PEROXIDASE-ACTIVITY IN ETHYLENE-TREATED, ABA-TREATED, OR MEJA-TREATEDRICE (ORYZA-SATIVA L) ROOTS

Changes of peroxidase (EC 1.11.1.7) activity in ethylene-, ABA- or met hyl jasmonate (MeJA)-treated rice (Oryza sativa L. cv. Taichung Native 1) roots were investigated. Guaiacol and syringaldazine were used as substrates for peroxidase activity determination. On a protein or fres h weight basis, activity of wall-bound guaiacol and syringaldazine per oxidase in air-grown roots decreased as growth advanced. In air-grown roots, soluble peroxidase activity on a fresh weight basis also decrea sed, but activity on a protein basis remained constant. In response to 10 mu l/l ethylene, root growth was strongly inhibited while, in cont rast, activity of cell wall-bound guaiacol and syringaldazine peroxida se on a protein or fresh weight basis increased. Activity of soluble p eroxidase on a fresh weight basis in ethylene-treated roots also incre ased, although soluble peroxidase activity per mg protein did not chan ge. ABA (10 mu M) or MeJA (50 mu M) also resulted in an inhibition of root growth but an increase of wall-bound guaiacol and syringaldazine peroxidase activity. Thus, activity of wall-bound peroxidase is invers ely related to plant hormone-mediated growth inhibition of rice roots.