Mycorrhizas

A mycorrhiza (Greek for fungus roots; typically seen in the plural forms mycorrhizae or mycorrhizas) is a mutualistic symbiotic association between beneficial fungi and the roots of over 90% of plant species. This partenership dates back over 400 million years making it one of the original and longest lasting partnerships.

The association provides the fungus with a constant and direct supply of carbohydrates, sugars such as glucose and sucrose produced by the plant in photosynthesis. In return, the plant accesses an increased surface area to absorb water and nutrients, via the the fungal mycelium, a threadlike network of filaments coming out from the roots capable of exploring the external environmant and thus improving the absorption capabilities of the plant roots as well as significantly contributing to soil structure formation.

Mycorrhizal plants are often more resistant to various stresses like transplant shock, diseases, drought, salinity and toxic environments (heavy metal and hydrocarbons), to name but a few. These effects have been reported to be due to the improved water and mineral uptake, as well as, interactions with other beneficial soil micro-organisms.

Plants have been grown and in some cases selected against their ability to form mycorrhizal associations, under artificial conditions and/or using high chemical inputs (fetrilizer and pesticides) as an alternative to the poorly understood ancient partnership. Luckily, due to incresed scientific knowledge, high chemical input costs and greater environmental awareness, a renewed appreciation has stimulated new interest in our “old friends”.

Ectomycorrhizas

Ectoroot

Form associations predominantly in coniferous forest ecosystems (pine, spruce, fir etc.). The name comes from the fact that these fungi form certain characteristic structures like the hyphal mantal that changes the appearance on the outside of the roots. These are the easiest to spot as they also produce fruiting bodies, the mushrooms one can see when strolling in the forest and some that we eat (morels, truffles, etc…).

Endomycorrhizas

ARBUSCULAR MYCORRHIZA

Endoroot

Form associations with most agricultural, nursery and horticultural crops including broad-leafed trees (maple, ash, walnut etc.). Also known or have been referred to as, VA mycorrhizae or VAM. This name comes from their characteristic fungal structures--vesicles (V) and arbuscules (A)-which form within the cells of the roots and act as the nutrient interchange points between the beneficial mycorrhizal fungi and the plant. Even though they are the most abundant, these are more difficult to spot as they are microscopic and special stains are used to see them.

Plant Growth Promoting Mycorhizobacteria (PGPMB)

We define PGPMR’s as the fungi and bacteria from the root region (mycorhizobacteria) that colonize plant roots and stimulate plant growth. Postulated mode of actions are: symbiotic nitrogen fixation, effect on nodulation in legumes, effect on nutrient oxidation, solubilization and uptake by roots, hormone production, enhanced plant growth by siderophore production and enhanced plant growth by biocontrol activities.

Nitrogen Fixing Bacteria (NFB)

AZOSPIRULLUM

Free-living microaerophyillic bacteria, known to enter into associative symbiosis with xylem vessels of plant roots. Besides their ability to fix elemental nitrogen (25-40 kg N/ha/year), they are also known to secrete growth promoting substances, which enhance root proliferation and growth of crop plants.

RHIZOBIUM

Symbiotic bacteria (from the Greek words rhiza = root and bios = Life), known to fix nitrogen from the atmosphere in to a plant usable form, ammonium (NH4+), after becoming established inside root nodules of legume plants. In return the plant provides the bacteria with carbohydrates, proteins, and sufficient enough oxygen so as not to interfere with the fixation process.

Sulfur Oxidizing Bacteria (SOB)

These bacteria act to oxidize elemental sulfur, and a vital component of protein and enzyme systems, which in turn provides sulfate, the fourth major plant nutrient after N, P and K for plants.

Phosphorous Solubilizing Organisms (PSO)

Naturally occurring soil Phosphorous Solubilizing Bacteria (PSB) and fungi (PSF) that colonize plant roots and makes the ‘fixed’ mineral forms of less available soil phosphate immediately available for plant use. They promote greater phosphate use efficiency, which results in quick emergence, early vigor, greater stress tolerance, and more even maturity.

Biocontrol Agents

Biofungicides

TRICHODERMA SPP.

Highly-effective, non-toxic (humans) and environmentally safe beneficial fungi that grow on the entire plant root system. They protect roots from diseases caused by Pythium, Rhizoctonia and Fusarium by competing in the soil for nutrients and rhizosphere dominance with the phyto-pathogenic fungi mentioned above. In presence of sufficient organic carbon it produces enzymes having lytic effect on target fungi and in contrast in adverse conditions it produces toxins which are equally harmful. Compatible with mycorrhizae.

BACILLUS SUBTILIS

A Gram-positive, catalase-positive, ubiquitous, non-toxic (humans) bacterium commonly found in soil water, air and decomposing plant residues. B. subtilis has the ability to produce a tough, protective endospore, allowing the organism to tolerate extreme environmental conditions like heat and desiccation. Formulated into inoculants, it is well-known in the scientific community for its ability to suppress the development of common soil-borne disease organisms and for inducing plant growth promoting responses. As the bacteria colonize the root zone of the host plant, a protective sheath forms that completely covers the root system. This protective sheath contributes to improved plant health, growth and vigor.

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