Molecular Hydrogen Maintains the Storage Quality of Chinese Chive through Improving Antioxidant Capacity

Research Progress of Hydrogen Rich Water in Preservation of Postharvest Horticultural Products: A Review

The perishable nature of horticultural products and unfavorable factors during storage lead to postharvest losses and shelf life limitations. As an effective hydrogen (H2) supplier, hydrogen-rich water (HRW) is regarded as a new green postharvest preservation strategy of horticultural products. This review presents a complete overview of the application advance of HRW for the preservation of horticultural products, including the potential production mechanisms of hydrogen in plants, the preparation and application methods of HRW, and potential mechanisms of HRW in improving the quality of postharvest horticultural products. The findings show that HRW can maintain the quality and stress tolerance of horticultural products by regulating metabolic pathways and molecular responses, including oxidative defense, energy homeostasis, respiration, cell-wall intergrity, ethylene biosynthesis, related gene expression and phytohormones signaling crosstalk. The information obtained in this review is expected to provide a scientific basis for the application of HRW for the preservation of postharvest horticultural products.

Hydrogen Gas Fumigation Combined with Nano-Film Packaging Extend the Storage of Button Mushrooms (Agaricus bisporus)

To extend the shelf life of button mushrooms, the optimal fumigation doses for hydrogen gas treatment were screened through sensory evaluation, combined with browning index and weight loss rate in this study. Then, using H2 fumigation combined with polyethylene film packaging as a control, changes in the sensory quality, reactive oxygen species, browning-related enzyme activity and the nutritional quality of mushrooms treated by H2 fumigation combined with nano-film packaging (H2 + NA) during low-temperature storage were dynamically tracked. The preservation effect of H2 + NA on mushrooms after harvest was investigated, and its mechanism was also analyzed. The storage validation test showed that the optimum H2 fumigation time was 2 h, and the H2 + NA-treated mushrooms had a fuller appearance, maintained whiteness well, showed a slow increase in reactive oxygen species, antioxidant enzyme activities remained at high levels, a high retention rate of protein content was observed, and there was a good antibacterial effect. This study indicates that H2 fumigation combined with nano-film packaging can improve the storage quality of button mushrooms and may prolong low-temperature shelf life by 4-5 d compared to conventional commercial polyethylene film packaging.

Hydrogen gas: A new fresh keeping agent of perishable horticultural products

Hydrogen gas (H2), a gaseous signaling molecule, is involved in plant growth and development. This review collates emerging evidence to show that H2 regulates the postharvest senescence of horticultural products through critical biochemical processes, including the improvement of antioxidant systems, the activation of cell wall metabolism, the promotion of energy metabolism, the inhibition of ethylene biosynthesis and the regulation of bacterial communities. Additionally, the interactions between H2 and other signaling molecules are also discussed. This paper presents the current status of H2 research in terms of its biological effects and safety in postharvest products by combining the research results on the molecular mechanisms of biological effects and H2 signaling. The action mechanism of H2 for postharvest preservation is also proposed, and it reflects the complexity and diversity of the pathways involved. Furthermore, a growing body of evidence has found a large number of downstream pathways or targets for the medical effects of H2. Therefore, the scientific and practical aspects of H2 biology are proposed for the postharvest preservation of horticultural products.

Hydrogen Fertilization with Hydrogen Nanobubble Water Improves Yield and Quality of Cherry Tomatoes Compared to the Conventional Fertilizers

Although hydrogen gas (H2)-treated soil improves crop biomass, this approach appears difficult for field application due to the flammability of H2 gas. In this report, we investigated whether and how H2 applied in hydrogen nanobubble water (HNW) improves the yield and quality of cherry tomato (Lycopersicon esculentum var. cerasiforme) with and without fertilizers. Two-year-long field trials showed that compared to corresponding controls, HNW without and with fertilizers improved the cherry tomato yield per plant by 39.7% and 26.5% in 2021 (Shanghai), respectively, and by 39.4% and 28.2% in 2023 (Nanjing), respectively. Compared to surface water (SW), HNW increased the soil available nitrogen (N), phosphorus (P), and potassium (K) consumption regardless of fertilizer application, which may be attributed to the increased NPK transport-related genes in roots (LeAMT2, LePT2, LePT5, and SlHKT1,1). Furthermore, HNW-irrigated cherry tomatoes displayed a higher sugar-acid ratio (8.6%) and lycopene content (22.3%) than SW-irrigated plants without fertilizers. Importantly, the beneficial effects of HNW without fertilizers on the yield per plant (9.1%), sugar-acid ratio (31.1%), and volatiles (20.0%) and lycopene contents (54.3%) were stronger than those achieved using fertilizers alone. In short, this study clearly indicated that HNW-supplied H2 not only exhibited a fertilization effect on enhancing the tomato yield, but also improved the fruit's quality with a lower carbon footprint.

