Salinity restricts agricultural use of soils in many dry and irrigated regions. High salt concentrations make water uptake more difficult, disrupt ion balance and can substantially reduce photosynthesis, growth and yield. A scientific review by Heikham Evelin, Rupam Kapoor and Bhoopander Giri brings together research on how arbuscular mycorrhizal fungi – AMF – can support plants under these conditions.
The article is not a single field study, but an evaluation of numerous studies using different plants, fungal species and experimental conditions. Its central conclusion is therefore not that AMF eliminate salinity. Suitable fungus–plant partnerships can instead alleviate several consequences of stress at the same time and thereby stabilise plant function.
AMF do not desalinate soil. They can, however, help plants cope more effectively with the physiological consequences of an existing salt burden.
A widespread natural partner
AMF live in close symbiosis with the roots of a large proportion of land plants. Within root cells, they form finely branched arbuscules as exchange surfaces: the plant supplies energy-rich carbon compounds, while the fungus uses its hyphal network to explore soil spaces that roots alone find difficult to reach. In particular, this allows relatively immobile nutrients such as phosphorus to reach the plant more efficiently.
Salt stress also affects the fungus. Spore germination, hyphal growth and root colonisation may decline as salinity rises. The outcome therefore depends substantially on whether fungal strain, host plant and site conditions are compatible.
Growth and biomass under salt stress
In many of the experiments reviewed, mycorrhizal plants under salt stress developed more shoot and root biomass, larger leaf areas or higher yields than non-mycorrhizal comparison plants. This advantage is not based on one mechanism. It arises from the interaction of better nutrition, more stable water relations, more functional photosynthesis and various protective responses.
Nutrient uptake and ion balance
High sodium and chloride concentrations compete with important plant nutrients and can impede their uptake. The review frequently describes improved phosphorus nutrition in mycorrhizal plants and – depending on the experiment – improved nitrogen, potassium, calcium and magnesium status. A more favourable potassium-to-sodium ratio is especially important: potassium is needed for numerous enzyme and cellular functions, while excessive sodium disrupts these processes.
AMF do not act like a simple salt filter. They alter nutrient acquisition, root activity and, in some cases, ion distribution within the plant. This can result in more balanced nutrition despite a stressed soil solution.
Water relations and osmotic adjustment
Saline soil water has a low water potential. Although water is present, plants find it more difficult to absorb – physiologically resembling drought. Mycorrhizal plants show a more favourable water status in many studies. The wider reach of fungal hyphae, changes in root hydraulics and the accumulation of osmotically active substances such as soluble sugars or proline can contribute.
These substances help retain water in cells and maintain turgor. Their role is not identical in every plant–fungus combination; increased proline can indicate either active adjustment or stress.
Photosynthesis and oxidative protection
Salt stress impairs chlorophyll, stomata and photosystems. Mycorrhizal plants often retain more chlorophyll, more favourable gas exchange and higher photosynthetic rates. This leaves more energy for growth, repair and support of the fungal partner.
At the same time, salt stress produces reactive oxygen species that can damage membranes and proteins. AMF influence antioxidant enzymes and protective compounds. The review’s findings are not uniform: depending on the plant, fungus and stress level, enzyme activities were higher, unchanged or lower. What is clear is that symbiosis can alter the overall stress condition; the direct contribution of individual antioxidants requires differentiated interpretation.
No universal solution
The effects of AMF are context-dependent. Salinity, soil type, phosphorus supply, temperature, plant age and the specific host–fungus combination influence the result. A preparation therefore cannot guarantee a functional symbiosis. At very high salinity, fungal colonisation itself may also be severely restricted.
In practice, AMF are most effective as part of a living, plant-supported soil system – connected with suitable vegetation, organic inputs, minimal soil disturbance and water and salt management that addresses the cause of the burden.
Why this matters for regenerative soil work
The findings support a central idea of the RED Method: soil fertility does not arise solely from quantities of available nutrients, but from relationships. AMF extend the functional reach of roots and connect nutrition, water relations and stress adaptation. People can improve the conditions for this partnership – but the living system itself must establish and maintain it.
More detailed version for subscribers
The unabridged version examines colonisation, ion balance, water relations, photosynthesis, osmolytes, antioxidant systems, limitations and practical interpretation in greater depth.
Read the unabridged version