Spirogyra reproduces by the following three ways, such as-
1) Vegetative reproduction
2) Sexual reproduction and
3) Asexual reproduction
Sexual reproduction: It usually occurs in two following ways
- Scalariforrn conjugation and
- Lateral conjugation
Scalariforrn conjugation: When conjugation occurs between two gametes (male and female) of two different filaments of the same species lying close to each other parallelly, with the help of a conjugating tube. it is called scalariforrn conjugation.
Process: Two heterothallic filaments bearing different gametes, come close to each other parallelly and they are covered with a gelatinous membrane.
Formation of conjugation tube
- Two outgrowths are formed out of walls of two cells lying opposite to each other
- These two outgrowths grow up and come in contact with each other and the touching point fuses to form a conjugation tube
- When these tapes of conjugating tubes are formed at many places in between two filaments, the whole structure seems to be a ladder.
Formation of gametes:
i) This time, due to dehydration, protoplasm contracts, giving rise to gametes of similar structure
ii) In this case, all the cells of one filament, turn into motile mare gametes and all the cells of other filament turn into static female gametes.
2) Lateral conjugation: When conjugation occurs between two cells remaining side by side of the same filament, it is known as lateral conjugation.
Process: Lateral conjugation occurs in two ways, such as-
I) Direct type of lateral conjugation
II) Chain type of lateral conjugation
Direct type of lateral conjugation:
- Conjugating tube is formed out of two cells remaining side by side, one acts as male gamete (active) and the other as female gamete (static)
- The male gamete (n) enters the female gamete (n) of the nearest cell and fertilizes it breaking the partition wall
- Through fertilization, a zygospore is formed containing diploid number of chromosomes
- In favourable condition, zygospore gives rise to a new Spirogyra plant through germination
- This type of conjugation is found in Spirogyra jogensis.
II) Chain type of lateral conjugation:
i) Any side of the partition wall of two cells remaining side by side of the same Spirogyra filament, breaks down forming a passage called conjugation tube.
ii) During this time, the protoplasm of the two adjacent cells participating in conjugation contracts by losing water to form two different gametes
iii) The active gamete (male gamete} unites (n+n) with the inactive gamete (female gamete) of the nearby cell producing zygospore (2n).