4. Mycorrhiza
Mycorrhizae literally translates to “fungus-root.”
Mycorrhiza defines a (generally) mutually beneficial
relationship between the root of a plant and a fungus that
colonizes the plant root
In many plants, mycorrhiza are fungi that grow inside the
plant’s roots, or on the surfaces of the roots
5. Cont…….
In their relationship:
• Fungus facilitates water and nutrient uptake in the plant
• Fungus supplies the plant with water and mineral
nutrients, such as phosphorus (P), zinc (Zn), manganese
(Mn) and copper (Cu) taken from the soil
• Plant provides food and nutrients created by
photosynthesis to the fungus
• Plant makes organic molecules by photosynthesis and
supplies them to the fungus in the form of sugars or lipids
6. Cont…….
Not all plants will have mycorrhizal
associations
In environments in which water and
nutrients are abundant in the soil, plants do
not require the assistance of mycorrhizal
fungi, nor might mycorrhizal fungi
germinate and grow in such environments
Mycorrhizas are present in about 92% of
the studied plant species, with arbuscular
being the predominant form in the plant
kingdom
7. Types of
Mycorrhiza
On the basis of morphological and
anatomical features, Mycorrhiza
are divided into 3 types:
A. Ecto-Mycorrhiza
B. Endo-Mycorrhiza
C. EctendoMycorrhiza
8. A. Ectomycorrhiza (EcM)
Ectomycorrhiza is a type of mycorrhiza that
forms a sheath around the roots of plants
Ectomycorrhiza form a compact mantel of
hyphae on the outer surface of plant roots,
but do not penetrate plant root cells
However, hyphal strands penetrate the root
surface and grow between cortical root
cells
9. Cont…….
EcM associations occurs between the
roots of around 10% of plant families,
mostly woody plants
Fungi belonging to
the Basidiomycota, Ascomycota,
and Zygomycota
This type of mycorrhiza is found in trees
such as pines and oaks
10. B. Endomycorrhiza
About 85 percent of the plant
families in the world are
colonized by endomycorrhiza
Endomycorrhiza penetrates
the cell walls of the roots of
plants and colonize
epidermal and fleshy cortical
cells of plant roots
This type of mycorrhiza is
found in plants such as
tomatoes, potatoes, carrots,
and legumes
11.
12. C. Ectendomycorrhiza
Ectomycorrhizas consist of a hyphal sheath, or mantle,
covering the root tip and a Harting net of hyphae
surrounding the plant cells within the root cortex
In some cases the hyphae may also penetrate the plant
cells, in which case the mycorrhiza is called an
Ectendomycorrhiza
Ectendomycorrhizas are restricted mostly to the plant
families Pinus (pine), Picea (spruce) and to a lesser
extent Larix (larch)
13. Cont…….
The term ectendomycorrhiza should be used as a purely
descriptive name for mycorrhizal roots which exhibit the
characteristics of both:
• Ectomycorrhizas
• Endomycorrhizas
17. 1. Arbuscular Mycorrhizae
Arbuscular mycorrhizae are branched structures that
penetrate the cell walls of plant roots
This type of mycorrhiza is found in most plants, including
grasses, shrubs, and herbs
The fungi involved in this relationship belong to the
phylum Glomeromycota
It is estimated that around 80% of all plant species form
arbuscular mycorrhizal partnerships
18. Cont…….
The mycorrhizal fungi colonize the roots of the host plant,
forming structures called arbuscules and vesicles within
the root cells
Arbuscules are tree-like structures that facilitate nutrient
exchange between the fungus and the plant
Vesicles are storage organs within the root cells that
contain lipids and carbohydrates
19.
20.
21. 2. Ericoid mycorrhiza
Ericoid mycorrhiza is another type of
symbiotic association between plants and fungi
Specifically involves plants from the Ericaceae
family
It includes heathers, rhododendrons,
blueberries, and various other acid-loving
plants
The fungi involved in ericoid mycorrhizal
associations are typically members of the
fungal group known as Ascomycota
(Hymenoscyphus ericae)
22. Cont…….
Ericoid mycorrhizal associations are well-suited for plants
in acidic soils
In ericoid mycorrhizal associations, the fungal hyphae
(thread-like structures) of the ascomycete fungi penetrate
the cell
Fungal sheath, harting net and vesicles are absent
23.
24. 3. Arbutoid mycorrhizas
Found in the plant order Ericales
Family Ericaceae is represented, with arbutoid
mycorrhizas
Formed in the genera Arctostaphylos and Arbutus
Arbutoid associations are also found in the Pyrolaceae
family of the Order Ericales
Fungi of arbutoid mycorrhizas are basidiomycetes
25. Cont…….
A fungal sheath or mantle of between 20 and 80 mm
covers the roots
The sheath can also provide an important store of
nutrients, to be released to the plant when nutrient levels
are sufficiently depleted
Arbutoid associations produce an intercellular harting net,
usually restricted to the outer layer of root cells
26.
27. 4. Monotropoid mycorrhizas
Fungi colonising achlorophylous plants in the
Monotropaceae family (but now included within the
Ericaceae), such as:
Monotropa hypopitys (in Europe)
M. uniflora (North America)
These never actually penetrate the plant cell walls
This feature was sufficiently distinct to warrant the
creation of a new class of mycorrhizas: the monotropoid
mycorrhizas
28. Cont…….
Fungi belonging to Basidiomycota
Fungal sheath and harting net is present along with
extensive intracellular penetration, with coils of hyphae
filling large volumes in many cells
The root system of Monotropa is highly adapted to
gaining all its nutrients via mycorrhizas
Its roots are surrounded in a dense fungal sheath, from
which hyphae spread into the soil
29.
30. 5. Orchidaceous mycorrhizas
The Orchidaceae is one of the largest families in the plant
kingdom, with more than 20,000 species identified, most
distributed in the tropics and subtropics
All orchids have a stage where they are non-
photosynthetic
Therefore dependent on external sources of nutrients
In the vast majority of cases, it is just the seedling stage
that is obligately mycorrhizal
31. Cont…….
Orchid seeds are very small (around 0.3 - 14 mg per seed)
and contain little nutrient reserves
Mycorrhizal fungi can provide the nutrients, and
particularly carbohydrates, needed to grow, and in fact,
most orchid seeds will not germinate unless they have
been infected by an appropriate fungus
The mycorrhizal fungi in orchids are Basidiomycota, and
in particular Rhizoctonia species with which many
orchids are associated