Document Type : Research Paper

Authors

• niloufar Rezaei ¹
• Fatemeh Sefidkon ²
• hassan ali naghdibadi ³

¹ PhD graduate, Department of Horticultural Science and Agronomy, Science and Research Branch, Islamic Azad University, Tehran, Iran

² *- Corresponding author, Professor, Research Institute of Forests and Rangelands, Agricultural Research, Education and Extension Organization (AREEO), Tehran, Iran, E-mail: sefidkon@rifr-ac.ir

³ Associate Professor, Medicinal Plants Research Center, Institute of Medicinal Plants, ACECR, Karaj, Iran.

Abstract

Background and Objective: The cultivation of medicinal plants, including savory (Satureja), is increasing worldwide. Savory, containing thymol and carvacrol in its essential oil, holds significant importance. This study aims to investigate the effects of planting density and soil fertility on the physiological traits and antioxidant enzyme activities of savory under rainfed conditions. Considering the importance of these factors in enhancing plant resistance to stress, this research was conducted to determine the optimal planting density and soil fertility for boosting antioxidant activities and promoting the sustainable development of savory.
Methodology: This study was conducted as a field experiment at the Hamand Absard Research Station in Damavand during the 2017–2018 and 2018–2019 growing seasons. The experiment was arranged in a split-plot design within a randomized complete block design (RCBD) with two factors. The main factor consisted of three fertilizer levels: (1) control (no fertilizer), (2) decomposed cattle manure (30 tons per hectare), and (3) straw enriched with ammonium sulfate (10 tons per hectare). The sub-factor included three planting densities: 2.67, 4, and 8 plants per square meter. Planting was performed using standard savory seeds. Land preparation involved plowing, disking, and leveling. Fertilizers were applied according to the treatments before planting. Irrigation was limited to rainfed conditions only. Leaf samples were collected at the full flowering stage. The measured physiological traits included relative leaf water content, total chlorophyll, proline content, electrolyte leakage, ion leakage, malondialdehyde content, and antioxidant enzyme activities (catalase, peroxidase, and superoxide dismutase). Samples were analyzed in the laboratory after harvest to evaluate the effects of treatments on the studied parameters. Data was analyzed using SAS software, and mean comparisons were performed using Duncan’s multiple range test at a 5% significance level.
Results: This study demonstrated that planting density and organic fertilizer treatments significantly influenced the physiological traits and antioxidant defense responses of Satureja spicigera under rainfed conditions. The highest relative water content (87.67%) and the lowest electrolyte leakage (47.19%) were recorded in the treatment with cow manure and a low planting density of 2.67 plants per square meter, indicating improved water status and membrane stability. In contrast, increasing planting density reduced chlorophyll content and relative water content, while levels of proline, electrolyte leakage (ELI), and malondialdehyde (MDA) increased, reflecting greater stress intensity under high-density conditions. The application of cow manure and ammonium sulfate-enriched straw improved physiological performance and significantly reduced oxidative stress markers. These treatments promoted better osmotic regulation and membrane protection, contributing to greater stress tolerance. Interestingly, the highest activities of antioxidant enzymes, catalase, peroxidase, and superoxide dismutase were observed in the unfertilized control under high-density planting. This suggests that the plant naturally boosts its enzymatic antioxidant defenses under more stressful conditions, particularly when nutrients are limited. In conclusion, the results highlight that integrating organic fertilization with optimal planting density can enhance drought resilience by maintaining physiological stability and reducing oxidative damage. These practices not only support the sustainable cultivation of Satureja spicigera in water-limited environments but also improve the plant’s overall functional and medicinal quality.
Conclusion: The results of this study show that savory (Satureja spicigera) has a good ability to grow and develop under rainfed conditions and demonstrates significant capacity to enhance its antioxidant activity. The combined use of organic fertilizers, especially cow manure, along with an appropriate planting density, is practical in improving physiological traits, increasing resistance to environmental stresses, and strengthening the plant’s enzymatic defense system. Implementing these findings can be valuable in enhancing productivity, ecological sustainability, and food security in areas with limited water resources.

Keywords

• superoxide dismutase
• proline
• chlorophyll
• cow manure

Main Subjects

• Agriculture and horticulture