Pteridophytes
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Ferns are a group of plants adapted to live on land. The dominant generation in ferns is the sporophyte generation, which represents the adult fern plant with true roots, an underground stem, and large compound leaves. Spores are produced in clusters called sori on the underside of leaves and are dispersed by wind. When spores germinate, they produce a small heart-shaped gametophyte generation that bears male and female sex organs requiring water for fertilization to occur and form a new sporophyte fern plant.
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Pteridophytes
- 1. PTERIDOPHYTES - FERNS Pteridophytes are a group of plants that are adapted to live on land. Ferns mostly occur in moist , shady environments. Unlike the Bryophytes , the sporophyte generation is the dominant generation in ferns. The adult fern plant represents the sporophyte generation The fern has true roots , stems and leaves. i.e. it is not a thallus. In most ferns (excluding tree ferns) the stem is a horizontal , underground rhizome Adventitious roots develop from the rhizome, anchor the plants in the soil and absorb water and mineral salts. The green compound leaves (fronds) with long leaf stalks develop from buds on the rhizome Well-developed vascular tissue (xylem and phloem) is present.
- 3. structure continued. The sporophyte is perennial and therefore produces spores over many generations Clusters of sporangia are found on the underside of leaves. These clusters of sporangia are called sori (singular : sorus) spores are released from the sporangia and dispersed by the wind. When a spore germinates, it gives rise to a green, heart-shaped prothallus, that represents the gametophyte generation.
- 4. FERNS the gametophyte generation is less prominent , has a shorter lifespan and disappears after one cycle of gamete formation and fertilisation.
- 5. ferns structure continued Rhizoids on the ventral (lower) surface of the prothallus anchor it in the soil. Male and female sex organs , which produce sperm and ova respectively , are also found on the ventral surface of the prothallus. Released sperm need water to move to the ovum in the female sex organ Fertilisation is dependent on water After fertilisation occurs, a zygote is formed and this gives rise to the new fern plant (sporophyte). Initially, the young sporophyte lives parasitically on the gametophyte. When the young sporophyte is independent (absorbs its own water and mineral salts and can photosynthesise), the prothallus disappears. https://www.youtube.com/watch?v=avK7hGnaRAY (Video is 18 minutes long. Please watch at your leisure)
- 7. OVERVIEW PTERI DOPH YTES Structure of dominant generatio n (Sporoph yte ) Vascula r tissue Spor es/se eds Fruit Depend ency on water for reprod uction ferns True roots, underground stem, large compound leaves Xylem and phloem present spores none Water is needed for fertilisation