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.
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