General characteristic features of Pteridophytes

General characteristic features of Pteridophytes:

•            Plant body is sporophyte (2n) and it is the dominant phase. It is differentiated into root, stem and leaves.

•            Roots are adventitious.

•            Stem shows monopodial or dichotomous branching.

•            Leaves may be microphyllous or megaphyllous.

•            Stele is protostele but in some forms siphonostele is present (Marsilea)

•            Tracheids are the major water conducting elements but in Selaginella vessels are found.

•            Sporangia, spore bearing bag like structures are borne on special leaves called sporophyll. The sporophylls gets organized to form cone or strobilus. Example: Selaginella, Equisetum .

•            They may be homosporous (produce one type of spores-Lycopodium) or Heterosporous (produce two types of spores-Selaginella). Heterospory is the origin for seed habit.

•            Development of sporangia may be eusporangiate (development of sporangium from group of initials) or leptosporangiate (development of sporangium from single initial).

•            Spore mother cells undergo meiosis and produce spores (n).

•            Spore germinates to produce haploid, multicellular green, cordate shaped independent gametophytes called prothallus.

•            Fragmentation, Resting buds, root tubers and adventitious buds help in Vegetative reproduction.

•            Sexual reproduction is Oogamous. Sex organs, namely antheridium and archegonium are produced on the prothallus.

•            Antheridium produces spirally coiled and multiflagellate antherozoids.

•            Archegonium is flask shaped with broad venter and elongated narrow neck. The venter possesses egg or ovum and neck contain neck canal cells.

• Water is essential for fertilization.

After fertilization a diploid zygote is formed and undergoes mitotic division to form embryo.

• Pteridophytes show apogamy and apospory.