What is Pteridophytes?
Pteridophytes come under the class of cryptogams as they do need to produce seeds and flowers, they are the first vascular plants i.e. they have xylem and phloem.
They have the sporophytic phase as the dominant phase of their life cycle. They reproduce via spore formation. Pteridophytes are commonly found in shady and damp conditions with the exception of some species which may grow in soil. Pteridophytes include horsetails and ferns.
What are the Uses of Pteridophytes?
1. They are used in medicines
2. Act as soil binders
3. Grown as ornamental plants.
Pteridophytes plant body is well differentiated into true stem, root, and leaves. The leaf size may vary from very small (Selaginella) to large ones (Ferns). Pteridophytes are classified into four classes Psilopsida (Psilotum); Lycopsida (Selaginella), Sphenopsida (Equisetum), and Pteropsida (Pteris, Dryopteris, Adiantum).
What is the Sporophytic Phase?
Sporophyte has sporangia which bear leaf-like structures known as "Sporophylls". Sporophylls sometimes form distinct structures called "Strobili" or "Cones". Sporangia contain spore mother cells where spores are produced by the process of meiosis. These spores develop into free-living multicellular photosynthetic gametophytes known as "Prothallus".
What is the Gametophytic phase?
Gametophytes bear a male sex organ called antheridia and a female sex organ called archegonia. Megaspores and microspores give rise to female and male gametophytes. Antheridia produces antherozoids which are transferred to archegonia through the water. The requirement of water for fertilization and specific growing conditions restricts the occurrence of Pteridophytes in specific regions. Fusion of male gamete with female egg results in zygote formation. The zygote develops into an embryo inside the female gametophyte. This event also known as seed habit is an important step in evolution. Zygote further differentiates to produce sporophytes which are the dominating phase in the life cycle of Pteridophytes.
What is the type of Pteridophytes based on spore similarity
Homosporous
If spores produced are of a similar kind it is referred to as homosporous.
Heterosporous
If spores formed are of a different kind with one being large known as macrospores and the other being small known as microspores. It is referred to as Hetero Spores e.g. Selaginella.