Soybean is an important oil crop with multiple uses. Soybeans can grow in various soil types and climates; however, salt stress reduces their yield. Plant growth-promoting microorganisms are an environmentally benign way to combat stress and boost plant tolerance. In the present study, we have identified plant growth-promoting bacteria that can produce indole acetic acid (IAA) and induce distinct growth characteristics in soybean plants under salt stress. The YNA40 isolate was identified as Acinetobacter pittii through 16S rRNA sequencing and phylogenetic analysis. A pure culture of Acinetobacter pittii YNA40 was subjected to chromatographic and mass spectrometry selected-ion monitoring (GC-MS/SIM) for IAA quantification. The results revealed that the YNA40 bacterial strain showed a significantly higher IAA concentration (473.88 ng/mL) at 4% sodium chloride (NaCl). Moreover, in a salt-stress condition, inoculation with Acinetobacter pittii YNA40 was able to induce increased shoot length (23.48%), shoot weight (24%), root length (2.47%), and root weight (44.82%) compared to the uninoculated control. Therefore, soybean seedlings were inoculated with YNA40 to examine their potential for promoting growth and reprogramming after salt stress. Inoculation with YNA40 isolates mitigated the salt stress and significantly improved the growth of the plant, enhanced the chlorophyll contents, and improved the quantum efficiency of chlorophyll fluorescence, total phenolic content, flavonoid content, the diphenyl-1-picrylhydrazyl (DPPH) activity, and antioxidant activities of soybean plants during and after salt stress. The present research demonstrated that the application of the YNA40 isolate is promising for reducing salt stress in soybean plants and helps plants grow better in a salt-stressed environment.

Plant growth-promoting rhizobacteria (PGPR) and biochar (BC) are recognized as effective biological agents for enhancing stress tolerance and mitigating heavy metal toxicity in crops. Therefore, this study aims to investigate the effects of the cadmium (Cd)-resistant PGPR strain Leclercia adecarboxylata HW04 (>4 mM Cd resistance) on soybean plants exposed to 300 μM Cd. HW04 was observed to possess the innate ability to synthesize indole-3-acetic acid and exopolysaccharides, which facilitated the absorption of Cd in the medium. Scanning electron microscopy (SEM) images revealed that HW04 effectively colonized the porous structure of BC. Their combined treatment significantly enhanced photosynthesis and improved the morphological characteristics of soybean plants. Additionally, the Cd content in soybean shoots significantly increased following both the sole or combined treatments of BC and HW04. However, the combined treatments significantly reduced Cd content in the roots and soil by 31% and 47%, respectively. HW04 inoculation alone increased Cd content in the roots by 43.7% while lowering it in the soil by 7.4%. Additionally, the co-application of HW04 and BC significantly enhanced calcium (Ca) and magnesium (Mg) assimilation while promoting Cd/Fe accumulation in soybean shoots. The higher expression of signaling cascade genes, including GmCaMK1 and GmCDPK5 (Ca signaling) and GmMAPK4a and GmMAPK7 (MAP kinase signaling), in the co-applied crops further validate the findings. The increase in abscisic acid levels and the decrease in salicylic acid levels after HW04 and BC application were correlated with enhanced stress tolerance in crops. These findings suggest that the combined application of HW04 and BC could serve as an effective, eco-friendly approach for mitigating heavy metal toxicity in crops and promoting phytoremediation.

Salinity hinders plant growth, posing a substantial challenge to sustainable agricultural yield maintenance. The application of plant growth-promoting rhizobacteria (PGPR) offers an emerging strategy to mitigate the detrimental effects of high salinity levels. This study aimed to isolate and identify gibberellin-producing bacteria and their impact on the seed germination of Malva verticillata (mallow) and Brassica oleracea var. italica (broccoli) under salt stress. In this study, seven bacterial isolates (KW01, KW02, KW03, KW04, KW05, KW06, and KW07) were used to assess their capacity for producing various growth-promoting traits and their tolerance to varying amounts of salinity (100 mM and 150 Mm NaCl). The findings revealed that KW05 and KW07 isolates outperformed other isolates in synthesizing indole-3-acetic acid, siderophores, and exopolysaccharides and in solubilizing phosphates. These isolates also enhanced phosphatase activity and antioxidant levels, including superoxide dismutase and catalase. Both KW05 and KW07 isolate highlight the growth-promoting effects of gibberellin by enhancing of growth parameters of Waito-C rice. Further, gas chromatography–mass spectrometry validation confirmed the ability of KW05 and KW07 to produce gibberellins (GAs), including GA₁, GA₃, GA₄, and GA₇. Seed germination metrics were enhanced due to the inoculation of KW05 and KW07. Moreover, inoculation with KW05 increased the fresh weight (FW) (7.82%) and total length (38.61%) of mallow under salt stress. Inoculation with KW07 increased the FW (32.04%) and shoot length of mallow under salt stress. A single inoculation of these two isolates increased broccoli plants’ FW and shoot length under salt stress. Gibberellin-producing bacteria helps in plant growth promotion by improving salt tolerance by stimulating root elongation and facilitating enhanced absorption of water and nutrient uptake in salty environments. Based on these findings, they can play a role in boosting agricultural yield in salt-affected areas, which would help to ensure the long-term viability of agriculture in coastal regions.

