###### Abstract
This level of ROS generation, based on some evidence, has been suggested to be connected to their limited natural involvement in developmental processes [18] or the regulation of morphogenetic processes associated with phytohormones such as cytokins and auxins [19]. On the other hand, stressful environmental conditions excessively accelerate cellular ROS concentrations [20] at levels exceeding the antioxidant scavenging capacities [11; 17] employed by plants to neutralise excess ROS production [21]. This feature potentially leads to oxidative stress along with damage to membrane lipids, proteins, and nucleic acids and eventually results in cell death [4; 22; 23]. Abiotic stress-induced programmed cell death (PCD) is a genetically controlled process in which the intensity of detrimental factors is harnessed through increased ROS generation [24]. Environmental stress factors involved in exerting disturbance on the delicate balance between ROS production and ROS removal pathways include but not limited to drought, salinity, high irradiance, extreme temperatures, heavy metals, pollution, and pathogen infection [22; 25; 26]. Plant adaptation to the oxidative stress caused by elevated ROS concentrations is often consistent with many key factors, among which are stress duration and severity, instantaneous cellular energy status, plant growth stages, ROS cellular level, and antioxidant capacity [27]. Generally, ROS-scavenging systems in plants are comprised of ascorbate (AA), glutathione (GSH), carotenoids, \(\alpha\)-tocopherol, prolines, flavonoids, and phenolic compounds as non-enzymatic antioxidants, monodehydroascorbate reductase (MDHAR), dehydroacorbate reductase (DHAR), superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX), glutathione reductase (GR), and guaiacol peroxidase (GPX) as well as low molecular mass (LMS) antioxidants and/or enzymatic antioxidants [20; 21; 27; 28; 29]. It is well reported that increased activity of antioxidant enzymes or non-enzymatic antioxidants in response to unprecedented environmental stresses helps to ameliorate the degree of damage caused by oxidative stress [5; 26]. For instance, in green bean (_Phaseolus vulgaris_ L.) plants affected by salinity stress, a subtle increase in the activity of CAT and APX antioxidants was observed in salt-tolerant GS57 and salt-sensitive 4F-89 genotypes, which was consistent with increased fresh and dry weight in these plants [30]. Similarly, an overall increase was reported in antioxidant enzymes (i.e., APX, SOD, GPX, CAT and GR) of some traditional rice plants suffering from drought stress [31]. The upregulation of AA, GSH, phenolics, phytochelatins (as GSH oligomers), and sugars as non-enzyme-based antioxidants was induced in Antarctica in _Colobanthus quitensis_ ([PERSON]) [PERSON] by copper stress treatment [32]. Plant growth-promoting rhizobacteria (PGPRs) are known to be beneficial microorganisms and play a contributing role in reinforcing plant response to stressful conditions [33]. Typically, after colonising the rhizosphere or endo-rhizosphere of plants, the PGPRs adopt several direct and/or indirect mechanisms to promote plant growth at the expense of tackling abiotic stresses [33; 34; 35; 36]. Some of these mechanisms include the induction of osmolyte accumulation [37], the activation of the antioxidant defence system [38], the up/downregulation of stress-responsive genes [39; 40], and alteration in root morphology in acquisition of stress tolerance [41; 42]. PGPR-induced drought or salinity tolerance in biological systems mainly occurs though induction of physical and chemical alterations in plants, which are collectively referred to as PGPR-induced systemic tolerance (IST) [43; 44]. For instance, a consortium of three PGPR strains, viz. _Bacillus subtilis_ SM21, _Bacillus cereus_ AR156, and _Serratia_ sp.