Salinity stress has become a major threat to worldwide crop production. Exogenous melatonin (MT) has appeared as a promising treatment against salt stress in several plant species. However, MT effect on the tolerance of sorghum plants under different saline conditions (moderate and severe) remains ambiguous. This study was carried out to explore the impact of MT (0, 50, 100 and 200 µM) as a foliar application on sorghum seedlings grown under moderate and severe saline conditions using sodium chloride, NaCl (75 and 150 µM NaCl). Salinity treatments were applied as solution in sand medium in pots. The results demonstrated that rising salinity level negatively affected plant growth, photosynthetic pigments (chlorophylls and carotenoids), leaf water status and ionic homeostasis (sodium, potassium, and calcium ions). Applied-MT specifically at 100 or 200 µM enhanced the osmotic balance, cell membrane stabilizing and leaf relative water content. These effects were associated with an obvious restriction to the level of hydrogen peroxide, lipid peroxidation (malondialdehyde content) and methylglyoxal. Moreover, antioxidant activities of peroxidase, catalase, superoxide dismutase, and ascorbate peroxidase enzymes were modulated by MT treatments. Molecular docking modeling assessment illustrated top-ranked confirmations between MT and the target antioxidant enzymes. MT forms multiple hydrogen bonds with key amino acid residues for glycine (A: 162), tryptophan (A: 41), leucine (A: 165), tyrosine (A: 235) in the active site of ascorbate peroxidase. The alkyl interactions with leucine (A: 37), arginine (A: 38) and cysteine (A: 168) also contribute to its high affinity. Despite sorghum plant is commonly moderately tolerant to salinity stress, the results of this study confirmed its high sensitivity to a wide range of saline conditions at early growth stages. Melatonin spraying led to improvements in various morphological, physiological and biochemical mechanisms that harmonized together to confer stress resistance to salt-stressed sorghum seedlings.

Background: Engineered nanoparticles (ENPs) have attracted considerable attention because of their potential role in enhancing crop tolerance to abiotic stresses, particularly salinity. Salinity is one of the major environmental constraints limiting crop productivity worldwide, as it adversely affects plant growth, physiological performance, nutrient uptake, and ionic balance. Results: In this context, the present study evaluated the effects of foliar application of calcium–phosphate–potassium (CaPK) fertilizers in both bulk and nanoparticle (CaPK-NP) forms on the growth, physiological performance, and gene expression analysis of faba bean ( Vicia faba L.) under saline field conditions during two growing seasons (2021–2022). To achieve this objective, foliar sprays of bulk CaPK and CaPK-NPs were applied at concentrations of 8 and 16 mL L⁻¹. Key growth traits, photosynthetic performance, antioxidant activity, ion balance, and the expression of selected ion transporter genes namely SOS1 , VHA2 , VFK1 , and KUP7 were assessed to better understand the mechanisms underlying salt stress mitigation. The results showed that the 8 mL L⁻¹ bulk CaPK treatment consistently improved growth, photosynthetic pigments, antioxidant responses, nutrient uptake, and the Na⁺/K⁺ balance compared with untreated plants. Furthermore, gene expression analysis demonstrated the upregulation of ion transport-related genes, suggesting improved ionic homeostasis under saline conditions. Notably, the application of 16 mL L⁻¹ bulk CaPK resulted in the greatest enhancement of yield parameters. Although CaPK-NPs also improved several measured parameters, bulk CaPK frequently produced comparable or even greater enhancements under the experimental conditions. Conclusions: These findings suggest that foliar CaPK application may contribute to improved salinity tolerance in faba bean. However, further multi-location studies and long-term environmental assessments are still required before making broader agricultural recommendations.

The goal of the current study was to assess the effects of saline irrigation on the secondary metabolites and essential oil contents of three significant aromatic and medicinal plants, Pelargonium graveolens L., Mentha longifolia L., and Chrysanthemum frutescens L., using different NaCl levels (0, 50, 75, and 100 mM). Our results indicated that the levels of total phenols, flavonoids, tannins, saponins, and alkaloids in the methanolic extracts increased in response to salinity in the three investigated plants. The GC-MS analysis of the essential oils (EOs) showed that some major compounds increased significantly at the high salinity levels (75 and 100 mM NaCl). The EOs anticancer activity of the three plants against the human hepatocellular carcinoma cell line (HepG2) and human colorectal carcinoma (HCT-116) revealed that the P. graveolens L. EO exhibited the most potent cytotoxic effect with IC ₅₀ values of 0.66 and 1.87 µg/ml, at 50 mM NaCl, respectively. The treated M. longifolia L. EOs showed the most potent cytotoxic effect against HepG2 and HCT-116 at 75 mM NaCl with IC ₅₀ values of 2.32 and 7.47 µg/ml, respectively. Otherwise, M. longifolia L. crude extracts and EOs exhibited the highest DPPH free radical scavenging activity.