PATHWAY IN THE SALMON LINES OF WHEAT - ULTRASTRUCTURAL STUDIES

The ultrastructure of the egg apparatus of the sexual (aestivum)-Salmo n line (aS) and the isogenic but alloplasmic (kotschyi)-Salmon line (k S) of the Salmon system of wheat was studied by transmission electron microscopy 3 days before and during anthesis. Additionally, the zygoti c stage of aS, 17 h after pollination, was included. Metabolic activit y of egg cells from the sexual line aS was low 3 days before anthesis and increased dramatically after pollination and fertilization. This t iming of increased activity was evident because of changes occurring i n the egg cell nucleus and nucleolus, polysomes, endoplasmic reticulum and Golgi apparatus, and the completion of the cell wall around the z ygote. In contrast to the sexual line, the egg cell of the parthenogen etic line showed high activity 3 days before anthesis. The metabolic a nd ultrastructural characters observed in the nucleus and cytoplasm of the kS line 3 days before and during anthesis corresponded with those of the isogenic sexual line aS during anthesis and 17 h after pollina tion, respectively. High metabolic activity observed in the persistent synergid of kS may be connected with the occurrence of additional emb ryos in seeds (twins) of this line.