Question

Under what conditions algae enter the palmella Stage ?

Answer 1

Hint: The palmella stage is formed under unfavorable conditions such as shortage of water, excess of salts, etc. The protoplast of the parent cell divides to make many daughter protoplasts but they do not form zoospores.

Complete step by step Answer:
Palmella stage is formed under desiccation conditions and also in the presence of toxic salts.
A colonial aggregate of immobile non-flagellated individuals occurring regularly in the life cycle or in response to increased firmness of medium of some flagellated green algae or plantlike flagellates (as members of the genera Euglena and Chlamydomonas).
Sexual reproduction in algae results in the formation of zygospores.
- ‘Algae’ is an informal term used for a large group of organisms that include diverse life forms. They are primarily photosynthetic, eukaryotic organisms. They are surrounded by a thick cell wall. It is made up of cellulose and carbohydrates. Various other chemical components like pectin, silica, and agar are also seen. They exhibit a wide range of reproductive methods like vegetative reproduction, simple asexual cell division, and complex forms of sexual reproduction.
- During the sexual reproduction of algae, two competent cells recognize each other, conjugate, and lead to fertilization. This forms a zygote, which by secreting a thick wall, acts as a penetrating spore, called ‘zygospores’, which help in penetration, dispersal, and multiplication.
- Many small algae reproduce asexually by fragmentation, whereas larger algae reproduce by spores. - A few red algae produce ‘monospores’ that are carried by water currents and upon germination produce a new organism.
- Some green algae produce non- motile spores called ‘aplanospores’, while others produce ‘zoospores’, which lack true cell walls.
- The life cycles of sexually reproducing algae is variable. In some, the dominant stage is the sporophyte, while in others it is the gametophyte.

Notes:
- Zygospore is a dormant stage with a large food reservoir and thick resistant cell wall.
- Oospores are thick- walled sexual spores. They develop from a fertilized oosphere in some algae fungi and oomycetes.
- Zoospores are motile asexual spores. They use flagellum as a locomotory organ. They are also called ‘swarm spores.’
- Zygote formation is seen in Chlamydomonas during oogamy.