Algae: An Introduction
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
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
What are the three types of asexual reproduction in plants?
Which algae is found in freshwater?
What is plurilocular gametangia.?
What are the largest algae?
Which algae is rich in protein?
FAQs on Difference Between Unilocular and Plurilocular Sporangia
1. What is the fundamental difference between unilocular and plurilocular sporangia?
The fundamental difference lies in their cellular structure and the type of spores they produce. Unilocular sporangia are large, single-celled structures that produce haploid zoospores through meiosis. In contrast, plurilocular sporangia are multicellular, filament-like structures that produce diploid zoospores through mitosis.
2. In which type of algae are unilocular and plurilocular sporangia commonly found?
Both unilocular and plurilocular sporangia are characteristic features of certain brown algae (Phaeophyceae), with Ectocarpus being a classic example studied in botany. These structures are crucial for the alga's asexual and sexual reproduction cycles, demonstrating a distinct alternation of generations.
3. Why are spores from unilocular sporangia haploid, while those from plurilocular sporangia are diploid?
This difference is due to the type of cell division involved. Unilocular sporangia arise on a diploid sporophyte and undergo meiosis (reductional division), which halves the chromosome number, resulting in haploid (n) zoospores. Plurilocular sporangia, also on a diploid sporophyte, undergo mitosis (equational division), where the chromosome number remains the same, producing diploid (2n) zoospores.
4. How does the structure of a unilocular sporangium differ from a plurilocular one?
The structural differences are significant:
Unilocular Sporangium: It is a single, enlarged, and often spherical or pear-shaped cell. Its name 'uni-' means one, referring to the single chamber or locule.
Plurilocular Sporangium: It is a multicellular structure composed of hundreds of small, cubical cells arranged in vertical rows, forming a cone-like or elongated filament. Its name 'pluri-' means many, referring to the numerous chambers or locules.
5. What is the functional difference between a plurilocular sporangium and a plurilocular gametangium in Ectocarpus?
While structurally similar, their function and the plant body they grow on are different. A plurilocular sporangium develops on a diploid (2n) sporophyte and produces diploid zoospores for asexual reproduction. A plurilocular gametangium develops on a haploid (n) gametophyte and produces haploid gametes for sexual reproduction.
6. What role do these two types of sporangia play in the life cycle of brown algae like Ectocarpus?
They play distinct roles in the alternation of generations:
Unilocular sporangia are responsible for starting the gametophytic generation. Their haploid zoospores germinate to form haploid gametophyte plants.
Plurilocular sporangia are involved in asexual reproduction of the sporophyte generation. Their diploid zoospores germinate to produce more diploid sporophyte plants, effectively multiplying this phase of the life cycle.
7. Under what conditions does Ectocarpus favour the production of plurilocular sporangia over unilocular ones?
Ectocarpus typically produces plurilocular sporangia under favourable environmental conditions (e.g., suitable temperature, light, and nutrients). This allows for rapid asexual multiplication of the well-adapted diploid sporophyte. The formation of unilocular sporangia, which involves the more complex process of meiosis, is often triggered by changes in environmental conditions or the maturation of the plant, initiating the sexual phase of the life cycle for genetic recombination.
