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Plant Gene and Trait, 2013, Vol.4, No.20, 109
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Figure 4 Effect of H
2
O
2
pre-treatment on APX (A), MDHAR
(B), DHAR (C), and GR (D) activities in mustard seedlings
under drought stress. Other details as in figure 3
pre-treatment had little influence in DHAR activity
under drought stress conditions.
Drought stress treatment resulted in a slight decrease
(15%) in GR activity when compared to control group
(Figure 4D). H
2
O
2
pre-treatment also showed a
non-significant increase (23%) in GR activity as
compared to control. Compared with drought stress
treatment, treatment with H
2
O
2
+drought showed a
significant (P<0.01) increase (32%) in GR activity.
1.3 Effects of
H
2
O
2
pre-treatment on CAT, GST and
GPX activities
The influence of exogenous H
2
O
2
pre-treatment
on
CAT, GST and GPX activities is presented in Fig. 5.
The activity of CAT declined significantly (23%) in
response to drought stress whereas a significant
increase (29%) was observed in H
2
O
2
pre-treated
drought-stressed seedlings as compared to control
(Figure 5A). Importantly, H
2
O
2
pretreated drought
stressed seedlings also showed a significant increase
(66%) in CAT activity as compared to the seedlings
subjected to drought stress without pre-treatment.
As compared to the control group, drought stress
resulted in a non-significant increase (13%) in GST
activity whereas a significant (P<0.01) increase (53%)
was observed in H
2
O
2
pre-treated drought-stressed
seedlings (Figure 5B). Surprisingly, H
2
O
2
pre-treated
Figure 5 Effects of H
2
O
2
pre-treatment on the activities of CAT
(A), GST (B) and GPX(C) in mustard seedlings under drought
stress conditions. Other details as in figure 3
drought-stressed seedlings showed a significantly
higher (37%) GST activity as compared to the
seedlings subjected to drought stress alone.
A significant (P<0.01) enhancement (40%) of GPX
activity was observed in response to drought stress as
compared to the control group (Fig. 5C). Compared
to control, treatment with H
2
O
2
+drought also brought
a significant (P<0.01) increase (34%) in GPX activity.
No significant variation in GPX activity was
observed in H
2
O
2
pre-treated and non-treated
drought-stressed seedlings.
1.4 Effects of
H
2
O
2
pre-treatment on glyoxalase
system enzymes
Seedlings exposed to drought showed a significant
(P<0.01) increase (28%) in Gly I activity as compared
to the control group (Figure 6A). The H
2
O
2
pre-treatment brought a significant (P<0.01) increase
(36%) in Gly I activity as compared to the control.
No significant variation in Gly I activity was
observed in H
2
O
2
pre-treated and non-treated
drought-stressed seedlings.
When comparing to the control group, the activity of
Gly II was found to be repressed by 33% under
drought stress conditions (Figure 6B). Treatment with
H
2
O
2
+drought also showed a significant (P<0.01)
decrease (19%) in Gly II activity relative to control.