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Exogenous 2,4-Epibrassinolide Alleviates Alkaline Stress in Cucumber by Modulating Photosynthetic Performance
Wenjing Nie1, Qinghai He1,2, Jinzhao Ma1
1Shandong Engineering Research Center of Functional Crop Germplasm Innovation and Cultivation Utilization, Yantai Engineering Research Center of Plant Stem Cell Targeted Breeding, Shandong Institute of Sericulture, Yantai 264001, China.
Plants (Basel, Switzerland)
|January 11, 2025
Summary
Brassinosteroids (BRs), specifically 24-epibrassinolide (EBR), enhance cucumber salt tolerance by improving photosynthesis and antioxidant systems under alkaline stress. EBR application mitigates growth inhibition and reactive oxygen species accumulation.
Area of Science:
- Plant Physiology
- Biochemistry
- Molecular Biology
Background:
- Brassinosteroids (BRs) are known to improve plant salt tolerance, but their role in regulating photosynthesis under alkaline salt stress remains unclear.
- Alkaline salt stress, induced by sodium bicarbonate (NaHCO3), severely impacts plant growth and photosynthetic efficiency.
- Understanding the molecular mechanisms of BRs in mitigating alkaline stress is crucial for improving crop resilience.
Purpose of the Study:
- To investigate the mechanisms by which brassinosteroids (BRs) regulate photosynthesis in cucumber under alkaline salt stress.
- To determine the effects of exogenous 24-epibrassinolide (EBR) on plant growth, photosynthetic electron transport, gas exchange, and gene expression under NaHCO3 stress.
- To elucidate the role of EBR in chlorophyll synthesis and reactive oxygen species (ROS) scavenging under alkaline conditions.
Main Methods:
- Cucumber plants were subjected to alkaline stress using NaHCO3, with and without exogenous 24-epibrassinolide (EBR) application.
- Measurements included plant growth parameters, chlorophyll content, photosynthetic electron transport, gas exchange (Pn, Gs, E), and chlorophyll fluorescence (Fv/Fm, ΦPSII, Fv'/Fm', qP).
- Gene expression analysis of antioxidant (AsA-GSH cycle) and Calvin cycle genes, along with enzyme activities (Chlase, PBGD), was performed.
Main Results:
- NaHCO3 stress significantly inhibited cucumber growth and photosynthesis, reducing chlorophyll content and key photosynthetic parameters.
- EBR application alleviated growth inhibition, reduced ROS accumulation, and improved photosynthetic performance under alkaline stress.
- EBR enhanced the expression of antioxidant and Calvin cycle genes, improved chlorophyll synthesis by modulating PBGD and Chlase activity, and stabilized the photosynthetic electron transport system.
Conclusions:
- Exogenous 24-epibrassinolide (EBR) effectively mitigates the detrimental effects of alkaline salt stress on cucumber photosynthesis.
- EBR enhances plant resilience by stabilizing the photosynthetic electron transport system, promoting the Calvin cycle, and bolstering antioxidant defenses.
- This study highlights the significant role of BRs in improving plant tolerance to alkaline stress, offering insights for agricultural applications.
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