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Аннотация: The development of pollen tubes and ovules and the formtion of embryos and endosperm after different types of pollination: self-pollination, cross-pollination and wind-pollination were studied in ten clones of Pinus silvestris. Pollination and fertilization took place in all types of pollination. At a certain stage of development, however, embryos in some seeds began to degenerate. This degeneration was followed by a breaking down of the endosperm and resulted in empty seeds. The percentage of degenerated seeds was highest after self-pollination, considerably lower after wind-pollination. The results indicate that inviable zygotes, homozygous for lethal or sub-lethal genes, are formed after self-pollination and explain the high percentage of empty seeds usually found after this type of pollination. Wind-pollination may to some extent involve self-pollination. No clone was found to be quite self-sterile, but the differences in self-fertility between the clones were rather great.
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