Pteridophytes – The First True Terrestrial Plant

The term Pteridophyta is derived from the Greek words pteron meaning feather and phyton meaning plant. The plants in this group have leaves that resemble feathers. This name was first coined by Haeckel in 1866, and they are the most primitive living and fossil vascular plants.

Pteridophytes are the first terrestrial vascular plants to have true roots, stems, and leaves. They are vascular cryptogams, meaning they have a well-developed vascular system. In the plant kingdom, pteridophytes occupy a position between bryophytes and gymnosperms, as they share some characteristics with both bryophytes and gymnosperms.

The similarities with bryophytes include:

1. The presence of a sterile jacket around the sex organs.
2. The requirement of water for fertilization.
3. The alternation of generations.
4. The formation of spores.

The similarities with gymnosperms include:

1. The dominant plant body is the sporophyte.
2. The differentiation of the sporophyte into true root ,stems and leaves.
3. The presence of a vascular system for conduction.

General Characteristics of Pteridophytes

1. In the life cycle of Pteridophytes, the dominant phase is the sporophyte, the main plant body.
2. The main plant body is differntiated into true roots, stems, and leaves.
3. Pteridophytes possess well developed vascular system(xylem and phloem).
4. Pteridophytes thrive in cool, damp, and shady environments, although they can also flourish in sandy soil.
5. Pteridophytes exhibit a wide range of forms, sizes, and structures.
6. All living pteridophytes are herbaceous, except for a few woody tree ferns.
7. The stems of pteridophytes bear leaves, which can be either microphyllous (small) like in Selaginella or megaphyllous (large) like in ferns.
8. The primary embryonic roots are short-lived and are replaced by adventitious roots.
9. The pteridophytes reproduce by haploid spores which are produced in a special structure called sporangium.
10. Plants can be either homosporous, producing only one type of spore, or heterosporous, producing two types of spores: microspores and megaspores.
11. The sporangia produce haploid spores by meiosis in spore mother cells.
12. These spores developed into small but multicellular free-living, thalloid gametophytes called prothallus.
13. The gametophyte possesses male reproductive structures (antheridia) or female reproductive structures (archegonia). The fusion of gametes leads to the formation of a diploid zygote.
14. Microspore germinates and gives rise to male gametophyte which bears the male sex organs antheridia.
15. Megaspore germinates and gives rise to female gametophytes which bears the female sex organs archegonia
16. The male gametes are called antherozoids and produced inside the antherdium.
17. Water is essential for fertilization, as the male gamete must swim through water to reach the archegonium. Once there, the male gamete fuses with the egg present in the archegonium, resulting in the formation of a diploid zygote.
18. The Zygote develops into new sporophytic plant body.