What are mycorrhizae?
The word ”mycorrhizae” is derived from the Greek words: mykes—meaning fungus, and rhiza—meaning root. Mycorrhizae are specialized, beneficial fungi that establish symbiotic relationships with plant roots. It is estimated that as much as 90% of the world’s land plants develop some kind of symbiosis with mycorrhizae.
How do they work?
The mycorrhizal fungi penetrate growing plant root tissues, surround the root mass, and extend far into the surrounding soil, encompassing a much greater volume of soil than that occupied by the plant’s own roots and root hair system. The fungi’s long thread-like mycelia are especially effective in capturing moisture and nutrients from the soil, particularly nitrogen and phosphorous. The fungi consume the nutrients, but more importantly, they generously share them with the roots of the host plant. In return, the host plant provides the fungi with photosynthesized nutrients, especially sugars.
Building great soil structure
Mycorrhizae also act as an important soil-binding agent, significantly contributing to friable soil texture. Their countless long filaments, called hyphae, tend to accumulate in the soil over a period of time and can persist for months or even years. Larger soil particles, particularly the sand-sized fraction, tend to be held together by these hyphae. The filaments tend to have sticky surfaces from extracellular polysaccharides, which are sugars processed and exuded by the mycorrhizae. Additionally, the tips of developing root hairs likewise secrete polysaccharidic mucigel, a similarly sticky, plant-produced substance. Together, these sticky materials enable the filamentous hyphae to strongly adhere to the soil particles, physically binding and enmeshing them together to form tiny, semi-stable aggregates. This aggregate structure increases in the root zone, encouraging further root growth, which in turn attracts more mycorrhizae, leading to more aggregation and so on, perpetuating the process.
What does this process mean to the gardener?
Mycorrhizae help to absorb nutrients, assist in drought tolerance, and create ideal garden soil structure: soil that drains, breaths, and retains optimum moisture. The near perfect ”coffee-grounds” soil texture often found in fastidiously maintained organic gardens are an example of long-term mycorrhizal soil activity.
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