This review delves into the role of plant growth-promoting microbes (PGPMs) in sustainable agriculture by enhancing soil health, improving plant stress tolerance, and controlling diseases. PGPMs, which include bacteria, fungi, and other microorganisms, are increasingly recognized as important contributors to promoting eco-friendly agricultural practices. Their ability to improve nutrient availability, stimulate plant growth, and protect crops from environmental stressors makes them a cornerstone for resilient and efficient farming systems. By reducing dependency on synthetic fertilizers and pesticides, PGPMs play a vital role in preserving environmental resources, minimizing greenhouse gas (GHG) emissions, and combating climate change’s negative impacts. This article thoroughly explores the complex interactions between PGPMs, soil nutrients, plant pathogens, and abiotic stressors. It also examines how these interactions influence phytohormone production and signaling pathways, ultimately impacting crop growth and development. Furthermore, this review discusses how PGPMs enhance nutrient uptake, modulate plant immune responses, and improve stress resilience, offering a holistic understanding of their multifaceted contributions to farming. By synthesizing current research and highlighting future directions, this review underscores the potential of PGPMs to revolutionize agricultural activities, ensuring food security and environmental sustainability in the face of global challenges.

The effect of melatonin (MT) on potato plants under drought stress is still unclear in the available literature. Here, we studied the effect of MT as a foliar application at 0, 0.05, 0.1, and 0.2 mM on potato plants grown under well-watered and drought stressed conditions during the most critical period of early tuberization stage. The results indicated that under drought stress conditions, exogenous MT significantly (p ≤ 0.05) improved shoot fresh weight, shoot dry weight, chlorophyll (Chl; a, b and a + b), leaf relative water content (RWC), free amino acids (FAA), non-reducing sugars, total soluble sugars, cell membrane stability index, superoxide dismutase (SOD), catalase (CAT), guaiacol peroxidase (G-POX), and ascorbate peroxidase (APX) compared to the untreated plants. Meanwhile, carotenoids, proline, methylglyoxal (MG), H₂O₂, lipid peroxidation (malondialdehyde; MDA) and abscisic acid (ABA) were significantly decreased compared to the untreated plants. These responses may reveal the protective role of MT against drought induced carbonyl/oxidative stress and enhancing the antioxidative defense systems. Furthermore, tuber yield was differentially responded to MT treatments under well-watered and drought stressed conditions. Since, applied-MT led to an obvious decrease in tuber yield under well-watered conditions. In contrast, under drought conditions, tuber yield was substantially increased by MT-treatments up to 0.1 mM. These results may imply that under water deficiency, MT can regulate the tuberization process in potato plants by hindering ABA transport from the root to shoot system, on the one hand, and by increasing the non-reducing sugars on the other hand.

Melatonin was found in plants in the late 1990s, but its function, signaling, and interaction with other phytohormones still unclear. Melatonin research in plants has increased substantially in recent years, including reports on the impact of this putative plant hormone under biotic and abiotic stress situations. Temperature extremes, salt, drought, hypoxia or anoxia, nutrient deficiency, herbicides, UV radiation stress, and heavy metal toxicity are all important obstacles to horticulture crop production worldwide. To deal with these environmental challenges, plants have evolved complex signaling networks. Phytohormones are essential for controlling plant growth, development, and stress responses. Melatonin, a pleiotropic chemical present in a variety of species, has recently emerged as a powerful regulator of plant abiotic stress tolerance. The purpose of this review is to investigate the interplay between melatonin and phytohormones in the control of abiotic stress responses in horticultural crops. We explore the interactions of melatonin with several phytohormones under various abiotic stresses.

Improving the physiological status expressed in adjusting the osmolytes and nutrients balance of plant cell is a crucial matter for ameliorating the hazards of salinity. In this context, humic substances have a significant role for stimulating the plant tolerance to various stresses. Therefore, the current study aimed to assess the importance of foliar spray of humic acid (0 and 150 mg L⁻¹) for avoiding the effect of salt stress (0, 4000 and 8000 mg L⁻¹) on vegetative growth of pittosporum plant, protein, proline, peroxidase activity and nutrient components related to salinity. The treatments were arranged in a randomized complete block design with 3 replicates. Results revealed that the highest vegetative growth was recorded with mg L⁻¹ humic acid. While, salinity levels of 4000, and 8000 mg L⁻¹ led to increases in protein, proline peroxidase activity, and chloride and sodium inions. Compared to humic acid-untreated plants, application of humic acid under salinity level of 4000 mg L⁻¹ enhanced plant height, root fresh weight plant⁻¹, root dry weight plant⁻¹, shoot fresh weight plant⁻¹ and shoot dry weight plant⁻¹ by 12.6, 10.9, 17.7, 43.4, 19.4%, respectively, in the second season. Humic acid application under all salinity levels showed favorable effect for keeping leaves in both seasons, since fallen leaves number was reduced. The increases in potassium (K) content reached about 12.0 and 22.4% under 4000 mg L⁻¹ and 8000 mg L⁻¹, respectively, owing to humic acid application. Protein, proline content and peroxidase activity showed the minimal values under humic acid × salinity level of 4000 mg L⁻¹. It could be concluded that application of humic mitigates the harmful effect of salinity and improves the vegetative growth parameters and physiological status of pittosporum plants while increases the uptake of beneficial nutrients.

Silicon plays a crucial role in enhancing plant tolerance to various abiotic and biotic stresses, including drought, salinity, heavy metals, and pathogen/pest attacks. Its application has shown promising results in improving stress tolerance and productivity in medicinal plants. This review synthesizes findings from numerous studies investigating the mechanisms by which silicon confers stress tolerance, including the regulation of antioxidant systems, water relations, nutrient homeostasis, phytohormone signaling, and stress-responsive gene expression. Additionally, it examines the effects of silicon supplementation on the production of valuable secondary metabolites and essential oils in medicinal plants. Silicon application can significantly mitigate stress-induced damage in plants, including medicinally important species such as borage, honeysuckle, licorice, Damask rose, savory, basil, and eucalyptus. The deposition of silicon in cell walls provides physical reinforcement and acts as a barrier against pathogen invasion and insect herbivory. Furthermore, silicon fertilization can enhance the production of valuable secondary metabolites in medicinal crops under stress conditions. The findings underscore the potential of silicon fertilization as a sustainable strategy for improving the productivity and quality of medicinal crops under changing environmental conditions, highlighting the need for further research to elucidate the molecular mechanisms underlying silicon-mediated stress tolerance and practical applications in medicinal plant cultivation.

Table grape berries are classified as a perishable crop that deteriorates quickly after harvest. The application of melatonin after harvest was found to be effective for retarding senescence and slowing ripening. In the current study, we tested the influence of two melatonin concentrations (50 and 100 µmol) as a postharvest application on quality, bioactive compounds, and enzyme activities of grape berries cv “Crimson” stored at 0 ± 1 °C and 90% relative humidity (RH) for 35 days. Our results indicated that melatonin application extends the shelf-life of berries by reducing weight loss and maintaining total soluble solids (TSS), titratable acidity (TA), berry adherence strength, and firmness. Melatonin treatment also reduced pectin methyl esterase (PME) and polygalactouranase (PG) enzyme activities compared to the control. Moreover, O₂^•− and H₂O₂ rates in berries were reduced by high melatonin concentration. Moreover, peroxidase (POD) and catalase (CAT) enzyme activities were increased by melatonin application. Our findings suggested using melatonin postharvest to increase shelf life and maintain quality attributes during refrigerated storage, which could be advantageous on a large scale.