Spirogyra

One of the most common forms of free-floating freshwater algae is the spirogyra algae. You can find it on the surface of ponds, lakes, pools and other stagnant water sources. The word Spirogyra has been derived from two Greek words – Speria (meaning coil) and gyras (meaning twisted). 

Thus, from its name, you can also derive the basic structure of spirogyra. However, before learning more about its shape and characteristics, let us take a look at its classification, which is crucial in understanding some of its traits which are mentioned later.

Spirogyra Classification

Division

Chlorophyta

Class

Chlorophyceae

Order

Zygnematales

Family

Zygnemataceae

Genus

Spirogyra

Species

Spirogyra maxima, S. elongate, S.adnata, S. negnecta, etc. 

 

Now that you know more about the classification of spirogyra, learn about some of the primary traits shown by such algae.

Spirogyra Characteristics

Spirogyra algae will exhibit the following characteristics – 

  • Ranging between two and ten, spiral-shaped ribbon-like chloroplasts exist inside them. Each chloroplast houses several pyrenoids.

  • Their bodies are characterised by multicellular filaments, which is present underneath a mucilaginous sheath.

  • You can find pectin and cellulose on the cell walls of such algae.

  • Reproduction occurs both sexually and vegetatively.

  • Spirogyra mostly exists in slow-running water bodies, such as ponds, pools and smaller lakes. One can identify it through the silky sheen that it gives off on the water’s surface. 

  • Vegetative reproduction only occurs at lower temperatures. In all other conditions, sexual reproduction is the preferred method for fertilisation. 

Before learning about its structure, check out this spirogyra diagram, where one cell has been magnified to point out its various parts.

Vegetative Structure of Spirogyra

Refer to the points below to assess the structure of spirogyra algae in its vegetative state.

  • Cells are green-coloured, un-branched filamentous and cylindrical shaped. 

  • Basal differentiation is absent in free-floating species.

  • In sedentary species, basal differentiation may occur in the form of an attachment organ, called holdfast or haptera.

  • The cell walls have three distinct layers, and they are striated.

  • The outer layer is composed of pectose, while the other two cell wall layers are made out of cellulose.

  • Some species may show an additional yearly growth of cellulose in the cross wall, leading to the formation of replicate walls. 

  • A granular, vacuolated protoplast exists as a thin lining inside cell walls. This layer is also known as the primordial utricle.

  • A tonoplast separates a vacuole from the cytoplasm surrounding it. This tonoplast is a semi-permeable membrane.

Before proceeding further, let us see how much you learned till now.

Multiple Choice Question

Q. Which of the Following is Present Inside Spirogyra Chloroplasts?

  1. Tonoplast

  2. Haptera

  3. Cellulose

  4. Pyrenoid

Ans. (d) Pyrenoid

Reproduction in Spirogyra

As stated previously, spirogyra follows two types of reproduction, namely vegetative and sexual.

  1. Vegetative Reproduction of Spirogyra

Fragmentation is responsible for the vegetative reproduction in such algae. The cell walls of two adjoining cells weaken and form fragments, which turn into filaments through their cellular division. In some cases, this filament breaks due to external injuries to the cell as well.

  1. Sexual Reproduction of Spirogyra

In sexual reproduction, conjugation occurs between two morphologically identical gametes. Each of these gametes is known as gametangium. One of them is motile, while the other is non-motile. Sexual reproduction occurs through one of two types of conjugation – scalariform or lateral conjugation.

What is Scalariform Conjugation?

In scalariform conjugation, two filaments come together and subsequently lie together. You can compare the resulting structure to that of a ladder. Some characteristics of such reproduction include – 

  • Male and female gametes fuse together, leaving one of them empty and the other full of zygotes. 

  • The fusion occurs through conjugation canals formed between the two cells lying next to each other during this reproduction.

  • Zygotes escape from the parent filament after the latter decays. After escaping, these zygotes germinate when conditions are favourable.

What is Lateral Conjugation?

Here, the conjugation occurs between adjacent cells within the same filament. The cells participating in the conjugation develop protuberances. As these protuberances increase, cellular matter from one cell fuses with the other. Such a conjugation leads to the formation of diploid zygospore. Such conjugation is also known as chain-like conjugation.

Life Cycle of Spirogyra

To understand the life cycle of a spirogyra, consult the diagram below. 

In this cycle, the alternation of haploid and diploid generation is noted. The former phase tends to be longer. However, the diploid generation is relatively much short-lived. Furthermore, diploid is restricted to the zygospore alone.

Preparation and Rest is a Must!

Now that you know all about spirogyra algae, take some time out for yourself as well. Preparation for NEET is a serious matter, requiring determination and discipline. However, ensure that you are mindful of your health as well. Derive plenty of nutrition from a balanced diet and sleep for at least 7-8 hours every day.  

While learning about spirogyra reproduction or any other topic, avoid panicking. Plan out your lessons for each day and set achievable, short-term goals. Gauge your progress regularly by solving question papers from previous years. 

Best of luck!

FAQ (Frequently Asked Questions)

1. What is the Size of Spirogyra?

Ans. Spirogyra can range between 10-100 µm in width. They can go up to several centimetres in length.

2. Why is Spirogyra Considered Autotrophic?

Ans. Spirogyra contains chlorophyll, which they can utilise to conduct photosynthesis. Therefore, the ability of spirogyra to produce their own food is what classifies them as autotrophic.

3. What is the Primary Difference Between Lateral and Scalariform Conjugation?

Ans. Scalariform conjugation occurs between two filaments of cells lying side by side, while the lateral conjugation occurs between two adjoining cells. Additionally, scalariform conjugation is also known as a ladder conjugation since it forms a structure resembling a ladder. Lateral conjugation, on the other hand, forms a chain.

4. What is the Specific Condition for the Occurrence of Vegetative Reproduction in Spirogyra?

Ans. Vegetative reproduction primarily occurs only when temperatures fall. However, under normal or higher temperature conditions, spirogyra primarily follows a sexual reproductive system.