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<p>Bleaching of <i>Betaphycus gelatinae</i> caused by high light intensity not only diminishes aquaculture productivity and product quality but also exacerbates coastal eutrophication and undermines ecosystem stability. In this study, optimal concentrations of indole-3-acetic acid (IAA), gibberellin (GA) and salicylic acid (SA) were determined, and a graded light-stress system of 130–280&#xa0;μmol photons m⁻<sup>2</sup>&#xa0;s⁻<sup>1</sup> was established to evaluate the effects of these phytohormones on growth, photosynthetic performance, antioxidant capacity, and osmotic regulation under light stress. At low doses, all three exogenous hormones promoted growth, with 50&#xa0;μg L⁻<sup>1</sup> identified as the optimal dose common to all. In subsequent experiments across a light gradient, bleaching severity increased significantly with light intensity; with high light stress inducing marked pigment degradation and tissue damage. Under 280&#xa0;μmol photons m⁻<sup>2</sup>&#xa0;s⁻<sup>1</sup> the protective effects of the hormones diverged: IAA demonstrated superior efficacy in preserving thallus integrity, reducing morphological damage by 23% and significantly increasing chlorophyll, R-phycoerythrin (R-PE), and proline by 56%, 30%, and 119%, respectively. In contrast, GA and SA exhibited poorer performance than the control under high light intensity, showing reduced levels of phycobiliproteins, chlorophyll, and compromised morphology. In recovery assays, IAA-treated thalli exhibited a more rapid restoration of pigment content and tissue integrity upon return to normal light conditions, indicating a sustained protective effect post-stress. We conclude that IAA enhances the photoadaptive capacity of <i>B. gelatinae</i> by coordinately upregulating antioxidant defenses and the accumulation of osmoprotectants, thereby alleviating thallus bleaching under light stress. These findings provide practical technical support for large-scale cultivation of <i>B. gelatinae</i> in high light intensity environments and offer a theoretical foundation for developing light management and hormone-regulation strategies in resilient cultivation of economic macroalgae.</p>

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Exogenous phytohormones as protective agents against high light-induced bleaching in Betaphycus gelatinae

  • 期刊论文

  • 发表日期：

    2026年7月18日

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  • Zexu Liu,
  • Haolong Zheng,
  • Xiangyu Wu,
  • Shouguo Yang,
  • Han Yang,
  • Yifang Zhao,
  • Yixuan Xing,
  • Xianming Tang,
  • Zhifeng Gu,
  • Yaohua Shi,
  • Feng Yu

摘要

Bleaching of Betaphycus gelatinae caused by high light intensity not only diminishes aquaculture productivity and product quality but also exacerbates coastal eutrophication and undermines ecosystem stability. In this study, optimal concentrations of indole-3-acetic acid (IAA), gibberellin (GA) and salicylic acid (SA) were determined, and a graded light-stress system of 130–280 μmol photons m⁻2 s⁻1 was established to evaluate the effects of these phytohormones on growth, photosynthetic performance, antioxidant capacity, and osmotic regulation under light stress. At low doses, all three exogenous hormones promoted growth, with 50 μg L⁻1 identified as the optimal dose common to all. In subsequent experiments across a light gradient, bleaching severity increased significantly with light intensity; with high light stress inducing marked pigment degradation and tissue damage. Under 280 μmol photons m⁻2 s⁻1 the protective effects of the hormones diverged: IAA demonstrated superior efficacy in preserving thallus integrity, reducing morphological damage by 23% and significantly increasing chlorophyll, R-phycoerythrin (R-PE), and proline by 56%, 30%, and 119%, respectively. In contrast, GA and SA exhibited poorer performance than the control under high light intensity, showing reduced levels of phycobiliproteins, chlorophyll, and compromised morphology. In recovery assays, IAA-treated thalli exhibited a more rapid restoration of pigment content and tissue integrity upon return to normal light conditions, indicating a sustained protective effect post-stress. We conclude that IAA enhances the photoadaptive capacity of B. gelatinae by coordinately upregulating antioxidant defenses and the accumulation of osmoprotectants, thereby alleviating thallus bleaching under light stress. These findings provide practical technical support for large-scale cultivation of B. gelatinae in high light intensity environments and offer a theoretical foundation for developing light management and hormone-regulation strategies in resilient cultivation of economic macroalgae.