Mosses

Question 1

What are the three phyla of bryophytes?

Answer 1

1. Marchantiophyta - Liverworts
2. Anthocerophyta - Hornworts
3. Bryophyta - Mosses

Question 2

Bryophyte evolution:

Answer 2

• the three phyla diverged independently
• liverworts and hornworts are reasonable models of early plants
• mosses are most closely related to vascular plants

Question 3

What is bryophyte reproduction?

Answer 3

• alteration of generations
• the gametophyte consists of gamete producing structures = gametophores and rhizoids
• gametophores are haploid, photosynthetic and gamete producing
• gametes are produced in gametangia
• gametophytes are dominant phase of life cycle
  
  • sporophytes are smaller and present only part of year
• bryophyte spores are homosporous = same size
• spores germinate and grow by mitosis into branched, one cell thick filaments = protonemata
• protonemata produces meristems and they produce gametophytes

Question 4

What are rhizoids?

Answer 4

• bryophytes are anchored by multicellular filaments = rhizoids
• they are not composed of tissues
• not photosynthetic
• lack specialized conducting cells
• do not play primary role in water and mineral absorption

Question 5

Leave morphology:

Answer 5

• commonly only one or few cells thick to enhance water and mineral absorption from moist environment
• water and mineral transport often external to gametophore
• moss leaves may have one or more costa (nerve)
• they lack lignin vascular cells

Question 6

What are hydroid and leptoid cells?

Answer 6

• hydroid = conduct water in gametophyte
• leptoids = conduct organic compounds in gametophyte
• are not speciliazed

Question 7

What are guide cells?

Answer 7

• noticeably large cells that are continuous with the cells that make up rest of leaf blade (lamina)

Question 8

The cell differentiation of the seta:

Answer 8

• most mosses consits of the following concentric layers:
  
  • hydroid and leptoid cells
  • parenchyma cells
  • supportive stereid cells
  • epidermal cells

Question 9

What are the two general growth habits of moss?

Answer 9

1. Acrocarpus
   * are erect with apical sporophyte
2. Pleurocarpus
   * decumbent or feather-like with lateral sporophytes

Question 10

What is the perichaetium?

Answer 10

• whirl of leaves around the achegonium that will eventually produce the sporophyte

Question 11

Moss sporophyte structure and function

Answer 11

Structure

• consist of foot, elongated stalk (seta) and sporangium (capsule)

Function

• foot = gathers nutrients and water from parent gametophyte
• seta = conducts nutrients and water to capsule
• capsule = dispersal of spores

Question 12

The structure and function of moss capsule:

Answer 12

• capsule (sporangium) is site of meiosis and spore production
• when immature covered by calyptra = protective cap of gametophyte tissue
• upper part of capsule = peristome that is specialized for gradual spore release

Question 13

What is sphagnum moss?

Answer 13

• wetland moss
• forms deposits = peat
• does not decay readily because of phenolic compounds and acidic secretions inhibiting bacterial activity
• important for carbon reservoirs

Question 14

The structure of sphagnum leaf:

Answer 14

• have live cells = small photosynthetic cells that surround dead cells
• have dead cells = hyaline cells that store water with large pores and cross walls

Question 15

Restoration measures for Rithet’s Bog:

Answer 15

• water table sufficient to support peat moss growth
• remove shore pine canopy
• use experimental design BACI (before after control impact)
• have two controls = spatial (using paired plots) and temporal (before and after assessment)
• it is partly nested design