Hydrogen Gas Improves the Postharvest Quality of Lanzhou Lily (Lilium davidii var. unicolor) Bulbs

Hydrogen gas (H₂) is an important molecular messenger in animal and plant cells and is involved in various aspects of plant processes, including root organogenesis induction, stress tolerance and postharvest senescence. This study investigated the effect of H₂ fumigation on the quality of Lanzhou lily scales. The results indicated the H₂ remarkably declined the color variation and browning degree in Lanzhou lily scales by suppressing the activity of phenylalanine ammonia-lyase (PAL), peroxidase (POD) and polyphenol oxidase (PPO). Moreover, H₂ significantly alleviated the degradation of soluble proteins and soluble sugars in Lanzhou lily scales during postharvest storage, mitigating the decline in nutritional quality. This alleviating effect of H₂ might be achieved by increasing the endogenous H₂ concentration. Collectively, our data provide new insights into the postharvest quality reduction of Lanzhou lily scales mitigated by H₂ fumigation.

Molecular Hydrogen Improves Rice Storage Quality via Alleviating Lipid Deterioration and Maintaining Nutritional Values

Improvement of the storage quality of rice is a critical challenge for the scientific community. This study assesses the effects of the irrigation with hydrogen nanobubble water (HNW) on the storage quality of rice (Oryza sativa 'Huruan1212'). Compared with ditch water control, after one year of storage at 25 °C and 70% RH, the HNW-irrigated rice had higher contents of essential amino acids, especially lysine. Importantly, the generation of off-flavors in the stored rice was significantly decreased, which was confirmed by the lower levels of volatile substances, including pentanal, hexanal, heptanal, octanal, 1-octen-3-ol, and 2-heptanone. The subsequent results showed that the HNW-irrigated rice not only retained lower levels of free fatty acid values, but also had increased antioxidant capacity and decreased lipoxygenase activity and transcripts, thus resulting in decreased lipid peroxidation. This study opens a new window for the practical application of HNW irrigation in the production and subsequent storage of crops.

Nitric Oxide Acts as an Inhibitor of Postharvest Senescence in Horticultural Products

Horticultural products display fast senescence after harvest at ambient temperatures, resulting in decreased quality and shorter shelf life. As a gaseous signal molecule, nitric oxide (NO) has an important physiological effect on plants. Specifically, in the area of NO and its regulation of postharvest senescence, tremendous progress has been made. This review summarizes NO synthesis; the effect of NO in alleviating postharvest senescence; the mechanism of NO-alleviated senescence; and its interactions with other signaling molecules, such as ethylene (ETH), abscisic acid (ABA), melatonin (MT), hydrogen sulfide (H2S), hydrogen gas (H2), hydrogen peroxide (H2O2), and calcium ions (Ca2+). The aim of this review is to provide theoretical references for the application of NO in postharvest senescence in horticultural products.

Editorial for Special Issue: “Production and Role of Molecular Hydrogen in Plants”

Molecular hydrogen (H2) is an extremely small molecule, which is relatively insoluble in water and relatively inert [...]

Preharvest application of hydrogen nanobubble water enhances strawberry flavor and consumer preferences

The improvement of fruit flavor is a challenge for producers and breeders. This study investigated the effects and mechanisms of preharvest hydrogen nanobubble water (HNW) application on the flavor of cultivated strawberry (Fragaria × ananassa 'Benihoppe'). Compared with surface water, HNW enhanced the volatile profiles, sugar-acid ratio, and sensory attributes (e.g., aroma, flavor, and overall liking) with/without fertilizer application. Meanwhile, flavor components such as esters (e.g., ethyl hexanoate), acids (e.g., hexanoic acid), and soluble sugars (including glucose, fructose, and sucrose) significantly contributed to increased strawberry flavor achieved with HNW. Importantly, HNW may alleviate the negative effects of fertilizers on strawberry fruit aroma. Further study elucidated that the aroma-related genes (including FaLOX, FaADH, FaAAT, FaQR, FaOMT, and FaNES1) were involved in the accumulation of specific volatiles after HNW treatment. This study provided evidence that the practical application of H₂ can improve horticultural product quality at a lower carbon cost.

