Effect of polyethylene glycol-induced drought stress on chlorophyll content and the antioxidant defense system in wheat seedlings

Document Type : Original Article

Author

Assistant Professor, Department of Agriculture and Plant Breeding, Faculty of Agriculture, Yasouj University, Yasouj, Iran

Abstract

Introduction
Drought stress is one of the main factors affecting the physiology and metabolism of crops such as wheat, leading to a reduction in yield and its components. Drought is among the most destructive and significant abiotic stresses in agriculture. Under drought stress, the imbalance between energy absorption and its utilization in the photosynthetic apparatus leads to the accumulation of reactive oxygen species (ROS) and the plant's inability to detoxify them, ultimately resulting in membrane damage and oxidative stress symptoms. Because it is challenging to create and maintain a defined soil water potential in the soil, drought stress is often imposed using osmotic agents that create controlled osmotic potentials. This approach is widely used to study the effects of drought on seed germination and related physiological traits. This study was conducted to investigate the effect of polyethylene glycol (PEG)-induced drought stress on chlorophyll content and the antioxidant defense system of wheat seedlings.
 
Materials and methods
The experiment was conducted as a factorial arrangement in a randomized complete block design (RCBD) with three replications. The experimental treatments consisted of five levels of drought stress induced using polyethylene glycol 6000 (PEG 6000) at osmotic potentials of 0, −1.5, −3.0, −4.5, and −6.0 bar, along with seeds of two irrigated wheat varieties, Sirvan and Baharan.
 
Results and discussion
Analysis of variance showed that the effects of drought stress and variety were significant for total chlorophyll, proline, ascorbic acid, total phenols, flavonoids, catalase (CAT), peroxidase (POD), ascorbate peroxidase (APX), superoxide dismutase (SOD), and glutathione reductase (GR). The interaction between drought stress and cultivar was significant only for POD activity. Based on the mean comparison results, drought stress had an adverse effect on the leaf chlorophyll content of both wheat cultivars. Increasing the severity of drought stress further reduced leaf chlorophyll content, and the lowest total chlorophyll content (2.51 mg g⁻¹ fresh leaf weight) was observed under the −6 bar drought stress treatment. Drought stress influenced the antioxidant defense system of the wheat cultivars, such that under drought conditions, the levels of non-enzymatic antioxidants and the activities of enzymatic antioxidants increased. Under severe drought stress at −6 bar, the highest levels of leaf proline (2.8 mg g⁻¹), ascorbic acid (11.66 mg g⁻¹), and flavonoids (15.48 mg g⁻¹) were obtained. At this osmotic potential, APX activity was highest (6.53 nmol.min⁻¹.g⁻¹). However, the highest total phenol content (12.70 mg•g⁻¹) was observed at −3.0 bar osmotic potential. At the osmotic potential of −4.5 bar, the highest activities of CAT (32.16 nmol min⁻¹ g⁻¹), POD (12.96 nmol min⁻¹ g⁻¹), SOD (1.53 μmol min⁻¹ g⁻¹), and GR (0.84 μmol min⁻¹ g⁻¹) were obtained.
 
Conclusion
Based on the present results, drought stress triggered the activation of both enzymatic and non-enzymatic antioxidant components, which function to mitigate oxidative damage and reduce the adverse effects of drought on chlorophyll and other cellular organelles, thereby enhancing the plant's ability to tolerate stress conditions. Moreover, compared with the Baharan cultivar, Sirvan exhibited higher leaf chlorophyll, greater levels of non-enzymatic antioxidants, and higher activities of enzymatic antioxidants, indicating superior performance under drought stress. Given the superior performance of Sirvan over Baharan, Sirvan has greater potential for cultivation under dry conditions and can be recommended for water-limited environments. However, where possible, drought stress should be minimized through adequate irrigation for both cultivars to achieve higher yields

Keywords

Main Subjects

References

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Environmental Stresses in Crop Sciences
Volume 18, Issue 4
December 2025
Pages 529-546

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  • Receive Date: 29 April 2024
  • Revise Date: 13 June 2024
  • Accept Date: 16 June 2025

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