Define the Pteridophytes in plant kingdom
The Pteridophytes include horsetails and ferns. Pteridophytes are used for medicinal purposes and as soil-binders. They are also frequently grown as ornamentals. Evolutionarily, they are the first terrestrial plants to possess vascular tissues are:
1. Xylem and
2. Phloem.
In the case of pteridophytes, the main plant is a sporophyte which is differentiated into true root, stem and leaves. These organs contain well-differentiated vascular tissue. The leaves in pteridophyta are small (microphylls) as in Selnpinelln or large (macrophylls) as in ferns. The sporophytes bear sporangia that are subtended by leaf-like appendages called sporophylls. In some cases sporophylls may form distinct compact structures called strobili or cones (Selaginella, Equisetum). The sporangia produce spores by meiosis in spore mother cells.
Sporophytes bear sporangia which produce spores. spores Germs germinate to form gametophytes that require cool, moist places to grow. Gametophytes have male and female sex organs called antheridia and archegonia, respectively. Water is required for the transfer of male gametes to the archegonium, where the zygote is formed after fertilization. The zygote produces a sporophyte. The development of the zygotes into young embryos take place within the female gametophytes. This event is a precursor to the seed habit considered an important step in evolution. The pteridophytes are further classified into four classes:
1. Psilopsida (Psiloturn),
2. Lycopsida (Selaginella, Lycopodium),
3. Sphenopsida (Equisetum) and
4. Pteropsida (Dryopteris, Pteris, Adiantum)
The characteristics of Pteridophytes
Pteridophytes are seedless.
Pteridophytes are multicellular.
Pteridophytes reproduce through spores.
Pteridophytes are independent and free-living organisms.
Pteridophytes have a well-differentiated plant body into root, stem and leaves.
(Selaginella)
(Equisetum)
(Fern)
(Salvinia)
Economical importance of pteridophytes
Ferns are grown as ornamental plants for their graceful fronds. The rhizome and petioles of the fern Dryopteris give a vermifuge drug. The sporocarps (a water fern) of Marsilia used as food by some tribal peoples.