Mycorrhizae: The great allies in the mitigation of drought effects

Increasingly recurrent droughts and water scarcity are major challenges for agriculture worldwide. Mycorrhizae, associations between fungi and plant roots, are an effective solution to mitigate these adverse effects. This article explores how mycorrhizae can help plants better tolerate drought and improve water use efficiency.

What are Mycorrhizae?

Mycorrhizae are symbiotic relationships between soil fungi and plant roots.
These mutualistic associations allow for increased nutrient and water uptake. There are two main types of mycorrhizae:

1. Arbuscular mycorrhizae (AM): they penetrate inside root cells, forming
   structures called arbuscules and vesicles. They are the most common and are found in more than 90% of plants.
2. Ectomycorrhizae (ECM): they form a network around the roots and penetrate the
   root cell walls, without going deep into them. They are found on trees and shrubs in forest areas.

Negative effects of drought on plants

Drought negatively affects plants in several ways:
● Reduced Photosynthesis: Lack of water limits the opening of the stomata,
reducing the entry of carbon dioxide and, therefore, reducing photosynthetic
activity.
● Dehydration and Wilting: Excessive water loss can lead to
dehydration and wilting of plants.
● Growth Inhibition: Water shortage affects the growth and development of
roots and new shoots.
● Increased Susceptibility to Diseases: Drought stressed plants are
more susceptible to diseases and pests.

How do mycorrhizae help mitigate the effects of
drought?

Improved Water Absorption

Mycorrhizae increase the ability of plants to absorb water in several ways:

1. Extension of the root system: The hyphae of mycorrhizal fungi, which
   would be equivalent to the roots of vegetables, extend the root system of
   plants, allowing them to explore a larger volume of soil in search of
   water.
2. Water Absorption in Dry Areas: Hyphae can access small
   porosities in the soil that roots cannot reach (due to their thickness), extracting
   water that would otherwise be out of reach of the plant.

Water Balance Regulation

Mycorrhizae help plants regulate their water balance and maintain adequate levels of hydration
:

1. Improved stomatal conductance: Mycorrhized plants can regulate
   better the opening of their stomata, optimizing transpiration.
2. Transpiration Rate Regulation: Under moderate
   drought conditions, mycorrhizal plants can maintain a more
   constant transpiration rate, which helps avoid extreme water stress.

Production of Protective Substances

Mycorrhizae induce the production of protective substances in plants:

1. Accumulation of Osmoprotectants: Compounds such as proline and soluble sugars
   that protect plant cells from water stress.
2. Activation of Antioxidant Enzymes: Help reduce cell damage caused by
   oxidative stress during drought.

Soil Structure Improvement

Mycorrhizae contribute to the improvement of soil structure, improving water infiltration, retention and availability:

1. Soil Aggregation: The hyphae of mycorrhizal fungi produce substances such as
   glomalin, which help to form soil aggregates, improving its structure and
   water retention capacity.
2. Increased Porosity: Improves infiltration and water storage in the soil.

Scientific evidence

Numerous studies have demonstrated the benefits of mycorrhizae in conditions of
drought:

● Research In corn, wheat and other extensive crops: It has been
shown in numerous studies that plants associated with
arbuscular mycorrhizae have higher water use efficiency and higher
grain yields, under rainfed growing conditions or after periods of high
temperatures.
● In vegetables: Research in crops such as tomato and lettuce
indicates that mycorrhizae allow optimizing the use of water and fertilizer, while reducing the incidence of pests and diseases. This allows for reduced input use and higher crop quality.
● In woody crops: In citrus, stone fruit and nuts, mycorrhizae have been shown to improve resistance to water and salt stress, and better crop establishment in new plantings.

Practical application in agriculture

Soil and Seed Inoculation

To take advantage of the benefits of mycorrhizae in improving tolerance to water stress, and
other types of stress such as heat or salt stress, farmers can inoculate their soils or seeds with suitable mycorrhizal fungi.

Mycorrhizal Strain Selection

It is important to select mycorrhizal strains that are most effective for the specific crops
and soil conditions. There are strains that may be less effective than others
under some conditions.

Importance of the use of multiprimer products

It is common to find products containing a single generic mycorrhizal strain (species), which may not be adapted to the growing conditions. It is advisable to use multi-strain (multi-species) products, with greater adaptability and thus maximize the chances of success. Some examples of species are: Rhizophagus irregularis, Funneliformis mosseae, Septoglomus deserticola, Claroideoglomus etunicatum and Claroideoglomus claroideum.

Sustainable Soil Management

Sustainable agricultural practices, such as reduced tillage, use of organic fertilizers
and reduced use of chemical pesticides, can favor the establishment and effectiveness of mycorrhizae
.

Conclusion

Mycorrhizae are powerful allies in the fight against the effects of drought and lack of
water in agriculture. They increase water absorption and retention, improve the regulation of the water balance of plants and strengthen their natural defenses. By incorporating mycorrhizal products into agricultural practices, it is possible to increase crop resilience to drought and water scarcity, and promote a more sustainable and productive agriculture
.