From Ovule to Seed in a Gynosperm

The evolution of vascular tissue solved the terrestrial problems of supporting the plant body and obtaining water and minerals from the soil. However, the challenges of reproduction and dispersing offspring on dry land remained. In contrast to seedless plants, which produce flagellated sperm that need moisture to reach an egg, seed plants--gymnosperms and angiosperms--have pollen grains that carry their sperm producing cells through the air. In addition, the offspring of seedless plants are sent off into the world as haploid, single celled spores that must survive independently as gametophytes before producing the next sporophyte generation. Seed plants launch next generation sporophytes that are ready to grow. In seed plants, a specialized structure within the sporophyte houses all reproductive stages, including spores, eggs, sperm, zygotes, and embryos. In gymnosperms such as pines and other conifers, this structure is called a cone. Cones are modified shoots that serve a reproductive function. -Biology book page 348-349

 

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