Abstract

Under copper (Cu) stress, the activities of some enzymes involved in the antioxidant defense system in leave cells of Cu accumulator Elsholtzia haichowensis were investigated. Our results showed that Cu treatment significantly increased the activities of plasma membrane-bound nicotinamide adenine dinucleotide phosphate (NADPH) oxidase, apoplastic peroxidase (POD), apoplastic superoxide dismutase (SOD), symplastic SOD and symplastic ascorbate peroxidase (APX) in leaves of E. haichowensis, when additional treatment with N-N-diethyldithiocarbamate as an inhibitor of SOD, NaN₃ as an inhibitor of peroxidase, diphenyleneiodonium as an inhibitor of NADPH oxidase and 1, 2-dihydroxybenzene-3, 5-disulphonic acid as an O₂^- scavenger and Cu-induced activities of antioxidant enzymes in leave cells of E. haichowensis were significantly inhibited. The results suggested that plasma membrane NADPH oxidase and apoplastic POD can be responsible for the accumulation of H₂O₂ in mesophyll cells of E. haichowensis under copper stress. In the leaf symplast, however, Cu-induced activities of SOD and APX may be important in avoiding the build-up of toxic H₂O₂concentrations.

Key words: Elsholtzia haichowensis, leave, copper, inhibitor, antioxidant enzyme.