Mycorrhizal Symbioses (Definition)

Mycorrhizal symbiosis refers the intimate beneficial association of certain groups of soil fungi with the root systems of higher plants. These associations create a specialized root structure, which facilitates nutrient uptake and exchange between both partners (plant-fungi).

The plant provides the fungus with sources of carbon (glucose and fructose from photosynthetic processes). In return, the fungus provides the plant with nutrients, and water in amounts greater than the plant would be able to obtain alone. This nutrient exchange between both symbionts is mutualistic (mutually beneficial).

Mycorrhizal symbioses are classified according to their colonization patterns in roots:

1. Ectotrophic mycorrhizal symbiosis:

• Fungal mycorrhizal mycelium densely grows around the absorbing roots.
• The internal hyphal growth is restricted to the intercellular spaces of the cortical tissue of roots.

2. Endotrophic mycorrhizal symbiosis:

• Mycorrhizal hyphae are able to invade the cortical cells.
• The invasion of hyphae to cortical cells causes an invagination of the plasmalemma.