Molecular Plant Breeding 2016, Vol.7, No.17, 1-7
3
between cold acclimated and non-acclimates leaves 24 h after acclimation.
In our study, we observed increasing of patterns of antioxidant enzyme activities in both aerial and root system
under cold stress comparing with control in tolerant and sensible ecotypes. Whereas, under these activities were
more pronounced in root than in aerial (leaves and shoots) tissues (Figure 1). The result was in agreement with the
findings of Wang et al., (2009). Furthermore, Kuk et al. (2003) obtain similar results, where they explain that the
antioxidant activity in rice is higher in the roots than in the leaves. Under cold stress the activities was better in
root than in aerial tissues. (Figure 1A; Figure 1B). In tolerant ecotype (Cil 126), the guaicol POD activity in the
aerial tissues (leaves and shoots) (Figure 1A) was found increased in T4 treatment (0.174 5x10
-3
µmole/min/g FM)
compared with control. This level of activity was substantially degreased at the 6 days of cold treatment (1.1x10
-3
µmoles/min/g FM) compared with control (1.17x10
-3
µmoles/min/g FM). Nevertheless, dropped sharply at the
beginning of cold treatment (T2) (0.080 0x10
-3
µmoles/min/g FM) compared with control (0.161 5x10
-3
µmoles/min/g FM). In the roots, the guaicol POD activity (Figure 1B) showed accounted for a steady increase in
treated plantlets compared to the control plants according to the duration of treatment. Furthermore, POD activity
at T6 cold treatment (1.54x10
-3
µmoles/min/g FM), showed a significant increase (
P≤0.05)(data not
showed)
compared to the control (1.19x10
-3
µmoles/min/g FM).
Figure 1A: Aerial vegetative tissues peroxidase activity in
M. ciliaris
Krockers
.
ecotypes (Cil 126 and Cil 123) seedlings untreated
(controls): (T02, T04, and T06) and treated with different durations (T2, T4, and T6) under cold stress. Data are shown as mean ±SD
of three independent measurements
Figure 1B: Root vegetative tissues peroxidase activity in
M. ciliaris
Krockers
.
ecotypes (Cil 126 and Cil 123) seedlings untreated
(controls): (T02, T04, and T06) and treated with different durations (T2, T4, and T6) under cold stress. Data are shown as mean ±SD
of three independent measurements
In sensible one (Cil 123), the same tendency of guaicol POD activity was observed but with less intensity
compared to the tolerant ecotype. It is more cleared that the guaicol peroxidases activity was greater in root tissue
than in aerial tissues in two contrasting ecotypes (Figure 1A; Figure 1B). Kuk et al., (2003) obtain similar results,
where they explain that the antioxidant activity in rice is higher in the roots than in the aerial parts (buds). On
another side, Okuda et al., (1991) stippled that H
2
O
2
content increase sharply in wheat leaves under chilling stress.
Lee et al., (2009) highlighted the same trend. These authors argue that the roots are most affected by cold stress
and energy metabolism pathway in rice roots is more affected by the cold stress. Cold stress causes inhibition of
photosynthesis in leaves and influence on various metabolic reactions that are at the origin of the overproduction
of H
2
O
2
(Larkindale et al., 2005). Regarding Gasparet al., (1992) and Kukavicaet al., (2007), these authors noted
that the production of peroxidases was actively involved in root growth.
1.2 Effect of cold stress on peroxidase isoforms pattern
Guaicol peroxidases are known to utilize different substrates to metabolize H
2
O
2
. When guaiacol was used as a
