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Prothallus of the tree fern Dicksonia antarctica (note new moss plants for scale) Spore-bearing plants, like all plants, go through a life-cycle of alternation of generations. The fully grown sporophyte, what is commonly referred to as the fern, produces genetically unique spores in the sori by meiosis.
Pteridophyte life cycle. Just as with bryophytes and spermatophytes (seed plants), the life cycle of pteridophytes involves alternation of generations. This means that a diploid generation (the sporophyte, which produces spores) is followed by a haploid generation (the gametophyte or prothallus, which produces gametes). Pteridophytes differ ...
The gametophyte produces gametes (often both sperm and eggs on the same prothallus) by mitosis. A mobile, flagellate sperm fertilizes an egg that remains attached to the prothallus. The fertilized egg is now a diploid zygote and grows by mitosis into a diploid sporophyte (the typical fern plant).
In most ferns, for example, in the leptosporangiate fern Dryopteris, the gametophyte is a photosynthetic free living autotrophic organism called a prothallus that produces gametes and maintains the sporophyte during its early multicellular development.
Female willow trees (megasporophytes) produce flowers with only carpels (modified leaves that bear the megasporangia). Megaspores germinate producing megagametophytes; at maturity one or more archegonia are produced. Eggs develop within the archegonia. The carpels of a willow produce ovules, megasporangia enclosed in integuments.
Its prothallus contains glandular trichomes. It usually has 32 spores per sporangium, but many with only 16 have been observed, produced from eight 2n mother cells. [8] It is diploid and has 60 chromosomes in its root tip cells. [9]
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Lycopods reproduce asexually by spores. The plants have an underground sexual phase that produces gametes, and this alternates in the lifecycle with the spore-producing plant. The prothallium developed from the spore is a subterranean mass of tissue of considerable size, and bears both the male and female organs (antheridia and archegonia). [6]