Chlorophyta

Diversity = Great

Genra = 450 & Species = 7,000

Color

The color of Chlorophyta range from Green to Orange. The orange color is due to Carotenoids which form the Accessory Pigments for this Division.

Their Photosynthetic Pigments are Similar to those of Vascular Plants.

Chlorophyll a, b are typically present along with

a, b Carotene plus Xanthophylls.

The Cell Wall is very similar to that of terrestrial plants because its main components are Cellulose & Pectins.

Occurrence

This Division has a larger number of Freshwater speceis than Marine species. Marine species tend to be larger than those found in freshwater. However, the Chlorophyta do not produce organisms that approach the size of large Kelps

A few speceis exist on snow fields and AlgaeAntarcticSnow.jpg (23037 bytes) Glaciers. They tend to have high concentrations of Carotenoids which are responsible for the red hue of the cells. These are called "Snow Algae". They can be found in the Rocky Mountains, the Cascades the Arctic and Antarctic as well as most areas where there are permenant or semipermanent snow-fields. It would be interesting to see if they occurred on the volcanic peaks of Hawai'i.

Untroden Red Snow

Red Snow containing foortprints of a Yeti named David Webb

Life Modes - They are autotrophs. FlagelatedCellHue.jpg (11097 bytes)

Some speceis form Symbioses with Lichens, Hydra & Mollusks.

Ultrastructure

They are Eukaryotes and have the "Usual Suspects" when it comes to organelles.

Some species form Cell Plates that are similar to those found in land plants.

There are many speceis that have Flagella.

Volvox26bNihonFlagella400Lab.jpg (42925 bytes) Volvox26bNihonFlagella400Embos.jpg (52577 bytes)

Chloroplasts have the typical Double Boundary Membrane.

The Thylakoids can produce Parallel Bands of Three Thylakoids or Thylakoids whch have Irregular Stacks as well as Grana.


Chloroplasts Irregular Bands Stacking Thylakoids	Chloroplast Bands of 3 Thylakoids	Chloroplasts with Grana

Chloroplast Shape varies. The trend is towards an increase in Surface Area.

Common Chloroplasts Shapes include

Cup Filament Star Reticulate (Net) Banded

NONE have the Discoid Shape of most Terrestrial Plants

Spirogyra has spiral Chloroplasts	Ulothrix has band-shaped Chloroplasts	Zygnema has Star-shaped Chloroplasts
Chalmydomonas has one cup-shaped Chloroplast	Cladophora has many small oval Chloroplasts	Mougeotia has a flat Chloroplast. The disk-like areas are Pyrenoids.

Pyrenoids occur in most species.

PyrenoidChlamyLab.jpg (55954 bytes)

Pyrenoid in Chlamydomonas

Starch is the major storage product.

Starch is stored in the Stroma of the Chloroplast.

This is unusual for Algae. It tends to make the Chloroplasts have a lumpy appearance. Note the Chalmydomonas above.

Most Algae store starch in the Cytoplasm.

Morphological Diversity

There is a wide range of morphological diversity . There are Unicellular, Filamentous, Siphonous, Multicellular, Colonial, Parenchymatous, Motile, Nonmotile types.

A Unicellular Form Volvox is a Colonial Alga	Cladophora is a Filamentous AlgaAcetabularia is Coenocytic & is called Siphonous because it has one large cell with many Chloroplasts and Nuclei.
Coleochaete is Parenchymatous

Their Size Ranges from microns to 8 m.

The Chlorophyta have been divided into several Classes by some Taxonomists. These are indicated below. This classification may be dated but it will help us keep track of major groups as we study their morphological and reproductive adaptations.

Chlorophyceae = Largest # of Species

Predominately Fresh Water

Charophyceae = Most Complex

Lead to Land Plants

Ulvophyceae = Primarily Marine

Marine Species -> Isomorphic Alteration of Generations

Only Chlorophytes with Alternation of Generations with Sporic Meiosis

Ulva

Broad Thallus

Two Cells Thick

Cells

1 Nucleus

1 Chloroplast

Length= Up to 1 m

Holdfast -> Anchorage

Ulva Life Cycle

Dioecious Haploid Thalli

Gametophytes -> Marginal Gametangia

Single Cells -> Mitosis -> Biflagellate Gametes

Zoospores (Motile) (+ Male) (- Female)

Syngamy

Zygote -> Diploid Thallus Sporophyte (2N)

Isomorphic

Identical to Gametophytes

Meiosis -> Zoospores (Gametes)

Anisogamous + Male &

- Female (Larger)

Haploid Gametophytes

Siphonous Forms

Large Cells with Many Nuclei (Coenocytic)

Common in Tropical Waters

Genera (All in Hawaii)

Codium

Symbiotic in Mollusks

M -> Graze on Codium

Chloroplasts Persist

Respiratory Canal

Nudibranchs Produce Surplus Oxygen

Caulerpa

BryopsisBIDOD300.jpg (39867 bytes)
Bryopsis

Bryopsis

Ventricaria (Valonia)

Halimeda

Calcareous Walls

Accumulates AntiFeeding Chemicals

Discourages Grazing

Charophyceae

Growth Forms

Unicell -> Filaments ->
Complex Parenchymatous Organization

Some -> Cell Plate & Phragmoplast

Example Genera

Desmids (Unicellular) & Spirogyra (Filamentous)


Closterium - A Desmid	Spirogyra

Plant-Like Forms

Ancestors thought -> Terrestrial Plants

Charales

Coleochchaetales

Mitosis = Same as Terrestrial Plants

Dissolution of Nuclear Envelope

Cell Plate Formation

Phragmoplast

Oogamous Sexual Reproduction

ColeoColonies240.jpg (18337 bytes)

Coleochaaete Colonies

Coleochaete

Surface Growth in Ponds

Marginal Meristem -> Disk-Shape

Several Layers Thick

Parenchymaous Growth

Ancestral Traits ->

Coleo100-240.jpg (26755 bytes)

Coleochaete 100 X

Similar to Terrestrial Plants

Multicellular Antheridia

Flagellar Apparatus

Peroxisomes

Zygotes Protected by Unicellular Layer


Coloechaete 400X	Coloechaete 1000X