Document Type : Research Paper - Oil seed
Authors
- Ali Mohammadi Kharkeshi
- Elyas Rahimi Petroudi
- Fazl Shirdel Shahmiri
- Hamid Reza Mobasser
- Alireza Daneshmand
Department of Agronomy, Faculty of Agriculture, Qaemshahr Branch, Islamic Azad University, Qaemshahr, Iran
Abstract
Introduction
Sesame (Sesamum indicum) is an important oilseed crop due to its high content of oil, antioxidants, and protein. Drought is one of the most destructive abiotic stresses that significantly affects all quantitative and qualitative traits of sesame. Silicon (Si) is a micronutrient that plays a crucial role in protecting plants against abiotic stresses. This efficiency is due to silicon's ability to synthesize phytoalexins and phenolics in response to these stresses. Additionally, cytokinins (CKs) can reduce the damage to plants caused by various abiotic stresses. Cytokinin plays a crucial role in regulating growth and maintaining the stability of the photosynthetic system during stress periods. It also modulates many physiological activities induced by drought stress. Accordingly, this study aimed to investigate the effects of silicon and cytokinins on the activity of antioxidant enzymes and sesame seed yield under drought stress conditions.
Materials and methods
This experiment was conducted in 2020 and 2021 as a split factorial in a randomized complete block design with three replications. The experiment was carried out at the Firoozkandeh Agricultural Research Station, located 6 km north of Sari city (36°48'N, 53°5'E, and 8 m above sea level), Mazandaran province, northern Iran. The treatments included drought stress (no stress or control, moderate stress, and severe stress) as the main factor, and silicon (no silicon or control, soil-applied calcium silicate, and foliar-applied nanosilicon), and cytokinin (no cytokinin or control and foliar-applied cytokinin) as sub-factors. Moderate and severe drought stress were applied through irrigation after 100 and 200 mm of evaporation from a Class A evaporation pan, respectively. The traits studied included grain yield, concentration of photosynthetic pigments, antioxidant enzyme activity, proline content, silica concentration, oleic acid, and linoleic acid. Data analysis was performed using SAS 9.2 and MSTAT-C statistical software. The least significant difference (LSD) test at the 5% probability level was used for mean comparisons.
Results and Discussion
The results showed that with increasing levels of drought stress, the concentrations of chlorophylls a and b decreased by 13.1% and 10.8%, respectively. The maximum concentration of chlorophyll a was obtained with foliar application of nanosilicon and cytokinin (2.176 mg g-1 FW). The maximum catalase enzyme activity under severe drought stress conditions was observed with foliar application of nanosilicon and cytokinin (0.4187 unit mg-1 protein). The activity of guaiacol peroxidase enzyme reached its maximum under moderate drought stress conditions with the same foliar applications (0.2868 unit mg-1 protein). In the years 2020 and 2021, foliar application of nanosilicon resulted in the highest proline content (0.4344 and 0.4439 mg g-1 FW, respectively). Additionally, in 2021, the highest proline content was obtained with foliar application of cytokinin (0.4415 mg g-1 FW). Grain yield decreased by 32.7% with increasing levels of drought stress. The maximum grain yield was obtained with foliar application of nanosilicon (1647 kg ha-1), and foliar application of cytokinin also increased grain yield by 6.6%. Oleic acid was only affected by drought stress and showed an increasing trend with increasing drought stress level.
Conclusion
Overall, the results showed that drought stress reduced chlorophyll concentration and grain yield, as well as increased oleic acid. Simultaneous foliar application of nano-silicon and cytokinin increased chlorophyll concentration and separately led to an increase in grain yield. Simultaneous foliar application of nano-silicon and cytokinin also enhanced the increasing effect of drought stress on enzyme activity.
Keywords
- Abiotic stress
- Nutrition
- Nanoparticles
- Photosynthetic pigments
- Antioxidant activity
- Quantitative yield
Main Subjects
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