Kingdom Fungi: Modes of Reproduction, Classification, Economic Importance, Practice Problems and FAQs

You must be knowing that people working on removing mould infestation from properties always wear masks while working. Why do you think they do so?? Does the term ‘fungal spore’ seem familiar in this context?? Yes, you are correct! They wear masks to protect themselves from inhaling the fungal spores in the air. But what are these fungal spores?

Spores are the microscopic reproductive units of fungi. You must be wondering how fungi reproduce via these spores?? Keep reading to know more.

You will also be amazed to know that the type of spores produced is also an important criteria to classify fungi. Come, let us learn more about reproduction in fungi and how they are classified.

Table of contents

• Reproduction in Fungi
• Classification of Fungi
• Economic importance of fungi
• Practice Problems of Kingdom Fungi
• FAQs of Kingdom Fungi

Reproduction in Fungi

Fungi reproduces vegetatively, asexually and sexually.

Vegetative reproduction

Vegetative reproduction in fungi can be via the following methods - 

Fragmentation

The mycellia breaks into fragments, each of which grow into separate mycellia.

Budding

A small outgrowth or bud develops from the parent body and develops into a new organism, as is seen in yeast.

Fission

Unicellular fungi like yeasts reproduce vegetatively by fission. The parent cell undergoes cell division to form two daughter cells.

Asexual Reproduction

Asexual reproduction takes place by the formation of different types of spores. These spores are formed by mitotic division and are called mitspores. Asxual spores are usually haploid in nature and germinate into new haploid organisms.

Sporangiospores

They are formed in sporangia formed at the tip of fungal filament. The fungal filaments on which sporangia are formed are called sporangiophores. Numerous sporangiospores are present in the sporangia and are released by rupture of the sporangia. The formation of sporangiospores takes place endogenously.

Sporangiospores are of two types -

Conidiospores

The formation of conidia takes place exogenously. These conidia are thin-walled, non-motile spores that are borne at the tip of the special hyphal branches called conidiophores.

Oidia

The formation of oidia occurs by fragmentation of hyphae. 

Sexual Reproduction in Fungi

Fungi reproduces sexually by the formation of gametes.

Sexual reproduction in fungi complestes in 3 steps:

1. Plasmogamy: This is the first stage of sexual reproduction in which the protoplasts of two cells belonging to two different mycellia fuse with each other but their nuclei do not fuse. This results in the formation of a single cell with two nuclei. This binucleate or dikaryotic stage is called dikaryon (n+n).
2. Karyogamy: In this stage, the nuclei present in the cell fuse with each other to form a diploid nucleus which is known as synkaryon.
3. Meiosis: In this stage, the diploid zygote cell undergoes meiotic division to form haploid sexual spores or meiospores which upon germination form new fungal filaments.

Fungi reproduces sexually by the formation of sexual spores such as oospores, zygospores, ascospores, basidiospores.

Types of Gametic Fusion During Sexual Reproduction

Fusion between gametes during sexual reproduction can be of three types - 

• Isogamy - fusion between gametes of the same size.
• Anisogamy - fusion between gametes of dissimilar size.
• Oogamy - fusion between a smaller motile male gamete and a larger non-motile female gamete.

Classification of Fungi

Fungi are further classified on the basis of type of mycelium, type of sexual and asexual spores they produce.

Phycomycetes

They are mainly found in aquatic environments, moist decaying wood and are obligate parasites. Mycelium in these fungi is aseptate (without septa) and coenocytic (multinucleated protoplasm). They reproduce asexually by sporangiospres and sexually by zygospores or oospores. The male sex organ is antheridia and female sex organ is oogonia. The fusion between gametes can be isogamous or anisogamous. The diploid zygote formed during sexual reproduction undergoes meiosis to form haploid spores which can germinate into new fungal hyphae.

Phycomycetes are further classified into two categories:

Oomycetes

These fungi have a cellulosic cell wall. Asexual reproduction in oomycetes is by means of zoospores and sexual reproduction is mediated by oospores. Examples - Phytophthora infestans, Albugo candida, etc.

Zygomycetes

The cell wall of fungi belonging to zygomycetes is made up of chitin. They reproduce asexually by sporangiospoes. Sexual reproduction takes place through zygospores. Example: Bread mould (Rhizopus), Mucor.

Ascomycetes

They are commonly known as ‘sac fungi’. Mycelium of these multicellular fungi is branched and septate. Some rare varieties of ascomycetes, such as yeast, are unicellular. Members of ascomycetes are saprophytic decomposers or parasitic. Many saprophytic varieties are coprophilous, i.e, they grow on dung.

They reproduce vegetatively by budding and asexually by conidia (exogenously). Sexual reproduction is by ascospores produced endogenously within sac like structures called asci (sing. ascus) which are borne on fruiting bodies known as ascocarps. 4 to 8 ascospores are present in one ascus.

Examples: Penicillium, Aspergillus, Claviceps, Morchella, Neurospora, truffles, morels. Neurospora is called ‘Drosophila of the plant kingdom’ and is used for the study of genetics in the plant kingdom. Truffles and morels are highly sought after edible fungi.

Basidiomycetes

They are commonly known as ‘club fungi’. Mycelium in basidiomycetes is branched and septate. They are mainly found in soil, on logs, tree stumps and as parasites in living plant bodies. Some varieties are plant pathogens and cause diseases such as rusts and smuts.

