BROWN ALGAE · HETEROKONTOPHYTA (PART II)
Notebook Requirements (12 drawings)
1. Macrocystis pyrifera – 4 drawings (thallus, scimitar blade (apical end), cross
section of sporophyll, and sporophyll blade)
2. Nereocystis leutkeana –2 drawings (thallus and lateral section)
3. Laminaria setchellii – 1 drawings (thallus)
4. Alaria marginata – 1 drawing (thallus and cross section of sporophyll)
5. Egregia menziesii – 1 drawing (at least 2 different blade types and/or terminal
blade)
6. Lessoniopsis littoralis – 1 drawing (thallus)
7. Unknowns – 2 Thallus drawings and steps in key
C. Order Laminariales
Family Laminariaceae
Species: Macrocystis pyrifera
•
Examine and sketch the thallus of M. pyrifera. Label stipe, blades, sporophylls,
holdfast, pneumatocysts and location of intercalary meristem
•
Examine and sketch the apical end of M. pyrifera noting the scimitar blade.
•
Draw a sporophyll blade and a vegetative blade.
Q: Where is each type of blade located on the thallus? How can you visually tell them
apart from each other?
Species: Nereocystis leutkeana
To transport sugars throughout the plant body of this large kelp, Nereocystis (and M.
pyrifera) has sieve tubes in the outer medulla.
•
Draw the thallus of N. leutkeana, label stipe, pneuomatocyst, holdfast sporophylls,
and sori (if present).
•
Prepare and draw a lateral section of the stipe. Identify and label mucilage ducts (if
visible - in cortex), sieve plates (in medulla)/sieve elements (trumpet hyphae), cortex
and medulla. Work on this together to get a good cross section.
Q: What is the purpose of sieve plates?
Q: Compare and contrast Macrocystis and Nereocystis: What morphological
differences are there? Which species is annual? Which is perennial? What
environment are each species found? (hint, check MAC)
Q: What is the life history of Laminariales?
Q: For algae in Laminariales – Is the macro-thallus (the algae we have in the water
table) 1N or 2N? Understand the lifecycle of this order.
Species: Laminaria setchellii
The holdfast of this species is composed of stiff, branched haptera. Each holdfast produces
a single, long stipe. Sori appear as irregular darkened patches on the blades, but not all
blades have sori.
1. Examine and draw the overall thallus. Label holdfast, stipe, blade and sori (if
present).
Family Alariaceae
Species: Alaria marginata
•
Sketch thallus, label holdfast, stipe, terminal blade, midrib, sporophylls and sori (if
present)
•
Draw a cross section through a sorus patch of Alaria, label sporangia, cortex, and
medulla.
Family Lessoniaceae
Species: Egregia menziesii
• Draw thallus. Label the rachis (specialized
blade/central axis = “midrib”) and identify and
label the blades coming off the rachis (see
diagram for different types of blades). Also label
pneumatocysts.
Simplified blade types found in Egregia menziesii.
Filiform Blade
Stipitate Blade
Spatulate Blade
Q: Where is the meristematic region of thallus?
Pneumatocyst
Species: Lessoniopsis littoralis
1. Sketch the thallus of L. littoralis, label stipe, blades, holdfast, sporophylls and sori.
(Hint: see your MAC for a description of the sporophylls).
H. Unknowns
As in previous labs, key to species (and draw) the two unknowns presented to you. Be sure
to write out each step of your path through the dichotomous.
Life Cycle of the Laminariales
Diplohaplontic
e.g. Laminaria setchellii
antheridia
produce sperm
1N zoospores
1N gametophytes
syngamy
meiosis occurs in
unilocular sporangia
sori on
2N adult
oogonium
2N embryonic
sporophyte