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Michael Phillips shares green man ways to grow healthy through biological alchemy.
How Fungi and Plants Work Together
Excerpt: Hyphal Lysis
Molecular insights into more complex variations on nutrient flow are being revealed at a fast pace. Yet there's a flip side to mycorrhizal nutrient delivery that's too often overlooked. Like the swallow song of summer, all good times eventually come to an end. Each round of hyphal investment has a fixed life span of varying degrees. How this will tie into healthy plant metabolism in the next chapter should absolutely flip your gourd. Let's start by establishing the concept of hyphal lysis.
The disintegration of a cell and the subsequent release of protoplasm describe the end of time for a fungal hypha. This is lysis, involuntary cell death, resulting from the rupture of the cell wall after being cut off from adjacent hyphae. Consider the abandoned arbuscule, having served as a productive intraradical interface for the allotted seven days (give or take), closing down in what's in truth a stressful environment. It is inside the root cell, awash in extracellular fluids, stretching the cell membrane almost unbearably. Something has got to give. Each degenerating arbuscule gets shut off by a cross wall, thus preventing backflow of nutrients. Stay focused now. Complex fungal nutrients are being released directly into plant fluids. Meaning what exactly? Phantasmagoria!
Lysis results in the release of structural cell wall proteins, acidic polysaccharides, lipids, and polyphosphates. High concentrations of calcium are made available. The fungus literally gives its all to the plant. Nutrient flow via extracellular fluids will go in numerous directions -- new root ventures, rich exudates to draw more microbes, upward into leaves and shoots, the next fungal bay over, perhaps even into that nutrient-dense apple. The resulting energy gained by the plant in turn makes possible greater investment in immune function by the plant.
The collapse of arbuscules within root cells is
one way by which mycorrhizal fungi contribute
"partially built nutrition" to robust plants.
Microscopic photography (with selective staining
of fungal structures and live imaging)
has revealed that droplets of lipids are
released into the root cortex following lysis.
Courtesy of Y. Kobae et al.,
"Lipid Droplets of Arbuscular Mycorrhizal
Fungi Emerge in Concert with Arbuscule
Collapse," Plant Cell Physiology
55 (2014): 1945–1953.
Lipids formed through the conversion of glucose to triglycerides represent stored energy for any life form. Much ado should be made about fats. Japanese researchers did precisely that in 2014 by revealing the first direct link between arbuscule collapse and the streaming of lipid droplets into the root cortex. The emerging lipids in all likelihood were preformed and held within the arbuscular trunk rather than being integrated on the spot. Lipid synthesis in mycorrhizal fungi involves interaction with the fatty nature of the root cell membrane along with "bidirectional streaming" of protoplasm from arbuscule to intraradical hyphae to extraradical mycelium and back. That some of the good stuff gets shared with plant hosts when the arbuscule gate shuts at the time of lysis makes complete sense.
And yet this runs counter to what scientists thought even a decade ago. The pace of knowing on our part does not alter how creation works. New research like this simply gives us another piece of the puzzle to contemplate in the fascinating montage that makes life possible.
Nor does the extraradical mycelium last forever. The law of ebb and flow mandates that all parts of a fungal organism come available in due time. The ongoing spectacle of microbe consuming microbe offers no assurance to mycorrhizal fungi of a species pass. Actinomycetes in particular are quite capable of decomposing chitin, the structural component of fungal cell walls. Perennial plants going into dormancy at year's end experience an autopilot version of nutrient release. Root systems enter a sleepier phase. Fungi go into spore mode and hide away as hyphal fragments in roots and crevice places. Mycelial structure dissolves; a portion gets taken in by roots in more complex forms; the bulk assimilates into the jaws of the soil food web. Fungal death again contributes carbon and elemental nutrients in high concentration.
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