Osmotic stress is a serious physiological disorder that affects water movement within the cell membranes. Osmotic stress adversely affects agricultural production and sustainability and is largely caused by soil salinity and water stress. An integrated nitrogen-fixing bacteria (NFB) soil amendment and an exogenous foliar application of Aloe vera leaf extract (ALE), and moringa leaf extract (MLE) were evaluated on roselle (Hibiscus sabdariffa L.) growth, calyx yield, secondary metabolites, and tolerance to osmotic stress in salt-affected soil. The osmotic stress markedly decreased above- and below-ground development of the roselle plant, but integrated NFB soil amendment with ALE or MLE foliar application significantly alleviated its negative impacts. Broadly, an improvement was observed in chlorophyll, carbohydrates, and protein levels following NFB and extracts foliar application, as well as a significant enhancement in antioxidant production (total phenols, ascorbic acid, and FRAP), which decreased peroxide production and increased stress tolerance in plants. Under osmotic stress, the roselle calyx revealed the highest anthocyanin levels, which declined following NFB soil amendment and foliar extract application. Additionally, an enhancement in nitrogen (N), phosphorus (P), and potassium (K) contents and the K/Na ratio, along with a depression in sodium (Na) content, was noticed. The integrated application of Azospirillum lipoferum × ALE exhibited the best results in terms of enhancing above- and below-ground growth, calyx yield, secondary metabolites, and tolerance to osmotic stress of the roselle plants cultivated in the salt-affected soil.

Due to the growing knowledge about the microorganism–plant relationship, medicinal plants have gained great attention in their bio fertilization programs using biostimulants based on microorganisms. Plectranthus amboinicus (Lour.) Spreng. is a perennial herb belonging to the family Lamiaceae and has therapeutic and nutritional properties attributed to its natural phytochemical compounds, which are highly valued in the pharmaceutical industry. A pot experiment was conducted to evaluate the efficiency of Rhodotorula muciligenese (Y1), Candida sake (Y2), Candida apicola (Y3), and Candida kunwiensis (Y4) yeast strains in concentrations of 0 (C1), 1 × 10⁴ (C2), 1 × 10⁷ (C3), and 1 × 10⁹ (C4) CFU mL⁻¹ on the growth performance, productivity, and antioxidant activity of P. amboinicus plants. Yeast applications promoted growth attributes, nutritional value, and antioxidant activity in P. amboinicus leaves. Candida apicola exhibited the greatest root growth, herb weight, and essential oil production; it also stimulated carbohydrates, protein, and mineral content, as well as DPPH and FRAP activities. Whereas Rhodotorula muciligenese recorded the lowest values in this respect, among the concentrations used, the 1 × 10⁷ CFU mL⁻¹ concentration showed the highest values in this respect. These new findings showed that the foliar application of Candida apicola not only maximized the growth and productivity but also maximized the nutritional value and antioxidant activity of P. amboinicus.

Syzygium cumini (L.) Skeels (jamun) is an ornamental tree species that is sensitive to salinity. Salinity stress is a major challenge, particularly in regions with saline irrigation water. In the present study, the ameliorative potential of foliar application of an aqueous extract of Delonix regia (Poinciana) flowers (PFE) to saline water-irrigated jamun seedlings was investigated over a period of two years. PFE was effective in mitigating the harmful effects of salinity on plant growth, physiology, and biochemistry. Salinity-induced reductions in plant height, leaf area, and biomass which were significantly alleviated by PFE foliar application. The extract also enhanced antioxidant activity, as indicated by increased ferric reducing antioxidant potential (FRAP) and phenolic content, while also reducing hydrogen peroxide (H₂O₂) levels and membrane damage as indicated by the accumulation of malondialdehyde (MDA). Additionally, the foliar application of PFE promoted the accumulation of free proline, an essential osmo-protectant, further enhancing the plant’s resilience to salinity stress. These findings highlight the potential of PFE as an eco-friendly bio-stimulant to improve salinity tolerance in jamun and pave the way for sustainable salinity management strategies in other crops as well.

Sprouts are an attractive food product that contains high amounts of nutritional substances and has pro-health features. Sprout consumption has strongly increased despite its potential risk to health due to its microbial load. Both the safety and shelf life of sprouts may be negatively affected by a high microbial load. To reduce the microbial contamination in sprouts before consumption, the initial microbial load on the seeds needs to be controlled. Many herbal sprouts have been recommended for diabetes, and fenugreek is one of these sprouts. Thus, the current experiment aimed at disinfecting fenugreek seeds using microwave (5, 10, and 20 s) and hot water (30, 45, and 60 s) treatments for different durations. The best-disinfected sprouts with the highest nutritional properties were used to evaluate their influence on streptozocin-induced diabetic rats in comparison with fenugreek seed feeding. Microwave treatments showed the highest sprout length, fresh weight, total free amino acids, antioxidants, reducing sugars, and total phenols. Additionally, microwave seed treatments showed the lowest bacteria and mold counts on sprouts produced relative to hot water treatments, and the best seed treatment was a microwave for 20 s, which gave the best values in this respect. Feeding diabetic rats with different fenugreek seeds or sprout rates (0, 5, 7.5, and 10% w/w) improved body weight, restricted the growth of glucose levels, lowered total cholesterol and triglycerides, and improved HDL compared with the positive control group, and fenugreek sprouts at higher rates showed the maximum improvements in blood glucose, total cholesterol, and triglycerides. Treating fenugreek seed with microwave radiation for 20 s to disinfect the seeds before sprouting is recommended for lowering the microbial load with optimum nutritional and antioxidant activity, and feeding diabetic rats with these sprouts at the rate of 7.5 and 10% had promising effects on hyperglycemia and associated disorders.

Plant secondary metabolites provide a unique basis for medications, flavorings, and industrial biochemicals. These metabolites frequently accumulate in plants exposed to environmental stressors (e.g., drought stress), as a mechanism for adaptation and resistance. Plectranthus amboinicus (Lour.) Spreng is a semi-succulent Lamiaceae species valued for its curative properties and essential oil, the concentration of which is heavily impacted by irrigation levels. This investigation reveals a novel study into the physiological and molecular mechanisms of P. amboinicus by correlating field capacity (FC) levels with metabolite accumulation and specific gene expression. We examined the impact of six irrigation levels (0, 20, 40, 60, 80 and 100%; denoted as FC-0 to FC-100) on growth, essential oil (EO) yield, and carvacrol biosynthesis during the 2022 and 2023 seasons. Data revealed that plants subjected to the FC-0 exhibited the lowest growth parameters. However, these plants also presented a higher essential oil percentage and carvacrol concentrations, in addition to an increase in polyphenols and antioxidant enzymes, with greater oxidative substances accumulation (H ₂ O ₂ and MDA). Moreover, these plants presented higher gene expression of CYP71D178 and CYP71D180 genes. While increasing water level caused an increase in growth parameters, with a decline in the antioxidant activity. Increasing the water level to FC-100 increased the essential oil by approximately four fold but resulted in a decline in carvacrol content as compared to FC-0. Generally, water deficiency reduces crop yield, whereas irrigation increases plant productivity. However, in medicinal and aromatic plants, the relationship is distinct; in Plectranthus amboinicus, water deficiency showed a strong positive correlation with the secondary metabolite’s generation. In conclusion, the current report provides for the first time a molecular framework for P. amboinicus by depicting the expression patterns of CYP71D178 and CYP71D180. We revealed that these genes elaborate as the primary molecular shifts regulating carvacrol biosynthesis influenced by specific irrigation levels.