Hydrogen gas (H₂) regulates plant responses to abiotic and biotic stresses. Abscisic acid (ABA) might alleviate the adverse effects of drought stress. However, the mechanisms by which ABA and H₂ ameliorate plant drought stress are unclear. Here, tomato “Micro-Tom” seedlings were used to investigate the interaction between H₂ and ABA under drought conditions. The results showed that both hydrogen-rich water (HRW) and ABA increased plant height, stem diameter and root activity of tomato seedlings under drought stress, with optimal concentrations of 75% and 150 μM, respectively. HRW or ABA treatment was able to enhance drought tolerance by increasing photosynthesis, antioxidant enzyme activity and gene expression of antioxidant enzymes under drought stress. Fluridone (FLU), a synthetic inhibitor of ABA, significantly diminished the positive effects of HRW on plant height, stem diameter and root activity under drought stress, suggesting that ABA might play a crucial role in H₂-enhanced drought resistance in tomato seedlings. The results revealed that the ABA content in the PEG + HRW treatment was 18% higher than that in the polyethylene glycol (PEG) treatment alone. Furthermore, we found that H₂ enhanced endogenous ABA content by increasing zeaxanthin epoxidase (ZEP), 9-cis-epoxycarotenoid dioxygenase (NCED) and abscisic aldehyde oxidase (AAO) activities and the expression of SlZEP, SlNCED, and SlAAO. PEG + HRW treatment increased ZEP and NCED activities, which were 13% and 40% higher than those of PEG treatment, respectively. Meanwhile, the transcription levels of SlSnRK2 and SlAREB were upregulated by HRW or ABA under drought stress, whereas this upregulation was reversed by FLU. Thus, our results demonstrate that H₂ was able to enhance drought resistance by regulating ABA biosynthesis and the expression of ABA signal transduction genes in tomato seedlings.

氢气 (H ₂ ) 调节植物对非生物和生物胁迫的反应。脱落酸（ABA）可能减轻干旱胁迫的不利影响。然而，ABA和H ₂改善植物干旱胁迫的机制尚不清楚。在这里，番茄“Micro-Tom”幼苗用于研究 H ₂和 ABA 在干旱条件下。结果表明，富氢水（HRW）和ABA均能增加干旱胁迫下番茄幼苗的株高、茎粗和根系活性，最佳浓度分别为75%和150 μM。HRW或ABA处理能够通过增加干旱胁迫下的光合作用、抗氧化酶活性和抗氧化酶的基因表达来增强耐旱性。Fluridone (FLU) 是一种 ABA 的合成抑制剂，在干旱胁迫下显着降低了 HRW 对株高、茎粗和根活动的积极影响，表明 ABA 可能在 H _{2 中起}关键作用- 增强番茄幼苗的抗旱性。结果表明，PEG+HRW处理中ABA含量比单独使用聚乙二醇（PEG）处理高18%。此外，我们发现 H ₂通过增加玉米黄质环氧化酶 (ZEP)、9-顺式环氧类胡萝卜素双加氧酶 (NCED) 和脱落醛氧化酶 (AAO) 的活性以及SlZEP、SlNCED和SlAAO的表达来增强内源性 ABA 含量。PEG + HRW 处理增加了 ZEP 和 NCED 活性，分别比 PEG 处理高 13% 和 40%。同时，SlSnRK2和SlAREB的转录水平在干旱胁迫下被 HRW 或 ABA 上调，而这种上调被 FLU 逆转。因此，我们的结果表明，H ₂能够通过调节番茄幼苗中ABA 的生物合成和ABA 信号转导基因的表达来增强抗旱性。