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Effects of salinity, high irradiance, ozone, and ethylene on mode of photosynthesis, oxidative stress and oxidative damage in the C 3 /CAM intermediate plant Mesembryanthemum crystallinum L.
Author(s) -
HURST A. C.,
GRAMS T. E. E.,
RATAJCZAK R.
Publication year - 2004
Publication title -
plant, cell and environment
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.646
H-Index - 200
eISSN - 1365-3040
pISSN - 0140-7791
DOI - 10.1046/j.0016-8025.2003.01133.x
Subject(s) - mesembryanthemum crystallinum , crassulacean acid metabolism , oxidative stress , halophyte , photosynthesis , superoxide dismutase , biochemistry , oxidative phosphorylation , chemistry , ethylene , biology , salinity , botany , ecology , catalysis
The occurrence of oxidative stress and oxidative damage in the halophyte Mesembryanthemum crystallinum during C 3 /crassulacean acid metabolism (CAM) transition evoked by salinity and high irradiance was investigated. The hypothesis tested was that CAM induction will effectively protect M. crystallinum against oxidative damage even under additionally applied oxidative stress via ozone (150 p.p.b.) exposure. Salinity (0.4 m NaCl), high irradiance and ozone induced the cytosolic CuZn‐superoxide dismutase (SOD; EC 1.15.1.1) transcript abundance and activity indicating oxidative stress. However, ozone did not induce CAM. Contrary to the hypothesis, that ethylene may be involved in CAM induction, gassing with ethylene (200 p.p.b.) did not lead to CAM, but revealed that in M. crystallinum ethylene biosynthesis is induced by autostimulation. A putative fragment of the hitherto unknown nu‐cleotide sequence of 1‐aminocyclopropane‐1‐carboxylate oxidase (ACC; EC 4.4.1.14) was isolated and used as a specific probe against the ACC oxidase transcript to monitor oxidative damage. Ozone exposure increased the ACC oxidase expression only in plants with C 3 ‐photosynthesis which also showed severe necrosis and reduced photosynthetic activity, whereas plants in CAM mode (salt induced) remained unaffected. Natural stressors such as salinity and high irradiance induce CAM and up‐regulate the ARS component CuZn‐SOD very effectively to protect M. crystallinum from oxidative damage even when additional oxidative stress such as ozone is present.