This review explores the intricate relationship between plants and bacterial endophytes, revealing their multifaceted roles in promoting plant growth, resilience, and defense mechanisms. By selectively shaping their microbiome, plants harness diverse endophytic bacterial strains to enhance nutrient absorption, regulate hormones, mitigate damage, and contribute to overall plant health. The review underscores the potential of bacterial endophytes in self-sustaining agricultural systems, offering solutions to reduce reliance on fertilizers and pesticides. Additionally, the review highlights the importance of endophytes in enhancing plant tolerance to various environmental stresses, such as drought, salinity, extreme temperatures, and heavy metal toxicity. The review emphasizes the significance of understanding and harnessing the mutualistic relationship between plants and endophytes for maximizing agricultural yields and promoting sustainable farming practices.

In the context of anthropogenic evolution, various sectors have been exploited to satisfy human needs and demands, often pushing them to the brink of deterioration and destruction. One such sector is agrochemicals, which have been increasingly employed to achieve higher yields and bridge the gap between food supply and demand. However, extensive and prolonged use of chemical fertilizers most often degrades soil structure over time, resulting in reduced yields and consequently further exacerbating the disparity between supply and demand. To address these challenges and ensure sustainable agricultural production, utilization of microorganisms offers promising solutions. Hence, microorganisms, particularly effective microorganisms (EMs) and plant growth-promoting microbes (PGPMs), are pivotal in agricultural biomes. They enhance crop yields through active contribution to crucial biological processes like nitrogen fixation and phytohormone synthesis, making vital nutrients soluble and acting as natural enemies against pests and pathogens. Microbes directly enhance soil vigor and stimulate plant growth via the exudation of bioactive compounds. The utilization of EMs and PGPMs reduces the need for chemical inputs, leading to lower costs and reduced environmental pollutants. Furthermore, beneficial soil microflora produces growth-related metabolites and phytohormones that augment plant growth and support stress resilience. Microbes also help plants tolerate various abiotic stresses, including metal stress, salt stress, and drought stress, through various mechanisms. Understanding the interactions and activities of microorganisms provides valuable insights into their potential use to manage stress in plants. Thus, by leveraging the full potential of microorganisms, we can develop healthier agroecosystems that contribute sustainably to meet the growing global food demands.

Different physical and chemical techniques are used for the decontamination of Cr⁺⁶ contaminated sites. The techniques are expensive, laborious, and time-consuming. However, remediation of Cr⁺⁶ by microbes is viable, efficient, and cost-effective. In this context, plant growth-promoting rhizobacteria Acinetobacter bouvetii P1 isolated from the industrial zone was tested for its role in relieving Cr⁺⁶ induced oxidative stress in sunflower. At the elevated Cr⁺⁶ levels and in the absence of P1, the growth of the sunflower plants was inhibited. In contrast, the selected strain P1 restored the sunflower growth under Cr⁺⁶ through plant growth–promoting interactions. Specifically, P1 biotransformed the Cr⁺⁶ into a stable and less toxic Cr⁺³ form, thus avoiding the possibility of phytotoxicity. On the one hand, the P1 strengthened the host antioxidant system by triggering higher production of enzymatic antioxidants, including catalases, ascorbate peroxidase, superoxide dismutase, and peroxidase. Similarly, P1 also promoted higher production of nonenzymatic antioxidants, such as flavonoids, phenolics, proline, and glutathione. Apart from the bioremediation, P1 solubilized phosphate and produced indole acetic acid, gibberellic acid, and salicylic acid. The production of phytohormones not only helped the host plant growth but also mitigated the harsh condition posed by the elevated levels of Cr⁺⁶. The findings mentioned above suggest that P1 may serve as an excellent phyto-stimulant and bio-remediator in a heavy metal-contaminated environment.

The aim of the current study was to isolate endophytes from the roots of Rhazya stricta and assess their potential to improve the growth of drought-stressed sunflower seedlings. The potential role of the isolated endophytic fungus was initially screened by using two rice varieties (mutant rice cultivar Waito-C: Gibberellins deficient; and Dongji byeo: Gibberellins-producing normal cultivar). A significant (p < 0.05) increase in various growth attributes of both rice varieties associated with one of the isolates i.e., N4 was noticed. Furthermore, the N4 isolate was tested for its role in improving the agronomic attributes of sunflowers under drought stress. The symbiotic association significantly (p < 0.05) improved the host growth and protection from PEG-induced drought stress. The drought mitigation in N4-associated sunflower seedlings can be linked with the regulation of phytohormones, stress-related metabolites, low-molecular-weight proteins and sugars, and scavenging of reactive oxygen species (ROS). Microscopic analysis revealed that the potent endophytic fungal strain consisted of thin and hyaline hyphae, forming dense olive-green mycelia (4–5 cm in dm) with black flask-shaped fruiting bodies. Based on the ITS sequence homology and phylogeny, the strain was identified as Fusarium proliferatum (MG251448). The results of this study concluded that this phytohormone-secreting endophyte can improve crop productivity in dry areas where drought stress is the main challenge faced by crops.

The aim of the current study was to assess the cadmium (Cd) phytoremediation potential of Helianthus annuus L. that was exposed to 50, 100, and 150 mg/kg of cadmium for 15, 30, and 60 days with application of EDTA (Ethylenediaminetetraacetic acid) in the soil and IAA (indole acetic acid) as a foliar spray. The results indicated that the concentration, duration of exposure, and amount of Cd affect the phytoremediation potential. The maximum Cd was observed at 60 days (32.05, 16.86, and 10.63%) of Cd application, compared to 15 (2.04, 0.60, and 1.17%) or 30 days (8.41, 3.93, and 4.20%, respectively), in a dose-dependent manner. The application of EDTA in the soil and foliar IAA enhanced the Cd accumulation in the plants at 15, 30, and 60 days of exposure, with maximum accumulation at 60 days. Exposed plants with foliar IAA application showed 64.82%, 33.77%, and 25.84% absorption at 50, 100, and 150 mg/kg, respectively. Apart from higher absorption, the cadmium translocation to the edible part of the plants ceased, i.e., the seeds had 0% accumulation. The interesting fact was recorded that efficient phytoremediation was recorded at 15 days of exposure, whereas maximum phytoremediation was recorded at 60 days of exposure. To minimize the stress, the host also produced stress-related metabolites (i.e., flavonoids, phenolics, proline, and sugar) and antioxidants (i.e., catalases and ascorbate peroxidases). From the current evidence, it could be assumed that the use of EDTA and IAA, along with hyperaccumulating plants, could be a possible green method to remediate Cd-contaminated soil efficiently in a short period of time.