Mehri Mahdavifard; Sadegh Mousavi-Fard; Abdolhossein Rezaei Nejad; Hasan Mumivand; Mohammad Kazem Souri
Abstract
Objective: This study aimed to evaluate the combined effects of ultraviolet (UV) radiation and nutrient supplementation with magnesium (Mg) and manganese (Mn) on mitigating oxidative stress, regulating biochemical pathways, and enhancing essential oil yield in Lavandula angustifolia grown under hydroponic ...
Read More
Objective: This study aimed to evaluate the combined effects of ultraviolet (UV) radiation and nutrient supplementation with magnesium (Mg) and manganese (Mn) on mitigating oxidative stress, regulating biochemical pathways, and enhancing essential oil yield in Lavandula angustifolia grown under hydroponic conditions.
Method: The experiment was conducted over two consecutive harvests (2021–2022) in the research greenhouse of Lorestan University. A split-plot time design in a randomized complete block design (RCBD) with three replications was employed. Nutritional treatments used a Hoagland-based control solution containing 2 mM Mg and 2.9 µM Mn, with additional treatments formed by halving or doubling these concentrations. Main plots were allocated to three UV levels: no exposure (control), UV-A, and UV-B; subplots encompassed 11 nutrient treatments. Measured variables included essential oil content and yield, total chlorophyll, carotenoids, proline, and catalase (CAT) activity, among other physiological and biochemical traits.
Result: UV-A combined with high Mg and Mn (4 mM Mg and 4.18 µM Mn) produced the highest essential oil percentage (4.03–4.48%) and yield (4.13–5.01 kg ha⁻¹) across both harvests. UV-B reduced chlorophyll content, with a less pronounced decline in the second harvest. High Mg with baseline Mn mitigated light stress, yielding the highest chlorophyll content under non-stress conditions in the second harvest. Carotenoid content was greater in the first harvest and generally increased with greater UV stress, reaching a maximum of 2.26 mg g⁻¹ fresh weight under UV-B with low Mg and Mn; the lowest carotenoids (1.06 mg g⁻¹ FW) occurred in the second harvest under no UV with high Mg and moderate Mn. UV-B combined with low Mg and Mn significantly elevated proline accumulation, whereas higher Mg and Mn levels reduced proline under the same conditions.
Conclusion: A nutrient combination of 4 mM Mg and 4.18 µM Mn, especially under UV-A, effectively alleviates UV stress and enhances physiological status and essential oil production in Lavandula angustifolia. The UV-A treatment with 4 mM Mg and 4.18 µM Mn was the most effective, reducing UV-induced stress and improving chlorophyll and carotenoid contents and essential oil yield. The second harvest exhibited superior performance, likely due to improved physiological conditions. Overall, integrating UV-A exposure with optimized Mg and Mn nutrition appears to be a promising strategy to improve both quantity and quality of Lavandula angustifolia under stressful growing conditions.