Hydrogen-rich water promotes elongation of hypocotyls and roots in plants through mediating the level of endogenous gibberellin and auxin

Safe Farming: Ultrafine Bubble Water Reduces Insect Infestation and Improves Melon Yield and Quality

Melon pest management relies on the excessive application of pesticides. Reducing pesticide spraying has become a global issue for environmental sustainability and human health. Therefore, developing a new cropping system that is sustainable and eco-friendly is important. This study found that melon seedlings irrigated with ultrafine water containing H2 and O2 (UFW) produced more root hairs, increased shoot height, and produced more flowers than the control irrigated with reverse osmosis (RO) water. Surprisingly, we also discovered that UFW irrigation significantly reduced aphid infestation in melons. Based on cryo-scanning electron microscope (cryo-SEM) observations, UFW treatment enhanced trichome development and prevented aphid infestation. To investigate whether it was H2 or O2 that helped to deter insect infestation, we prepared UF water enrichment of H2 (UF+H2) and O2 (UF+O2) separately and irrigated melons. Cryo-SEM results indicated that both UF+H2 and UF+O2 can increase the density of trichomes in melon leaves and petioles. RT-qPCR showed that UF+H2 significantly increased the gene expression level of the trichome-related gene GLABRA2 (GL2). We planted melons in a plastic greenhouse and irrigated them with ultrafine water enrichment of hydrogen (UF+H2) and oxygen (UF+O2). The SPAD value, photosynthetic parameters, root weight, fruit weight, and fruit sweetness were all better than the control without ultrafine water irrigation. UFW significantly increased trichome development, enhanced insect resistance, and improved fruit traits. This system thus provides useful water management for pest control and sustainable agricultural production.

Hydrogen-rich water: a key player in boosting wheat (Triticum aestivum L.) seedling growth and drought resilience

In the modern world, wheat, a vital global cereal and the second most consumed, is vulnerable to climate change impacts. These include erratic rainfall and extreme temperatures, endangering global food security. Research on hydrogen-rich water (HRW) has gained momentum in plant and agricultural sciences due to its diverse functions. This study examined the effects of different HRW treatment durations on wheat, revealing that the 4-h treatment had the highest germination rate, enhancing potential, vigor, and germination indexes. This treatment also boosted relative water content, root and shoot weight, and average lengths. Moreover, the 4-h HRW treatment resulted in the highest chlorophyll and soluble protein concentrations in seeds while reducing cell death. The 4-h and 5-h HRW treatments significantly increased H2O2 levels, with the highest NO detected in both root and shoot after 4-h HRW exposure. Additionally, HRW-treated seeds exhibited increased Zn and Fe concentrations, along with antioxidant enzyme activities (CAT, SOD, APX) in roots and shoots. These findings suggest that HRW treatment could enhance wheat seed germination, growth, and nutrient absorption, thereby increasing agricultural productivity. Molecular analysis indicated significant upregulation of the Dreb1 gene with a 4-h HRW treatment. Thus, it shows promise in addressing climate change effects on wheat production. Therefore, HRW treatment could be a hopeful strategy for enhancing wheat plant drought tolerance, requiring further investigation (field experiments) to validate its impact on plant growth and drought stress mitigation.

The Role and Mechanism of Hydrogen-Rich Water in the Cucumis sativus Response to Chilling Stress

Cucumber is a warm climate vegetable that is sensitive to chilling reactions. Chilling can occur at any period of cucumber growth and development and seriously affects the yield and quality of cucumber. Hydrogen (H₂) is a type of antioxidant that plays a critical role in plant development and the response to stress. Hydrogen-rich water (HRW) is the main way to use exogenous hydrogen. This study explored the role and mechanism of HRW in the cucumber defense response to chilling stress. The research results showed that applying 50% saturated HRW to the roots of cucumber seedlings relieved the damage caused by chilling stress. The growth and development indicators, such as plant height, stem diameter, leaf area, dry weight, fresh weight, and root length, increased under the HRW treatment. Photosynthetic efficiency, chlorophyll content, and Fv/Fm also improved and reduced energy dissipation. In addition, after HRW treatment, the REC and MDA content were decreased, and membrane lipid damage was reduced. NBT and DAB staining results showed that the color was lighter, and the area was smaller under HRW treatment. Additionally, the contents of O₂^- and H₂O₂ also decreased. Under chilling stress, the application of HRW increased the activity of the antioxidases SOD, CAT, POD, GR, and APX and improved the expression of the SOD, CAT, POD, GR, and APX antioxidase genes. The GSSG content was reduced, and the GSH content was increased. In addition, the ASA content also increased. Therefore, exogenous HRW is an effective measure for cucumber to respond to chilling stress.

