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Role of Endophytes, Plant Growth Promoting Rhizobacteria

salinity, and temperature stress (Nakmee et al., 2016). AMF mediated

abiotic stress tolerance involved a diverse type of mechanisms including:

(i) facilitation of nutrients and water uptake; (ii) accumulation of organic

solutes, stress hormones and expression of stress responsive genes; (iii)

alteration in plant physiology like osmotic adjustment, photosynthesis,

gaseous exchange; (iv) improved antioxidant enzyme system; and (v).

heavy metal chelation and elimination of pollutants from soil (Diagne et

al., 2020). An overall mechanism of AMF mediated abiotic stress toler­

ance is summarized in Figure 3.5.

FIGURE 3.5 Possible mechanism of AMF mediated abiotic stress tolerance in plants.

3.6.1.1 AMF AND DROUGHT STRESS TOLERANCE

Drought stress is one of the major factors responsible for low productivity

of crop plants. Due to the low water availability in the soil, plant closes their

stomata which eventually decreases photosynthetic rate as gaseous exchange

get hampered. During drought AMF improved plant fitness through both

drought mitigation and drought tolerance. AMF enhanced water uptake

ability in plants which helps in drought mitigation and a combination of

direct benefits provide strength to plants for drought tolerance (Bernardo et

al., 2019). Root colonization of AMF increased root surface area for water

absorption and also helps to penetrate a greater extent of the soil. Several