Salinity-induced stress is widely considered a main plant-growth-limiting factor. The positive effects of melatonin in modulating abiotic stresses have led this hormone to be referred to as a growth regulator in plants. This study aims to show how melatonin protects fenugreek against the negative effects of salt stress. Different amounts of melatonin (30, 60, and 90 ppm), salinity stress (150 mM and 300 mM), and the use of both salinity and melatonin were used as treatments. The results showed that applying different melatonin levels to salinity-treated fenugreek plants effectively prevented the degradation of chlorophyll a, chlorophyll b, total chlorophyll, and carotenoid contents compared with salinity treatment without melatonin application. Besides, melatonin increases the biosynthesis of enzymatic and non-enzymatic antioxidants, thereby adjusting the content of reactive oxygen species, free radicals, electrolyte leakage, and malondialdehyde content. It was observed that applying melatonin increased the activity of potassium-carrying channels leading to the maintenance of ionic homeostasis and increased intracellular water content under salinity stress. The results revealed that melatonin activates the defense signaling pathways in fenugreek through the nitric oxide, auxin, and abscisic acid-dependent pathways. Melatonin, in a similar vein, increased the expression of genes involved in the biosynthesis pathway of diosgenin, a highly important steroidal sapogenin in medical and food industries, and hence the diosgenin content. When 150 mM salinity stress and 60 ppm melatonin were coupled, the diosgenin concentration rose by more than 5.5 times compared to the control condition. In conclusion, our findings demonstrate the potential of melatonin to enhance the plant tolerance to salinity stress by stimulating biochemical and physiological changes.

High-temperature stress is widely considered a main plant-growth-limiting factor. The positive effects of 24-epibrassinolide (EBR) as analogs of brassinosteroids (BRs) in modulating abiotic stresses have led this hormone to be referred to as a growth regulator in plants. The current study highlights the influence of EBR on enhancing tolerance to high-temperature and altering the diosgenin content in fenugreek. Different amounts of EBR (4, 8, and 16 μM), harvesting times (6, and 24 h), as well as temperature regimes (23 °C, and 42 °C) were, used as treatments. EBR application under normal temperature and high-temperature stress resulted in decreased malondialdehyde content and electrolyte leakage percentage, while the activity of antioxidant enzymes improved significantly. Exogenous EBR application possibly contributes to activating the nitric oxide, H₂O₂, and ABA-dependent pathways, enhancing the biosynthesis of abscisic acid and auxin, and regulating the signal transduction pathways, which raises fenugreek tolerance to high-temperature. The SQS (eightfold), SEP (2.8-fold), CAS (11-fold), SMT (17-fold), and SQS (sixfold) expression, considerably increased following EBR application (8 μM) compared to the control. Compared to the control, when the short-term (6 h) high-temperature stress was accompanied by EBR (8 μM), a sixfold increase in diosgenin content was achieved. Our findings highlight the potential role of exogenous 24-epibrassinolide in mitigating the high-temperature stress in fenugreek by stimulating the biosynthesis processes of enzymatic and non-enzymatic antioxidants, chlorophylls, and diosgenin. In conclusion, the current results could be of utmost importance in breeding or biotechnology-based programs of fenugreek and also in the researches related to the engineering of the biosynthesis pathway of diosgenin in this valuable plant.

