Nanosilver-Promoted Lateral Root Development in Rice is Mediated through Hydrogen Peroxide

Nanosilver (10(-9) m) refers to particles comprising 20-15,000 silver atoms, exhibiting high stability and specific surface area. At present, nanosilver has been used in agricultural cultivation and production. This study examined the effects of nanosilver on growth and development of rice root systems. Study results showed that fresh weight of rice belowground organs and root length both increased significantly by 5% and 25%, respectively, after rice radicles were treated with 2 ppm of nanosilver for three days. However, the H2O2 level reached its peak at 2 days from treatment, but the activities of the antioxidant enzymes CAT, APX, and GR were inhibited by 2 ppm of nanosilver treatment. The results showed that nanosilver treatment inhibited the antioxidant enzyme activity of rice roots. The treatment of rice radicles with 5 mu M H2O2 promoted root development and the same was observed when nanosilver was used for treatment. Moreover, ascorbic acid (AsA) is a H2O2 scavenger and therefore rice root development was inhibited when AsA was added to rice radicles together with either treatment of nanosilver or H2O2. In summary, nanosilver treatment of rice radicles promoted root growth and development via the regulation of H2O2 and not the O-2(center dot-) pathway.