Arbuscule - Highly branched structure produced by arbuscular mycorrhizal fungi inside the cell lumen of their host. Arbuscules are considered to be the key element of the symbiotic nutrient exchanges between the plant & the fungus.

Arbuscular mycorrhiza - Widespread type of endomycorrhizal interactions involving fungi of the phylum Glomeromycota, the hyphae of which reach the root inner cortex & develop highly branched structures called arbuscules.

Ascomycetes - Phylum of the kingdom fungi characterized by a microscopic sexual reproductive structure called  ascus, a single cell containing non-motile spores. Ascomycetes include macroscopic fungi live in symbiosis with forest trees.

Aseptate endophytes - Plant colonizing fungi with syncytial hyphae that lack transversal walls (septa).

Basidiomycetes - Phylum of fungi the sexual reproduction of which is accomplished in club-shaped cells called basidia that bear external spores. Several basiomycetes develop ectomycorrhizas.

Ectomycorrhiza - Symbiosis between higher plants & fungi belong to Asco- & Basiomycetes, in which fungal hyphae surround the root tips & develop between epidermal cells but never enter the cell lumen.

Endomycorrhiza - Group of mycorrhizal symbiosis involving fungal penetration inside living cells of the root epidermis & cortex.

Extraradical mycelium - Hyphal network that develops in the rhizosphere, in which it absorbs inorganic nutrients that are transferred to the host plant through intraradical hyphae.

Hyphopodium - Specialized hypha of an arbuscular mycorrhizal fungus, often branched & swollen, which adheres to the root epidermis before intracellular fungal penetration.

Intraradical Hyphae - Network of hyphae from mycorrhizal fungi that colonizes the host root tissues.

Metagenomics - Analysis of genetic material obtained from environmental samples.

Nodulation (Nod) factors - Signalling molecules produced by nitrogen fixing bacteria (rhizobia) & eliciting nodule initiation & bacterial uptake in the roots of legumes. They are lipochitooligosaccharides consisting of an acylated chitin oligomeric backbone carrying various functional group substitutions at the terminal or non-terminal residues.

Pathogen - Organism that receives its nutrients from a host causing a disease.

Perifungal interface - Thin apoplastic compartment that surrounds each intracellular fungal structure inside plant tissues. The interface consists of plant cell wall components & is bordered by an invagination of the plant plasma membrane.

Presymbiotic phase - Phase is the life cycle of mycorrhizal fungi that precedes contact with the host plant. During this phase, fungal development is not supported by the nutrients of plant origin.

Saprotroph - Organism that obtains nutrients from dead organic matter.