Mechanisms for Tolerance to Drought Stress in Plants Inoculated with (AM) Arbuscular Mycorrhizal Fungi: A Review

The expansion of areas affected by drought stress through out the world has a negative impact on yield as well as production of crops, making drought stress the most significant abiotic stress that limits the growth of plants. The use of (AMF) arbuscular mycorrhizal fungi is a effective strategy that combat the impact of this drought stress in a very sustainable manner, given the increase in the tolerance to drought stress in plants inoculated with these fungi; however, the exact mechanism is unknown due to the response depends particularly on the drought stress type and is specific to the (AMF) arbuscular mycorrhizal fungi and the plant. This review describes the mechanisms that explain how exactly the AMF colonization in roots can modify the plant response during a drought stress, as well as its relationship with physiological processes that determine yield, photosynthesis and photoassimilate partitioning. These mechanisms may include modifications in the content of plant hormones, like jasmonic acid (JA) and absicic acid (ABA). The JA appears to be involved in the stress signal in mycorrhizal plants through an increase ABA concentration. Also, there is enhancement of plant water status, stomatal conductance, nutritional status and responses of plant to cope up with a water deficit, antioxidant activity and osmotic adjustment. These modifications cause an increase in CO2 assimilation and photoassimilate production, improving plant growth during a drought stress.