麝香草酚通过调节抗氧化系统、渗透平衡 及光合特性提升西瓜幼苗耐盐性

Thymol enhances salt tolerance in watermelon seedlings by regulating antioxidant system, osmotic balance, and photosynthetic characteristics

摘要

【目的】明确麝香草酚（thymol）缓解盐胁迫下西瓜幼苗生长受抑的效果与生理机制，为设施西瓜次生盐渍化治理及植物源水乳剂开发提供依据。【方法】以‘早佳8424’幼苗为材料，通过梯度筛选确定NaCl半抑制浓度为120 mmol·L^-1；在此条件下设置不同Thymol浓度进行叶面喷施处理，测定氧化损伤指标（MDA）、抗氧化酶活性（SOD、CAT、POD）、渗透调节物质（可溶性蛋白、脯氨酸）、光合特性（叶绿素a）及叶片总酚含量。【结果】60 μmol·L^-1 Thymol为最优处理浓度。与单纯盐胁迫相比，该处理下叶片和根尖MDA含量分别显著降低22.7%和32.6%（P<0.05）；叶片SOD、CAT和POD活性分别显著提高12.5%、41.9%和39.3%（P<0.05）；叶片和根尖可溶性蛋白含量分别显著提高11.3%和12.1%（P<0.05），而脯氨酸含量分别显著降低54.4%和28.2%（P<0.05）；叶绿素a含量显著提高23.8%（P<0.05）；叶片总酚含量提高50.9%，但差异不显著（P>0.05）。【结论】外源喷施60 μmol·L^-1 thymol可显著缓解盐胁迫对西瓜幼苗的伤害，其机制在于增强抗氧化系统活性、减轻氧化与渗透损伤并改善光合状态，从而促进幼苗生长，为设施西瓜抗盐调控及植物源抗盐水乳剂的研制提供新思路与理论依据。

Abstract

[Objective] This study aimed to evaluate the efficacy and physiological mechanisms of thymol in alleviating salt stress in watermelon seedlings, with the goal of addressing secondary salinization in protected cultivation and supporting the development of plant-derived anti-salt emulsifiable formulations. [Method] Using ‘Zaojia 8424’ seedlings as the material, the semi-inhibitory NaCl concentration was determined through gradient screening and established as 120 mmol·L^-1. Under this salt stress condition, different concentrations of thymol were applied via foliar spraying. Measured parameters included oxidative damage markers (MDA), antioxidant enzyme activities (SOD, CAT, and POD), osmotic regulators (soluble protein and proline), photosynthetic characteristics (chlorophyll a), and total phenolic content in leaves. [Result] Thymol at 60 μmol·L^-1 was identified as the optimal concentration. Compared to salt stress alone, this treatment resulted in the following: MDA content decreased by 22.7% in leaves and 32.6% in root tips; activities of SOD, CAT, and POD in leaves increased by 12.5%, 41.9%, and 39.3% (P < 0.05), respectively; soluble protein content increased by 11.3% in leaves and 12.1% in root tips (P < 0.05); proline levels decreased by 54.4% in the leaves and 28.2% in the root tips (P < 0.05); chlorophyll a content increased by 23.8% (P < 0.05); and total leaf phenolics increased by 50.9% (P > 0.05). [Conclusion] Foliar application of 60 μmol·L^-1 thymol significantly alleviates salt stress in watermelon seedlings by enhancing the antioxidant defense system, reducing oxidative and osmotic damage, and improving photosynthetic performance. These findings support the potential use of thymol in developing plant-based anti-salinity emulsifiable concentrates for sustainable cultivation practices.

关键词

麝香草酚 / 西瓜幼苗 / 盐胁迫 / 抗氧化酶活性 / 渗透调节

Key words

thymol / watermelon seedlings / salt stress / antioxidant enzyme activity / osmoregulation

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