Topic 11: Phaeophyceans (Brown Algae)

Question 1

• Do phaeophyceans have unicellular species?

Answer 1

NO!
They have microscopic life stages but even these are multicellular

Question 2

• What is the thallus of pseudoparenchymatous algae composed of?

Answer 2

A pseudoparnchymatous thallus is composed of many many filaments that appear to be 3D

Question 3

Describe the 3 main components of the cell wall in brown algae, and their functions.

Answer 3

The cell wall of brown algae is composed of alginic acid, cellulose and fucans

Alginic Acid: hydrophilic polysaccharide, primary matrix component (20-40% dry weight), strengthen, dessication presentation, ion exchange

Cellulose: Minor 1-10% of dry weight, for structural support

Fucans: sulfated polymers of L-fucose and other sugars, not well understood function, possibly anchor zygotes and germlings to substrate

Question 4

• What compound is extracted from harvested phaeophyceans for industrial applications?

Answer 4

Alginic acid is extracred commercially for many things

Paper and textiles
Waterproofing
Fireproofing fabrics
* Rubber and tires
* Shoe polish
* Paint
Food thickening
Pharacuetical

Question 5

What is the name of the pigment that confers the characteristic dark
green/olive brown color in phaeophyceans?

Answer 5

This is the fucocxanthin

Question 6

• Describe the different modes of meristematic growth

Answer 6

Diffusive: cell division throughout thallus

Single-apical cell: one-cell wide filament
Apical meristem: one cells that can grow in additional directions

Intercalary meristem: between stipe and blades, tissue grows in 2 directions

Meristoderm: surface growth region, girth increase

Basal meristematic activity: growth from just the basal region

Question 7

Where is intercalary meristem located on the thallus?

Answer 7

Between stipe and blade tissue, grows in 2 directions

Question 8

• Draw the 3 different types of life cycles common in Phaeophyceans.

Question 9

• Indicate the name of each life cycle based on the nature of meiosis (i.e.
  where meiosis occurs) and on the morphological similarity/dissimilarity of the generations.

Question 10

• Define: ‘alternation of generations’

Answer 10

Alternation of generations has to do with the fact that there are free-living stages in the life cycle that have different ploidy

Question 11

• What are plurilocs and unilocs, and where are they found?

Answer 11

Plurilocs are a sexual structure that exist on the gametophytes to produce gametes (plurilocular gametangium)
Plurilocs can also exist on the sporphytes and produce asexual spores (plurilocular sporangia)

Unilocs can only exist on the sporophyte. They are sexual structures that produce zoospores to then develop into the gametophytes

Question 12

• Draw a labeled sketch of a mature sporophyte in kelp (name all the parts).

Question 13

• What is the primary world distribution of kelp with air bladders?

Answer 13

The occur on the west coast of the pacific of north America and south America

They also exist on the East cost of the NZ south island and West coast of NZ north island

Sargasso sea

Question 14

• Describe the tissue differentiation in the kelp thallus.

Answer 14

Meristoderm: outer layer of pigmented cells

Cortex: colorless cells

Medulla: internal with sieve elements, translocation of solutes/ions to basal regions

Intercalary meristem: stipe blade junction