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 (H2O2 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.
High soil salinity significantly hampers plant growth and crop yield by disrupting metabolic functions and causing oxidative, osmotic, and ionic stress. This study investigated the combined effects of naphthalene acetic acid (NAA) and salicylic acid (SA) in reducing salt stress in cucumber (Cucumis sativus L.) cv. AR-8, filling a knowledge gap regarding multilateral plant growth regulator (PGR) interactions under saline conditions. Cucumber seedlings were subjected to 80 mM NaCl, with or without 200 ppm NAA and 300 ppm SA. Salt stress notably decreased seedling vigor, biomass, and chlorophyll levels. However, combined NAA and SA treatments significantly mitigated these effects, leading to improvements in leaf area, plant height, and root activity compared to untreated stressed plants. The PGRs also enhanced fruit quality by increasing vitamin C, soluble sugars, and protein content. Additionally, they reduced oxidative stress markers such as electrolyte leakage and lipid peroxidation, while boosting antioxidant enzyme activities like catalase, ascorbate peroxidase, superoxide dismutase, and peroxidase. The treatments further influenced carbohydrate and nitrogen metabolism by modulating key enzymes, including sucrose phosphate synthase, glutamine synthetase, glutamate synthase, and glutamate dehydrogenase. This research highlights the synergistic effect of NAA and SA in promoting cucumber tolerance to salt stress and offers new insights into using multiple PGRs for crop resilience in saline environments. Future studies should aim to optimize PGR combinations and explore their molecular mechanisms in different crops under various stress conditions.
Abstract Long-term storage can erode the value of Apiaceae fruits through volatilization and compositional drift of their essential oils (EOs). This study evaluated UV-C pre-treatment (25 min) and packaging type as practical approaches to preserve EO quality in fennel ( Foeniculum vulgare ), anise ( Pimpinella anisum ), cumin ( Cuminum cyminum ), and caraway ( Carum carvi ) fruits stored for 12 months in four packages (jute, polyethylene 120 µm, polyethylene 150 µm, and an antifungal film). EO profiles were monitored by GC–MS at 0, 3, 6, 9, and 12 months; antifungal efficacy was assessed against Rhizoctonia solani , Alternaria solani , and Fusarium oxysporum ; and key EO constituents were docked against cutinase (PDB: 1xzb). At baseline, fennel EO was dominated by estragole (49.97% in control; 57.13% after UV-C) and anethole (20.02%); anise EO was rich in anethole (63.79% in control; 64.93% after UV-C); cumin EO was characterized by γ-terpinen-7-al (21.56% in control; 25.89% after UV-C) and cuminaldehyde (19.62% in control; 20.33% after UV-C); and caraway EO contained high levels of carvone (41.60% in control; 47.69% after UV-C) and D-limonene (24.36% in control; 33.11% after UV-C). After 12 months, hermetic packaging (150 µm and antifungal film) better preserved the dominant chemical signature of each EO under UV-C, with estragole at 85.16% in fennel (antifungal), anethole at 72.63% in anise (150 µm), cuminaldehyde at 37.46% in cumin (antifungal), and carvone at 63.14% in caraway (antifungal). Overall, combining UV-C with hermetic/antifungal packaging provides an effective strategy to maintain Apiaceae EO composition and bioactivity during extended storage.
Water scarcity and rising fertilizer costs challenge the sustainable cultivation of medicinal and aromatic plants in arid regions. This study evaluated the interactive effects of irrigation intervals (21, 28, and 35 days) and potassium sources (potassium sulfate and feldspar) and rates on growth, yield, essential oil productivity, and nutrient status of fennel (Foeniculum vulgare Mill.) over two consecutive seasons in Middle Egypt. Extending irrigation intervals significantly increased soil electrical conductivity while reducing soil-available potassium, whereas soil pH, organic matter, and bulk density remained unaffected. Frequent irrigation (21 days) markedly enhanced vegetative growth, yield components, seed yield, and essential oil yield, producing up to 69.7 L ha−1 oil compared with 50.5–52.0 L ha−1 under 35-day intervals. Potassium fertilization significantly improved plant performance across all irrigation regimes, with potassium sulfate at 120 kg K2O ha−1 consistently producing the highest plant height (≈173 cm), number of umbels (≈45 plant−1), 1000-seed weight (≈13 g), seed yield, and oil yield. Potassium sulfate at 120 kg K2O ha−1 consistently outperformed feldspar, though high-rate feldspar (572 kg K2O ha−1) significantly improved performance over the control, indicating potential as a supplementary source. Extending irrigation to 28 days reduced water application by approximately 23% compared to 21-day intervals, with acceptable yield levels when combined with adequate potassium supply. Potassium application enhanced seed and herb N, P, and K concentrations and mitigated the adverse effects of prolonged irrigation intervals, particularly under moderate water stress (28 days). Significant irrigation × potassium interactions confirm that optimal potassium nutrition improved water-use efficiency and reproductive performance. Overall, integrating frequent or moderately extended irrigation with an adequate potassium supply—especially soluble potassium sulfate—offers an effective strategy to sustain fennel productivity and essential oil yield under water-limited conditions.
Roselle calyces are regarded as a source of anthocyanins and many nutrients. Despite their high therapeutic and nutritional value, fresh calyces are highly perishable, necessitating efficient preservation methods. Traditional drying, although cost-effective, often degrades heat-sensitive nutrients due to uncontrolled conditions. This study evaluates the efficiency of two precision drying technologies, specifically a hybrid smart solar dryer (HSSD) and a smart hot air rotary drum dryer (DD), at temperatures of 30°C, 40°C, and 50°C. The investigation focuses on drying kinetics and energy consumption while examining the calyces' physicochemical properties. Findings revealed that the hybrid smart solar dryer consumed 19.61, 21.57, and 24.38 kWh/batch of total energy, whereas the smart hot air rotary DD recorded 19.93, 21.52, and 16.3 kWh/batch at 30°C, 40°C, and 50°C. Notably, microstructural analysis showed that the DD produced less cellular collapse than the hybrid smart solar dryer. The highest total anthocyanin (303.09 mg/100 g) and furfural content (43.90%) were preserved in calyces dried at 30°C and 40°C with the DD, respectively. Conversely, the hybrid smart solar dryer at 50°C was more effective in preserving total phenols and vitamin C. Overall, this research emphasizes that the smart hot air rotary drum dryer operated at 40°C can be considered a blueprint for balancing efficient drying kinetics with the retention of valuable quality measurements, especially the anthocyanin. Future studies should focus on longitudinal economic viability, carbon credit potential, and the scalability of these technologies for other industrial medicinal and aromatic plants.
