Involvement of Hormone- and ROS-Signaling Pathways in the Beneficial Action of Humic Substances on Plants Growing under Normal and Stressing Conditions

Figure 5

Effect of HA application in roots of rice plant. Histochemistry for determining the location of reactive oxygen species (ROS) ( and H₂O₂) (a); membrane integrity (release of electrolytes) (b); superoxide dismutase (SOD) (c); and catalase (CAT) (d) enzymatic activity. The root application HA in plants modulates ROS content in the roots where superoxide anions () appear to be greater in cell elongation content region, while the H₂O₂ content seems to have greater differentiation in region (a). The presence of ROS seems to modify the permeability of the membrane (b) but under control exercised by the antioxidant metabolism (c and d). (These figures were modified from the original papers published at García et al. [18] for better adapting to this review.)

(a)

(b)

(c)

(d)