Increasingly recurrent droughts and water scarcity are major challenges for agriculture worldwide. Mycorrhizae, partnerships 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:
- 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.
- Ectomycorrhizae (ECM): form a network around the roots and penetrate into the root cell walls, without forming
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 stomata,
reducing the influx of carbon dioxide and thus reducing photosynthetic activity.
photosynthetic activity.
● Dehydration and wilting: Excessive water loss can lead to dehydration and wilting.
● Growth Inhibition: Water shortage affects the growth and development of roots and new shoots.
● Increased Susceptibility to Disease: Plants stressed by drought are more susceptible to diseases and pests.
How do mycorrhizae help mitigate the effects of drought?
Improved Water Absorption
Mycorrhizae enhance the ability of plants to absorb water in several ways:
- Extension of the root system: The hyphae of the mycorrhizal fungi, which are the
equivalent to plant roots, extend the root system of plants, allowing them to explore a greater volume of water.
root system of plants, allowing them to explore a larger volume of soil in search of water.
water. - Water Absorption in Dry Areas: The hyphae can access small porosities in the soil where they can
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.
adequate levels of hydration:
- Improved Stomatal Conductance: Mycorrhizal plants are able to better regulate the opening of their
better regulate the opening of their stomata, optimising transpiration. - Regulation of transpiration rate: In conditions of moderate drought, mycorrhizal plants
In moderate drought conditions, mycorrhizal plants can maintain a more constant transpiration rate, which helps to prevent
constant, which helps to avoid extreme water stress.
Production of Protective Substances
Mycorrhizae induce the production of protective substances in plants:
- Accumulation of Osmoprotectants: Compounds such as proline and soluble sugars that protect plant cells from water stress.
- Activation of Antioxidant Enzymes: Help to reduce cell damage caused by oxidative stress during drought.
Improved Soil Structure
Mycorrhizae contribute to the improvement of soil structure, improving water infiltration, retention and availability:
- Soil Aggregation: the hyphae of mycorrhizal fungi produce substances such as glomalin, which help to form soil aggregates, improving soil structure and water retention capacity.
- Increased Porosity: Improved infiltration and storage of water in the soil.
Scientific evidence
Numerous studies have demonstrated the benefits of mycorrhizae under drought conditions:
● Research In maize, wheat and other extensive crops: it has been.
studies have shown that plants associated with arbuscular mycorrhizae have
arbuscular mycorrhizae have higher water use efficiency and grain yields under drought conditions
grain yields, under rainfed growing conditions or after periods of high temperatures.
temperatures.
● In vegetables: Research on crops such as tomato and lettuce indicates that mycorrhizae can
indicate that mycorrhizae allow optimisation of water and fertiliser use, 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 stresses such as heat or salt stress, farmers can inoculate their soils or seeds with suitable mycorrhizal fungi.
Selection of Mycorrhizal Strains
It is important to select mycorrhizal strains that are most effective for the specific crop and soil conditions. There are strains that may be less effective than others in some conditions.
Importance of using multi-strain products
It is common to find products containing a single generic mycorrhizal strain (species), which may not be adapted to the crop conditions. It is advisable to use multi-strain (multi-species) products, which are more adaptable and thus maximise the chances of success. 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, the use of organic fertilisers and the
fertilisers and reduced use of chemical pesticides can favour the establishment and effectiveness of mycorrhizae.
establishment and effectiveness of mycorrhizae.
Conclusion
Mycorrhizae are powerful allies in the fight against the effects of drought and water shortage in agriculture. They increase water uptake and retention, improve the regulation of the water balance of plants and strengthen their natural defences. By incorporating mycorrhizal products into agricultural practices, it is possible to increase crop resilience to drought and water scarcity and promote more sustainable and productive agriculture.
