Green Synthesized Titanium Oxide Nanoparticles Promote Salt Tolerance in Soybean.

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 (TiO NPs) promoted soybean growth even under salt stress. To further enhance the growth-promoting effect of TiO 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)-TiO NPs. To clarify the promoting mechanism in soybean of GS-TiO NPs under salt stress, immunoblot analysis was performed. The abundance of vacuolar H-ATPase decreased in roots by salt stress was recovered with GS-TiO NPs. In contrast, the abundance of glutathione reductase increased in roots and hypocotyls by salt stress was recovered with GS-TiO NPs. Furthermore, hydrogen peroxide production increased in roots with salt stress that was restored by treatment with GS-TiO NPs. These results suggest that GS-TiO NPs may restore soybean growth by detoxifying hydrogen peroxide, which increases under salt stress, with upregulating reactive oxygen species scavenging systems.