Binds auxin, endogenous flavonoids and the phytoalexin camalexin and may be involved in regulating the binding and transport of small bioactive natural products and defense-related compounds during plant stress. Binds a series of heterocyclic compounds, including lumichrome, harmane, norharmane and indole-3-aldehyde. In vitro, possesses glutathione S-transferase activity toward 1-chloro-2,4-dinitrobenzene (CDNB) and benzyl isothiocyanate (BITC). Acts as glutathione peroxidase on cumene hydroperoxide, linoleic acid-13-hydroperoxide and trans-stilbene oxide, but not trans-cinnamic acid or IAA-CoA. glutathione + RX = a halide anion + an S-substituted glutathione + H(+) Homodimer. Plasma membrane vesicles. Expressed in the root-shoot transition zone and root tips. By ethylene, auxin, glutathione, salicylic acid, copper, paraquat, acetochlor, metolachlor and the pathogens P.syringae and Hyaloperonospora parasitica. Belongs to the GST superfamily. Phi family.