NaCl treatment markedly enhances H₂O₂‐scavenging system in leaves of halophyte <i>Suaeda salsa</i>

Abstract

The C 3 halophyte Suaeda salsa L. grown under the high concentration of NaCl (200 m M ) was used to investigate the role of the hydrogen peroxide (H 2 O 2 )‐scavenging system [catalase, ascorbate peroxidase, glutathione reductase (GR), ascorbic acid, and glutathione (GSH)] in removal of reactive oxygen species. The activity of catalase (CAT, EC 1.11.1.6), ascorbate peroxidase (APX, EC 1.11.1.11), and GR (EC 1.6.4.2) increased significantly after 7 days of NaCl treatment. The isoform patterns of CAT and GR were not affected, but the staining intensities were significantly increased by NaCl treatment. Activities of both the thylakoid‐bound APX or GR and stromal APX (S‐APX) or GR in the chloroplasts were markedly enhanced under high salinity. Fifty percent of APX in the chloroplasts is thylakoid‐bound APX. S‐APX and GR activity represented about 74–78 and 64–71% of the total soluble leaf APX and GR activity, respectively. Salt treatment increased the contents of ascorbic acid and GSH. By contrast, a decreased content of H 2 O 2 was found in the leaves of NaCl‐treated S . salsa . The level of membrane lipid peroxidation decreased slightly after NaCl treatment. The plants grew well with high rate of net photosynthesis under high salinity. These data suggest that upregulation of the H 2 O 2 ‐scavenging system in plant cells, especially in the chloroplasts, is at least one component of the tolerance adaptations of halophytes to high salinity.