"One flower, one world, one leaf, one bodhi." Small and large, momentary and eternal, sometimes do not contradict each other. For example, in a grain of soil, there is also a world in which plants, animals, and microorganisms are wrestling.
A lively world of soil
The world of soil may seem tedious, but in reality, hundreds of millions of soil creatures are alive in it.
In most cases, soil fauna is located on the top layer of soil organisms, such as mites and spingtails in the soil, which feed on fungi and detritus in the soil. Plants, on the other hand, often act as cannibalized, providing nutrients to other organisms in the soil. So the plant seems to be perpetually at the bottom and has no chance to fight back?
Food webs in the soil
(Image source: Landscape for Life)
If you think that, you're dead wrong.
Plant counterattacks may be staged underground at all times, and this battle is led by fungi.
Soil animals are killed, who is the real culprit?
Fungi in the soil, like plants, don't have a good time — they're all on the menu of bullettails. But in a feeding experiment, scientists studying feeding networks in the soil found that when feeding a fungus, the bullettails that have always fed on fungi not only did not eat, but even were killed miserably, almost completely destroyed. However, when fed with other fungi, the slings are almost always alive and thrive.
The survival of the slingtails after the addition of different fungi to the soil where the squids are raised: the red part represents the syllabus and the blue part represents the two-color wax mushroom
(Image source: Reference 1)
After dissecting the corpses of the killed bullettail insects, the scientists found that their bodies had been occupied by hyphae. This anti-bullettail fungus is Laccaria Bicolor, a large basidiom (what we usually call mushrooms) that use hyphae to invade the body of the bullettail to kill it and thus obtain nutrients.
Insects killed by the green zombie fungus, the soil fungus green zombie can kill more than 200 species of insects
(Image source: Wikipedia)
This is also the first time that the two-color wax mushroom has been shown to have the ability to catch insects, reversing the food chain with its own efforts. But surprisingly, the end of this reversed food chain nutrient flow is not the two-color wax mushroom, but the plant.
The "buying" big guy is actually "it"? Where is the evidence of murder?
Although soil fungi are not uncommon to kill animals, most of them are used to feed themselves, and "killing" is a necessity for life.
However, for two-tone wax mushrooms, the situation is much more complicated.
It is actually the exophytic mycorrhizal bacteria of plants, and forms a symbiotic relationship with the underground roots of plants: the hyphae of the two-color wax mushroom are wrapped in the roots of the plant, using their extensive hyphal network to absorb nitrogen, phosphorus and other nutrients from the ground, instead of the plant roots to obtain nutrients in the soil; plants use strong photosynthetic ability to provide them with carbon water, and the two are exchanged equally.
Ectomycorrhizae formed by two-color wax mushrooms with pine trees
(Image source: SciELO México)
Where does the nutrients obtained by the two-color wax mushroom kill insects go? Given the underground symbiotic relationship between the two-color wax mushroom and the plant, scientists speculate that this part of the nutrient may have flowed to the plant.
So, the question is, how to detect the flow of nutrients?
Because the two-color wax mushroom is a mycorrhizal bacterium of Pinus Strobus in North America, scientists have placed the slingtail, the two-color wax mushroom, and the North American josson in the same culture system, labeling the slingtail with nitrogen isotopes, tracking the flow of its final nutrients as prey, and thus verifying the conjecture.
To ensure that the slings placed in the soil can only be touched by fungal hyphae, the scientists wrapped the slingtails in nylon bags that only the fungal hyphae can pass through, isolating external variables. After two months, the movement of nitrogen isotopes was observed to determine the relationship between the three and the flow of nutrients.
Mycorrhizal system of bicolor wax mushroom and North American josson: the hyphae of bicolor wax mushroom invade the root cortex, and the two-color wax mushroom hyphae are stained orange-yellow in the cell space (Figure c).
(Image source: Reference 2)
The results of the experiment found that the pine tree did get an "offering" from the two-color wax mushroom!
North American josson has no insect-catching organs underground and does not kill slingtails, but in its seedlings up to 30% of the nitrogen element is a labeled nitrogen isotope. It is conceivable that it is through the mycorrhizal network that the two-color wax mushroom transfers the nutrients obtained by its "killing" to the North American josson.
