What Are Mycorrhizae?
Mycorrhizae are symbiotic associations that form between the roots of most plant species and fungi. The term Mycorrhiza literally means “fungus root” and was first described by a German forest pathologist in 1885. It was estimated that 95% of all plant species belong to the genera that form Mycorrhizae. Little things run the world and this is especially true when it comes to getting plants established. Under natural conditions, plants live in close association with Mycorrhizae. Estimates of mycorrhizal filaments present in healthy soil are astonishing.
Several kilometers of filaments can be present in less than a thimbleful of soil associated with growing plants. Figure 1 shows just how complex these organisms are and how highly branched they are throughout the soil. The hyphae act as a link between the roots and the soil to increase nutrient uptake.
How do Mycorrhizal Fungi work?
Mycorrhizal root systems increase the absorbing area of roots 10 to 1000 times thereby greatly improving the ability of the plants to utilise the soil resources. Mycorrhizal fungi are able to absorb and transfer all of the 15 major macro and micro nutrients required for plant growth. Mycorrhizal fungi release powerful chemicals into the soil that dissolve hard to capture nutrients such as Phosphorous. This extraction process is particularly important in plant nutrition and explains why non mycorrhizal plants require higher levels of fertility to maintain their health. Mycorrhizal fungi form an intricate web that captures and assimilates nutrients from the soil to the root. They are also involved in a wide variety of other activities that benefit plant establishment and growth. The same web of fungi is very important for water uptake and storage. In non-irrigated conditions, plants inoculated with mycorrhizae are under far less drought stress compared to untreated plants.
Mycorrhizal fungi also improve soil structure. The intricate web of hyphae produced by these organisms also produces humic compounds and “glomalin” which is a soil glue. This glue binds soils into aggregates and improves soil porosity. Figure 2 shows a soil aggregate covered in glomalin/ (stained green) and this shows just how critical mycorrhizae are in all soil types. In sandy or compacted soils, the ability of mycorrhizal fungi to promote soil structure is of great importance.
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