Exogenous cytokinin and salicylic acid enhances antioxidant activity, photosynthetic efficiency and yield in sunflower (Helianthus annuus L.) under drought stress

Articles in Press

Document Type : Original Article

Authors

Department of Plant Production and Genetics, Faculty of Agriculture, Shahid Chamran University of Ahvaz, Ahvaz, Iran

10.22108/ijpb.2026.149279.1457

Abstract

This study was conducted to evaluate the effects of Cytokinin (CK) and Salicylic Acid (SA) application on photosynthetic characteristics, antioxidant activity, and yield performance of sunflower under drought stress conditions. The experiment was arranged as a split-plot based on a randomized complete block design with three replications at Shahid Chamran University of Ahvaz during the 2022–2023 growing season. The main factor included two irrigation levels: 80% and 40% of soil field capacity, representing optimal and deficit water conditions, respectively. The sub-factor consisted of five hormonal treatments: control (no application), CK 25 µM + SA 200 µM, CK 25 µM + SA 400 µM, CK 50 µM + SA 200 µM, and CK 50 µM + SA 400 µM. Results showed that drought stress significantly reduced photosynthetic rate, stomatal conductance, chlorophyll pigments, carotenoid content, seed yield, and seed oil percentage. In the control treatment, photosynthetic rate decreased from 4.4 to 1.0 mmol m⁻² s⁻¹ and stomatal conductance declined from 113 to 44 mmol m⁻² s⁻¹ under drought stress. In contrast, antioxidant enzyme activities including catalase, peroxidase, and superoxide dismutase markedly increased under water deficit conditions. The combined application of cytokinin and salicylic acid significantly improved physiological and biochemical traits under both irrigation conditions. The highest photosynthetic rate (8.8 mmol m⁻² s⁻¹), total chlorophyll content (2.34 mg g⁻¹ FW), catalase activity (1000 mg protein min⁻¹), and seed yield (3213 kg ha⁻¹) were obtained from the application of 50 µM cytokinin + 400 µM salicylic acid. Overall, combined application of cytokinin and salicylic acid enhanced drought tolerance in sunflower through improving photosynthetic capacity and antioxidant defense mechanisms.

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Journal of Plant Biological Sciences

Articles in Press, Accepted Manuscript
Available Online from 29 August 2026

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History

  • Receive Date: 11 June 2026
  • Revise Date: 26 August 2026
  • Accept Date: 29 August 2026

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