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Algal Morphology

I. Internal thallus morphologies II. External thallus morphologies III.Algal Growth

Unicells- solitary cells can be motile or non motile ex. Chlamydomonas

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

Uniseriate- cells occuring in a single row

Multiseriate- consisting of several rows of cells in a longitudinal seriesin one or two planes

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

Codium

Utricles -swollen, terminal end of the siphon

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Coenocytic thallus construction - What does this allow? What special issues does it raise?

• Chloroplast movement

• Herbivory – healing • Well developed cytoskeleton • Repairs membrane in 1-2 seconds

Terrestrial Leaf Algal blade

Cortex-pigmented cortical cells

Medulla – unpigmented medullary cells

Limited cell differentiation compared to terrestrial plants…

• cuticle • parenchyma (palisade, spongy) • veins • epidermal • guard cells • stomates

Parenchyma – undifferentiated, isodiometric cells generated by a meristem

Cells division in any plane , not filamentous

Hypnea

Pseudoparenchyma- form of thallus composed of interwoven continuous filaments, superficially resembles parenchyma

Filaments

Sarcodiotheca

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Parenchymatous vs. Pseudoparenchymatous

Mazzaella

Petalonia

Polysiphonous – composed of tiers of vertically elongated cells, transversely arranged, the lateral cells around a central axis (siphon)

central cell surrounded by 4 or more pericentral cells

Polysiphonia

Reds only

Complete Cortication

Ceramium nitens Filament (Central Tissue)

Cortical Cells (Outer Tissue)

Cortication – elaboration of polysiphonous condition where pericentral cells continue to proliferate

Ceramium

Partial Cortication

Cortical Cells (Banded Pattern)

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II. External thallus morphologies

Can affect: - Photosynthesis - Nutrient uptake - Resistance to herbivory - Resistance to physical disturbance (e.g. wave stress)

stipe

holdfast

blade

thallus

Algal morphology:

sori

branching forms non-branching forms

Chaetomorpha Cladophora

Filamentous

Filamentous

Chaetomorpha

Derbesia

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Prostrate / Procumbent: trailing on the ground

Ralfsia Hildenbrandia

“Petrocelis” stage Petrospongium

Foliose = a sheet of cells, blade like, no stipe

Monostromatic – one cell thick Distromatic - two cells thick Polystromatic – many cells thick

Ulva

Bladed- flattened leaf like thallus, may have a stipe Stipitate = has a stipe

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Saccate = sac-like

Botryocladia Halosaccion

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

Cystoseria osmundacea Sargassum muticum -catenate series -singly

Midrib-thickened longitudinal axis of flattened branch or blade

Alaria fistulosa

Undaria sp.

Midvein-a delicate median line of cells, the blade is thicker through this region

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Tubular- tube of cells, hollow in center

Calliarthron cheiliosporiodes

Geniculum (flexible joint)

Intergeniculum (hard part

between genicula)

Geniculate corallines

• upright

•articulated

•geniculate

Non-geniculate corallines

• crustose

• encrusting

•non - geniculate

Branched- axillary divisions

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Dichotomous/Bifurcate

Pectinate/Secund Whorled/Verticillate

Pinnate-feather-like, regular branching Distichous-branching on both side of the axis, irregular

Opposite Alternate

Monopodial-having a distinct main axis of continuous growth & giving off branchlets Sympodial- apparent main axis does not extend by continuous growth

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stoloniferous/rhizoidal

Holdfast Characteristics

hapterous

holdfast

discoid

Where on the algal thallus does cell division occur? “Meristem” = area of cell division and growth

apical

basal

intercallary

III. Algal growth

Apical growth =Apical cell or apical meristem 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

“transition zone”

• Growth in both directions away from meristem • Usually between stipe and blade (or blade and pneumatocyst)

Diffuse growth =

No defined area of cell division or growth; occurs throughout the thallus

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Trichothallic Growth: Cells divide to form hair (filament) above and thallus below (in this case, psuedoparenchymatous polysiphonous…)

Filaments

Thallus

Polysiphonia

Heterotrichous growth – filamentous growth in 2 directions, results in thallus composed of both prostrate + erect components

Upright Form

Prostrate Form (Crustose, spreading)

Lithophyllum congestum