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چکیده
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An experiment was performed as a split-plot design based on a randomized
complete block (RCB) with three replicates. The aim was to explore
physiological traits, catalase (CAT) and peroxidase (POD) activity associated
with cold and freeze stress in four barley genotypes (two stress-tolerant
genotypes and two sensitive genotypes). The genotypes were regarded as
sub-plots and five temperature levels (namely 20, 4, 0, ¡4, ¡8C) as main
plots. The results revealed that the hydrogen peroxide (H2O2) and
malondialdehyde (MDA) content increased through freeze and cold stress
from 20 to 4C. This increase was more in the sensitive genotypes than in
the tolerant ones. Subsequent to the increase in lipid peroxidation, the
membrane stability index (MSI) decreased, thereby increasing the electrolyte
leakage. The sensitive genotypes demonstrated greater reduction in
the studied parameters. Upon the increase in the H2O2 content, the
antioxidant enzymes CAT and POD also increased in order to collect and
prevent H2O2 from damaging the cell and the plant. Compared with the
sensitive ones, the tolerant genotypes indicated more increase in the
enzymes. The H2O2 and MDA content decreased from ¡4 to ¡8C, which
could be due to intracellular freezing in the sensitive genotypes, but due to
the detoxifying of the antioxidant enzymes in the tolerant genotypes.
Compared with the POD content, the increase in the CAT content through
cold stress was more, which could mean that it was possibly CAT which acted
as the main inhibitor of H2O2 in cold stress in the barley plan
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