Two plants of the same species grow side by side. One is assaulted by insects, one not. On an individual plant, some leaves get eaten, some not. This doesnt happen at random, but is caused by the fungi that live within the foliages and roots of the plant.
Imagine you are holding a shoot of the dahlia plant, pictured below. How many species do you have in your hand? The answer is most certainly not one, but likely somewhere between 20 and 30. This is because every plant has fungi and bacteria that live on its surface( called epiphytes) and within its tissues( called endophytes ).
If the stem is still attached to its roots then the number of species would easily double. The roots contain lots of endophytes and a separate group of fungi, called mycorrhizas. These fungis grow into plant roots and form a symbiotic relationship in which the fungus donates nutrients( principally phosphate and nitrate) to the plant, in return for a supplying of carbon.
Dahlia is full of fungi. Alan Gange, Author
There has been a recent upsurge of interest in these fungi, as their presence can affect the growth of insects that assault plants. Research at Royal Holloway has shown that mycorrhizal fungi reduce the growth of many bugs, by increasing the plants chemical defenses. Our most recent run shows that endophyte fungu, the ones that live within plant tissue, can also cause plants to make novel chemicals.
So both endophytes and mycorrhizas can be thought of as plant bodyguards, where both partners benefit from business associations. The fungi gain refuge and resources, while the plant gains a natural pest protection system. The challenge is to exploit this natural system in agriculture and horticulture. However, these sorts of fungi are rare in crop plants thanks to years of fungicides, fertilisers and plant breeding, and modern harvests have far fewer natural fungal partners than their equivalents in the wild.
The mushroom get sugar and oxygen from the tree and returns minerals and carbon dioxide. jps/ www.shutterstock.com
Plants Can Opt Their Fungal Partners
In a wildflower grassland, many plants grow in close proximity but these plants can have entirely different fungal bodyguards. Although the plants grow in the same conditions, with the same spores floating around, they appear to select which fungi colonise their tissues.
Perhaps more intriguing is that different fungi exert different effects on bugs, a phenomenon called ecological specificity. In nature, plants seem to select the fungu that will provide them with maximum benefit. If were to use this in agriculture, current challenges is to find the right combinations of fungus that will provide crops with protection against pests and diseases.
There is a separate group of fungi, called entomopathogens, that kill bugs. These fungi can also live within plant tissues, meaning that if an insect eats an infected leaf, it ingests a killer fungus. There is evidence that plants particularly allow these most beneficial of bodyguards to colonise their tissues extensively more so than other tissue-dwelling fungi.
The Fungal Internet
The chemicals produced by all of these fungi travel throughout the plant. Some fungi in the root can change the host plants chemistry to keep leaf-feeding insects largely at bay, which may well be one reason why cultivating a rich soil full of useful microbes can lead to reduced pest problems above ground.
Fungal-tree internet: underground mycelia can transports alarm chemicals from plant to plant. sigur/ www.shutterstock.com
Other mycorrhiza( root) fungi can change the chemical makeup of a plants leaves, and we have found that these chemicals can attract parasitoid bugs to give another level of defence they can reduce insect growth by making foliages less edible, while simultaneously helping the plant to bellow parasitic insects that assault the herbivores.
Perhaps even more exciting is the discovery that networks of fungu in the clay can link many plants together. The mushrooms you see above ground are simply the fruiting the organizations of a larger organism below the surface, composed of thread-like material called mycelium.
Each mycelial thread( a hypha) has a structure like a drain tube. When plants are assaulted by insects, they make alarm chemicals that are transported to neighbouring plants through this tube network. Unattacked plants respond to these alarm signals by producing chemicals to ward off an impending attack.
This may be why no-dig gardening is suppose by many to produce healthier harvests than commercial agriculture, where this fungal network is continuously disrupted by ploughing.
Plants and fungi do not exist in isolation, but instead form a cooperative in the war against insect pests. Even better is that the fungis are perfectly edible if you had a salad recently, youll have plenty of endophytes within your belly right now.
Read more: www.iflscience.comContinue reading