1. Spirogyra.docx final (1)

Zygospore germination requires the outer wall of the spore to absorb water, swell up, and burst, exposing the inner layer as a cylindrical germ tube.

A zygospore is a thick-walled diploid sexual spore formed during the sexual reproduction of Spirogyra, released after the decay of the female filament, and serves as a resting spore resistant to unfavorable environmental conditions.

Spirogyra reproduces through vegetative reproduction (fragmentation), asexual reproduction (akinete and aplanospore formation), and sexual reproduction (conjugation).

Lateral conjugation occurs between cells of the same filament in homothallic species and can happen through indirect or direct methods, leading to the fusion of male and female gametes and the formation of a zygote or zygospore.

Aplanospore is a thin-walled non-motile asexual spore produced under unfavorable conditions by more than 20 species of Spirogyra, formed when a vegetative cell loses water, rounds up, secretes a thin wall, and develops into a spore.

During germination, a cylindrical germ tube is formed, which divides transversally to create a two-celled structure.

Chloroplasts in Spirogyra are spirally coiled ribbon-like structures that are involved in photosynthesis and contain pyrenoids that store starch.

Scalariform conjugation is a type of sexual reproduction that occurs between cells of two different filaments of opposite strains, where the cells lie parallel and close under a common sheath, forming a conjugation tube through which male gametes pass to fuse with female gametes, resulting in zygote formation.

Spirogyra is commonly found floating in freshwater resources like ponds, lakes, and ditches, and some species are also found in slow-running streams or rivers.

Spirogyra is a green algae belonging to the class Chlorophyceae, comprising more than 300 species, most of which are free-floating, while some are attached to substratum by rhizoids.

Vegetative reproduction in Spirogyra occurs by fragmentation, where mechanical damage or death of intercalary cells leads to the formation of fragments that can grow into new filaments.

The filament gets detached from the substratum and becomes free-floating Spirogyra.

Akinetes are thick-walled resting spores formed during unfavorable conditions among some species of Spirogyra, which can germinate into new filaments when conditions become favorable.

The lower cell forms rhizoids that attach to the substratum, while the upper cell divides repeatedly to form a new filament.

Before germination, the diploid nucleus of the zygote divides meiotically into haploid nuclei, with three degenerating and only one becoming functional.

The thallus of Spirogyra is an unbranched multicellular filamentous structure formed by the arrangement of cylindrical cells head to head in a single row.

The cell wall of Spirogyra is double-layered, with the outer layer made of pectin and the inner layer made of cellulose.