Algal Morphology

Algal Morphology
Unicells- solitary cells can be motile or non motile
ex. Chlamydomonas
I. Internal thallus morphologies
II. External thallus morphologies
III.Algal Growth
Colony- an assemblage of individual cells, variable or
predictable number of cells, flagellated or non motile
coenobium- predictable number
and arrangement of cells
ex. Volvox
Filamentous- daughter cells remain attached to each other
following cell division forming a chain of cells
Coenocytic/ Siphononous – one large multi-nucleate cell
lacking crosswalls
Uniseriate- cells occuring in a single row
Utricles -swollen, terminal
end of the siphon
Multiseriate- consisting of
several rows of cells in a
longitudinal seriesin one or
two planes
Codium
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Limited cell differentiation compared to terrestrial plants…
Terrestrial Leaf
Coenocytic thallus construction -
Algal blade
What does this allow?
• Chloroplast movement
What special issues does it raise?
• Herbivory – healing
• Well developed cytoskeleton
• Repairs membrane in 1-2 seconds
• cuticle
• parenchyma (palisade, spongy)
• veins
• epidermal
• guard cells
Medulla
• stomates
Parenchyma – undifferentiated, isodiometric cells
generated by a meristem
Cells division in any plane , not filamentous
Cortex-pigmented cortical cells
– unpigmented medullary cells
Pseudoparenchym a- form of thallus composed of interwoven
continuous filaments, superficially resembles
parenchyma
Sarcodiotheca
Filaments
Hypnea
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Parenchymatous
vs.
Pseudoparenchymat ous
Polysiphonous – composed of tiers of vertically elongated
cells, transversely arranged, the lateral cells around a
central axis (siphon)
Reds only
central cell surrounded by 4 or more pericentral cells
Polysiphonia
Petalonia
Mazzaella
Cortication – elaboration of polysiphonous condition where pericentral
cells continue to proliferate
Filament
(Central Tissue)
Ceramium nitens
Cortical Cells
(Outer Tissue)
Complete Cortication
Ceramium
Cortical Cells
(Banded Pattern)
Partial Cortication
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II. External thallus morphologies
Algal morphology:
sori
Can affect:
thallus
blade
- Photosynthesis
- Nutrient uptake
stipe
- Resistance to herbivory
holdfast
- Resistance to physical disturbance (e.g. wave stress)
Chaetomorpha
Filamentous
non-branching forms
branching forms
Filamentous
Chaetomorpha
Cladophora
Derbesia
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Foliose = a sheet of cells, blade like, no stipe
Monostromatic – one cell thick
Distromatic - two cells thick
Polystromatic – many cells thick
“Petrocelis” stage
Petrospongium
Prostrate / Procumbent: trailing on the ground
Ulva
Hildenbrandia
Bladed- flattened leaf like thallus, may have a stipe
Ralfsia
Stipitate = has a stipe
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Saccate = sac-like
Pneumatocysts-a large float containing gas found in heterokontophyta
-provide buoyancy to lift the blades toward the surface,
allowing them to receive more sunlight for Ps
- can hold O2, CO2, CO
Botryocladia
Cystoseria osmundacea
Halosaccion
Midrib-thickened longitudinal axis of flattened
branch or blade
-catenate series
Sargassum muticum
-singly
Midvein-a delicate median line of cells,
the blade is thicker through this region
Alaria fistulosa
Undaria sp.
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Tubular- tube of cells, hollow in center
Geniculate corallines
Geniculum
(flexible joint)
Intergeniculum
(hard part
between genicula)
• upright
•articulated
•geniculate
Non-geniculate corallines
Calliarthron cheiliosporiodes
Branched- axillary divisions
• crustose
• encrusting
•non - geniculate
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Dichotomous/Bi fur cate
Pectinate/Secund
Whorled/Verticillate
Pinnate-feather-like, regular branching
Distichous-branchi ng on both side of the axis, irregular
Opposite
Alternate
Monopodial-havi ng a distinct main axis of continuous
growth & giving off branchlets
Sympodial- apparent main axis does not extend by continuous
growth
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III. Algal growth
Holdfast Characteristics
apical
holdfast
intercallary
basal
stoloniferous/rhizoidal
hapterous
Where on the algal thallus does cell division occur?
discoid
Apical growth =Apical cell or apical meristem
“Meristem” = area of cell division and growth
Multiaxial- several longitudinal medullary filaments,
each derived from an apical cell
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Uniaxial- one longitudinal central filament forming the axis
Apical around margin
Intercalary
Intercalary growth
Diffuse growth =
No defined area of cell division or growth;
occurs throughout the thallus
“transition zone”
• Growth in both directions away from meristem
• Usually between stipe and blade (or blade and pneumatocyst)
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Trichothallic Growth: Cells divide to form hair (filament)
above and thallus below
Heterotrichous growth – filamentous growth in 2 directions, results
in thallus composed of both prostrate + erect components
(in this case, psuedoparenchymatous polysiphonous…)
Polysiphonia
Upright Form
Filaments
Thallus
Prostrate Form
(Crustose, spreading)
Lithophyllum congestum
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