Mycorrhizal Association

Tara H. Shkur

2012

The fungus-root

symbiotic relationship

is called

“Mycorrhizae”

Mycorrhizae0 The most prevalent beneficial organisms associated with

plants, however, are soil-inhabiting fungi that form mutualistic root–fungal associations referred to as mycorrhizas

0 All mycorrhizas have intimate contact between hyphae and plant cells in an interface where nutrient exchange occurs.

0 Majority of plants form mycorrhizas, it is likely to lie somewhere between 80% and 90%. In many of these associations between 10% and 30% of the food produced by the plant moves through to the fungi.

Mycorrhizae0Mycorrhizas are found in a wide range of habitats,

including deserts, lowland tropical rainforests, high latitudes and altitudes

0Uptake of nutrient and Mineral nutrient acquisition from soil is considered to be the primary function of mycorrhizas, in addition to it’s roles in ecology, and man economic uses..

The pioneering work of Frank , resulted in the recognition of two broad subdivisions of mycorrhizas, Ectomycorrhizas and Endomycorrhizas

Mycorrhizae Types

Two major types of mycorrhiza occur in Nature

Endomycorrhiza “vesicullar-arbuscular” (common in more than 80 % of terrestrial plant species)

Ectomycorrhiza (specific to conifers and some broadleaved woody species) %15 of plants

There exists other types: Ericoid, Orchid, monotropoid mycorrhiza of less ecological importance.

EctomycorrhizaThe formation of a mantle or sheath of hyphae that covers considerable portions of lateral roots, the development of hyphae between root cells form a complex highly branched structure called the Hartig net,

Ectomycorrhiza: root tip of Pinus nigra colonised by ectomycorrhizal fungus

Ectomycorrhizas are usually found on tree species although a few shrub and herbaceous species may also develop this association. A detailed list of the conifer and angiosperm families.

*Fungi groups withlarge fruiting bodies, e.g. mushrooms,truffles and puffballs.

Ectomycorrhiza

Ectomycorrhizas can also confer pathogen resistance to their plant partner, and they are more effective at this, compared to AM roots

It has been estimated that between 5,000 and 6,000 species of fungi form ecto- or ectendo-mycorrhizas. Around 4,500 of these are epigeous (have above-ground fruiting bodies), but up a quarter are hypogeous (with underground fruiting bodies) such as truffles

White Truffles (Tuber magnatum). Fly agaric (Amanita muscaria).

EndomycorrhizaThey are either Vesicular

or Arbuscular;

Consists of hyphae that meander between the cortex cells, and often enter them.

Vesicular-arbuscular mycorrhiza: Highly colonized root of maize dyed with trypan blue. Mycorrhizal formations are clearly visible: 1) vesicles; 2) arbuscules

Main cellular features of the arbuscular endomycorrhiza

Hyphae from a germinating spore infect a root hair and can grow within the root between root cortical cells and also penetrate individual cells, forming arbuscules. These are finely branched clusters of hyphae, which are thought to be the major site of nutrient exchange between fungus and plant.

Fully developed arbuscule of Glomus mosseae in cortical cell

•Arbuscules: transfer organs of the mycorrhizae.

•Hyphae: connect root to soil. Act as pipeline

•Spores: resting, lipid filled structures.

Is the seed of the fungus world.

•Identification is based on these.

Many common desert plants, including cacti, are heavily mycorrhizal.. indicating that mycorrhizas have a particularly important role in water relations in dry ecosystems and in soils with poor water retention

Reasons, why the studyof mycorrhizas is important ?

0Mycorrhizas increase nutrient uptake from the soil.

0 Mycorrhizal fungi can be used in the biocontrol of pathogenic fungi and nematodes.

0 Some mycorrhizal fungi can bind heavy metals thus protecting plants from toxic levels of these substances.

0Mycorrhizas have a positive effect on the establishment of plant communities.

If no other factors are limiting, growth will be proportional to the amount of P absorbed by plants.

Mycorrhizae may supply up to 80%* of the plant P.

Agricultural advantages

• Allow plants to draw more nutrients and water from the soil, including phosphorus• Result in vigorous and healthy plants• Accelerate rooting• Increase plant survival• Increase drought tolerance and others stresses• Enhance flowering and fruiting

Ecological Importance0 Improvement of soil structure • Stimulation of

beneficial microbial activity0Water infiltration improvement • Reduction of

erosion and nutrient leaching

0AM ; also contribute to microaggregate formation in soils due to the production of a glycoprotein called “glomalin”; glycoprotein that acts as a glue for soil structure.

0Aggregate formation reduces decomposition of SOM, maintaining C in the soil. SOM also holds water and retains nutrients.

Reference:

0Books:-Mycorrhiza anatomy and cell biology-Mycorrhiza symbiosis 2nd edition

0Websites:-http://mycorrhizas.info/index.html

-http://en.wikipedia.org/wiki/Mycorrhiza -http://www.mycorrhizae.com/ -http://www.world-of- fungi.org/Assets/Mostly_Mycology/Diane_Howarth/mycorrhizal%20types.htm

Thanks for your attention