The underground market ...

A cubic inch of soil contains about 7 billion fungal lifeforms and 1 billion bacteria. The complex interactions of these entities, in conjunction with their plant partners, is akin to a cutthroat marketplace where ruthless supply and demand dictate how zealously guarded resources are to be used by the parties in question is readily seen by the video above and the text below. Enjoy.

Kiers surrounded some nodules on soybean plants with an almost nitrogen-free air supply, making the bacteria in those nodules useless to the plant. She found that the plant reacted by shutting off the supply of oxygen to those bacteria, drastically reducing their reproduction. It seemed the relationship between the bacteria and the soybeans, far from being a happy friendship, was an uneasy détente, with the plant imposing crippling sanctions on any bacterial partners that failed to earn their keep. 

Kiers then switched from bacteria to fungi. While bacteria might nestle into the roots of select groups of plants, fungi are without question the masters of the underground domain. Certain fungi spread through vast areas and commingle with just about every plant they encounter, even sending thready tendrils known as hyphae directly into plants’ roots. (The name for these fungi — “mycorrhizae” — literally fuses the Latin myco-, meaning “of fungi,” with the Greek rhiza, or “root.”) Indeed, the mycorrhizal world forms a sort of inversion of the vegetable one, with branching fungal networks extending downward, mirroring the branching stems and limbs of the plants reaching skyward.

Factoids ...

But what really distinguishes the fungal world is its diversity and complexity. A spoonful of soil contains more microbial individuals than there are humans on Earth. “It’s the most species-dense habitat we have,” said Edith Hammer, a soil ecologist at Lund University in Sweden. A single plant might be swapping molecules with dozens of fungi — each of which might in turn be canoodling with an equal number of plants. It’s a promiscuous party down there.

By growing carrot roots and fungi in segmented petri dishes that held unequally distributed nutrient resources, Kiers and her colleagues demonstrated that the organisms favor symbiotic partners that have more to offer in nutrient exchanges.

The underground market ... indeed.