Lecture 4: Brown algae /stramenopiles and brown algae
TSAR
telonemia, rhizaria
alveolata
stramenopiles
oomycetes of of phyt… casued the irish famine
introduction to stramenopiles
they have one phase in their life cycle where they have heterokont flagella
lineage supported by molecular data and a morphological synapomorphy
presence of flagellate cells during their life cycle
heterokont (unequal) flagella
longer flagella with tripartite (a base, a tubular shaft, and one or more terminal hairs) tubular hairs (…
diversity of stramenopiles
diatoms and brown algae are the best known members
the group also includes
heterotrophic protists
parasites of plants and animals
environmental clades
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secondary endosymbiosis
a heterotrophic eukaryote engulfs a green or red algal cell (also eukaryotic), aquiring its plastid
…….
the outer cell wall can sometimes be a part of the ER in a heterokont
secondary red plastids arose more than once
…….
cytology and some properties
cell wall
cellulose microfibrils + matrix of alginates and fucans
alginates (alginic acid): located mostly within the intercellular matrix
fucans (sulfated polysaccharides):
function not well understood
……
alginates
alginic acid = polymer of mannuronic acid and guluronic acid, and Na+, …
more rigid algae if there is more Guluronic acid
plastid
plastids are specialised, membrane-bound organelles found in plant and algae cells
key types include chloroplasts (energy productino, pigments), and leucoplasts (starch/lipid storage)
phaeoplast (= chloroplasts of brown algae)
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pyrenoids
they are considered to be functinoally analogous to the carboxysomes of oxygenic cyanobacteria in containing aggregates of the enzyme Rubisco
photosynthetic reserves
main reserve: laminaran
water soluble; stored in cytoplasmic vacoules
does not form stainable grains
physods and phlorotannins
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morphology
there i no unicellular brown algae
simplest forms: uniseriate, branched filaments
heterotrich thallus: both creeping and upright branches
complex thallus forms
crusts
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reproduction
most brown algae have a diphasic sexual life cycle
alternation between …..
life cycle type
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