Bryophytes: Mosses and Liverworts

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BryophytesMosses and Liverworts
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General Characteristics

• Spore- producing plants that have no vascular
  tissue
• Usually live in moist, cool environments
• Must carry on all life functions where there is
  steady supply of moisture
• Cant compete with neighboring vascular plants

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Mosses

• Small
• Leafy stems
• Grow in dense carpets or tufts
• See page 595 for examples of mosses

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Liverworts

• Small
• Grow in clumps
• Occur in many environments, from water to desert
• Have oily or shiny surface
• Two groups
• Thallose thallus broad ribbonlike body, looks
  like lobed leaf
• Leafy creeping, 3 rows of flat, thin leaves
  attached to stem

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Reproduction

• Alternation of generations between diploid
  sporophyte and haploid gametophyte (like all
  plants)
• Only plant division where gametophyte generation
  is dominant

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Structure of Mosses

• Protonema small, green filament of cells that
  develops into either male or female gametophyte
• Antheridium reproductive structure in which
  sperm are produced
• Archegonium reproductive structure in which eggs
  are produced

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Life Cycle of a Moss(Diagram on p. 597)

• 1. Sporophyte generation develops from
  gametophyte
• 2. Spores are produced by meiosis in capsule of
  sporophyte
• 3. Spore capsule ripens, bursts, releases
  spores. Spore germinates to form a protonema
• 4. Atheridium develops on male gametophyte
• 5. Archegonium develops on female gametophyte
• 6. Sperm are released and swim to archegonium
• 7. Fertilization takes place inside archegonium
• 8. Zygote divides by mitosis to form new
  sporophyte

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Asexual Reproduction in Bryophytes

• Vegetative reproduction plant gives rise to new
  individuals without going through the alternation
  of generations
• Mosses can break into pieces when it is dry and
  brittle
• With the arrival of wetter conditions, each piece
  then becomes a whole plant
• Gemmae tiny, haploid boides that grow in cups on
  surface of gametophyte