Increased incidence of abiotic stresses impacting adversely plant growth and productivity in major crops is being witnessed all over the world. Therefore, as a result of such stress factors, plant growth under the stress conditions will be less than the non-stress conditions. Growing concerns and global demand for correct, environmentally- friendly techniques exist to reduce the adverse e ff ects of plant stress. Under such stressful conditions, the role of interactions of plant and bene fi cial microorganisms is of great signi fi cance. Application of plant growth pro- moting rhizobacteria (PGPRs) is a useful option to decrease these stresses and is now widely in practice. Plants inoculated with PGPRs induce morphological and biochemical modi fi cations resulting in increased tolerance to abiotic stresses de fi ned as IST (induced systemic tolerance). PGPRs increase plant growth and resistance to abiotic stresses through various mechanisms (more than one mechanism of action) such as production of ACC (1- aminocyclopropane-1-carboxylate) deaminase, reducing production of stress ethylene, modi fi cations in phyto- hormonal content, induction of synthezing plant antioxidative enzymes, improvement in the uptake of essential mineral elements, extracellular polymeric substance (EPS) production, decrease in the absorbtion of excess nutrients/heavy metals, and induction of abiotic stress resistance genes. Experimental evidence also suggests that stimulated plant growth by these bacteria is the net result of various mechanisms of action that are activated simultaneously. In this review paper, we reviewed the action mechanisms through which PGPRs could alleviate abiotic stresses (salinity, drought, heavy metal toxicity, and nutritional imbalance) in plants. Use of PGPRs is predicted to become a suitable strategy and an emerging trend in sustainable enhancement of plant growth. Generally, ACC deaminase and IAA-producing bacteria can be a good option for optimal crop production and production of bio-fertilizers in the future due to having multiple potentials in alleviating stresses of salinity, drought, nutrient imbalance, and heavy metals toxicity in plants. This review paper also emphasizes future research needs about the combined utilization of stress tolerant-PGPRs with multiple plant growth promoting (PGP) characteristics under environmental stresses.
