Hydrogen gas (H2) is a novel gaseous signaling molecule. Since 2007, more attention has been paid to the physiological functions and signal transduction pathways of H2. Thus, a new discipline, called hydrogen biology, has been gradually developed to elucidate the biological functions and corresponding molecular mechanisms of H2. Hydrogen biology can be divided into hydrogen medicine and hydrogen agronomy, according to its actual scope of application. In medicine, the anti-oxidative, anti-inflammatory, and anti-apoptotic effects of H2 have been discovered based on studies in multiple animal models and thereafter some clinical trials. In fact, H2 has ideal positive effects on ischemia/reperfusion, inflammatory-based acute tissue ischemic diseases and chronic degenerative diseases, such as Parkinson’s disease, Alzheimer’s disease, and atherosclerosis. In plants and agronomy, it was found that H2 could enhance plant tolerance against abiotic stress in alfalfa, rice and Arabidopsis, regulate growth, development, and nutritional values of cucumber, tomato, kiwifruit, sprouting vegetable, black barley and edible fungi. It is also demonstrated that H2 could extend the vase life of lisianthus, rose and lily cut flowers, and improve the resistance of livestock against pathogens. In this paper, the history of hydrogen biology is described firstly, and it is proposed that electrolyzed water might be the first source of hydrogen medicine. The determination approaches of H2, the synthetic pathway(s) of endogenous H2, and the progresses of molecular mechanism and corresponding signal transduction of hydrogen biology were reviewed. Subsequently, the application status of hydrogen medicine and hydrogen agronomy was introduced from the perspectives of delivery, biological effects and safety of H2. It is very interesting that the selective antioxidant mechanism of molecular hydrogen can not fully explain the existing biological effects of H2, reflecting the complexity and diversity of this discipline. Finally, some important scientific and practical issues of hydrogen biology are proposed. Importantly, we pointed out that further development in hydrogen medicine depends on a large number of clinical trials with high reliability. Meanwhile, hydrogen agriculture also relies on largescale field trials with multi-year and multi-site experiments in the future.
佛山市农业科技项目（佛财预2019【140】号）和国家自然科学基金项目（No.31371546, No.31972396） 以及上海交通大学氢科学中心的经费支持