This document summarizes the types and development of mycorrhizal symbiosis. It discusses: 1. There are several types of mycorrhizal associations including ectomycorrhiza, ectendomycorrhiza, ericoid mycorrhiza, and VA mycorrhiza. 2. The development of the mycorrhizal symbiosis occurs through asymbiotic and symbiotic stages, beginning with spore germination and hyphal growth, followed by recognition signals between the plant and fungi leading to appresorium formation and penetration of root cells. 3. In the mature symbiotic phase, the fungi form specialized structures inside root cells like arbuscules

1. MYCORRHIZA, TYPES,
DEVELOPMENT OF SYMBIOSIS
PRESENTED BY:
NEHA SHARMA
Punjab Agricultural University

2. INTRODUCTION
• Myco- fungi, rhiza- root
• Coined by Frank (1885)
• Structure developed as a result of symbiotic
association between fungi and higher plant
roots.
• Can be in stems (e.g. orchids)

3. Fungi spreads as-
• EXTRARADICAL MYCELIUM
grow inside the soil for nourishment
• INTRARADICAL MYCELIUM
i. grow in between and inside the parenchyma
cells of plant roots.
ii. forms structures- vesicles, arbuscules.

4. TYPES
• ECTOMYCORRHIZA
• ECTENDOMYCORRHIZA
• ERICOID MYCORRHIZA
• ARBUTOID MYCORRHIZA
• MONOTROPOID MYCORRHIZA
• ORCHIDACEOUS MYCORRHIZA
• VA MYCORRHIZA

5. 1. ECTOMYCORRHIZA
• mainly Basidiomycota.
• e.g.- Amanita muscaria, Boletus, Scleroderma citrinum
• Plant type- Pinus, Poplar, Oak, Eucalyptus.
• exists in temperate, semi-arid regions.
• Nutrients absorbed by the fungal mantle are transported
to roots through Hartig’s net.
• Y-shaped rootlets- visible feature.

6. 2. ECTENDOMYCORRHIZA
• ECTO like- mantle + Hartig’s net (reduced)
• ENDO like – intracellular penetration
• Plant type- Pinus (pines), Picea (spruce)
• Fungi type- Ascomycetes (Wilcoxina)

7. 3. ERICOID MYCORRHIZA
• Fungi type- Ascomycetes
(Rhizoscyphus, Sebacina)
• Plant type- family Ericaceae, tribe
Ericoidae
• Form intracellular hyphal coils
• The fungus digests polypeptides
saprotrophically and passes
absorbed nitrogen to the host
plant

8. 4. ARBUTOID MYCORRHIZA
• Transition between ecto- and endo-mycorrhiza
• Fungi type- Basidiomycetes (Boletus, Scleroderma)
• Plant type- family Ericaceae, tribe Arbutoidae, genera
Arbutus
• Feature- intracellular coils in outer cortical cells
alongwith mantle and Hartig’s net

9. 5. ORCHID MYCORRHIZA
• Fungi type- Basidiomycetes
(Rhizocotonia solani, Sesbania,
Russula)
• Plant type- orchids
• Forms internal coils
• Orchid seedling is achlorophyllous, so, depends on the
fungal partner for utlizing complex carbon sources.

10. 6. MONOTROPA MYCORRHIZA
• Plant type- achlorophyllous,
Family Monotropaceae (Monotropa hypopitys)
• Fungi type- Arbustus, Pyrola
• depend on fungi for carbon and energy
• Neighbouring plants- beech, oak, spruce, pine
• Carbohydrates pass from conifer to Monotropa via their
common mycorrhizal partner.
• Sheath + Hartig’s net, limited hyphal penetration into
epidermal cells.

11. 7. VA MYCORRHIZA
• most widespread (70-90%)
• Fungi type- phylum Glomeromycota,
• 7 genera- Acaulospora, Gigaspora, Glomus, Sclerocystis,
Scutellospora, Entrophospora, Gerdemannia
• aseptate, forms intracellular hyphae in cortex
• 2 structures
i. Arbuscules-
• transfer mineral nutrients from fungi
• transfer sugars from host to fungi
ii. Vesicles- storage organ of P as phospholipids

13. DEVELOPMENT OF MYCORRHIZA-HOST
ROOT SYMBIOSIS
• A programmed sequence of phenotypic changes,
due to specific recognition between the two
partners- host plant and fungal symbiont.
• Involves 2 stages-
1. Asymbiotic stage
2. Symbiotic stage

14. I. ASYMBIOTIC STAGE
• Exist as multi-nucleated round shaped resting spores.
• Fungi uses its triglyceride, glycogen reserves.
• Under suitable water, temp. conditions-
Spores germinate & nuclei from the spore move into the
extending mycelium.
• If host root absent- growth ceases (2-4 weeks)

15. II. SYMBIOTIC STAGE
• Begins with the colonization of hyphae with
compatible root.
• After attachment-
i. Appresorium formed (fungus enters in cortex).
i. Formation of specialized structures- inter- & intra-
cellular hyphae, coils, arbuscules.

16. PRE-
SYMBIOTIC
• Response of fungi
to plant signals
• Response of plant
to fungi signals
EARLY
SYMBIOTIC
• Appresorium
development
• Penetration of AM
fungi
MATURE
SYMBIOTIC
• Arbuscule
development
• Nutrient transfer
SYMBIOTIC
PHASE

17. (A) PRE-SYMBIOTIC PHASE
I. RESPONSE OF AM FUNGI TO PLANT DERIVED SIGNALS
• Strigolactones- short lived compound, forms a conc.
gradient, stimulates spore germination.
• 5-deoxy-strigol: identified by fungi, leads to-
i. Induction of branching
ii. Enhanced fungal growth
iii. Increased mitochondrial activity

18. II. RESPONSE OF PLANT TO FUNGI
DERIVED SIGNALS
• Myc factors- soluble, fungus signalling molecule.
In plants-
• Induces transcriptional activation of plant symbiosis
related genes.
• Induce Ca oscillations in root epidermal cells- with the
binding of LysM domain of NAG.
• When LysM binds to chitin perception system of root
cells, induces Ca oscillations of lower frequency.

19. (B). EARLY SYMBIOTIC PHASE
I. APPRESORIUM DEVELOPMENT
• Appresorium- A flattened, hyphal organ that facilitates
the penetration of cells or tissues of other organisms.
• AM fungi forms a special type of appresoria called as
hyphopodia, developed from mature hyphae.
• Formation – 1st morphological sign due to successful
pre-symbiotic recognition events.

20. II. PENETRATION OF AM FUNGI
• Due to sequential chemical and
mechanical stimulation, plant
cells produce a PPA.
• Fungal hypha enters the PPA,
guides the fungus through root
cells towards the cortex.
• In inner cortex, the fungus
leaves the plant cell, enters the
apoplast, branches and grows
laterally along the root axis.

21. (C). MATURE SYMBIOTIC PHASE
1. ARBUSCULE DEVELOPMENT
• Hyphae induce the development of PPA-like structures
in inner cortical cells, enter the inner cortical cells and
branch to form arbuscules.
• Vesicles, function as storage organs of the fungus.
• New spores are typically synthesized outside of the
plant root at the leading tip of individual fungal hyphae.

23. overview

24. II. SYMBIOTIC INTERFACE AND NUTRIENT
TRANSFER

25. THANKS