The application of N-acetylglucosamine (GlcNAc) and melatonin (Mel) in agriculture could be a promising avenue for improving crop resilience and productivity, especially under challenging environmental conditions. In the current study, we treated the cucumber plant with GlcNAc and Mel solely and combinedly under salt stress (150 mM) then studied photosynthetic attributes using the transient OJIP fluorescence method. The results showed that the combination of GlcNAc × Mel significantly improved the plant morphological attributes, such as root and shoot biomass, and also improved chlorophyll and photosynthetic components. The mineral elements such as K, Mg, Ca, and P were significantly elevated, whereas a lower influx of Na was observed in GlcNAc × Mel treated cucumber shoots. A significant reduction in abscisic acid was observed, which was validated by the reduction in proline content and the increase in stomatal conductance (Gs), transpiration rate (E), and substomatal CO₂ concentration (Ci). Furthermore, the activities of antioxidants such as polyphenol and flavonoid were considerably improved, resulting in a decrease in SOD and CAT with GlcNAc × Mel treatment. In addition, GlcNAc × Mel treatment dropped levels of the toxic radical Malondialdehyde (MDA) and elevated amino acids in cucumber shoots. These findings suggest that the combination of GlcNAc × Mel could be an effective elicitor for modeling plant metabolism to confer stress tolerance in crops.

Globally, cadmium (Cd) stress dramatically reduces agricultural yield. Illite, a natural clay mineral, is a low-cost, environmentally acceptable, new promising method of reducing the heavy metal (HM) stress of cereal crops. In research statistics, there is little research on stress tolerance behavior of Illite (IL) on an experimental soybean plant. In the present study, we took IL and examined it for tolerance to Cd, as well as for other plant-growth-promoting (PGP) characteristics in Glycine max (soybean). The results showed that applying clay minerals in different concentrations enhanced the level of SA (defense hormone) and reduced the level of ABA (stress hormone). Cd 1 mM significantly reduces plant growth by altering their morphological characteristics. However, the application of IL significantly enhanced the seedling characteristics, such as root length (RL), 29.6%, shoot length (SL), 14.5%, shoot fresh biomass (SFW), 10.8%, and root fresh biomass (RFB), 6.4%, in comparison with the negative control group. Interestingly, IL 1% also enhanced the chlorophyll content (C.C), 15.5%, and relative water content (RWC), 12.5%, in all treated plants. Moreover, it resulted in an increase in the amount of superoxide dismutase (SOD), phenolics, and flavonoids in soybean plants, while lowering the levels of peroxidase (POD) and H₂O₂. Furthermore, compared to control plants, soybean plants treated with the Illite exhibited increased Si absorption and lower Cd levels, according to inductively coupled plasma mass spectrometry (ICP-MS). Thus, the IL can operate as an environmentally beneficial biofertilizer and sustainable approach under Cd stress by promoting plant development by activating signaling events.

Invasive weed species exhibit both advantages, such as the potential for allelochemicals in bioherbicide development, and risks, including their threat to crop production. Therefore, this study aims to identify an allelochemical from Solidago altissima, an invasive weed species. The dose-dependent effects of S. altissima shoot and root extracts (SSE, SRE) on the signaling in the forage crop Trifolium repens and germination in various weed species (Echinochloa oryzicola, Cyperus microiria, Alopecurus aequalis, Portulaca oleracea, and Amaranthus retroflexus) were evaluated. The results showed that the T. repens seedlings treated with root extracts exhibited a significant decrease in plant height, dry weight, and chlorophyll content, along with an increase in H₂O₂ levels. Additionally, antioxidant activities, such as superoxide dismutase, catalase, and peroxidase enzyme activities, were significantly elevated in T. repens treated with SRE. Moreover, SRE treatment significantly inhibited the seed germination of all tested weed species in a concentration-dependent manner. Gas chromatography-mass spectrometry analysis of S. altissima root extract identified a high concentration of methyl kolavenate, a clerodane diterpene predicted to act as a phytotoxic agent. These findings highlight the potential of S. altissima for the development of crop-protective agents while emphasizing its potential risks in agriculture.