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Difference Between Unilocular and Plurilocular Sporangia

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Algae: An Introduction

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You may be surprised to know that oxygen for breathing for aquatic animals is produced by algae. Did you know there are so many varieties of algae? Some of the algae are red-colored, some of the algae are brown-colored, and some of the algae are green due to the presence of different pigments. Ectocarpus is also one of the brown algae. Both types of sporangia are present in ectocarpus unilocular and plurilocular.

What is Ectocarpus?

Ectocarpus is a type of fungus. It is a brown alga and has a filament known as filamentous algae. It is a type of marine algae found all over the world. There are two main species of Artocarpus - Ectocarpus siliculosus, and Ectocarpus fasciculatus. Its thallus is branched and has erect and prostrate branches. Cells of filament are uninucleate and cylindrical. Their cell wall is composed of cellulose and pectin. These algae are brown-colored due to the presence of a pigment called fucoxanthin.

What is Sporangia?

A sporangium is a structure present in fungus, algae, certain plants, and some other organisms. These structures make and store spores.

Reproduction In Ectocarpus

There are both types of reproduction in Artocarpus - asexual and sexual.

  • Asexual Reproduction - This type of reproduction takes place by biflagellated zoospores. Now, these zoospores may be haploid or diploid. If spores are produced in unilocular sporangia, then haploid spores are produced. These spores are produced by meiotic division. These zoospores are uninucleated and pyriform. Plurilocular sporangia produced diploid spores by mitosis. The plurilocular sporangia do not play any role in the alternation of generation.

  • Sexual Reproduction - There may be the isogamous or anisogamous type of sexual reproduction in ectocarpus. Generally, ectocarpus is isogamous and homothallic but some of the ectocarpus may be heterothallic and anisogamous. Gametes are produced in plurilocular gametangia. The gametogenesis divides by mitotic division and forms hundreds of cells. Then after these cells transform into biflagellated gametes. Then these gametes release through gametangium. Gametes fused to form a zygote, and later this zygote developed into a sporophyte containing unilocular and plurilocular sporangia.

What is Unilocular Sporangia?

Unilocular sporangia are single-cell, enlarged structures produced by brown algae that undergo meiotic division to make zoospores. The unilocular sporangia develop small branchlets. Then meiotic division occurs along with mitotic division to make a large number of zoospores. These zoospores are also known as meio zoospores because they are produced by meiotic division.

What are Plurilocular Sporangia?

These plurilocular sporangia are also produced by brown algae and developed from terminal cells of branchlets. Around 5-12 cells are produced from plurilocular sporangia. And the temperature required for sporangia production is 13-16°C.

Difference Between Unilocular and Plurilocular Sporangia

Unilocular Sporangia

Plurilocular Sporangia

It is a kind of sporangia that contains one locule and is unicellular

These sporangia are multilocular and also multinucleated

Produced haploid spores

Produced diploid spores

Made of single cell

Made of a large number of cells

The shape of unilocular sporangia is ellipsed

Whereas the shape of plurilocular sporangia is spherically elongated

Undergo meiosis

Undergo mitosis

Generally found at a cooler temperature

These are found at a warmer temperature

Important Questions

1. What is the function of plurilocular sporangia?

Ans: It is a multi-chambered sporangium that undergoes mitotic division to make zoospores. Then these spores after fusion make zygote which further makes sporophytes. These spores are also known as mitospores.

2. In which of the following algae do unilocular sporangia occur?

Ans: Unilocular sporangia are found in ectocarpus which is a brown alga. This alga produces unilocular sporangia generally at 13°C. And plurilocular sporangia at 19°C.

3. Is a zygote haploid or diploid?

Ans: A zygote is always diploid as it is formed by the fusion of male and female haploid gametes, a process known as fertilization.

Interesting Facts

  • There are more than 4 lakh varieties of algae

  • There are more algae in oceans than stars in the universe, for eg. If we take a drop of water it would contain more than 1000 algae in it

  • Algae is a very rich source of protein and vitamins.

  • Many space travelers use algae as food supplements

  • Algae is also used as an alternative to fossil fuel

  • All plants of the present time evolved from algae.

Key Features

  • In this article, we studied ectocarpus which is a type of marine brown algae

  • They reproduce by both asexual and sexual methods.

  • Sporangia are the structures found in ectocarpus and other algae, and fungus for asexual reproduction. There are two types of sporangia, unilocular sporangia, and plurilocular sporangia.

  • Sporangia are the structures that produce and store spores.

  • Gametogeniaise the structures that produce gametes for sexual reproduction.

Practice Questions

  1. What are the three types of asexual reproduction in plants?

  2. Which algae is found in freshwater?

  3. What is plurilocular gametangia.?

  4. What are the largest algae?

  5. Which algae is rich in protein?

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FAQs on Difference Between Unilocular and Plurilocular Sporangia

1. Describe the life cycle of Artocarpus.

Ectocarpus has a haplodiplontic life cycle. Two distinct phases are seen in the life cycle of the ectocarpus haploid gametophyte phase and the diploid sporophytic phase. These are called isomorphic because morphologically both phases are similar in structure. Diploid sporophytes produce haploid spores by the meiotic division, then these spores germinate to form a gametophytic body. Gametophytic bodies make gametes which fuse to form diploid bodies called sporophytes. Then these sporophytes again produce spores by meiotic division. This cycle keeps on running.

2. What are the similarities between unilocular and plurilocular sporangia?

There are many similarities between unilocular and plurilocular sporangia. Some of the similarities are explained below:

  • Ectocarpus produces both types of sporangia that are unilocular and plurilocular sporangia which is a brown alga 

  • A sporophyte is a diploid body that produces both unilocular and plurilocular sporangia 

  • Both unilocular and plurilocular sporangia help in asexual reproduction

  • Both of these spores produce flagellated zoospores which means they have two flagella, so these spores can move.

3. Explain the morphology of ectocarpus

Ectocarpus is brown marine algae, it can grow up to 30 cm. They have a branched structure and a small ball-shaped appearance. Their thallus is differentiated into the prostate and erect system. It helps to understand the genetic polymorphism that acts as a molecular marker. Their cell is rectangular and covered by a thick cell wall. Pyrenoid-like bodies are also present. Laminarin and mannitol are reserved food materials and are uninucleated. Chromatophores are of various shapes such as discoid, ribbon-shaped, etc. 


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