Roles of hydrogen gas in plants: a review

Hydrogen gas (H-2) was first identified as a unique molecular messenger in animals. Since H-2 was reported as a novel antioxidant, it has been proven effective in treating many diseases. However, the studies concerning H-2 in plants are just beginning to emerge. Here, two paths of H-2 production in plants have been reported, namely, hydrogenase and nitrogenase. H-2 has positive effects on seed germination, seedling growth, adventitious rooting, root elongation, harvest freshness, stomatal closure and anthocyanin synthesis. H-2 also can enhance plant symbiotic stress resistance commonly through the enhancement of antioxidant defence system. Moreover, H-2 shows cross talk with nitric oxide, carbon monoxide and other signalling molecules (for example, abscisic acid, ethylene and jasmonate acid). H-2 can regulate the expression of responsive genes under abiotic stress and during adventitious roots formation and anthocyanin biosynthesis. Future work will need to focus on the molecular mechanism of H-2 and its crosstalk with other signalling molecules in plants. With its promising application in agriculture, hydrogen agriculture will be welcomed in the near future.