Rhodophyta-2    

Organelles

Nucleus

They are Eukaryotes and have True Chromosomes. N = 2 - 90

Some simple organisms are Uninucleate.

Complex Organisms are Multinucleate (Coenocytic).

There can be  100 to  1000 Nuclei per cell!

Cell Division & New Wall Organization

The New Cell Wall exhibits Annular Growth.New Wall formation starts from the Outside and proceeds centripetally (towards the center).This is similar to closing an Iris Diaphragm like the Field Diaphragm of a microscope or the diaphragm in a camera lens or in your eye. This is similar to what we saw with Cyanophyta.

A large opening remains between the two cells.

A Protein Plug completely blocks cytoplasmic continuity.

Chloroplasts

There can be from one to many chloroplasts per cell.

Simple Forms have 1 to several.

Larger More Complex Forms have many small chloroplasts.

Ultrastructure

Chloroplasts have a Double Limiting Membrane with Solitary Thylakoids that are Widely Spaced. This is partly due to the presence of Phycobilisomes which protrude above the surface of the Thylakoids.

Chloroplast of Laurencia	Chloroplasts (C) and Starch from a Red Alga	Chloroplast showing Thylakoids with Phycobilisomes

Pyrenoids may be present. These have high
Concentrations of RUBISCO, the enzyme
involved in the Fixation of CO2. Pyrenoids may allow carbon fixation at lower CO2 levels.

The Stroma (matrix) is homogenous &

DNA is present.

Starch (Floridean Starch) is stored in the Cytoplasm which also contains, Mitochondria, Dictyosomes, Endoplasmic Reticulum & Ribosomes.