# Nitric oxide is involved in hydrogen gas-induced cell cycle activation during adventitious root formation in cucumber.
> キュウリの不定根形成における水素ガス誘導性細胞周期活性化への一酸化窒素の関与


## Abstract

Using cucumber (Cucumis sativus 'Xinchun 4') explants, this study examined how hydrogen-rich water (HRW) drives adventitious root organogenesis. A dose-dependent response was observed, with 50% HRW eliciting the greatest biological effect. HRW elevated nitric oxide (NO) levels in a time-dependent manner and promoted G1-to-S phase cell cycle transition. Expression of cell cycle regulators—CycA, CycB, CDKA, and CDKB—was upregulated by both HRW and exogenous NO. Application of a NO scavenger, a NOS-like enzyme inhibitor, or nitrate reductase inhibitors (tungstate and NaN3) partially reversed HRW-induced root formation, cell cycle activation, and associated gene expression changes. These findings indicate that NO functions as a downstream signaling component in the H2-mediated pathway governing adventitious root development.

### Mechanism

HRW stimulates NO accumulation, which in turn promotes G1-to-S cell cycle transition by upregulating CycA, CycB, CDKA, and CDKB expression, thereby facilitating adventitious root organogenesis in cucumber explants.

## Bibliographic

- **Authors**: Zhu Y, Liao W, Niu L, Wang M, Ma Z
- **Journal**: BMC Plant Biol
- **Year**: 2016 (2016-06-28)
- **PMID**: [27352869](https://pubmed.ncbi.nlm.nih.gov/27352869/)
- **DOI**: [10.1186/s12870-016-0834-0](https://doi.org/10.1186/s12870-016-0834-0)
- **PMC**: [PMC4924243](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4924243/)
- **Study type**: in vitro study
- **Delivery route**: hydrogen-rich water
- **Effect reported**: positive
- **H2 concentration**: 50%

## Delivery context

Hydrogen-rich water is a low-risk delivery route, but the achievable systemic hydrogen dose is bounded. For clinical applications, inhalation is the most efficient route; inhalation, however, carries explosion risk, and concentration matters (empirical LFL of 10% applies to inhalation environments; high-concentration devices are documented in the Consumer Affairs Agency accident database and are not recommended).

## Safety notes

Hydrogen-rich water is a low-risk delivery route, but the achievable systemic hydrogen dose is bounded. For clinical applications, inhalation is the most efficient route; inhalation, however, carries explosion risk, and concentration matters (empirical LFL of 10% applies to inhalation environments; high-concentration devices are documented in the Consumer Affairs Agency accident database and are not recommended).

See also:
- [Inhalation concentration and LFL / UFL](https://h2-papers.org/en/safety-notes/inhalation-concentration)
- [Consumer Affairs Agency accident cases](https://h2-papers.org/en/safety-notes/accident-cases)
- [Inhalation safety threshold lineage](https://h2-papers.org/en/safety-notes/lineage)

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> **Cite as**: H2 Papers — PMID 27352869. https://h2-papers.org/en/papers/27352869
> **Source**: PubMed PMID [27352869](https://pubmed.ncbi.nlm.nih.gov/27352869/)