ABSTRACT The underlying mechanism of mediation of plant salt tolerance by cinnamic acid (CA) is unclear. We aimed to investigate the influence of exogenously applied CA on the growth, antioxidant system, and ionic balance of sweet pepper under salinity stress. A set of sweet pepper seedlings was pretreated with 150 mM NaCl for 2 days. Then, 50 μM exogenous CA was applied, and the seedlings were allowed to grow for 7 more days while subject to salinity treatment every other day. The vegetative parameters, photosynthetic characteristics, nitric oxide (NO) signalling, ion leakage, antioxidant capacity, and ion contents were measured. Decreased Na+ and Cl− contents and reduced lipid peroxidation were observed after application of CA, resulting in improved photosynthesis through upregulation of the antioxidant system and proline accumulation. CA regulated the antioxidant system by increasing the activities of antioxidant enzymes and influenced the concentrations of nonenzymatic antioxidants (flavonoids). Increased NO and enhanced cyclic guanosine monophosphate biosynthesis were observed in CA-treated plants. CA treatment elevates NO and flavonoid content, enhances antioxidant activity, alleviates lipid peroxidation, and increases proline level and K+/Na+ ratio in salt-stressed plants. Exogenous CA could be considered as an economical practice for enhancing sweet pepper performance under salt conditions.

中文翻译：

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外源肉桂酸减轻甜椒（Capsicum annuum L.）幼苗的盐分胁迫

摘要 肉桂酸（CA）介导植物耐盐性的潜在机制尚不清楚。我们旨在研究外源应用 CA 对盐胁迫下甜椒的生长、抗氧化系统和离子平衡的影响。一组甜椒幼苗用 150 mM NaCl 预处理 2 天。然后，应用 50 μM 外源 CA，让幼苗再生长 7 天，同时每隔一天进行盐处理。测量了植物参数、光合特性、一氧化氮 (NO) 信号、离子泄漏、抗氧化能力和离子含量。应用 CA 后观察到 Na+ 和 Cl- 含量降低，脂质过氧化减少，通过上调抗氧化系统和脯氨酸积累导致光合作用得到改善。CA 通过增加抗氧化酶的活性来调节抗氧化系统，并影响非酶抗氧化剂（类黄酮）的浓度。在 CA 处理的植物中观察到 NO 增加和环磷酸鸟苷生物合成增强。CA 处理提高 NO 和类黄酮含量，增强抗氧化活性，减轻脂质过氧化，并增加盐胁迫植物的脯氨酸水平和 K+/Na+ 比率。外源 CA 可以被认为是一种在盐条件下提高甜椒性能的经济做法。CA 处理提高 NO 和类黄酮含量，增强抗氧化活性，减轻脂质过氧化，并增加盐胁迫植物的脯氨酸水平和 K+/Na+ 比率。外源 CA 可以被认为是一种在盐条件下提高甜椒性能的经济做法。CA 处理提高 NO 和类黄酮含量，增强抗氧化活性，减轻脂质过氧化，并增加盐胁迫植物的脯氨酸水平和 K+/Na+ 比率。外源 CA 可以被认为是一种在盐条件下提高甜椒性能的经济做法。