Document Type : Research Paper

Authors

• Kobra Sepahvand ¹
• Abdolhossein Rezaei Nejad ²
• Sadegh Mousavi-Fard ³
• Reza Abolghasemi ⁴

¹ Department of Horticultural Sciences, Faculty of Agriculture, Lorestan University, Khorramabad, Iran

² Lorestan University

³ Department of Horticultural Sciences, Faculty of Agriculture, Shahrekord University, Shahrekord, Iran.

⁴ Department of Horticultural Sciences, Faculty of Agriculture, Lorestan University, Khorramabad, Iran.

Abstract

     Background and Objectives: Drought stress is a shortage of available water that limits normal plant growth and delays life cycle completion; it affects growth and development by inducing biochemical, physiological, and morphological changes. Identifying effective management strategies to alleviate drought stress can improve plant yield and quality. However, the effects of stress-mitigating agents such as nano calcium chloride and calcium carbonate on scented geranium (Pelargonium graveolens) characteristics have not been studied. Therefore, this study assessed the impact of foliar application of bulk and nano calcium chloride and calcium carbonate on selected antioxidant properties, essential oil content, and yield of scented geranium under drought stress.
Methodology: This experiment was conducted in 2023 at Lorestan University under greenhouse conditions using a factorial design in a completely randomized design (CRD) with four replications. The first factor was irrigation at two levels: no stress (80% of available water, control) and severe water deficit (20% of available water). The second factor was foliar application of calcium sources, calcium chloride and calcium carbonate in bulk and nano forms, each at concentrations of 5, 10, and 15 mM, along with a control (0 mM). In total, 13 treatments (26 treatment combinations) were evaluated. Rooted cuttings of Pelargonium graveolens were transplanted into 15-cm-diameter pots. After transplantation, plants were irrigated normally until full establishment. Foliar applications of calcium treatments were then initiated and applied every two weeks, 10 times in total. Drought stress treatments were imposed after the first foliar application according to scheduled irrigation intervals. At the end of the experiment (150 days after initiation), aboveground plant parts were harvested for biomass measurements. Fresh weights of leaves and stems were recorded immediately, and samples were then shade-dried to determine dry weights. Essential oils were extracted from dried, ground leaves by hydro-distillation in a Clevenger-type apparatus for three hours. To assess the activities of the antioxidant enzymes catalase (CAT), ascorbate peroxidase (APX), and superoxide dismutase (SOD), enzymes were extracted from frozen fresh leaf samples, and absorbance was read using a spectrophotometer.
Results: Analysis of variance showed that drought stress, calcium treatments, and their interaction significantly affected most evaluated traits (p < 0.01). Under 80% available water, 10 mM calcium carbonate increased catalase activity by 97.89% over the control (no foliar application). This increase was statistically similar to that from 15 mM nano calcium carbonate under the same irrigation condition or under 20% available water, which increased enzyme activity by 43.69%. Under 80% and 20% available water, 15 mM nano calcium carbonate increased superoxide dismutase activity by 72.34% and 15.48%, respectively, over the control. Under both irrigation levels, 15 mM nano calcium carbonate and nano calcium chloride increased flavonoid content by 50.37% and 39%, respectively, over the control. Under 80% available water, 15 mM calcium chloride increased essential oil yield by 56.86% over the control; this increase was statistically similar to that from 10 and 15 mM nano calcium chloride. Drought stress (20% available water) reduced essential oil yield. However, under drought conditions, 15 mM nano calcium carbonate increased essential oil yield by 80.95% over the control and was statistically similar to 10 and 15 mM nano calcium chloride.
Conclusion: Both bulk and nano calcium treatments affected enzymatic, antioxidant, and essential oil-related traits under both stress and non-stress conditions. Among the treatments, 15 mM nano calcium carbonate was the most effective for enhancing drought tolerance in scented geranium.

Keywords

• Antioxidant enzymes
• drought stress
• essential oil
• foliar application
• nano calcium carbonate

Main Subjects

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