Abiotic stresses, notably cold stress, significantly influence various aspects of plant development and reproduction. Various approaches have been proposed to counteract the adverse impacts of cold stress on plant productivity. The unique properties of nanoparticles contribute to an enhanced tolerance of plants to challenging conditions. This study explores the impact of titanium dioxide nanoparticles (TiO₂ NPs) on cold-stress tolerance in fenugreek, as well as genes expression involved in the diosgenin biosynthesis pathway. Varied concentrations of TiO₂ NPs (0, 2, 5, and 10 ppm) were sprayed on fenugreek plants subjected to cold stress at 10 °C during 6, 24, and 48 h. Our findings revealed that the utilization of 2 and 5 ppm of TiO₂ NPs, positively influenced pigments biosynthesis and enzymatic and non-enzymatic antioxidant activities. It also effectively reduced electrolyte leakage and malondialdehyde content, mitigating the adverse effects of cold stress. The study also highlighted TiO₂ NPs’ affirmative impact on defense signaling pathways, including abscisic acid, nitric oxide, and auxin, in fenugreek. Moreover, TiO₂ NPs significantly influenced the expression of genes related to diosgenin biosynthesis. Simultaneous exposure to cold stress and TiO₂ NPs led to a substantial increase in diosgenin content, with the upregulation of SEP, SQS, CAS, and SSR genes compared to control conditions. This research indicated that TiO₂ NPs application could effectively stimulate fenugreek biosynthesis of primary and secondary metabolites, consequently enhancing plant tolerance to cold stress. The study’s outcomes hold promise for potential applications in the metabolic engineering of diosgenin in fenugreek.

Background: Due to the factor of water deficit, which has placed human food security at risk by causing a 20% annual reduction in agricultural products, addressing this growing peril necessitates the adoption of inventive strategies aimed at enhancing plant tolerance. One such promising approach is employing elicitors such as 24-epibrassinolide (EBR) and yeast extract, which are potent agents capable of triggering robust defense responses in plants. By employing these elicitors, crops can develop enhanced adaptive mechanisms to combat water deficit and improve their ability to withstand drought condition. This study investigates the impact of different levels of EBR (0, 5, 10 µm) and yeast extract (0 and 12 g/l) on enhancing the tolerance of cowpea to water deficit stress over two growing seasons. Results: The findings of this study demonstrate that, the combined application of EBR (especially 10 µm) and yeast extract (12 g/l) can increase seed yield (18%), 20-pod weight (16%), the number of pods per plant (18%), total chlorophyll content (90%), and decrease malondialdehyde content (45%) in cowpea, compared to plants grown under water deficit stress without these treatments. Upon implementing these treatments, impressive results were obtained, with the highest recorded values observed for the seed yield (1867.55 kg/ha), 20-pod weight (16.29 g), pods number per plant (9), and total chlorophyll content (19.88 mg g⁻¹ FW). The correlation analysis indicated a significant relationship between the seed yield, and total chlorophyll (0.74**), carotenoids (0.82**), weight of 20 seeds (0.67**), and number of pods (0.90**). These traits should be prioritized in cowpea breeding programs focusing on water deficit stress. Conclusions: The comprehensive exploration of the effects of EBR and yeast extract across various levels on cowpea plants facing water deficit stress presents a pivotal contribution to the agricultural domain. This research illuminates a promising trajectory for future agricultural practices and users seeking sustainable solutions to enhance crops tolerance. Overall, the implications drawn from this study contribute significantly towards advancing our understanding of plant responses to water deficit stress while providing actionable recommendations for optimizing crop production under challenging environmental conditions.

In this study, screening of Artemisia dracunculus accessions was investigated under water deficit based on physiological and phytochemical traits. The results clearly indicated that water deficit significantly reduced the relative water content, chlorophyll, and carotenoid contents and increased malondialdehyde, electrolyte leakage, and antioxidant activities. The responses of tarragon accessions to water deficit, however, were inconsistent. The HPLC analysis revealed the presence of chlorogenic, syringic, ferulic, vanillic, chicoric, and p-coumaric acids as major phenolic acids, while quercetin and herniarin were detected as the predominant flavonoid and coumarin compounds in the extracts. Our findings revealed that the water deficit not only increased the amounts of herniarin, luteolin, apigenin, caffeic acid, and syringic acid, but also introduced quercetin that was not present under normal conditions in Estahbanat. Nevertheless, these results were highly impacted by the accession type. The results indicated that Hamadan, Varamin and Estahbanat accessions could be introduced as tolerant accessions. Given the very different responses of tarragon accessions to water deficit and the diversity between these accessions, the findings of the present study could be an effective step in identifying and achieving homogeneous, drought-tolerant and high-yield potential accessions, and may help tarragon breeding programs as well as development of cultivation.