2. OCCURRENCE
⢠Gr. oulos, woolly; thrix, hair
⢠About 30 sps
⢠Fresh water, (U. aequalis, U. zonata)
⢠saline (U. flacca, U. pseudoflacca)
⢠Lithophytes (U. implexa)
⢠Prefer cold water- rainy season to spring
⢠U.variabilis, U. oscillarina
⢠U. zonata, U.tennerima,
4. CELL STRUCTURE
⢠Outer pectin, inner cellulose
⢠Cytoplasm produce lining layer- primordial utricle
⢠Single nucleus, vacuole, single girdle shaped
chloroplast
⢠or C- shaped, collar-shaped or ring-shaped.
⢠One (U. rorida) or more (U. zonata) pyrinoids
7. TYPES OF ZOOSPORE
⢠The protoplast either develops into single zoospore (U.
fimbriata) or undergoes division and form 2, 4, 8, 16 or 32 units.
⢠Each unit contains single nucleus and cytoplasm
⢠i. Quadriflagellate macrozoospores- usually 4 per cell,
⢠ii. Quadriflagellate microzoospores- usually 8 per cell, and
⢠iii. Biflagellate micro- zoospores- usually 16-32 per cell.
8. ⢠Cell contents get enriched with food
⢠Two division- right angles
⢠Inner wall of cell develops into vesicle
⢠Macrozoospore swim in vesicle for some
time.
⢠Spore releases after vesicle dissolved
⢠swim for few to 24 hours
⢠Each spore has
⢠Band like chloroplast
⢠Pyrinoid
⢠Anterior stigma
⢠Pointed posterior end
⢠Anterior flagella
MACROZOOSPORE
9. ⢠Protoplast divides and produce 8,16 or
32 cells
⢠can swim for 2-6 days
⢠Each spore has
⢠Chloroplast
⢠Pyrinoids
⢠Stigma
⢠Pointed anterior end and round
posterior
⢠Quadri or biflagellate
MICROZOOSPORE
10.
11.
12. APLANOSPORE
⢠With the sudden change of environment towards unfavourable
condition during zoospore formation the protoplast units do not
form flagella and remain inside the mother cell as non-motile
units.
⢠These unicellular; uninucleate, thin walled non-motile units are
called aplanospores During favourable condition they germinate
after or before liberation from parent cell.
13. HYPNOSPORES
⢠During drought, sometimes the entire protoplast of a cell may
round up and forms a single thick walled structure, the
hypnospore. During favourable condition it germinates and
develops into a new filament.
14. AKINATES
⢠During extreme unfavourable condition
⢠Cell becomes enlarged, protoplast accumulates food material.
⢠Forms thick wall around itself.
⢠This thick walled resting vegetative cell is called akinetes
⢠It is found in U. zonata, U.acrorhiza, U. oscillarina etc.
15. PALMELLA STAGE
⢠Forms during drier condition
⢠Protoplasts divides and produce many aplanospores
⢠The wall of the aplanospore mother cell becomes mucilaginous.
⢠Consequently the wall of aplanospores also gets enveloped by mucilaginous
substance. These coverings protect the aplanospores against desiccation.
⢠In this way -many green round bodies become enclosed in a mucilaginous
mass, called palmella stage.
⢠During favourable condition these green bodies come out by the dissolution
of the mucilage covering and germinate into new plants.
16.
17. SEXUAL REPRODUCTION
⢠Isogamy
⢠During End of the season
⢠Heterothallic
⢠Homothallic (U. rorida)
⢠Gametangium- zoogamete = microzoospore
⢠Number of gametes may be 8, 16, 32 or 64.
⢠Gametes are morphologically similar, they are physiologically different and
designated as + and â strains.
⢠Zygote spindle shaped. Round off
⢠Resting period 5-8 months
⢠Meiosis â 4 meiospore (2+ and 2-)
⢠Parthenogenesis- parthenospore- azygospore