Recent studies on the botanical effects of hydrogen have shown that it is involved in signal transduction pathways of plant hormones and can improve the resistance of plants to stressors. There is suggestion that the use of hydrogen enriched water in the cultivation of crops can increase disease and pest resistance, increase growth rate and result in greater yield. This then promotes the potential to reduce herbicides, pesticides and fertilisers, leading to greater food security for consumers and a reduction in environmental damage by way of reducing runoff and improving waterway and oceanic ecosystems. Furthermore, it can delay postharvest ripening and increase the shelf life of many products.
The first finding of hydrogen effects on higher plants was in 1964. Little focus was given until recently when it was found that the hydrogen had significant beneficial effects in both human and animal organisms due to selectively reducing · OH and ONOO− which are two of the most toxic reactive oxygen species in a biological system. This discovery immediately attracted numerous researchers all over the world, and various new medical and biological effects of hydrogen have been reported since. Drought and salinity stresses often result in crop yield reduction and even death. Studies found that hydrogen water can improve the resistance to these and other stressors leading to disaster reduction or prevention as well as improvement of crop resistance to disease and pests.
Studies have found that hydrogen can regulate the expression of receptor protein genes of many plant hormones, including some plant hormones associated with disease resistance. Researchers have shown that hydrogen has an important regulation effect on plant physiological function and especially plays important roles in plant resistance to abiotic stress. The reduction of oxidative damage was considered to be one of the main mechanisms by which the hydrogen water treatment delays senescence and inhibits respiration. Field trials show that hydrogen enriched water seems to be a valuable option for agricultural production especially for soilless cultivation of crops, and may also have a positive effect on the taste and nutritional value of crops.
A major feature of modern agriculture is the extensive use of fertilizers and pesticides that may lead to potentially serious environmental pollution, soil degradation and food safety issues. Recent revelations suggest that the antioxidant properties of hydrogen or hydrogen gas mixtures may contribute significantly to the entire management system of agricultural cultivation and products, as it is completely natural, nontoxic and with no residue. It has a strong advantage of food safety compared with other chemical treatments of fresh agricultural products.
In light of these findings, a new approach is vital to the understanding of the substantial role that hydrogen and its electrons play in the overall health of a biological system. H2 can regulate the effects of plant hormones and therefore promote plant growth and health. It is envisaged that in the very near future, it will be commonplace for farmers to use hydrogen water irrigation (or watering system) to replace or partially substitute for pesticides and fertilizers to enhance crop resistance to disease, insect, drought and salinity stress, improve product quality and increase yield. This will not only gain the producer greater market value due to the cleanliness and quality of their produce, but have the added benefits of cost reductions to the business, protecting the environment and improving food security.
Molecular hydrogen (H2) was first identified as an antioxidant that could selectively reduce cytotoxicity in animals. Since then, the role of hydrogen in repairing many clinical disorders related to oxidative stress has been reported. Hydrogen also acts as an antioxidant or signaling molecule in plant developmental processes and responses to environmental stresses. Hydrogen promotes adventitious root formation and stomatal closure, and can enhance tolerance to various abiotic stresses, including high salinity, low temperature, drought, and high light by modulating reactive oxygen species (ROS) homeostasis.
ROS, such as superoxide anions (O2), hydroxyl radicals (OH ), and hydrogen peroxide (H2O2), are generated and detoxified to maintain a fine-tuned balance in plants. To sustain normal cellular ROS metabolism, the expression of many genes is up or down-regulated at the transcriptional and translational levels. These genes encode proteins that participate in ROS-producing and ROS-scavenging processes, and play critical roles in plant growth, development, and adaptation to stress.
Studies using clinical and experimental animal models in which hydrogen has been applied by inhalation of hydrogen gas, consumption of hydrogen-rich water, injection with hydrogen-saturated saline, and culture in vitro on H2-rich media have revealed that hydrogen is an important bioactive factor with antioxidant, anti-inflammatory, and anti-apoptotic effects on cells, tissues, organs, and individuals against oxidative injury. In plants, the protective roles have also been proven when seeds, seedlings, explants, and fruits were subjected to hydrogen treatment with hydrogen-rich water or media.
In plants, hydrogen gas (H2) enhances tolerance to several abiotic stresses, including salinity and heavy metals. However, the effect of H2 on fungal growth under different stresses remains largely unclear. In this study, hydrogen-rich water (HRW) was employed to characterize physiological roles and molecular mechanisms of H2 in the alleviation of three different stresses in basidiomycete Hypsizygus marmoreus. Results showed that HRW treatment, of which the H2 concentration was 0.8 mM, significantly reduced the toxicities of CdCl2, NaCl and H2O2, leading to significantly improved mycelial growth and biomass. These beneficial effects could be attributed to a significantly decreased formation of malondialdehyde (MDA). Besides, HRW treatment significantly increased the activities of antioxidants (SOD, CAT and GR) as well as the gene expressions of these antioxidants (SOD, CAT, and GR) at the mRNA level. In vivo detection of reactive oxygen species (ROS), including H2O2 and O2-, as well as lipid peroxidation provided further evidence that HRW could significantly improve tolerances of CdCl2, NaCl and H2O2. Furthermore, pyruvate kinase was activated in the mycelia treated with HRW, along with its induced gene expression, suggesting that HRW treatment enhanced the glucose metabolism. Taken together, our findings suggested that the usage of HRW could be an effective approach for contaminant detoxification in H. marmoreus, which was similar with the effects of HRW in plants, and such effects could be also beneficial in entire agricultural system.