Question

What are the three classes of bryophytes?

Answer 1

Answer:

Class I: Hepaticopsida ( Liverworts)

Class II: Anthocerotopsida ( Hornworts)

Class III: Bryopsida ( Mosses)

Explanation:

Bryophytes are small plants that grows in moist and shady places.They don't attain great heights because of absence of roots, vascular tissues, mechanical tissues and cuticle. They are terrestrial but require external water to complete their life cycle. Hence they are called as the" amphibians" of the animal kingdom.

Class I: Hepaticopsida or Hepaticae

• Gametophytic plant body is either thalloid or foliose. If foliose the lateral appendages are  without midrib.
• Rhizoids without septa
• Each cell in the thallus contain many chloroplasts
• Sex organs are embedded in the dorsal surface
• Capsule lacks columella
• Sporophyte may be simple having only one capsule or differentiated into root, seta and capsule
• It has 4 orders: Calobryales, Jungermanniales, Spherocarpales and Marchantiales

Class 2: Anthocerotae or Anthocerotopsids:

• Gametophytic plant body is simple, thalloid;thallus dorsiventra without air chambers shows no internal differentiation of tissues
• Scales are absent in the thallus
• Each cell of the thallus possess a single large chloroplast with a pyrenoid
• Sporophyte is cylindrical only partly dependent on gametophyte for its nourishment. It is differentiated into bulbous foot and cyclindrical capsule. Seta is meristematic.
• Endotheciumforms the sterile central column in the capsule. It have ony one order Anthocerotales

Class 3: Musci or Bryopsida

• Gametophyte is differentiated into prostrate protonema and an erect gametophores
• Gametophore ids foliose, differentiated into axis and lateral appendages like leaves but without midrib.
• Rhizoids are multicellular with oblique septa
• Elaters are absent in the capsule of sporangium
• The sex organs are produced in seperate branches immersed in a group of leaves.
• It has only three orders: Bryales, Andriales and Sphagnales

Bryophytes are used as a packaging material for fragile goods, glasswares etc.Mosses are good source of animal food in rocky and snow clad areas. Decoction prepared by boiling Sphagnum in water  is used for the treatment of eye disease.