Fungi Reproduction Study Guide

Introduction:

The majority of fungi are capable of both asexual and sexual reproduction. By budding, yeast multiplies asexually, and other fungi create spores to reproduce asexually. When two parents’ spores combine to produce a zygospore, sexual reproduction occurs.

Asexual Reproduction:

• In most cases of asexual reproduction, a single individual produces a genetic copy of the parent without the help of another individual.

1. FRAGMENTATION

• The fragmentation of a fungus’s thallus, or body, is perhaps the most basic form of fungal reproduction.
• Some yeasts, single-celled fungi, reproduce via simple cell division or fission.
• One cell divides into two daughter cells following nuclear division; after some growth, these cells divide, and ultimately a population of cells arises.

2. BUDDING

• Most yeasts and filamentous fungi have the ability to bud, which is another kind of asexual reproduction.

• In this process, a bud forms on the surface of either the yeast cell or the hypha, with the bud’s cytoplasm being continuous with that of the parent cell.

• The parent cell’s nucleus then splits, with one daughter nucleus migrating to the bud and the other remaining in the parent cell.

• The parent cell can produce numerous buds over its surface by continuously synthesising cytoplasm and repeating nuclear divisions.

• A bud can blossom through the same procedure once it has developed to a certain stage and even before it is split from the parent cell, can create a chain of cells in this manner.

• Eventually, individual buds pinch off the parent cell and develop into yeast cells.

• Pinched buds from a filamentous fungus’ hyphae act like spores, germinating and producing a germ tube structure, which grows into a new hypha.

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3. SPORES

Although certain fungi reproduce asexually by fragmentation, fission, and budding, the majority reproduce asexually through the generation of spores.

Asexually formed spores are known as mitospores, and they can be created in various ways.

A. Sporangiospore:

• These asexual spores are generated in sporangia, a sac-like structure (singular; saprangium).
• The sporangium is formed at the end of the sporangiophore, which is a peculiar, aerial hyphae.
• Sporangium contains a high number of haploid spores that are discharged when the sporangial wall is ripped open.

B. Conidiospore:

• Conidiospore or conidia are single-celled or multicellular structures that emerge from the tip or side of the aerial hyphal structure known as the conidiophore.
• Conidia differ from sporangiospores in that they are not generated within a sporangium or any other sac-like structure.
• Conidia can be found solitary or in groups.

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Sexual Reproduction

The fungus can adapt to different surroundings due to sexual reproduction, and it is also a major source of genetic variation. In many aspects, the mechanism of sexual reproduction in mushrooms is unusual.

• The fungus’ nucleus is squeezed at its middle, and spindle fibers generated within the intact nucleus tug the diploid chromosomes apart.
• Although it may be ejected from the nucleus or distributed inside the nucleus observable, the nucleolus is generally preserved and split across the daughter cells.

In fungi, sexual reproduction is divided into three stages:

1. Plasmogamy

2. Karyogamy

3. Meiosis

The diploid chromosomes are separated into two daughter cells with just one pair of chromosomes (a haploid state).

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1. PLASMOGAMY

• Plasmogamy combines two compatible haploid nuclei by fusing two protoplasts (the contents of two cells).
• Two nuclear types are present in the same cell, but the nuclei have not merged.

In plasmogamy, there are several strategies for bringing compatible nuclei together. Here are a few:

• Gametic copulation
• Gametangial copulation
• Somatic copulation
• Spermatization

2. KARYOGAMY

Karyogamy causes the haploid nuclei to fuse, resulting in the development of a diploid nucleus (i.e., a nucleus containing two sets of chromosomes, one from each parent). The zygote is the cell generated via karyogamy.

In most fungi, the zygote is the sole diploid cell throughout the whole life cycle. The dikaryotic state caused by plasmogamy in fungi is common and can last for several generations.

Karyogamy normally occurs relatively shortly after plasmogamy in the lower fungi. However, karyogamy and plasmogamy are separated in highly advanced fungi.

3.MEIOSIS

• Meiosis (cell division that decreases the number of chromosomes to one pair per cell) usually follows karyogamy and restores the haploid phase.

• Meiosis produces haploid nuclei, which are usually integrated into spores termed meiospores.

• Hermaphroditic fungi carry both male and female gametangia in a single member.

• Separate individuals, one male, and the other female, seldom produce gametangia of opposite sexes.

• Dioecious species are those that reproduce in two ways.

• In an individual of the opposite sex, dioecious organisms create sex organs.

Conclusion

• The majority of fungi are capable of both asexual and sexual reproduction, enabling them to adapt to changing environmental circumstances.
• By budding, yeast multiplies asexually, and other fungi create spores to reproduce asexually.
• When two parents’ spores combine to produce a zygospore, sexual reproduction occurs.

FAQs:

1. How do fungi reproduce?

Most fungi reproduce by producing spores that can withstand harsh circumstances like cold and lack of water. Fungi can form sexual meiotic and asexual mitotic spores depending on the species and circumstances. Some reproduce by asexual fission or fragmentation, each fragment creating its organism.

2. Why do fungi reproduce both sexually and asexually?

The majority of fungi are capable of both asexual and sexual reproduction, enabling them to adapt to changing environmental circumstances. When circumstances are steady, they can spread swiftly through asexual reproduction.

3. How do bacteria and fungi reproduce?

Bacteria reproduce through binary fission, an asexual process. Fungi reproduce in two ways: asexually and sexually, and fungal spores are used for sexual reproduction.

4. What are the reproductive parts of fungi?

Fungi reproduce by spores, which are the basic reproductive units. Until one or more fruiting bodies appear, the mycelium stays concealed. A mushroom cap is a fruiting body, the fungus’s spore-producing component.

5. Why do fungi prefer asexual reproduction?

For fungi that may reproduce sexually or asexually, the asexual pathway is preferable since it produces many spores/clones in a short length of time.

6. Which type of reproduction occurs in yeast?

Asexual reproduction via budding is the most frequent mechanism of vegetative development in yeast. A tiny bud (also known as a bleb or daughter cell) is generated on the parent cell. The parent cell’s nucleus separates into two daughter nuclei, which move into the daughter cell.

7. What role do spores play in the reproduction of fungi?

Spores have a role in a fungus similar to seeds in plants. Fungal spores are produced and dispersed by specialized fruiting bodies, such as the edible component of common mushrooms. Fungal spores germinate and develop into new individuals under the right moisture, temperature, and food availability circumstances.

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Sources:

1. Fungi Reproduction https://flexbooks.ck12.org/cbook/ck-12-biology-flexbook-2.0/section/8.10/primary/lesson/fungi-reproduction-bio/ Accessed on 8 Dec 2021
2. Fungi Reproduction. https://bio.libretexts.org/Bookshelves/Introductory_and_General_Biology/Book%3A_General_Biology_(Boundless)/24%3A_Fungi/24.1%3A_Characteristics_of_Fungi/24.1C%3A_Fungi_Reproduction Accessed on 8 Dec 2021
3. Reproductive processes of fungi https://www.britannica.com/science/fungus/Reproductive-processes-of-fungi Accessed on 8 Dec 2021
4. Reproduction in fungi https://www.onlinebiologynotes.com/reproduction-in-fungi-asexual-and-sexual-methods/ Accessed on 8 Dec 2021

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