Arbuscular Mycorrhizal Fungi and the Tolerance of Plants to Drought and Salinity

Abstract

Arbuscular mycorrhizal fungi are known to form symbiosis with plants in nature. From these symbioses, the fungi obtain carbon compounds from the plants and a niche to complete their life cycle, while the plants obtain access to unavailable nutrients and water resources. Arbuscular mycorrhizal fungi are usually considered to be beneficial for plants by improving different plant parameters as growth and photosynthetical rates. However, they are also believed to play a critical role in plant tolerance and resistance under different environmental stresses. In this chapter, we will focus on the effects of drought and salinity in plants and how the presence of arbuscular mycorrhizal fungi can affect plant responses to them. We will revise the current knowledge on the physiological, biochemical, and molecular plant–fungi responses to salt and drought and the different stress tolerance mechanisms involved in cell osmoregulation, ion balance, the role of aquaporins in water balance, and the plant antioxidant system and hormone regulation. The role of AM fungi in the resistance/tolerance of plants to salt and drought will be highlighted, as well as how the presence of AM fungi within the plant roots can determine the success of plants under salt- and/or drought-affected soils. Finally, new insights into the future role of AM fungi will be advised to help understand whole plant system responses to drought and salinity.