Mykoriisa

Mykoriisa is a symbiotic association between a fungus and the roots of a plant. In this relationship, the fungus colonizes plant roots and extends a network of hyphae into the soil, aiding in nutrient and water uptake while receiving carbohydrates produced by the plant through photosynthesis.

There are two major forms of mykoriisa. Ectomykoriisa (ectomycorrhiza) forms a fungal mantle around the outside of root tips and a Hartig net between the outer root cells, and is common in many forest trees. Endomykoriisa (arbuscular mycorrhiza, AM) involves fungal hyphae penetrating root cortical cells to form structures called arbuscules inside the cells. AM is widespread among land plants, including many herbaceous species and crops.

Ecologically, mykoriisa enhances the plant’s uptake of phosphorus, nitrogen, and micronutrients, as well as water, often improving drought tolerance and disease resistance. The fungal partner benefits by receiving carbon from the plant. Hyphal networks also contribute to soil structure and carbon storage, partly through the production of soil-binding proteins such as glomalin. Mycorrhizal networks can connect different plants, facilitating nutrient exchange and communication.

Distribution and applications: mykoriisa is found worldwide, especially in forests and grasslands. AM associations are common in many crops, while ECM associations occur with numerous tree species. In agriculture and restoration, mycorrhizal inoculants are used to improve plant establishment, growth, and resilience.

Etymology and history: the word derives from Greek mykes (“fungus”) and rhiza (“root”). The concept has a long history of study, with ectomycorrhizal relationships described in the 19th century. In Finnish, mycorrhiza is rendered as mykoriisa.