46

Biology and Biotechnology of Environmental Stress Tolerance in Plants, Volume 3

et al., 2013). Drought tensile tolerance and PGPR improve biomass, potential

of water, and reduce loss of water in stressed maize plants. These inoculants

lessen the antioxidant action while increasing sugar, proline, and free amino

acid synthesis in plants (Vardharajula et al., 2011).

2.4 MANAGING SALINITY STRESS

Farmers and agricultural scientists face a difficult problem in determining

soil salinity. The cumulation of harmful sodium and chlorine ions inside

the soil, as well as nutritional imbalances, have a significant impact on

plant growth and microbial activity. Inoculating PGP microorganisms and

endophytic microorganisms resulted in reduction of harmful salt effect on

many plants. Plant growth under salinity stress can be aided by PGP micro­

organisms through a variety of direct and indirect ways. Furthermore, the

biofilm generated by the PGPB under saline tensity is useful in reducing

the negative consequences (Kasim et al., 2016). In a salty situation, Azospi­

rillum inoculated lettuce seed demonstrated greater germination rate as well

as advancement in vegetative maturation than the control (Barassi et al.,

2006). In another survey, inoculating salt-resistant and salt susceptible chili

pepper with the growth-promoting bacteria Pseudomonas stutzeri reduced

the deleterious effects of brininess soil (Bacilio et al., 2016). Other species of

microorganisms tend to reduce the action of biofilm formation in response to

salinity stress when tested on grains of barley (Kasim et al., 2016). Reports

suggested that in some plants, great improvements in salinity toleration is

noticed when co-inoculation of AM fungi is done with salt-resistant bacteria.

For example, when the salt tensile maize plants are inoculated with R. intr­

aradices and Massilia sp. RK4, they together improved the colonization of

arbuscular mycorrhizal fungi (AMF) in the root resulting in accumulation of

the nutrients. These microbial as well as fungal interactions have a substan­

tial impact on maize plant salinity tolerance (Krishnamoorthy et al., 2016).

2.4.1 MECHANISM OF SALINITY STRESS TOLERANCE

The stimulation of growth under stress conditions is aided by the diversity

of salinity stress-resistant microorganisms (Table 2.2). Production of

phytohormone (e.g., auxin, cytokinin, ethylene, and gibberellins), fixation

of nitrogen, nutrients mobilization, and production of the siderophore are

examples of direct methods (Hayat et al., 2010). All of them are laced with

a unique mechanism of action as well as mode of operation. These actions