Agriculture Reference
In-Depth Information
Extreme
temperature
Heavy
metals
Flooding
UV
radiation
Drought
Oxidative
stress
Salinity
Ozone
Cell signaling
ROS
NADPH
OX
cGMP
O
2
-
H
2
O
2
NOS/NR
Protein nitration
GSH, GSNO
AsA
Carotenoids
Polyphenols
Antioxidant enzymes
Other thiol compounds
OXI1 protein kinase
OONO
-
NO
Gene expression of antioxidant enzymes
Activation
Fe
2+
/
3+
R•
RO•
ROO•
Stress Protection
R-NO
RO-NO
ROO-NO
[Fe-NO]
Cellular
antioxidant system
Protection to oxidative stress
Figure 11.4
Possible mechanisms of NO-induced oxidative stress protection. Adapted from Hasanuzzaman
et al.
(2013e), and
reproduced with permission of Springer Science + Business Media.
P. radiata
, presoaking of leaf discs with NO donor
(150 μM SNP) provided better protection against HT
stress-induced damage (Yang
et al.,
2006). Compared
with heat-shocked (45 °C, 90 min) leaf discs, the levels
of thiobarbituric acid-reactive substances (TBARS) and
H
2
O
2
and electrolyte leakage were reduced, while max-
imal quantum yield of PSII (
F
v/
F
m) was significantly
increased by SNP presoaking. The activities of antioxi-
dant enzymes (POD, CAT and SOD) suppressed by heat
shock were all restored by SNP presoaking. The effect of
NO was confirmed by the opposite results obtained
when the leaf discs were soaked in bovine haemoglobin
(a powerful NO scavenger). These authors concluded
that exogenous NO could prevent HT-induced damage
by promoting leaf photochemical activity, cell mem-
brane integrity and upregulation of the activities of
antioxidant enzymes (Yang
et al.,
2006). In
P. vulgaris
,
NO supplementation caused incomplete alleviation of
Ni toxicity by NO supplementation, as reported by
Mihailovic and Drazic (2011). Four-day exposure of the
seedlings to 0.2 mM NiCl
2
resulted in a marked increase
in soluble protein, Pro and SOD activity, whereas POD
and CAT activities were decreased. Nickel toxicity also
enzyme activities and decreased O
2
•
−
production, and
hence inhibited lipid peroxidation. Levels of H
2
O
2
, Pro
and Evan blue uptake in seedlings pretreated with
SNP were markedly lower than under drought stress,
indicating the operation of the antioxidant system in
them. Moreover, seedlings arising from H
2
O
2
or SNP
pretreatment enhanced the membrane stability, as
revealed from greatly reduced MDA content (Moussa &
Mohamed, 2011). Kumari
et al.
(2010) studied the effect
of foliar applied NO in alleviating the toxic effects of
short-term and long-term Cd stress on growth, oxidative
metabolism and Cd accumulation in
C. arietinum
.
Exogenous SNP decreased the Cd-induced ion leakage
and lipid peroxidation in chickpea. Cadmium treatment
for a short term resulted in a higher induction of the
CAT, POD, APX, GR and SOD activities as compared to
long-term Cd stress. However, upon NO supplementa-
tion these activities were upregulated further, associated
with a higher redox status of AsA and GSH. With
long-term and short-term Cd treatment, roughly 50%
and 12% reductions in seed yield were observed in
chickpea. However, the yield reduction was lower when
the plants were supplemented with an NO donor. In
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