Hydrogen-rich water treatment increased several phytohormones and prolonged the shelf life in postharvest okras

Hydrogen-rich water (HRW) treatment has been reported to delay the softening and senescence of postharvest okras, but its regulatory mechanism remains unclear. In this paper, we investigated the effects of HRW treatment on the metabolism of several phytohormones in postharvest okras, which act as regulatory molecules in fruit ripening and senescence processes. The results showed that HRW treatment delayed okra senescence and maintained fruit quality during storage. The treatment upregulated all of the melatonin biosynthetic genes such as AeTDC, AeSNAT, AeCOMT and AeT5H, contributing to the higher melatonin content in the treated okras. Meanwhile, increased transcripts of anabolic genes but lower expression of catabolic genes involved in indoleacetic acid (IAA) and gibberellin (GA) metabolism were observed in okras when treated with HRW, which was related to the enhanced levels of IAA and GA. However, the treated okras experienced lower abscisic acid (ABA) content as compared to the non-treated fruit due to the down-regulation of its biosynthetic genes and up-regulation of the degradative gene AeCYP707A. Additionally, there was no difference in γ-aminobutyric acid between the non-treated and HRW-treated okras. Collectively, our results indicated that HRW treatment increased levels of melatonin, GA and IAA, but decreased ABA content, which ultimately delayed fruit senescence and prolonged shelf life in postharvest okras.

Phytomelatonin and gasotransmitters: a crucial combination for plant physiological functions

Melatonin, a molecule that was first identified in animal tissues, has been confirmed to be involved as a potential phytohormone in a variety of plant physiological responses. It is considered primarily as an antioxidant with important actions in controlling reactive oxygen and reactive nitrogen species. In addition to its role in regulating plant growth and development, phytomelatonin is involved in protection against abiotic and biotic stresses. The 'gasotransmitter'-that is, a gaseous signaling molecule-is a new concept that has been advanced in the past two decades, with functions in animal and plant physiological regulation. Gasotransmitters including nitric oxide, carbon monoxide, hydrogen sulfide, methane, and, more recently identified, hydrogen gas are critical and indispensable in a wide range of biological processes. This review investigates the interrelationship between phytomelatonin and the above-mentioned gasotransmitters from the perspective of biosynthetic origin and functions. Moreover, the potential future research directions for phytomelatonin and gasotransmitters interactions are discussed.

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.

Hydrogen-rich water promotes the formation of bulblets in Lilium davidii var. unicolor through regulating sucrose and starch metabolism

HRW increased the content of starch and sucrose via regulating a series of sucrose and starch synthesis genes, which induced the formation of bulblets and adventitious roots of Lilium davidii var. unicolor. Hydrogen gas (H₂), as a signaling molecule, has been reported to be involved in plant growth and development. Here, the effect of hydrogen-rich water (HRW) on the formation of bulblets and adventitious roots in the scale cuttings of Lilium davidii var. unicolor and its mechanisms at the molecular levels were investigated. The results revealed that compared with distilled water treatment (Con), the number of bulblets and adventitious roots were significantly promoted by different concentrations of HRW treatment. Treatment with 100% HRW obtained the most positive effects. RNA sequencing (RNA-seq) analysis found that compared with Con, a total of 1702 differentially expressed genes (DEGs, upregulated 552 DEGs, downregulated 1150 DEGs) were obtained under HRW treatment. The sucrose and starch metabolism, cysteine and methionine metabolism and phenylalanine metabolism were significantly enriched in the analysis of the Kyoto encyclopedia of genes and genomes (KEGG). In addition, the genes involved in carbohydrate metabolism were significantly upregulated or downregulated (upregulated 22 DEGs, downregulated 15 DEGs), indicating that starch and sucrose metabolism held a central position. The expressions of 12 DEGs were identified as coding for key enzymes in metabolism of carbohydrates was validated by qPCR during bulblet formation progress. RNA-seq analysis and expression profiles indicated that the unigene levels such as glgc, Susy, otsA and glgP, BMY and TPS were well correlated with sucrose and starch metabolism during HRW-induced bulblet formation. The change of key enzyme content in starch and sucrose metabolism pathway was explored during bulblet formation in Lilium under HRW treatment. Meanwhile, compared with Con, 100% HRW treatment increased the levels of sucrose and starch, and decreased the trehalose content, which were agreed with the expression pattern of DEGs related to the biosynthesis pathway of sucrose, starch and trehalose. Therefore, this study suggested that HRW could promote the accumulation of sucrose and starch contents in mother scales, and decreased the trehalose content, this might provide more energy for bulblet formation.

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.

Downstream Signalling from Molecular Hydrogen

Molecular hydrogen (H2) is now considered part of the suite of small molecules that can control cellular activity. As such, H2 has been suggested to be used in the therapy of diseases in humans and in plant science to enhance the growth and productivity of plants. Treatments of plants may involve the creation of hydrogen-rich water (HRW), which can then be applied to the foliage or roots systems of the plants. However, the molecular action of H2 remains elusive. It has been suggested that the presence of H2 may act as an antioxidant or on the antioxidant capacity of cells, perhaps through the scavenging of hydroxyl radicals. H2 may act through influencing heme oxygenase activity or through the interaction with reactive nitrogen species. However, controversy exists around all the mechanisms suggested. Here, the downstream mechanisms in which H2 may be involved are critically reviewed, with a particular emphasis on the H2 mitigation of stress responses. Hopefully, this review will provide insight that may inform future research in this area.