Abstract
Soybean is rich in protein and functional ingredients, which are in high demand as a food material; however, it is vulnerable to environmental stress. On the other hand, the application of chemically synthesized titanium oxide nanoparticles (TiO2 NPs) promoted soybean growth even under salt stress. To further enhance the growth-promoting effect of TiO2 NPs on soybeans, they were biologically synthesized using orange peel extract. Root elongation of soybeans suppressed by salt stress was restored to the control level by treatment with green synthesized (GS)-TiO2 NPs. To clarify the promoting mechanism in soybean of GS-TiO2 NPs under salt stress, immunoblot analysis was performed. The abundance of vacuolar H+-ATPase decreased in roots by salt stress was recovered with GS-TiO2 NPs. In contrast, the abundance of glutathione reductase increased in roots and hypocotyls by salt stress was recovered with GS-TiO2 NPs. Furthermore, hydrogen peroxide production increased in roots with salt stress that was restored by treatment with GS-TiO2 NPs. These results suggest that GS-TiO2 NPs may restore soybean growth by detoxifying hydrogen peroxide, which increases under salt stress, with upregulating reactive oxygen species scavenging systems.