Phaeophyta
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Phaeophyte Characteristics:
1) Pigments?
2) Chloroplast structure?
3) Storage product?
4) Flagella?
Division: Stramenopiles
Many classes, mostly unicellular or colony of unicells:
• class: Chrysophyta
• class: Bacillariophyta
• class: Pyrrhophyta
• class: Euglenophyta
• class: Phaeophyceae***
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Phaeophyte Morphology
New features:
sori
thallus
blade
all thallous forms
pneumatocysts
stipe
holdfast
Pneumatocysts
- large float containing gas found
= provide buoyancy
- O2, CO2, CO
Cystoseria
catenate
Sargassum
singly
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Midrib
Fucus
Laminaria
Undaria sp.
Phaeophyceae Thallus Morphology:
- complex multicellular thalli
- simplest forms = branching filaments
- differentiation into cortex and medulla
- may grow large
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Phaeophyte Cell Wall Morphology
Two main components:
1. Cellulose = microfibrils
2. Alginic acid = surrounds the microfibrills
Human Uses for Alginates
- Ice-cream
- Frosting
- Paints
- Food
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Microscopic Phaeophyte Morphology
Only alga to transport sugar/photosynthate in sieve
elements
Transport in Plants vs. Algae
Independent Evolutionary Origins
Plants
- water and sugar
conducting cells
Algae
- conduct sugars and some
nutrients
- xylem
- all cells living
- sieve elements
- sieve elements
- companion cells
- no companion cells
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Phaeophyte Metabolites:
Tannins: (a.k.a. polyphenolic compounds and terpenes)
- protective, defense system
- physodes in the cytoplasm
More Phaeophyte Storage Products:
- laminarin and mannitol
- sugars
- storage products = cytoplasmic vacuoles
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Laminarin function
- polymer
- food storage
Seawater is hypotonic (less saline) than most algal cells
Mannitol function
- important in osmoregulation
- transporting organic material
- lowers freezing point
Phaeophyte Reproduction:
Gametangia = structure where gametes
are formed
Sporangia = structure where spores
are formed
uniseriate
Unilocular
Plurilocular
“unangia”
“plurangia”
multiseriate
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Phaeophyte Flagella:
Anterior
- movement
- long flagellum
Posterior
- steering
- short, smooth
-contains flavin
an eyespot acts a shading structure
or light reflector
Functional Anisogamy
How do the male gametes find the female ones?
Pheromones
Phaeophyceans produce sexual pheromones = crossreactivity?
Male gametes?
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Phaeophyte Habitat
Mostly marine
Intertidal and subtidal
Dominate colder waters = Northern hemisphere:
# of red species > # of brown species
# of red individuals << # of brown individuals
12 orders within the Phaeophyta
Our focus will be on the following 4 orders:
Class Phaeophyceae
Ectocarpales
Chordariales
Laminariales
Fucales
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Distinguishing among orders based on
1. Life History and Reproduction
- isomorphic/heteromorphic
- isogamous, anisogamous, oogamous
2. Macrothallus Construction
3. Growth
- diffuse, apical, intercalary, trichothallic, meristodermal
Class Phaeophyceae
Ectocarpales
Desmarestiales
Laminariales
Fucales
- mostly epiphytic
- uniseriate filaments
Celebrity genus: Ectocarpus
- opportunistic
- pheromone ectocarpene
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Life History of Ectocarpales:
Asexual reproduction by plurilocular sporangia = sporophyte
Sexual reproduction is dioecious and anisogamous
meiosis
Thallus Morphology and Growth
Body is macroscopic, multicellular,
filamentous
Prostrate system
Lateral branching
Cells uninucleate
Cold oceans
Apical growth
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Class Phaeophyceae
Ectocarpales
Desmarestiales
Laminariales
Fucales
- Saxicolous
- Low intertidal to subtidal
- “Acid weed”
Celebrity genus: Desmarestia
Life History of Desmarestiales
Heteromorphic life history, microscopic sphorophyte,
macroscopic gametophyte
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Morphology variable within the genus
- subtidal
-!disappears with kelp growth due to canopy
-!”Acid weed”: sulfate ions + water = sulfuric/malic acid
Desmarestia Growth
Trichothallic growth =
fine hairs or spines
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Class Phaeophyceae
Ectocarpales
Desmarestiales
Laminariales
Fucales
- Saxicolous
- Sporangia always unilocular
- Most have sieve cells/elements
-Pheromone lamoxirene
Life History of Laminariales
Diplohaplontic Alternation of Generations: organism having a separate
multicellular diploid sporophyte and haploid gametophyte stage, flagellated
sperm
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Laminariales General Morphology
sorus (pl: sori)
Sorus/sporophyll
Hapteran holdfast
blade
sporophylls
stipe
haptera
holdfast
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Intercalary growth
- growth in both directions
- between stipe and blade
Meristodermal Growth
Meristoderm/outer cortex
Inner cortex
Medulla – contains specialized cells
Meristodermal growth
Periclinal and Anticlinal cell division:
- periclinal = cell division parallel to
the plane of the meristoderm
-Anticlinal = cell division
perpendicular to the plane of the
meristoderm
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Transport
sieve elements, sieve cells, or trumpet hyphae
- transport
- outgrowths of cortex cells
- no division after formation
- sieve plates
Class Phaeophyceae
Ectocarpales
Desmarestiales
Laminariales
Fucales
Celebrity genera: Fucus, Silvetia, Pelvetiopsis, Sargassum, Cystoseira
- usually saxicolous
- unattached in few
cases
- unilocular gametangia
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Life History of Fucales
Diplontic: 2N thallus, the gametes are the only
haploid stage
Receptacle
- swollen tips of fucoids = meiosis
- terminal portion of a branch
Conceptacles
- gamete storage
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Conceptacles
Oogonia- female reproductive cell
containing
Antheridia- a male reproductive
structure
Monoecious
- having the male & female
reproductive structure borne on
the same individual plants
Dioecious
- having the male & female reproductive structure borne on
separate individual plants; said of the species
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Fucus
Silvetia
Midrib
Playdough stipe
8 eggs per oogonium
2 eggs per oogonium
Pelvetiopsis
Flattened stipe
1 egg per
oogonium
Sargasso Sea in the Atlantic
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Growth and Construction at a Glance
Isomorphic
Order
Construction
(Macrothallus)
Growth
(Macrothallus)
Ectocarpales
filamentous
diffuse
pseudoparenchyma
trichothallic
parenchyma
intercalary
Heteromorphic Desmarestiales
Laminariales
meristodermal
Diplontic
Fucales
parenchyma
apical
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