FIGURE 7.

Effects of silicon on superoxide anion radical (${\mathrm{O}}_{\mathrm{2}}^{\mathrm{•-}}$) levels in the roots of tomato seedlings grown under water stress. Data are shown as means ± SD (n = 3) for production rate of superoxide anion radical. Bars with the same letters are not significantly different at P < 0.05. The histochemical analysis was conducted 6 days after water stress, and the ${\mathrm{O}}_{\mathrm{2}}^{\mathrm{•-}}$ production rate was monitored using nitroblue tetrazolium. (A) Production rate of superoxide anion; (B) Histochemical staining.