Plants employ "fungal killers", and many more
Having figured out where the nutrients flow, new questions arise: In addition to offering nitrogen from the soil to plants, why should the two-color wax mushroom selflessly contribute the nitrogen in its hard-won "meat dish" to the North American josson?
Behind its "selfless" behavior, it may still be to exchange more nutrients with plants.
In another symbiotic fungus, scientists have confirmed that it is the carbohydrate that the fungus exchanges with the plant with "meat dishes". Not only the two-color wax mushrooms that are forced to catch insects, but also the green zombie bacteria that belong to the plant endophytes are also working hard to catch insects to provide nitrogen sources for plants.
Using the same isotopic labeling method, the scientists found that the green zombie bacteria transferred nitrogen from the prey to the plant, and the reward was the carbohydrates made by the plant. The exchange of carbon and nitrogen between the two is like a long-negotiated deal.
Schematic of the green zombie killing insects to supply nitrogen to plants
(Image source: Reference 3)
The same may be true of the trade between north American josson and two-tone wax mushrooms. Bugs are a high-quality source of nitrogen in the soil, so they are targeted by plants. But plants do not need to go down to catch insects in person, they only need to take the common currency- carbohydrates to the trading table, and the fungus will catch insects "to show their skills".
The formation of an underground trading network: I have everything you want
The mycorrhizal symbiotic network formed by plants and fungi has a long history. As early as 400 million years ago, plants formed a symbiotic relationship with fungi when they landed from the aquatic environment to the land, and the two went hand in hand to occupy the terrestrial ecosystem. Their abilities complement each other and combine strong and strong, resulting in the effect of "1 + 1 is greater than 2".
Plants use photosynthesis to make carbohydrates, which provide the basic raw materials for the survival of countless organisms. Compared with the root system of plants, the underground hyphal network of fungi has more powerful soil permeability, pervasive, and the acquisition of nitrogen, phosphorus and other substances in the soil is very efficient.
In the long process of cooperation, as many as 90% of plants and fungi have formed a mycorrhizal symbiotic relationship, plants do not treat invading hyphae as pathogens, and fungi do not invade, grow and spread indefinitely in mycorrhizal.
The mycorrhizal symbiosis system is like an underground trading market, with plants providing carbohydrates and fungi offering nutrients such as nitrogen and phosphorus.
In general, fungi do not need to exchange additional nitrogen, but the extensive underground trading network of plants and fungi makes the nitrogen available in the soil in short supply, while plants use the abundant carbon source in the air (carbon dioxide) to make excess carbohydrates, tempting symbiotic fungi to participate in the exchange. It may be for this reason that the two-color wax mushroom is forced to willingly catch insects and exchange the extra nitrogen it obtains, thus reversing the food chain in the soil in an incredible way, allowing the plant to eat "meat" silently.
"Belly Black" North American Josson: Hunter? prey?
In terms of strict carnivorous plant standards, North American Josson is naturally not an insectivore, and it has not personally fallen, after all, the evolution of the insectivorous route of "attracting, capturing and digesting insects" is too laborious. North American Josson chose to make good use of the ancestral photosynthetic self-supporting ability, constantly manufacturing photosynthetic products for exchange, and then beautifully open "meat". It can be said that this is essentially another victory for photosynthesis. Unexpectedly, the plants that seem to be stationary and slaughtered by others actually have the attribute of "belly black" and have a place in the underground trading market. There is nothing strange in the world, just in response to the recent saying, "High-end hunters always like to appear as prey."
bibliography:
1.Klironomos, John N., and Miranda M. Hart. "Animal nitrogen swap for plant carbon." Nature 410.6829 (2001): 651-652.
2.Martin, Francis, and Marc‐André Selosse. "The Laccaria genome: a symbiont blueprint decoded." New Phytologist 180.2 (2008): 296-310.
3.Behie, S. W., P. M. Zelisko, and M. J. Bidochka. "Endophytic insect-parasitic fungi translocate nitrogen directly from insects to plants." Science 336.6088 (2012): 1576-1577.
4.Behie, Scott W., et al. "Carbon translocation from a plant to an insect-pathogenic endophytic fungus." Nature communications 8.1 (2017): 1-5.