Write the general characteristic features of Pteridophytes.

Explanation

Characteristic features of pteridophytes :
1. Plant body is sporophyte (2n) and it is the dominant phase. It is differentiated into root, stem and leaves.
2. Roots are adventitious.
3. Stem shows monopodial or dichotomous branching .
4. Leaves may be microphyllous or megaphyllous.
5. Stele is protostele but in some forms sipphonostele is present (Marsilea).
6. Tracheidsa are the major water conducting elements but in selaginella vessels are found.
7. Sporangia, spore bearing bag like structures are borne on special leaves called sporophyll.
8. The sporophylls gets organized to form cone or strobilus. Eg: Selaginella, Equisetum.
9. Homosporous - produce one type of spores - Lycopodium.
10. Heterosporous -produce two types of spores- selaginella.
11. Heterospory is the origin for seed habit.
12. Spore mother cells undergo meiosis and produce spores (n) .
13. Spore germinates to produce haploid, multicellular green , cordate shaped independent gametophytes called prothallus.
14. Fragmentation, resting buds, root tubers and adventitious buds help in vegetative reproduction.
15. Sexual reproduction is oogamous. sex organs, namely antheridium and archegonium are produced on the prothallus.
16. Antheridium produces spirally coiled and multiflagellate anthrozoids.
17. Archegonium is flask shaped with broad venter and elongated narrow neck. The venter possesses egg or ovum and neck contain neck canal cells.
18. Water is essential for fertilization.
19. After fertilization a diploid zygote is formed and undergoes mitotic division to form embryo.
20. Pteridophytes show apogamy and apospory.