Epsilon Open Archive

Abstract

The development of pollen tubes and ovules and the formation of embryos and endorperm after different types of pollination: self-pollination, crosspollination and wind-pollination were studied in ten clones of Pinus sylvestris. Pollinization and fertilization took place in all types of pollination. At a certain state 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-pollinization, considerably lower after wind-pollination and smallest after cross-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-pollinization may to some extent involve self-pollination. No clone was found to be quite self-sterile, but the differences in selfertility~ between the clones were rather great.