Rhodophyta

Outline

Introduction

a.k.a. rhodophytes, red algae

mostly marine

of great economic importance

Cells

Flagella -- none!

Cell wall

fibrillar layer -- cellulose or polymers of other monosaccharides

amorphous layer -- mucopolysaccharides, e.g., agar, carrageenan

some deposit CaCO₃ -- coralline red algae

Chloroplasts -- typically:

chlorophylls a + carotenoids

phycobilisomes with especially phycoerythrin (also phycocyanin)

thylakoids single

2 membranes

reserve polysaccharide = Floridean starch, made by pyrenoid

Nucleus

mitosis: closed

nuclear envelope persists

spindle apparatus microtubules form inside nucleus -- organized by polar rings

cytokinesis

walls grow from outside... incompletely

pit plug fills the gap

secondary pit connections can be made

Morphology

various, usu. filamentous, esp. pseudoparenchymatous

Life cycle -- diplohaplontic, but with a difference...

three multicellular stages, two of them diploid

gametophyte -- makes gametes

carposporophyte -- makes carpospores in carposporangia

tetrasporophyte -- makes tetraspores in tetrasporangia

generations may be

isomorphic -- e.g., Polysiphonia

heteromorphic -- e.g., Porphyra

also asexual reproduction via monospores

Ecology

warm water marine (mostly)

mostly macroalgae, periphyton

some are:

• found in deep water
• coralline
• parasitic

Economic importance

agar

carrageenan

nori

Vocabulary

click here to go to Rhodophyta vocabulary