What is the role of Mycorrhiza in facilitating the phosphorus of the plant
Mycorrhizal fungi play an important role in phosphorus nutrition of plants. Most of the phosphorus is present in the soil in fixed form, which is unavailable to plants. Mycorrhizal fungi have the ability to solubilize the phosphorus present in fixed form, thus making it available to plants.
Please have a look at these useful links for more details.
Chapter Role of Mycorrhizal Symbioses in Phosphorus Cycling
Article Roles of Arbuscular Mycorrhizas in Plant Phosphorus Nutritio...
Chapter Role of Mycorrhizae in Plant Nutrition
Article Phosphorus nutrition of mycorrhizal trees
http://eeb.lu.lv/EEB/201309/EEB_11_Rai.pdf
all phosphorous in soil is not available to plants, thats the reason
http://www.plantphysiol.org/content/156/3/1050
introduction gives the role
Mycorrhizae are nick named as fungal roots, They associate themselves with higher plants as true friends and live and let live together harmoniously and mutually benefiting from each other. The mycorrhizae with their inherent ability to create an acidic environment solubilize the insoluble phosphates present in the soil and facilitate P absorption. The plant in turn provides its photosynthates to these fungal roots for their nourishment. Whereas, the mycorrhizae fail to do their job when chemical P fertilizers are added to the soil externally. Similar is the case with N fixing bacteria as well.
MYcorrhiza increase the surface area of root zone as due to secretion of auxins by endosymbiont, it leads to dichotomous branching of roots. the fungi also leads to moisture absorption by roots and thus helps in plant growth. further, mycorrhiza also helps in absorption of phosphorus by production of organic acids which leads to solubilization of fixed phosphorus.
AMF have the ability to excretephosphatases in the soil, enzymes catalyzing the release of inorganic phosphate ions that can correspond to 20-80% of the total soil P.
The ability of the mycorrhizae to extend beyond the naked root system can increase the root interface by 3 magnitudes or 1000 times. This can give plants extra ability to avoid drought and to increase nutrient content particularly immobile ones like phosphorus but also sulfur zinc, copper and others. The use of phosphorus can work to signal the less symbiosis synthetic fertilizers, pesticides and tillage can play havoc with symbiosis of mycorrhizal fungi. Mixed perennial forage plantings can foster a diverse and active mycorrhizal community highly favorable to crop production. The use of animal and plant system rotations known as mixed farming can improve the diversity and quantities of soil microrganisms and increase soil organic matter. Use of legumes and grasses for forages and the rotation of animal to plant production systems can increase the soil quality soil organic matter nutrients and help counteract environmental issues of monocultural farming. The best soils in all continents have originated out of grassland which have notable diversity and support large ruminant populations. With an abundant mycorrhizal association the crop production of crops like cereals can be optimized at about 20 to 25% of the phosphate needed to optimium plants without robust mycorrhizal development. Considering the potential of nonsustainable phosphorus supplies its high cost and environmental considerations the use of mycorrhizal inoculation can be used as an excellent opportunity of global farming constraints.
Soil-Water-Air-Plant-Animal Continuum is an excellent integral system when left to itself minus human interference based on greed. The human species has failed to be a part of this integral system due to which the planet Earth has been over stressed with attendant problems of climate change, global warming, environmental pollution and incidence of health problems and diseases of unknown etymology with no curative controls.
Mycorrhizae, due to their long mycellium (sometimes travel upto 1 metre), they can exploit more soil than roots to transport the plant available P from soil where plant root can not reach. AM fungi has been reported to release huge amount of acid phosphatase which help to mobilize plant unavailable organic P compound present in the soil. Moreover, they also influence the production of some organic acids which help in solubilizing plant unavailable inorganic P compounds.
Major two mechanism,
1: Solubilization of inorganic-P (readily available to plants as ionic-P form) and organic-P
2. Phosphatase produced by AM helps in hydrolyzing solubilized organic-P
Great learning. Thank you all for your responses and to Waqas for asking this very important question. However, from these answers I am thinking: How is it possible to assess the presence (even on a qualitative basis: ex.: poor, medium, many, etc.) of mycorrhizae in the field? Also how can farmers increase the richness of mycorrhizae in their field if they have none?
Dear Bruno Borsari, The ability to increase the activity of mycorrhizae would be to stimulated by mixed prairie communities which are largely mycorrhizal dependent and have huge mass of infection courts in their extensive root systems. The clean cultivation and the use of crops such as rape would represent a worse case situation. The presence of rotations and cover cropping can be favorable for maintaining and increasing mycorrhizae. The use of agrichemical and intensive P fertilization can have detrimental effects on the mycorrhizal communities.
Many thanks for your reply to my questions Dr. Hepperly. However, I would be interested to learn if there is a simple method to detect the presence of mycorrhizae that can give farmers an idea of whether or not these organisms are present in their fields. Intuitively, I understand that a polyculture of native plants will contribute with their cycle of life and decay, added to their root exudates to a diverse community of organisms in the soil (including mycorrhizae). How can we measure this?
The colonization of plant roots by mycorrhizae is assessed by clearing harvested roots and then staining for fungal structures of the mycorrhizae.
When soil samples are wet sieved the procedure can be used to isolate mycorrhizal sporangia these sporangia are different in their color and sizes which can be used to determine populations and species diversity. Attached is some mycorrhizal spores isolated by the wet sieving procedure.
Mycorrhiza increase the are of uptake and dissolve the insoluble phosphate and make it in available form. It also improve the biological property of the soil
While most emphasis has been given to Phosphorus and mycorrhizae also can increase other nutrients such as micronutrients in particular zinc whose widespread deficiency is problematic for plant, animal and human nutrition. In addition reports show other macro secondary and micronutrients can be effected positively. Since mycorrhizae improve plant water relationships they show optimum benefits in drought situation when crops are most needed.
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