Spirogyra

Question 1

Common name :

Answer 1

Pond silk / Water silk

Question 2

Habitat :

Answer 2

Spirogyra is commonly free floating fresh water algae, found in pond, lake , pools, slow running rivers.

Question 3

Habit :

Answer 3

Plant body is gametophytic thallus.
The thallus is long silky thread like structure called filament.

Question 4

Cell wall :

Answer 4

Rigid ,Protective , made up of outer Pectin and inner Cellulose, outer Pectin dissolves in water and forms Mucilage that make filament shiny and slippery structure.

Question 5

Cell membrane :

Answer 5

Present in between cell wall and cytoplasm. Generally made up of lipo-protein.

Question 6

Cytoplasm :

Answer 6

Cytoplasm is peripheral due to presence of central large vacuole , such type of cytoplasm is called primordial utricle.

Question 7

Chloroplast :

Answer 7

In each cell of spirogyra, there is presence of 1 (S. indica) - 16 (S. rectispora) chloroplasts.

Question 8

Some spirogyra are attached to the substratum with ?

Answer 8

Holdfasts

Question 9

Vacuole is situated at?

Answer 9

Center, surrounded by vacuolar membrane called tonoplast and a fluid mass called cell sap.

Question 10

Nucleus :

Answer 10

Single haploid well defined nucleus at the center vacuole due to presence of number of protoplasmic strands. Those protoplasmic strands join nucleus with cytoplasm.

Question 11

Reproduction in spirogyra is done by how many methods?

Answer 11

By all three methods :
1. Vegetative Propagation
2. Asexual Propagation
3. Sexual Propagation

Question 12

Vegetative propagation in spirogyra is done by?

Answer 12

It is the most common type of reproduction in Spirogyra that takes place by fragmentation due to mechanical injury, change of pH of water or death of intercalary cells. Each fragment later independently forms long filament of Spirogyra by repeated process of mitosis.

Question 13

Asexual reproduction in spirogyra is done by?

Answer 13

On unfavorable conditions it takes place by formation of two kinds of non-motile spores : akinetes and aplanospores.

Question 14

Akinetes :

Answer 14

Highly thick walled resistant non-motile spores formed by the cells of Spirogyra during extreme unfavorable condition by accumulation of large amount of food. During favorable condition, extra layers of akinete dissolves and divides several times mitotically to form a new filament of spirogyra.

Question 15

Aplanospores :

Answer 15

Thin walled , non-motile resting spores formed by Spirogyra during unfavorable condition by accumulation of some amount of food. During favorable condition, aplanospores germinate into new filaments of Spirogyra.

Question 16

Sexual reproduction in spirogyra takes place by?

Answer 16

Spirogyra shows conjugation type of sexual reproduction during favorable conditions when there is suitable environment and sufficient food. Conjugation is of isogamy type of sexual reproduction that involves transfer of male gamete to female gamete through a conjugation tube or by any other means. Spirogyra shows two types of conjugation, they are : Scalariform conjugation and Lateral conjugation

Question 17

Scalariform conjugation :

Answer 17

It is a ladder like conjugation that takes place in two different filaments of opposite strains (+ve and -ve) at night.
During scalariform conjugation, two filament of opposite strains come close to each other and le side by side parallelly and get surrounded a common sheath of mucilage. They form small outgrowth or protuberances (papillae) in opposite directions. These outgrowth dissolve by enzyme cytase and forms hollow tubular structure called conjugation tube. All protoplasmic mass of male gametangium is transferred to the female gametangium through the tube. They fuse to form highly thick walled diploid structure called zygospore.

Question 18

The three layers of zygospore are:

Answer 18

1. Exospore
2. Mesospore
3. Endospore