3. Kingdom Plantae - part 03 - Pteridophyta

 

3. Kingdom Plantae - part 03 - Pteridophyta


Pteridophyta (Pteron : feather, phyton : plant ) :
  • Evolutionarily, Pteridophytes are the first vascular and true land plants. Hence considered as the first successful terrestrial plants with true roots, stem and leaves. 
  • These plants have a primitive conducting system and they are the only Cryptogams with vascular tissues. 
  • The late Paleozoic era is regarded as the age of Pteridophytes. 
  • The group has about 400 genera and 11,000 species. 
  • The plants consist of pinnate (feather like) leaves.
  • Leaves may be small called microphylls (e.g. Selaginella) or large called macrophylls (e.g. Nephrolepis / fern).
  • Pteridophytes grow in moist and shady places. 
  • Pteridophytes show sporophytic and gametophytic stages in life cycle. 
  • e.g. Ferns, Horsetail. 
  • Some are aquatic (Azolla, Marsilea), xerophytic (Equisetum) and epiphytic (Lycopodium).
  • Pteriodphytes show heteromorphic alternation of generations in which the sporophyte is diploid, dominant, autotrophic and independent. 
  • It is differentiated into root, stem and leaves. 
  • The primary root is short lived and soon replaced by adventitious roots while the stem may be aerial or underground. 
  • Leaves may be -
  1. scaly - Equisetum 
  2. simple and sessile - Lycopodium or
  3. large and pinnately compound - Nephrolepis / Ferns.
  • In these members Xylem consists of only tracheids and Phloem consists of only sieve cells. 
  • Secondary growth is not seen in Pteridophytes due to absence of cambium.
Pteridophytes are classified as -
  1. Psilopsida- Psilotum
  2. Lycopsida - Selaginella and Lycopodium
  3. Sphenopsida - Equiesetum) and 
  4. Pteropsida - Dryopteris, Pteris and Adiantum)
Economic importance - 
  • Pteridophytes are Used for medicinal purpose and as soil binders.
  • Many varieties are grown as ornamental plants.

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