Mycorrhiza

Mycorrhiza refers to the symbiotic association between a fungus and the roots of a vascular plant. This relationship is of significant importance in ecology, agriculture, and forestry, as it enhances plant growth, nutrient uptake, and resistance to environmental stresses. The term "mycorrhiza" originates from the Greek words mykes, meaning fungus, and rhiza, meaning root.

Types of Mycorrhizae

There are several types of mycorrhizal associations, which are classified based on the morphology of the interaction and the phylogeny of the involved fungi. The two main categories are:

• Ectomycorrhiza (ECM) - In this type, the fungus envelops the outer layers of the plant root in a sheath and also penetrates the intercellular spaces of the root cortex to form a network known as the Hartig net. Ectomycorrhizae are commonly associated with trees in temperate and boreal forests, including species of oak, pine, and birch.

• Arbuscular mycorrhiza (AM) - This is the most common form, where the fungal hyphae penetrate the root cells, forming structures known as arbuscules and vesicles. AM fungi belong to the phylum Glomeromycota and are associated with a wide variety of plants, including many agricultural crops.

Other types include ericoid, orchid, and monotropoid mycorrhizae, each adapted to specific plant families or environmental conditions.

Function and Benefits

Mycorrhizal fungi play a crucial role in the soil ecosystem. They enhance plant nutrition by facilitating the uptake of water and nutrients, particularly phosphorus and nitrogen, from the soil. In exchange, the plant supplies the fungus with carbohydrates produced through photosynthesis. This mutualistic relationship increases plant biomass, improves soil structure, and enhances plant resilience to stressors such as drought, salinity, and heavy metal contamination.

Mycorrhizae also contribute to the carbon cycle by sequestering carbon in the soil. The extensive network of fungal hyphae increases soil carbon storage, which is vital for mitigating climate change.

Applications

The benefits of mycorrhizal associations have been harnessed in agriculture and forestry to improve crop yield, reduce the need for chemical fertilizers, and enhance reforestation efforts. Mycorrhizal inoculants are commercially available and are used to treat seeds or soils, promoting sustainable agricultural practices.

Research and Challenges

While the advantages of mycorrhizae are well-documented, research continues to explore the complexities of these associations, including specificity between plant and fungal species, the impact of environmental changes on mycorrhizal functions, and the potential for genetic engineering to enhance symbiotic benefits.

See Also

• Soil biology
• Symbiosis
• Plant nutrition
• Sustainable agriculture