Chlorophyceae

The members of Chlorophyceae are the green algae — the group whose fresh, grass-green colour makes them the most familiar of the algae.

Body organisation

The plant body of a green alga is not fixed to one design. It may be:

• Unicellular (a single cell),
• Colonial (many cells living together), or
• Filamentous (cells joined in threads).

Colour and pigments

These algae are usually grass green because the pigments chlorophyll a and chlorophyll b dominate. The pigments are not scattered loosely; they sit in well-defined chloroplasts. The shape of the chloroplast differs from species to species and can be discoid, plate-like, reticulate (net-like), cup-shaped, spiral or ribbon-shaped.

Pyrenoids and food storage

Most green algae contain one or more special storage bodies called pyrenoids, which lie within the chloroplasts. A pyrenoid holds protein in addition to starch. Some green algae store their reserve food instead as droplets of oil.

Cell wall

The cell wall is generally rigid and built in two layers — an inner layer made of cellulose and an outer layer made of pectose.

Reproduction

• Vegetative reproduction usually occurs by fragmentation of the thallus.
• Asexual reproduction takes place through flagellated zoospores, which are produced inside structures called zoosporangia. …