Overview
Also known Pteridophyte are a group of vascular plants composed of Lycophytes and Ferns that reproduce through spores. These plants first appeared roughly 420 million years ago and formed the first forests. Most live in moist enviorments, as the sperm fragile and must swim through a film of water to reach the egg for fertilization. From Latin Pteridium meaning “feather wing” + phyte (meaning plant).These were the first vascular plants to appear on Earth and currently there are around 9500 species across all phyla.
Evolution
Seedless vascular plants have made several evolutionary adaptation over the previous Bryophytes including
- The vascular system
- This includes leaves.
- Ferns have megaphylls or true leaves, while Lycophytes have microphylls
- Xylem and Phloem
- The traichids make up Xylem (made of dead cells) are like an aqueduct across the plant
- The phloem is responsible for transporting sugar and other organic compounds across the plant
- Roots or Rhizoids
- These rhizoids actually uptake water and nutrients instead of serving primarily of an anchor
- Life cycle changes
- The sporophyte becomes the dominant phase
- The gametophyte becomes independent
Structure
Starting at the bottom of the plant, the roots are true roots that are strengthend with ligin. This allows for the root to delve deeper and wider in order to absorb nutrients and water. The stalk then travels up to the axis, in which several leaves are attached. The entire leafy part is known as the frond. It primarily performs photosynthesis, in which the nutrients are transferred throughout the plant by phloem. The cellular tissue is lignified, which strengthens the tissue and allows for a larger plant.
Life Cycle
Sporangiums on the underside of the mature sporophyte makes spores. The spores are then dispersed via wind where they grow to be a mature, bisexual gametophyte. A sperm swims from the antheridium in a thin film of water and fuses with egg located in the archegonium. Fertilzation occurs and the zygote mitotically divides into a young sporophyte, which then matures.
Importance
- A very popular houseplant
- A large source of coal and fossile fuels
- Occasional food source
- Uses in pharmacy
- Absorption of arsenic or other heavy metals from the soil
- A small source of lumber
Bryophytes Seedless vascular plants Gymnosperms
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