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What are PTERIDOPHYTES ??
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What are PTERIDOPHYTES ??
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A pteridophyte is a vascular plant that disperses spores. Because pteridophytes produce neither flowers nor seeds, they are sometimes referred to as "cryptogams", meaning that their means of reproduction is hidden. Ferns, horsetails, and lycophytes are all pteridophytes.
ELEVEN THOUSAND
There are about eleven thousand different species of pteridophytes, making them the most diverse land plants after the flowering plants (angiosperms).
Ferns, horsetails (often treated as ferns), and lycophytes (clubmosses, spikemosses, and quillworts) are all pteridophytes. However, they do not form a monophyletic group because ferns (and horsetails) are more closely related to seed plants than to lycophytes.
The pteridophytes and other vascular plants also have vascular tissue specialized for tranporting sugar. These adaptations probably enabled pteridophytes to dominate the forests of the Carboniferous period. The remains of these ancient forests have great significance.
Pteridophyta is classified into four main classes:
1. Pteridophytes are considered as the first plants to be evolved on land:
It is speculated that life began in the oceans, and through millions of years of evolution, life slowly adapted on to dry land. And among the first of the plants to truly live on land were the Pteridophytes.
2. They are cryptogams, seedless and vascular:
Pteridophytes are seedless, and they reproduce through spores. They contain vascular tissues but lack xylem vessels and phloem companion cells.
3. The plant body has true roots, stem and leaves:
They have well-differentiated plant body into root, stem and leaves.
4. Spores develop in sporangia:
The sporangium is the structures in which spores are formed. They are usually homosporous (meaning: one type of spore is produced) and are also heterosporous, (meaning: two kinds of spores are produced.)
5. Sporangia are produced in groups on sporophylls:
Leaves that bear the sporangia are termed as sporophylls. The tip of the leaves tends to curl inwards to protect the vulnerable growing parts.
6. Sex organs are multicellular:
The male sex organs are called antheridia, while the female sex organs are called archegonia.
7. They show true alternation of generations:
The sporophyte generation and the gametophyte generation are observed in Pteridophytes. The diploid sporophyte is the main plant body.
Pteridophytes show alternation of generations. Their life cycle is similar to seed-bearing plants, however, the pteridophytes differ from mosses and seed plants as both haploid gametophyte and diploid sporophyte generations are independent and free-living. The sexuality of pteridophytic gametophytes can be classified as follows:
Dioicous: the individual gametophyte is either a male producing antheridia and sperm or a female producing archegonia and egg cells.
Monoicous: every individual gametophyte may produce both antheridia and archegonia and it can function both as a male as well as a female.
Protandrous: the antheridia matures before the archegonia.
Protogynous: the archegonia matures before the antheridia.