Figure 9.

A, A typical example of transient change of membrane potential upon the addition of 200 μm 2-hydroxybenzoic acid to root mature zone. The first arrow indicates commencing of the treatment, while the second arrow shows the moment when electrode was removed from the cell. B, Cell membrane potentials in root mature zones after 24 h treatment with various secondary metabolites. Data are means ± se (n = 16). C, ATPase hydraulic activity of 7-d-old barley root PM after 30 min treatment of 2-hydroxybenzoic acid, acetic acid, and Mn²⁺. 2-HBZ, 2-Hydroxybenzoic acid; 4-HBZ, 4-hydroxybenzoic acid.