micorrizici

Micorrizici are organisms that form mycorrhizal associations with plant roots. In most ecosystems these associations are fungal, although some bacteria participate as endophytes within the root zone. The term covers major groups such as arbuscular mycorrhizal fungi (AMF) belonging to Glomeromycota and ectomycorrhizal fungi (ECMF) that colonize many trees and shrubs. Plants provide carbohydrates to the fungi, which in turn enhance the plant's ability to acquire nutrients and water.

Arbuscular mycorrhizal symbiosis, the most widespread form, forms arbuscules and vesicles inside root cells, whereas ectomycorrhizal associations envelop root tips with a fungal mantle and create a Hartig net between outer root cells. These structural differences reflect distinct strategies for nutrient exchange and host specificity.

Micorrizici improve uptake of nutrients, especially phosphorus, zinc, and other micronutrients, and can improve water relations and soil structure. The fungi receive carbon from the plant, while supplying access to nutrients via extensive hyphal networks that explore soil volumes beyond the root zone. In soils, micorrizici influence plant resilience to drought, temperature stress, and some soil contaminants, and can affect plant community composition.

Ecologically, micorrizici are widespread in forests, grasslands, and agricultural soils. Some associations are obligate for certain hosts, while others are facultative and occur across diverse plant species. The symbiosis is ancient, with fossil records and molecular data indicating origins hundreds of millions of years ago, contributing to the success of terrestrial ecosystems.

In agriculture and restoration, micorrizici are used as inoculants to improve crop performance and soil health. Management practices that maintain native mycorrhizal communities—reduced soil disturbance, organic matter inputs, and crop diversification—support these organisms. Limitations include the variability of inoculant performance and the need for compatible host–fungus combinations and favorable soil conditions.