The Applications of Molecular Hydrogen in Horticulture

Improvements in the growth, yield, and quality of horticultural crops require the development of simply integrated, cost-efficient, and eco-friendly solutions. Hydrogen gas (H2) has been observed to have fertilization effects on soils by influencing rhizospheric microorganisms, resulting in improvements in crop yield and quality. Ample studies have shown that H2 has positive effects on horticultural crops, such as promoting root development, enhancing tolerance against abiotic and biotic stress, prolonging storage life, and improving postharvest quality of fruits, vegetables and cut flowers. In this review, we aim to evaluate the feasibility of molecular hydrogen application in horticulture and the strategies for its application, including H2 delivery methods, treatment timing, and the concentration of H2 applied. The discussion will be accompanied by outlining the effects of H2 and the likely mechanisms of its efficacy. In short, the application of H2 may provide novel opportunities for simple and cost efficient improvements of horticultural production in terms of increased yield and product quality but with low carbon dioxide emissions.

Molecular Hydrogen Increases Quantitative and Qualitative Traits of Rice Grain in Field Trials

How to use environmentally friendly technology to enhance rice field and grain quality is a challenge for the scientific community. Here, we showed that the application of molecular hydrogen in the form of hydrogen nanobubble water could increase the length, width, and thickness of brown/rough rice and white rice, as well as 1000-grain weight, compared to the irrigation with ditch water. The above results were well matched with the transcriptional profiles of representative genes related to high yield, including up-regulation of heterotrimeric G protein β-subunit gene (RGB1) for cellular proliferation, Grain size 5 (GS5) for grain width, Small grain 1 (SMG1) for grain length and width, Grain weight 8 (GW8) for grain width and weight, and down-regulation of negatively correlated gene Grain size 3 (GS3) for grain length. Meanwhile, although total starch content in white rice is not altered by HNW, the content of amylose was decreased by 31.6%, which was parallel to the changes in the transcripts of the amylose metabolism genes. In particular, cadmium accumulation in white rice was significantly reduced, reaching 52% of the control group. This phenomenon was correlated well with the differential expression of transporter genes responsible for Cd entering plants, including down-regulated Natural resistance-associated macrophage protein (Nramp5), Heavy metal transporting ATPase (HMA2 and HMA3), and Iron-regulated transporters (IRT1), and for decreasing Cd accumulation in grain, including down-regulated Low cadmium (LCD). This study clearly showed that the application of molecular hydrogen might be used as an effective approach to increase field and grain quality of rice.

Molecular Hydrogen: Is This a Viable New Treatment for Plants in the UK?

Despite being trialed in other regions of the world, the use of molecular hydrogen (H₂) for enhanced plant growth and the postharvest storage of crops has yet to be widely accepted in the UK. The evidence that the treatment of plants and plant products with H₂ alleviates plant stress and slows crop senescence continues to grow. Many of these effects appear to be mediated by the alteration of the antioxidant capacity of plant cells. Some effects seem to involve heme oxygenase, whilst the reduction in the prosthetic group Fe³⁺ is also suggested as a mechanism. Although it is difficult to use as a gaseous treatment in a field setting, the use of hydrogen-rich water (HRW) has the potential to be of significant benefit to agricultural practices. However, the use of H₂ in agriculture will only be adopted if the benefits outweigh the production and application costs. HRW is safe and relatively easy to use. If H₂ gas or HRW are utilized in other countries for agricultural purposes, it is tempting to suggest that they could also be widely used in the UK in the future, particularly for postharvest storage, thus reducing food waste.

Molecular hydrogen in agriculture

H₂ gas, usually in the form of H₂-saturated water, could play a useful role in improving many aspects of plant growth and productivity, including resistance to stress tolerance and improved post-harvest durability. Therefore, molecular hydrogen delivery systems should be considered as a valuable addition within agricultural practice. Agriculture and food security are both impacted by plant stresses, whether that is directly from human impact or through climate change. A continuously increasing human population and rising food consumption means that there is need to search for agriculturally useful and environment friendly strategies to ensure future food security. Molecular hydrogen (H₂) research has gained momentum in plant and agricultural science owing to its multifaceted and diverse roles in plants. H₂ application can mitigate against a range of stresses, including salinity, heavy metals and drought. Therefore, knowing how endogenous, or exogenously applied, H₂ enhances the growth and tolerance against numerous plant stresses will enhance our understanding of how H₂ may be useful for future to agriculture and horticulture. In this review, recent progress and future implication of H₂ in agriculture is highlighted, focusing on how H₂ impacts on plant cell function and how it can be applied for better plant performance. Although the exact molecular action of H₂ in plants remains elusive, this safe and easy to apply treatment should have a future in agricultural practice.