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!
sori
thallus
blade
stipe
holdfast
Pneumatocysts- !
!- large float containing gas found!
!!
!
!- O2, CO2, CO!
Cystoseria !
Catenate
!
!
!
!Sargassum !
!
!singly!
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Midrib
Fucus!
Laminaria!
Undaria sp.!
Phaeophyceae Thallus Morphology:!
-  complex multicellular thalli, adults never unicellular!
- simplest forms = branching filaments!
-  differentiation into cortex (outer pigmented cells) and
medulla (inner non-pigmented cells)!
!
-  may grow large ! over 40 meters long!
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Phaeophyte Cell Wall Morphology!
Two main components:!
!
1.  Cellulose ! microfibrils (1-10% of thallus dry weight)!
!
!
2.  Alginic acid ! surrounds the microfibrills (35% of
thallus dry weight)!
Human Uses for Alginates!
-  Ice-cream!
!
-  Frosting!
!
-  Paints!
!
!
-  Food = kombu in Japan; dried
and shredded laminarians!
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Microscopic Phaeophyte Morphology!
Only alga to transport sugar/photosynthate in sieve
elements!
Plasmodesmata = connections between adjacent cells,
formed during cell division = cell-to-cell transport of
photosynthetic products and cell communication !
Transport in Plants vs. Algae!
Independent Evolutionary Origins!
Plants!
- water and sugar
conducting cells!
Algae!
- conduct sugars and some
nutrients!
- xylem = non-living!
- all cells living!
- sieve elements = alive!
- sieve elements = alive!
- sieve elements lack
!organelles!
- sieve elements w/o organelles
except mitochondria!
- companion cells!
- no companion cells!
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Now, why are the Phaeophytes the
only algae that contain sieve elements?!
Phaeophyte Metabolites:!
Tannins: (a.k.a. polyphenolic compounds and terpenes)!
- protective, defense system!
- stored in special vesicles called physodes in the
cytoplasm!
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More Phaeophyte Storage Products:!
-
Laminarin and Mannitol are most abundant!
- always sugars!
- storage products in cytoplasmic vacuoles (no special
name); not associated with chloroplasts or pyrenoids !
!
Laminarin function!
-  storage glucan = polymer of glucose!
-  used as additive for pork patties!
-  main form of food storage in brown algae!
Mannitol function !
= sugar alcohol – originally from flowering ash!
-  important in osmoregulation- algae make more
mannitol to use up ions!
-  transporting organic material to different parts of
the thallus in large species!
- lowers freezing point!
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Phaeophyte Reproduction:!
Gametangia = structure where gametes
are formed !
Sporangia = structure !
where spores are formed !
uniseriate
Unilocular = spores/
gametes produced in a
single compartment!
!
unangia !
multiseriate
Plurilocular = many small
chambers (locules); one
spore/gamete per chamber!
!
plurangia !
Phaeophyte Flagella:!
attached laterally, never apically!
!
Anterior flimmer flagellum !
- movement!
- long flagellum with mastigoneme !
!
!
Posterior whiplash flagellum !
- steering!
- short, smooth flagellum!
- contains flavin!
!
!
an eyespot acts a shading structure
or light reflector!
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Functional Anisogamy
How do the male gametes find the female ones?
Pheromones = chemicals produced to elicit a specific
behavioral or physiological response
Phaeophyceans produce sexual pheromones = chemically
similar (unsaturated hydrocarbons = high cross-reactivity
Male gametes are VERY sensitive to pheromones = low
concentration will elicit a response
Phaeophyte Habitat!
Mostly marine (or at least brackish water)!
Intertidal and subtidal!
Dominate colder waters = Northern hemisphere: !
