Hydrogen-rich water irrigation promotes fruit ripening and nutritional composition in tomato

Hydrogen gas (H2), as a gaseous molecule, plays vital roles in plant growth and development. However, whether H2 plays a role in fruit ripening of tomato is still unknown. Here, we explore the effect of hydrogen-rich water (HRW) irrigation on fruit ripening and nutritional composition in tomato. HRW irrigation enhanced lightness (L* value) and redness (a* value), and declined yellowness (b* value), accelerated fruit color transition. HRW reduced chlorophyll a, chlorophyll b, and total chlorophyll content and enhanced carotenoid, lycopene, and lutein accumulation. Moreover, HRW promoted chlorophyll degradation-related and carotenoid-synthesis related gene expression. In addition, HRW modulated the cell wall component content, enhanced fruit softening-related enzyme activity, and upregulated fruit softening-related and ripening-related gene expression, but decreased fruit firmness. Also, HRW irrigation promoted the accumulation of sucrose, starch, soluble protein, and soluble sugar, as well as increasing the sugar-acid ratio and partial aroma composition. Therefore, H2 may be a promising eco-friendly way to improve tomato cultivation and other agricultural practices.