# Nitric oxide is required for hydrogen gas-induced 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に一酸化窒素が関与する


## Abstract

This study examined whether nitric oxide (NO) participates in hydrogen-rich water (HRW)-induced adventitious root formation using cucumber explants. Application of 50% and 100% HRW markedly enhanced adventitious root development. This promotion was suppressed by the NO scavenger cPTIO, the NOS inhibitor l-NAME, and the nitrate reductase (NR) inhibitor NaN3, indicating NO dependence. HRW elevated NO levels and increased both NOS and NR activities in a dose- and time-dependent manner, while also upregulating NR gene expression. Enzyme activity assays showed that HRW reduced peroxidase (POD) and indoleacetic acid oxidase (IAAO) activities while increasing polyphenol oxidase (PPO) activity; these effects were reversed by NO inhibitors. Collectively, the findings suggest that NO functions downstream of H2 in the plant signaling cascade governing root organogenesis.

### Mechanism

HRW activates NOS and nitrate reductase to elevate NO levels, which in turn modulates peroxidase, IAAO, and PPO activities, collectively driving adventitious root organogenesis in cucumber explants.

## Bibliographic

- **Authors**: Zhu Y, Liao W, Wang M, Niu L, Xu Q, Jin X
- **Journal**: J Plant Physiol
- **Year**: 2016 (2016-05-20)
- **PMID**: [27010347](https://pubmed.ncbi.nlm.nih.gov/27010347/)
- **DOI**: [10.1016/j.jplph.2016.02.018](https://doi.org/10.1016/j.jplph.2016.02.018)
- **Study type**: in vitro study
- **Delivery route**: hydrogen-rich water
- **Effect reported**: positive
- **H2 concentration**: 50–100%

## 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 27010347. https://h2-papers.org/en/papers/27010347
> **Source**: PubMed PMID [27010347](https://pubmed.ncbi.nlm.nih.gov/27010347/)