Asexual spores are generally not found but these fungi generally propagate vegetatively by fragmentation. As sex organs are absent, sexual reproduction is performed by somatogamy between two somatic cells of different strains. The process involves -

Fusion of protoplasts of two somatic cells (somatogamy) belonging to different strains between 

↓

Formation of dikaryon (n+n) as the nuclei have still not fused

↓

Dikaryon gives rise to club-shaped basidium

↓

Karyogamy (fusion of nuclei) and meiosis within the basidium results in the exogenous production of basidiospores.

 Basidia are borne on the fruiting bodies known as basidiocarps.

Examples: Ustilago (smut fungi), Agaricus (mushroom), Puccinia (Rust fungi), Puffballs, Bracket (Shelf) fungi

Puccinia (Rust fungi)

Puccinia causes rust in plants such as wheat. It is a parasitic fungus and requires two hosts to complete its life cycle - wheat (Primary host) and barberry (Secondary host). It forms four types of spores: aeciospores, uredospores, teliospores, basidiospores.

Ustilago (Smut fungi)

Ustilago causes smut in plants such as maize, barley, sorghum and sugarcane. Smut fungi infect seeds of plants and form black sooty spurs inside the seed.

Deuteromycetes

Deuteromycetes are called ‘fungi imperfecti’; because sexual reproduction is absent in this class of fungi. When the sexual forms of this fungi were discovered they were moved to either ascomycetes or basidiomycetes based on the type of spores they produce. Their mycelium is septate and branched. They reproduce asexually by conidia. They show a saprophytic or parasitic mode of nutrition. Some varieties help in mineral cycling and decomposition.

Example: Trichoderma, Alternaria, Colletotrichum

Economic Importance of Fungi

The fungi are economically important for several reasons such as -

• Many species of Mucor and Rhizopus are used to manufacture fumaric acid, lactic acid, citric acid and alcohol.
• Yeast is widely used in bread making and wine production.
• Some club fungi such as Agaricus are edible and widely used in cooking.
• Some fungi are used for the production of hallucinogens like LSD.

Practice Problems of Kingdom Fungi

Q1. Study the following steps of reproduction in basidiomycetes and choose the option that shows the correct sequence of steps.

1). Formation of basidia

2). Formation of dikaryon

3). Fusion of protoplast

4). Karyogamy

• A→ B → D → C
• C → B → A → D
• D → B → C → A
• B → C → A →D

Solution: Sex organs are absent in basidiomycetes. Hence, sexual reproduction is performed by somatogamy between two somatic cells of different strains. The process involves -

Fusion of protoplasts of two somatic cells (somatogamy) belonging to different strains between 

↓

Formation of dikaryon (n+n) as the nuclei have still not fused

↓

Dikaryon gives rise to club-shaped basidium

↓

Karyogamy (fusion of nuclei) and meiosis within the basidium results in the exogenous production of basidiospores.

Thus, the correct option is b.

Q2. A farmer sees that the seeds of his maize plant show the presence of black sooty spurs inside. Which of the following fungi do you think has infected his maize plants?

a). Puccinia

b). Ustilago

c). Neurospora

d). Agaricus

Solution: Ustilago is also known as smut fungi as it causes smut in plants such as maize, barley, sorghum and sugarcane. It forms black sooty spurs inside the seed.

Thus the correct option is b.

Q3. Find the odd one out.

a). Penicillium

b). Claviceps

c). Trichoderma

d). Neurospora

Solution: Penicillium, Claviceps and Neurospora belong to class Ascomycetes whereas Trichoderma belongs to class Deuteromycetes of kingdom Fungi.

Thus, the correct option is c.

Q4. Select the incorrect match.

a). Aplanospore - sexual spore

b). Basidiospore - sexual spore

c). Conidiospore - asexual spore

d). Oidia - asexual spore

Solution: Fungi produce asexually with the help of spores such as motile zoospores, non-motile aplanospores, conidiospores and oidia.

Sexual spores in fungi are - oospores, zygospores, ascospores and basidiospores.

Thus, the correct option is a.

FAQs of Kingdom Fungi

Question 1. What are sporangiospores?

Answer. Sporangiospores are asexual spores formed in sporangia formed at the tip of fungal filament. The fungal filaments on which sporangia are formed are called sporangiophores. Numerous sporangiospores are present in the sporangia and are released by rupture of the sporangia. The formation of sporangiospores takes place endogenously.

Sporangiospores are of two types - motile and flagellates zoospores and non-motile and non-flagellated aplanospores.

Question 2. What are the 4 main classes of fungi?

Answer. Based on the type of mycelium, type of sexual and asexual spores they produce, fungi are classified into 4 main classes -

1. Phycomycetes - further divided into oomycetes and zygomycetes
2. Ascomycetes
3. Basidiomycetes
4. Deuteromycetes

Question 3. Why are deuteromycetes called ‘fungi imperfecti’?

Answer. Deuteromycetes are called ‘fungi imperfecti’; because sexual reproduction is absent in this class of fungi. When the sexual forms of this fungi were discovered they were moved to either ascomycetes or basidiomycetes based on the type of spores they produce.

Question 4. State five important characteristics of phycomycetes.

Answer. The five important characteristics of phycomycetes are - 

• Mycelium in these fungi is aseptate (without septa) and coenocytic (multinucleated protoplasm). 
• They reproduce asexually by sporangiospres and sexually by zygospores or oospores. 
• The male sex organ is antheridia and female sex organ is oogonia. 
• The fusion between gametes can be isogamous or anisogamous. 
• Phycomycetes are further classified into two categories - oomycetes and zygomycetes.

Other Related Topics

Other Related Topic Of Biology

• Plant Kingdom Plantae
• Kingdom Animalia
• Habitat of Fungi
• Shape and structure of eubacteria
• Kingdom monera
• Nutrition respiration and reproduction in eubacteria