Plants Communicate Via Symbiotic Root Fungi

Zen-Haven August 11 2013

Human arrogance has always assumed we are evolutionarily superior to plants, but it appears that modern science may be the antidote to this egocentric view.

Researchers in the UK have discovered an extensive underground network connecting plants by their roots, serving as a complex interplant communication system… a “plant Internet,” if you will.

One organism is responsible for this amazing biochemical highway: a type of fungus called mycorrhizae. Researchers from the University of Aberdeen devised a clever experiment to isolate the effects of these extensive underground networks. They grew sets of broad bean plants, allowing some to develop mycorrhizal nets, but preventing them in others.

They also eliminated the plants’ normal through-the-air communication by covering the plants with bags. Then they infested some of the plants with aphids. The results were remarkable.

Most people have no idea how important mycorrhizal fungi are for plant growth. They really are one of the keys to successful growth of plants. In my own garden, I just purchased a 15 gallon vortex compost brewer in which I grow these fungi in large quantities for my ornamental and edible landscape.

Underground Communications Network Thwarts Infestation

The aphid-infested plants were able to signal the other plants, connected through mycorrhizae, of an imminent attack—giving them a “heads up” and affording them time to mount their own chemical defenses in order to prevent infestation.

In this case, the alerted bean plants deployed aphid-repelling chemicals and other chemicals that attract wasps, which are aphids’ natural predators. The bean plants that were not connected received no such warning and became easy prey for the pesky insects.

This study is not the first to discover plant communication along mycorrhizal networks. A 2012 article in the Journal of Chemical Ecology describes mycorrhizae-induced resistance as part of plants’ systemic “immune response,” protecting them from pathogens, herbivores, and parasitic plants.

And in 2010, Song et al published a report about the interplant communication of tomato plants, in which they wrote:

“CMNs [common mycorrhizal networks] may function as a plant-plant underground communication conduit whereby disease resistance and induced defense signals can be transferred between the healthy and pathogen-infected neighboring plants, suggesting that plants can ‘eavesdrop’ on defense signals from the pathogen-challenged neighbors through CMNs to activate defenses before being attacked themselves.”

Miles of Mycorrhizae in One Thimbleful of Soil

The name mycorrhiza literally means fungus-root. These fungi form a symbiotic relationship with the plant, colonizing the roots and sending extremely fine filaments far out into the soil that act as root extensions. Not only do these networks sound the alarm about invaders, but the filaments are more effective in nutrient and water absorption than the plant roots themselves—mycorrhizae increase the nutrient absorption of the plant 100 to 1,000 times.

In one thimbleful of healthy soil, you can find several MILES of fungal filaments, all releasing powerful enzymes that help dissolve tightly bound soil nutrients, such as organic nitrogen, phosphorus, and iron. The networks can be enormous—one was found weaving its way through an entire Canadian forest, with each tree connected to dozens of others over distances of 30 meters.

These fungi have been fundamental to plant growth for 460 million years. Even more interesting, mycorrhizae can even connect plants of different species, perhaps allowing interspecies communication.

More than 90 percent of plant species have these naturally-occurring symbiotic relationships with mycorrhizae, but in order for these CMNs to exist, the soil must be undisturbed. Erosion, tillage, cultivation, compaction, and other human activities destroy these beneficial fungi, and they are slow to colonize once disrupted. Therefore, intensively farmed plants don’t develop mycorrhizae and are typically less healthy, as a result.

Making Farming More Eco-friendly

The discovery that fungi may be providing plants with an early warning system has profound implications for how we grow our food. We may be able to arrange for “sacrificial plants” specifically designed for pest infestation so that the network can warn, and thereby arm, the rest of the crop. In order to feed the world’s increasing population, farmers must return to working WITH nature, instead of against it.

Raising food is really about building soil, and modern agricultural practices are degrading million year-old topsoils, without any attention to rebuilding them. Spreading toxic chemicals, monoculture, using genetically engineered seed, generating toxic runoff and destroying biodiversity are all examples of working against nature.

Mycorrhizae not only assist the plants in staying vital and healthy, but they enrich the soil and improve its productivity, add organic matter, protect crops from drought, and increase the overall balance and resilience of the ecosystem.

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