PTERIDOPHYTES (FERNS)

• A group of plants that adapted to life on land
• Ferns occur in moist, shady environments
• The sporophyte generation is the dominant generation in ferns- represented by the adult fern plant
• Adult Fern Plant- sporophyte

  
• The fern has true roots, stems and leaves, therefore it is not a thallus
• In most ferns, the stem is horizontal, underground rhizome
• Adventitious roots develop from rhizome, anchor plant in the soil and absorb water and mineral salts
• The green compound leaves (fronds) with long leaf stalks develop from buds in the rhizome
• Well-developed vascular tissue (xylem and phloem) is present in Pteridophytes
• The sporophyte generation is perennial and therefor produces spores over many generations
• Perennial: A plant that lives for more than two years.
• Clusters of sporangia are found on the underside of leaves. Clusters are called sori. (singular: sorus)

  
• Spores are produced within sporangium which is covered by an indusium. Indusium is modified leaf tissue that covers the sporangium to protect it until maturity.
• Spores are released from the sporangia and dispersed by the wind
• When a spore germinates it gives rise to a green, heart-shaped prothallus- represents gametophyte generation
• The gametophyte generation is less prominent, has a shorted lifespan and disappears after one cycle of gamete formation and ferilisation
• Rhizoids on the lower (ventral) surface of prothallus anchor it in the soil
• Male and female sex organs are also found on the ventral (lower) surface of prothallus
• Released sperm need water to move to the ovum in the female sex organ. Therefore, fertilisation is dependent on water
• After fertilisation occurs, a zygote is formed and gives rise to a new fern plant- sporophyte generations
• The young sporophyte will live parasitically on the gametophyte. When it is independent (absorbs own water and mineral salts, photosynthesises), the prothallus disappears
• Life Cycle of Pteridophytes