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Role of Endophytes, Plant Growth Promoting Rhizobacteria

Fe, P, K, and Cu content of shoot, increased plant biomass and fruit yields

(Al-Karaki et al., 2006). Zea mays inoculated with three strains of fungal

symbionts improved plant biomass under salt stress by enhancing proline

and potassium content in the shoot (Estrada et al., 2013).

3.6.1.3 AMF AND TEMPERATURE TOLERANCE

An extreme temperature (cold and heat) is another negative regulator of plant

growth. AM fungi colonization can induce temperature tolerance (Table 3.3)

in plants by accumulating osmolytes, enhancing photosynthesis, improving

nutrients and water uptake, and minimizing ROS accumulation (Nadeem

et al., 2013). At high temperature AMF helps plants by extension of root

surface area producing a mycelial network that ensures water uptake and

protects photosynthetic apparatus from damage (Zhu et al., 2012). During the

period of temperature stress, AMF reduced the emission of N2O from plant

by increasing nitrogen in the soil. It was reported that in low temperature

plants those are inoculated with AMF exhibited better growth and biomass

accumulation than those un-inoculated plants. For evidence, when Hordeum

vulgare inoculated with AMF under low temperature stress showed better

yield and biomass production (Hajiboland et al., 2019). Therefore, AMF can

induce tolerance in plants under extreme environmental conditions.

3.6.1.4 AMF AND HEAVY METAL TOLERANCE

Mining and industrial areas are more prone to heavy metal contamination.

Plants those are adopted these environments exhibited a greater proportion of

AMF colonization in the root. AMF are used as a heavy metal stress reducing

agents in contaminated soil area as it helps to eliminate metal from the soil

thus reducing heavy metal toxicity in plants (Wang, 2017). AMF provides

heavy metal remediation as their hyphae has the metal binding ability that

reduces the bioavailability of metals like Cd, Co, Zn, and Pb (Audet &

Charset, 2007). When maize plant is inoculated with Glomus sp. under heavy

metal contaminated soil it showed better biomass yields and higher P, K, and

Mg content in the root (Kaldorf et al., 1999). In a recent study it was found

that AMF can induce expression of some metal transporter. For instance, in

Rhizophagus irragularis a Zn transporter GintZn T1 was reported (Gonzalez-

Guerrero et al., 2016). Different AM fungi and their role in abiotic stress

tolerance in different plant species are presented in Table 3.3.