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EI-Shora H. M.
Activities of
antioxidative enzymes and senescence in detached Cucurbita pepo under Cu- and oxidative stress by H2O2
Abstract
The activities of antioxidative enzymes were
determined in detached leaves of Cucurbita
pepo exposed to either Cu stress or oxidative stress by hydrogen peroxide.
Cu reduced the activities of glutathione reductase (GR), catalase (CAT), and
ascorbate peroxidase (APOD), dehydroascorbate reductase (DHAR) but increased
the activity of superoxide dismutase (SOD). On the other hand, hydrogen
peroxide decreased the activities of GR, APOD, SOD, and DHAR but increased the
activity of catalase. The effects of Cu or hydrogen peroxide stress on the
different tested enzymes were minimized by pretreatment with ascorbic acid
(ASA), reduced glutathione (GSH) or both. Cu stress increased the levels of
endogenous hydrogen peroxide and malondialdehyde (MDA) but decreased the levels
of protein, chlorophyll a and chlorophyll b. Cu-promoted senescence and the
increase of MDA level were inhibited by ASA, GSH, benzoic acid (BA) or thiourea
(TU). Hydrogen peroxide stress increased MDA content but decreased the levels
of endogenous hydrogen peroxide, protein, chlorophyll a and chlorophyll b.
Hydrogen peroxide-induced senescence and the increase in MDA content were
inhibited by the various tested free radical scavengers.
Copyright (C) Chemistry Dept., Moscow State University, 2002
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