Specialised cells

stephanokont zoospores

Oedogoniales

massive band forms ring on surface,

connects basal bodies of 40 flagella just beneath plasma membrane

Charophyceae (3)

gyrogonites

zygote oospore enveloped by acetoresistant cell wall and calcified cells

meiosis produces filamentous Prochara

Zygnematophyceae

zygospores:

parthenospores

aplanospores

akinetes

zygospores

thick walled, dormant stage

often germinate in spring or at end of dry period when temporary pool/stream restored

parthenospores

develop from an unfertilized gamete after unsuccessful conjugation, and are therefore haploid

aplanospores

asexual, lack flagella

develop from an unfertilized gamete after unsuccessful conjugation, and are therefore haploid

akinetes

larger than regular cells, retaining some metabolic function unlike spores

Zygnema pre-akinets

essentially old vegetative cells.

When the medium begins to lack nutrients, the fiber stops dividing and the cell contents begin to thicken, lipid storage substances are formed and osmotically active substances accumulate, the cell wall thickens, more mucus forms around the fibers, and the chloroplasts are smaller, rounder, without lobes.

After some time, the fibers can also break down into shorter fibers, which helps them spread by wind.

These pre-akinets are resistant to drying out and osmotic stress

They still photosynthesize, but due to the lack of nutrients, they produce lipids and carbohydrates from them, which help them survive various stresses.

Zygogonium aplanospores

forms aplanospores (cells arising inside the mother cell), while a portion of the cytoplasm with a brown coloration remains in the original cell.

This is probably an elegant way for Zygogonium to get rid of too high a concentration of iron, which can be toxic to the cell.

statoliths

Charophyceae

precipitated crystals of barium sulfate in their cells, which are probably involved in the perception of gravitropic signals

Chara surface of internode (2)

covered by multinucleated cortical cells in two-three layers which are

encrusted with calcium carbonate

Dasycladales gametangial cyst (4)

nuclei enveloped by cell wall

further multiplication of nuclei

thick-walled cyst overcomes unfavourable period

in suitable conditions, isogametes formed in cyst, released through lid

Bryopsidineae zoospores (6)

often stephanokont

large number of flagella (approx 35 pairs)

arranged in wreath in apical part of zoospore

basal bodies arranged one next to the other

lower amorphour ring and upper unstriated ring, connect basal bodies and anchor them to cell

between basal bodies are microtubular roots alternating in number 6-4-6-4

Algaenans hypnozygotes

Chlamydomonas

Algaenans made of

aliphatic hydrocarbon chains, crosslinked

Algaenans zygospores

Dunaliella

Algaenans akinets

Haematococcus