# of red species > # of brown species!
# of red individuals << # of brown individuals !
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12 orders within the Phaeophyta
Our focus will be on the following 4 orders:
Class Phaeophyceae
Ectocarpales
Chordariales
Laminariales
Fucales
Distinguishing among orders based on
1.  Life History and Reproduction
- isomorphic/heteromorphic alternation of generations
- isogamous, anisogamous, oogamous
2.  Macrothallus Construction
3.  Growth
- diffuse, apical, intercalary, trichothallic, meristodermal
(a surface layer of cells (epidermis) that is capable of dividing =
is meristematic)
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Class Phaeophyceae
Ectocarpales
Desmarestiales
Laminariales
Fucales
-  mostly epiphytic
-  uniseriate filaments
Celebrity genus: Ectocarpus
-  opportunistic = excellent colonizers
- Female gametes releases pheromone
ectocarpene, hormosirene
Life History of Ectocarpales:!
Asexual reporduction by plurilocular sporangia = sporophyte!
Sexual reproduction is dioecious and anisogamous!
meiosis!
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Thallus Morphology and Growth!
Body is macroscopic, multicellular, filamentous!
!
Prostrate system - irregularly branched,
uniseriate and attached!
!
Lateral branching , series of elongated cells!
!
Cells uninucleate with discoid chromoplasts!
!
Distribution generally is cold oceans!
!
Growth apical though no specialized apical
cells!
Class Phaeophyceae
Ectocarpales
Desmarestiales
Laminariales
Fucales
-  Saxicolous
-  Low intertidal to subtidal
-  Acid weed
Celebrity genus: Desmarestia
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Life History of Desmarestiales
Heteromorphic life history, sphorophyte, macroscopic
gametophyte!
Morphology variable within the genus
-  subtidal = high light (abundant if disturbance has removed
canopy, e.g. El Nino, or urchin grazing)
- disappears with kelp growth due to canopy = shading
- Acid weed : cells accumulate sulfate ions from seawater +
water = sulfuric acid or malic acid, stored in vacuoles
=ANTIHERBIVORY, pH 0.8-1.8, bleaches other algae
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Desmarestia Growth!
Trichothallic growth = tips, sides and main axis have a fringe
along the margins !
!
Trichothallic growth filaments!
Class Phaeophyceae
Ectocarpales
Desmarestiales
Laminariales
Fucales
- saxicolous
-  sporangia always unilocular
-  most have sieve cells/elements
-  pheromone released by female
gametes lamoxirene
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Life History of Laminariales
Diplohaplontic Alternation of Generations: organism having a separate
multicellular diploid sporophyte and haploid gametophyte stage, flagellated
sperm
Laminariales General Morphology
sorus (pl: sori)
blade
sporophylls
stipe
Sorus/sporophyll - sporangia!
!
Hapteran holdfast = always
submerged, multiple
branches !
!
!
haptera
holdfast
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Microscopic gametophytes
Intercalary growth
- growth in both directions (away from meristem)
- between stipe and blade (or blade and pneumatocyst)
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Meristodermal Growth!
Meristoderm/outer cortex – !
Inner cortex – !
Medulla – !
Meristodermal growth gives thallus girth (mostly), mostly
periclinal cell division!
Periclinal and Anticlinal cell division:!
!
- periclinal = cell division parallel to
the plane of the meristoderm = girth!
-  anticlinal = cell division
perpendicular to the plane of the
meristoderm = length!
Transport
sieve elements, sieve cells!
- transport photosynthetic products!
-  outgrowths of cortex cells grow into the medulla!
-  sieve plates = specialized plasmodesmata between the sieve
elements that allow transport of sugars between cells!
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Class Phaeophyceae
Ectocarpales
Desmarestiales
Laminariales
Fucales
Celebrity genera: Fucus, Silvetia, Pelvetiopsis, Sargassum, Cystoseira
-  usually saxicolous
-  unattached in few
cases
-  unilocular gametangia
Life History of Fucales
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Receptacle
- swollen tips of fucoids where meiosis occurs
- terminal portion of a branch bearing numerous
embedded conceptacles
Conceptacles
- chambers where the gametes are stored
Conceptacles
Oogonia-
Antheridia-
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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
Gulf Stream, North Atlantic,
Canary and Equatorial!
!
home to Sargassum natans and
fluitans!
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Growth and Construction at a Glance!
Order
Isomorphic
Construction
(Macrothallus)
Growth
(Macrothallus)
Ectocarpales
Heteromorphic Desmarestiales
Laminariales
Diplontic
Fucales
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