The Mechanisms Involved in Improving the Tolerance of Plants to Salt Stress Using Arbuscular Mycorrhizal Fungi

Abstract

Salinity is considered as one of the most harming stresses faced by the plant in regard to its survival and productivity. A new biological approach “plant-microbe interaction” such as arbuscular mycorrhizal (AM) fungi to address salinity problem has recently gained momentum. Therefore, this chapter aims to provide a general overview about salinity and its effects on plant and soil, and the use of AM fungal inoculant applied to plants to alleviate salinity effects, and the mechanism of AM fungi to increase the tolerance of plants to salt stress with a crucial discussion of major accomplishments reported in this area. The results show that some mechanism of how AM fungi can increase the plant salt tolerance might work well in this regard. AM fungi maintain a superior K+:Na+ ratio that is considered as one of AM fungi’s strategies to improve tolerance to salt stress and boost absorption of P, K+, and Ca2+ over harmful Na+, thus sustaining lesser Na+:K+ ratio under salt stress. The improvement in chlorophyll as a result of AM fungi is owing in particular to the increased uptake of magnesium. AM fungi inoculation increases the activity of antioxidant enzymes in plants such as peroxidase (POD), superoxide dismutase (SOD), and catalase (CAT), which scavenge reactive oxygen species (ROS) and relieve salt stress. An additional salt tolerance mechanism by AM fungi increases the non-antioxidant of plants by accumulating osmolytes such as proline, which maintain the osmotic adjustment of plants under salinity stress. Thus, application of AM fungi inoculant is more probably due to its economic benefits under salt stress.