There is a close relationship between gas and organisms. Besides the involvement of carbon dioxide (CO2) and oxygen (O2) in photosynthesis, other gases, such as hydrogen (H2), methane, ethylene, carbon monoxide (CO) and hydrogen sulfide (H2S) are proved to be involved in various biological activities. From an evolutionary perspective, the origin of life on earth is the original atmosphere and ocean, the water and gas is the most important environmental conditions of the origin of life. The biological effects of all kinds of gas, has been more attention in the field of biomedicine.
As a colorless, odorless and tasteless gas, H2 is considered to be a physiologically inert gas, and it is generally regarded as a potential future energy source and an alternative to limited fossil fuel resources. H2 metabolism in bacteria and algae is well studied due to its important value in the field of new energy. However, the application of H2 in animal and human clinical medicine has not been drawn attention until 2007, a paper published in Nature Medicine that H2 can be selectively scavenge hydroxyl radicals and peroxynitrite. At present, the role of hydrogen has also become a hot research topic in the basic and clinical medicine, and studies have shown that H2 as an ideal antioxidant is effective in the treatment of many diseases and injuries. Effect of H2 in higher plants has not been well studied. Although early in 1947 H2 evolution in isolated chloroplasts was studied, whether hydrogenase exists in higher plants has found no clear evidence. Few reports have been made whether H2 has physiological effects on higher plants.
Dr. JIQING ZENG and researchers in South China Botanical Garden, made an exploratory research into the plant biological effects of H2. They found that the H2 acts as an important moderating effect on plant physiological function, especially involves in plant hormone signaling pathways and plays an important role in plant resistance to abiotic stress. Antioxidant enzyme activity was found to be increased and the transcription of corresponding genes altered when the effects of H2 on the germination of mung bean seeds treated with phytohormones was investigated. In addition, upregulation of several phytohormone receptor genes and genes that encode a few key factors involved in plant signaling pathways was detected in rice seedlings treated with hydrogen-rich water. The transcription of putative rice hydrogenase genes, hydrogenase activity, and endogenous H2 production were also determined. H2 production was found to be induced by abscisic acid, ethylene, and jasmonate acid, salt, and drought stress and was consistent with hydrogenase activity and the expression of putative hydrogenase genes in rice seedlings. Together, these results suggest that H2 may have an effect on rice stress tolerance by modulating the output of hormone signaling pathways. Base on these studies, postulate that H2 may be involved in the stress response in higher plants in the form of a gaseous plant hormone like ethylene or NO.
The finding has been published online in PloS ONE with the title "Molecular hydrogen is involved in phytohormone signaling and stress responses in plants"（(http://dx.plos.org/10.1371/journal.pone.0071038) ）. This is the first paper about the H2 regulation of plant hormone effect. The research may greatly promote the application of H2 in agricultural production.
