Video: Seed Production in Gymnosperm

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The adult sporophyte (e.g. pine tree) develops male and female cones on separate branches. Female cone develops two ovules on the upper surface of each cone scale; each ovule contains haploid megaspore. Male cones produce microspore by meiosis. The microspores develop into pollen grains. Each winged pollen grain is a four-cell male gametophyte. The female gametophyte grows producing two or more archegonia, each of which contains an egg. During pollination, a wind-born pollen grain falls near the opening in one of the ovule of the female cone. Each male gametophyte form a pollen tube that penetrate the tissue of the female gametophyte. When the pollen tube has grown into an archegonium, a sperm cell from the male gametophyte fertilizes the egg. The zygote develops into an embryo and a mature seed is produced. The female cone opens releasing the seeds. When condition is favorable the seed germinates to a new young sporophyte - a pine tree seedling.
Views: 3,453
Added: 11 years ago.
Topic: Botany


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