Document Type : Research Paper

Authors

• Hosein Ahmadi ¹
• Mohammad Reza Fatahi ¹
• Zabihollah Zamani ¹
• Majid Shokrpour ¹
• Mohammad Reza Morshedloo ²

¹ Department of Horticulture Science, Faculty of Agriculture and Natural Sciences, University of Tehran, Iran

² Department of Horticultural Science, Faculty of Agriculture, University of Maragheh, Maragheh, Iran.

Abstract

     Background and Objective: Thymus daenensis Celak. is an endemic medicinal plant of Iran valued for its high thymol content and essential oil content. A novel approach to enhancing plant tolerance to environmental stress is applying nanoparticles as bioelicitors. Nanosilicon and nanoselenium are among the nanoparticles that can enhance stress tolerance and improve plant performance by influencing physiological and biochemical pathways. This study assessed the combined effects of nanosilicon and nanoselenium treatments on the agronomic, phytochemical, and physiological traits of T. daenensis under drought stress.
 Methodology: The study was conducted in a research field using a split-plot experimental design. The experimental factors consisted of two water-stress levels (control and irrigation cessation before flowering) and five concentrations of the combined nanosilicon and nanoselenium treatment (0, 10, 20, 40, and 60 mg/L). We measured agronomic traits, including dry matter yield, essential oil yield, and thymol yield. We also determined mineral element concentrations (nitrogen, phosphorus, potassium, calcium, magnesium, and iron) and physiological indices (chlorophyll, malondialdehyde, and hydrogen peroxide). Multivariate regression analysis and artificial neural network (ANN) modeling were used to analyze the observed trends and model the data.
Results: The results showed that drought stress significantly reduced dry matter yield, essential oil yield, and thymol yield, with more pronounced reductions during the second harvest. Nano-elicitor application positively affected certain agronomic traits, particularly at a concentration of 10 mg/L, which increased dry matter yield by 18%. However, concentrations above 20 mg/L produced adverse effects and reduced plant performance. Regarding mineral element concentrations, nano-elicitor application increased the uptake of nitrogen, phosphorus, calcium, magnesium, and iron, whereas potassium levels remained largely unchanged under stress conditions. Physiological assessments showed that drought stress increased malondialdehyde and hydrogen peroxide levels, indicating enhanced oxidative stress. However, applying the nano-elicitors at 10 mg/L effectively reduced hydrogen peroxide levels under drought stress. ANN modeling demonstrated greater predictive accuracy than conventional regression models and proved to be a reliable approach for predicting plant performance under different stress and treatment conditions. The ANN model exhibited a lower standard deviation and a higher coefficient of determination (R²), exceeding 95% when predicting essential oil and thymol yield. The modeling results further demonstrated that artificial neural networks, as an artificial intelligence approach, provided more accurate predictions than six other commonly used regression models.
Conclusion: Overall, the findings indicated that nanosilicon and nanoselenium can positively affect certain agronomic and physiological traits of T. daenensis, although these effects depend on the application concentration and the prevailing stress conditions. Under drought stress, the 10 mg/L treatment produced the most favorable overall outcomes, as it improved yield and helped reduce oxidative stress. ANN modeling also demonstrated strong predictive performance and offered a useful and optimized approach for managing medicinal plant cultivation under stressful environmental conditions. Further research should examine the molecular mechanisms through which nano-elicitors influence plant regulatory and metabolic pathways. The findings suggest that applying nanosilicon and nanoselenium at appropriate concentrations may serve as a practical strategy to improve the performance of medicinal plants exposed to drought stress. However, additional studies are needed to clarify the physiological and molecular mechanisms through which these nanoparticles act in plants and to evaluate their long-term impacts on soil properties and the environment.

Keywords

• Drought stress
• nanosilicon
• nanoselenium
• thymol
• artificial neural network
• regression modeling

Main Subjects

• Phytochemistry (extraction, identification and measurement of active components)