Basic HTML Version
Plant Gene and Trait 2012, Vol.3, No.2, 6
-
12
http://pgt.sophiapublisher.com
9
remarkable difference without NaCl stress between TS
and NS. The decline range of the chlorophyll in the
leaves of TS was smaller than in the NS with NaCl
stress. There were remarkable differences under the
100 mmol/L and 150 mmol/L NaCl stress between TS
and NS (P <0.01) (Table 1).
Table 1 The chlorophyll content of leaf under the NaCl stress
Genotypes
Stress time
NaCl concentration (mmol/L)
0
50
100
150
NT
0 d
25.53
25.77
28.30
25.17
5 d
24.63
18.13
10.60
3.67
Decline range (%)
3.47%
29.58%
62.53%
87.27%
TS
0 d
25.7
24.7
25.6
24.1
5 d
20.5
18.7
17.5
12.5
Decline range (%)
3.50%
23.00%
37.89%
**
48.03%
**
Note: Differences between NS and TS values in the same treatment were significant at: *: P <0.05, **: P <0.01, according to
Duncan’s Multiple Range Test
Ke and Pan (1999) reported salt stress could lead to
disintegration of chloroplast fine structure and make
pigment protein complex instability, so the chlorophyll
was destroyed, and inevitably reduced the absorption
of light energy. The Table 1 showed that the
chloroplasts of NS were destroyed seriously, which of
TS were also a certain degree of damage under 150
mmol/L NaCl concentration level.
1.5 The root length
Under normal conditions, the root of the TS and NS
could grow very well. With the increase of the NaCl
concentration, the root growth was restrained, but the
root length of TS was longer than the NS. There were
remarkable differences under the 100 mmol/L and 150
mmol/L NaCl stress between TS and NS (P<0.01;
Figure 4). In addition, the author also found the more
fibrous root of the TS grew than the NS in 50 mmol/L
NaCl and 100 mmol/L NaCl concentration level. This
meant that the transgenic plants could be better to
resist salt harm.
2 Discussion
In the long course of evolution, the plant formed the
perfect and complex protection system including
enzymes and non-enzymatic antioxidant systems to
cope with oxidative stress (Du et al., 2001). The
SOD and APX are two key enzymes in the ROS
scavenging system (Perl et al., 1993; Badawi et al.,
2004), which could clear out active oxygen on
different path (Asada, 1999). Transgenic tobacco
Figure 4 The root length under NaCl stress under NaCl stress
Note: Values are the means of at least three different
experiments ± SD; Differences between NS and TS values in
the same treatment were significant at: *: P<0.05, **: P<0.01,
according to Duncan's Multiple Range Test
plants expressing both CuZnSOD and APX provide
stronger protection to methyl viologen (MV)-induced
oxidative stress than transgenic tobacco plants
expressing CuZnSOD or APX (Kwon, 2002). In this
study, we also confirmed that transgenic sweetpotato
plants expressing both CuZnSOD and APX improved
the salt resistance.
In view of the foregoing results, with NaCl concen-
tration increasing, the activity of SOD, APX, CAT and
POD in sweetpotato leaves was increased firstly and
then decreased, while in general condition, the activity
of these four enzymes in transgenic sweetpotato was
higher than no-transgenic sweetpotato. When antioxidant
enzyme activities increased, H
2
O
2
decreased in cell,
which increased the stability of membranes and CO
2
fixation because the enzymes of the Calvin cycle