Our Story Begins......
470 million years ago, when the first larger organisms started to colonise the land.
The first pioneers were lichens – an association between a fungus and a photobiont (an algae and/or cyanobacteria).
Like all fungi, lichen-fungi require carbon as a food source; this is provided in the form of simple sugars by their symbiotic photobionts, that are photosynthetic.
It was this association that allowed plants to leave the oceans.
The photobionts in return seem to to be provided with optimal living conditions and improved access to mineral nutrients which are provided because of fungal digestion outside their cells.
Simple mosses occupied the wetter areas and these too were associated with fungi. The mosses only had simple pseudo-roots that were not very good at extracting nutrients from the soil, so they associated with fungi that were much better suited for doing this. These associations are called mycorrhizas (my-coh-rise-ehs).
As the saying goes ‘the rest is history’; this is how plants learned how to garden. When we garden we use tools such as forks, spades and rakes. Plants use micorrhizae (mycorrhizae or Mycorrhizas is plural). Unlike our gardens a plants garden is entirely underground and you never normally see it.
So What are Micorrhizae?
Jumping forward 470 million years to today, a mycorrhiza is a mutualistic symbiosis between a fungus and a vascular plant that influences plant nutrition, community structure and nutrient cycling.
Mycorrhizal fungi remain largely invisible to us humans, apart from the occasional spore-producing mushroom and the miniscule or even microscopic individual threads called hyphae that are all interconnected into a net-like web called a mycelium.
How do Micorrhizae work?
When Mycorrhizas were first classified they were divided into two types of symbiosis: endotrophic and ectotrophic, (but there are now seven distinct symbioses).
In each, the fungus receives sugars from the plant and in exchange (because plants don’t give up their valuable sugar resources just for the fun of growing fungus gardens) the plant receives certain nutrients, water and protection against pathogens.
Endomycorrhizas were the first to evolve and are the most common type, usually not producing typical mushrooms. Most of the fungal structure is contained within the root, with the hyphae growing between the cell walls and the membranes (like wedging themselves in between a bicycle tire and the inner tube). They associate with a diverse array of plants including most crop plants, grasses, flowering plants and many trees.
Ectomycorrhizas are more advanced, growing close to the root surface they form a network inbetween the root cells and a sheath around the whole root system. From this they grow outwards searching for moisture and nutrition in the surrounding soil. Many Ectomycorrhizas produce mushrooms, edible or with other claims to fame. They associate with woody shrubs or trees and examples of their mushrooms are Amanitas, Chanterelles, and Truffles.
Plants have a limited ability to get moisture and nutrients for themselves, their roots have to be in direct contact with the soil and they can only grow to a certain level of ‘smallness’, limiting the area of soil they can access.
The individual hyphae of the mycelium of Micorrhizal fungi on the other hand can, as we have already mentioned, grow as small as ‘microscopic’. This allows them to access virtually every available millimetre of soil.
Mycorrhizal fungi can extend a plant’s root system up to 1000x playing a significant role in accessing and delivering hard-to-capture nutrients such as organic nitrogen, phosphorus, and iron. They also produce enzymes which can liberate Copper, Calcium, Magnesium, and Zinc which they then deliver to the plants.
Another key functions is their ability to accesss nutrient sources not directly available to plants such as insects, nematodes and rocks. Without Micorrhizae some plants would not be able to survive, let alone function to the best of their ability, and in many places whole forests or ecosystems would not exist without them. (See picture above).
The Wood-Wide Web
Ectomycorrhizal fungi also have some absolutely amazing abilities, not only can they help to protect their plants against diseases and toxins they also act as a sugar ‘delivery service’. Because ectomycorrhizal fungi connect entire communities of plants together on the same mycelium network they will ‘deliver’ sugar from plants that have plenty, to plants that don’t have enough.
This connection – the mycelium network also enables the plants to communicate with each other. If a predator attacks one plant it can send signals to all the other plants that are connected to the same network, allowing them to produce substances that deter that particular predator. This truly is an ‘internet’ made out of fungus leading it to be dubbed ‘The Wood-Wide Web’.
One particular mycelia of a fungus is the largest living organism on Earth; dubbed the ‘humongous fungus’ by the BBC it is a honey fungus measuring 2.4 miles (3.8 km) across in the Blue Mountains in Oregon.
Preserving & Restoring
Although soil fungi are extremely beneficial and ecologically influental they are also fragile. Using fungicides, pesticides, and inorganic fertilizer can eliminate them. Ploughing and double-digging break up their delicate hyphae and soil compaction from heavy machinery and vehicles can crush and destroy the critical networks.
Practicing no-dig and other permaculture methods coupled with adding Mycorrhizal fungi when you plant/transplant will help to ensure that you have a healthy population of these amazing organisms.
You only have to add them once, they will last forever as the plant will grow them.
After all plants are great gardeners.