Sexual reproduction in flowering plants: zygote formation and types of karyogamy

摘要

A short review of modern ideas concerning zygote developmental pattern and karyogamy types in flowering plants is presented. A set of concepts describing seven main periods in the egg cell and zygote genesis by complex of characters (differentiation and totipotency degree, polarity etc.) is proposed. Some specific features of a zygote (insulation, cell wall structure, and cell cycle) and the causes determining its uniqueness are examined. Revision of the classical embryological notions on the fertilization types in a view of the latest data on double fertilization in gymnosperms allowed to single out M-type of karyogamy in flowering plants. The relationships between the types of fertilization (premitotic, postmitotic, intermediate) and karyogamy (G_1-, S-, G_2-, M-), developmental stages and periods of cell cycle of zygote are discussed.