نوع مقاله : مقاله پژوهشی
عنوان مقاله English
نویسندگان English
The present study was conducted to evaluate the effects of foliar application of nano- and bulk forms of calcium chloride and calcium carbonate on the morphophysiological responses of scented geranium (Pelargonium graveolens L.) under water deficit stress. The experiment was conducted as a factorial experiment based on a completely randomized design with four replications. The first factor was irrigation level at two levels: control (80% available water) and severe water deficit stress (20% available water). The second factor comprised calcium chloride and calcium carbonate in both bulk and nano forms, each applied at concentrations of 5, 10, and 15 mM, along with a control treatment (0 mM). Analysis of variance showed that irrigation stress, calcium concentration, and their interaction significantly affected most of the evaluated traits (p ≤ 0.01). Application of 10 mM nano-calcium carbonate under 80% available water increased stem strength by 49.5% compared with the control. Foliar application of 15 mM nano-calcium carbonate under 20% available water increased stem strength by 125% compared with the unsprayed control under the same irrigation condition. Application of 15 mM nano-calcium carbonate under control and stress conditions improved the stress resistance index by 40.3% and 50.6%, respectively. In addition, foliar application of 15 mM nano-calcium carbonate and nano-calcium chloride under 80% and 20% available water, respectively, increased plant height by 31% and 45.7%, respectively, compared with the control. Overall, 15 mM nano-calcium carbonate was identified as the most effective treatment for enhancing drought tolerance in scented geranium.
کلیدواژهها English
Extended Abstract
Introduction
Scented geranium, scientifically known as Pelargonium graveolens L., is a perennial medicinal and ornamental plant belonging to the family Geraniaceae. The essential oil of this plant has been used for centuries in general medicine and dentistry. Owing to its antiviral, antibacterial, antifungal, cell-rejuvenating, astringent, calming, wound-healing, analgesic, antitumor, and antioxidant properties, scented geranium has been associated with various beneficial effects on human health and quality of life.
Water deficit stress is a major limiting factor for crop production in arid and semi-arid regions. In recent years, the application of engineered nanomaterials has been recognized as an innovative approach to mitigating the adverse effects of water deficit stress in plants.
In general, calcium is an essential element that plays a crucial role in plant responses to both biotic and abiotic stresses. Under stress conditions, osmotic regulation is associated with the absorption and accumulation of calcium ions, as well as increases in other ions and organic compounds. Studies have shown that calcium is essential for maintaining cell membrane integrity under various environmental stresses. Calcium nanoparticles (Ca-NPs) can modify pH, organic matter, and cation exchange capacity, thereby increasing the availability of otherwise limited mineral nutrients to plants.
The present study was conducted in the research greenhouse of the Faculty of Agriculture at Lorestan University to investigate the effects of foliar application of nano- and bulk forms of calcium chloride and calcium carbonate on the morphophysiological responses of scented geranium (Pelargonium graveolens) under drought stress conditions.
Materials and Methods
The experiment was conducted as a two-factor factorial experiment based on a completely randomized design (CRD) with four replications. The first factor was deficit irrigation at two levels: control (80% available water) and severe drought stress (20% available water). The second factor comprised calcium chloride and calcium carbonate in both bulk and nano forms, each applied at concentrations of 5, 10, and 15 mM, along with a control treatment (0 mM), resulting in 13 treatment levels and 26 treatment combinations applied as foliar sprays. During the warm season, a pad-and-fan cooling system was used to regulate the greenhouse temperature. The average daytime temperature ranged from 20 to 28°C, whereas the nighttime temperature ranged from 15 to 18°C. Relative humidity was maintained at 60–70%, and light intensity ranged from 400 to 500 µmol·m⁻²·s⁻¹. Data were analyzed using Minitab and SAS software, and graphs were prepared using Excel. Treatment means were compared using the Least Significant Difference (LSD) test at the 5% significance level.
Results and Discussion
Analysis of variance indicated that drought stress, different calcium concentrations, and the calcium × drought interaction significantly affected the morphological and physiological traits of the plant. Application of 15 mM nano-calcium carbonate under 80% available water increased plant height by 31% and stem diameter by 7.45% compared with the control. In addition, foliar application of 15 mM nano-calcium carbonate under severe drought stress (20% available water) resulted in a 140% increase in leaf number and a 53% improvement in water use efficiency compared with the control. These results demonstrate the positive effects of calcium-based materials, particularly nano-calcium carbonate, on plant growth and related traits under drought conditions.
Furthermore, application of 15 mM nano-calcium carbonate under 20% available water increased root fresh weight by 131% and root dry weight by 205% compared with the control. This treatment also resulted in a 125% increase in stem strength and a 3.4% increase in stem tissue density. Overall, the application of both nano- and bulk calcium materials under drought conditions improved the morphological and physiological characteristics of the plant, enhanced water use efficiency, and increased drought resistance. The greatest positive effects were observed with the application of 15 mM nano-calcium carbonate, which significantly improved plant performance and drought resistance, particularly under water stress conditions.
Nano-calcium carbonate, as a long-term reservoir, provides carbon dioxide to plants and may therefore enhance plant growth by increasing photosynthesis. Higher concentrations of carbon dioxide can suppress the activity of ribulose-1,5-bisphosphate oxygenase and reduce photorespiration.
Conclusions
Foliar application of bulk and nano forms of calcium compounds helped alleviate the adverse effects of drought stress on the morphophysiological and functional traits of scented geranium. Higher concentrations were more effective than lower concentrations. Among the calcium-containing treatments, nano-calcium carbonate had the greatest effect on the evaluated traits. The most effective treatment in this study was identified as 15 mM nano-calcium carbonate..
Author Contributions
ARN and KS planned and designed the research. KS performed the experiments. KS and SMF analyzed the data. ARN, KS, MSF and RA wrote and revised the manuscript.
Data Availability Statement
Data available on request from the authors.
Acknowledgements
This research was supported by Lorestan University, Iran.
Ethical considerations
The authors avoided data fabrication, falsification, plagiarism, and misconduct.
Conflict of interest
The author declares no conflict of interest.
