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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!

stipe

holdfast

blade

thallus

sori

Pneumatocysts- !!- large float containing gas found!! !

!!- O2, CO2, CO!

Cystoseria !! ! !Sargassum !Catenate ! ! ! !singly!

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Midrib

Undaria sp.!

Fucus!

Laminaria!

-  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!

Phaeophyceae Thallus Morphology:!

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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)!

-  Ice-cream!!

-  Frosting!!

-  Paints!

!

!-  Food = �kombu� in Japan; dried and shredded laminarians!

Human Uses for Alginates!

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Plasmodesmata = connections between adjacent cells, formed during cell division = cell-to-cell transport of photosynthetic products and cell communication !

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!

- xylem = non-living!

- sieve elements = alive!

- sieve elements lack!organelles!

- companion cells!

Algae!- conduct sugars and some nutrients!

- all cells living!

- sieve elements = alive!

- sieve elements w/o organelles except mitochondria!

- 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 !!

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!

Laminarin function!-  storage glucan = polymer of glucose!-  used as additive for pork patties!-  main form of food storage in brown algae!

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Phaeophyte Reproduction:!

Unilocular = spores/gametes produced in a single compartment!!�unangia�!

Plurilocular = many small chambers (locules); one spore/gamete per chamber!!�plurangia�!

Gametangia = structure where gametes are formed !Sporangia = structure !where spores are formed !

uniseriate multiseriate

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!

Phaeophyte Flagella:!

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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

Functional Anisogamy

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 !

Phaeophyte Habitat!

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12 orders within the Phaeophyta

Our focus will be on the following 4 orders:

Class Phaeophyceae

Chordariales Ectocarpales 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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Celebrity genus: Ectocarpus

Class Phaeophyceae

Desmarestiales Ectocarpales Laminariales Fucales

-  mostly epiphytic

-  uniseriate filaments

-  opportunistic = excellent colonizers - Female gametes releases pheromone ectocarpene, hormosirene

Life History of Ectocarpales:!

meiosis!

Asexual reporduction by plurilocular sporangia = sporophyte!Sexual reproduction is dioecious and anisogamous!

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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!

-  Saxicolous

-  Low intertidal to subtidal

-  �Acid weed�

Celebrity genus: Desmarestia

Class Phaeophyceae

Desmarestiales Ectocarpales Laminariales Fucales

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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

Desmarestiales Ectocarpales 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

stipe

holdfast

blade

sorus (pl: sori)

haptera

sporophylls

Sorus/sporophyll - sporangia!!Hapteran holdfast = always submerged, multiple �branches�!! !

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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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Meristoderm/outer cortex – !Inner cortex – !Medulla – !Meristodermal growth gives thallus girth (mostly), mostly periclinal cell division!

Meristodermal Growth!

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

Desmarestiales Ectocarpales 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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Conceptacles - chambers where the gametes are stored

Receptacle - swollen tips of fucoids where meiosis occurs - terminal portion of a branch bearing numerous embedded conceptacles

Oogonia-

Conceptacles

Antheridia-

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Fucus Silvetia Pelvetiopsis

Midrib Playdough stipe Flattened stipe

8 eggs per oogonium 2 eggs per oogonium 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 Construction

(Macrothallus) Growth (Macrothallus)

Isomorphic Ectocarpales

Heteromorphic Desmarestiales

Laminariales

Diplontic Fucales