Exogenous application of melatonin improves the growth and physiological properties of blueberry seedlings under salt stress

Abstract

Melatonin is a secondary messenger in plants that is involved in the regulation of abiotic stress responses, but it is unclear whether it enhances the adaptive capacity of blueberries to cope with salinity stress. The effects of exogenous application of melatonin (100, 200, and 300 μmol·L⁻¹) on the growth, photosynthetic characteristics, leaf anatomy, and physiological and biochemical properties of blueberry plants under mixed salt stress (90 mmol·L⁻¹: 30 mmol·L⁻¹ Na₂CO₃ + 60 mmol·L⁻¹ NaCl) were investigated. The results showed that blueberries under 90 mmol·L⁻¹ mixed salt stress had significant salt damage symptoms, with reduced blueberry biomass, reduced chlorophyll content, and photosynthesis inhibition. In contrast, melatonin-treated blueberries showed significantly reduced salt damage symptoms compared with stressed blueberry plants, with the optimum effect at 200 μmol·L⁻¹, along with increased chlorophyll content, improved photosynthetic capacity, and increased leaf thickness under stress. Melatonin treatment resulted in reduced malondialdehyde (MDA) content and relative electrolyte leakage (EL), increased K⁺ content, and decreased Na⁺ content in blueberry roots, stems and leaves, thereby reducing the toxic effects of mixed salts on blueberries. The results indicate that melatonin can mitigate the effects of mixed salt stress on blueberries and that foliar spraying of melatonin could alleviate mixed salt-induced damage to blueberries, with the optimum effect at 200 μmol·L⁻¹ treatment. This study provided a valuable basis for exploring the mechanism of exogenous melatonin action in blueberries in saline environments.

Keywords:

• Melatonin
• physiological mechanism
• leaf blade anatomy
• photosynthesis
• ionic content
• blueberry seedling

Acknowledgements

The authors would like to express their gratitude to the Fruit Quality Analysis Laboratory, Jilin Province Blueberry Research Centre for providing the materials used for the experiments and assistance during this study.

Author contributions

Conceptualization, W.J. and X.W.; Methodology, W.J.; Software, Y.W.; Validation, J.M., L.W. and L.L.; Formal Analysis, J.L.; Investigation, J.L.; Resources, L.W.; Data Curation, W.J.; Writing – Original Draft Preparation, W.J.; Writing – Review & Editing, L.W.; Visualization, Y.W.; Supervision, Y.W.; Project Administration, L.W.; Funding Acquisition, Y.W.

Disclosure statement

The authors declare no conflict of interest.

Data availability statement

All data included in this study are available upon request by contact with the corresponding authors.

Additional information

Funding

This research was funded by the Jilin Changchun Science and Technology Bureau Project (21ZGN10); Jilin Forestry and Grassland Bureau Project (No. JLT2022-01); Jilin Science and Technology Development Program Project (20200402083NC, 20200402113NC); and Jingyu County Science and Technology Development Program Project (XBJ202016). Funds have been secured to cover publication costs.