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Legume Genomics and Genetics 2012, Vol.3, No.2, 8
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theory foundation for choice of safe, effective biological
pesticide preventing dodder.
1 Results and Analysis
1.1 Effects of three plant extracts on growth and
development of dodder and soybean
Three plant extracts had certain effects on growth and
development of dodder and soybean (Table 1). Three
plant extracts in low concentrations had no significant
injury symptoms on dodder and soybean seedling.
While in high concentrations (0.25 g/mL), the extracts
gave a minimum damage rate of 48%, the most injury
rate was up to 78%, which was specifically manifested
in growth retardation, the reduction of haustorium
number and twine circle number, wilting and withering.
Under the treatment of plant extracts with high
concentrations, the injury rate of all plant extracts was
over 54%, except that of
Melia azedarach
bark was
only 7%; for instance,
Eucalyptus
leaves extracts had
a rate of 64%.
Melia azedarach
bark extract was
detrimental to dodder but very little to soybean
seedlings, which suggested the inhibitory effect of
Melia azedarach
bark extract on growth and
development of dodder.
1.2
Effects of three plant extracts on protective
enzymes of soybean
SOD is the first defense line that protected plant cells
from free radical (Hernández et al., 2001), for it can clear
the O
-
2
away by transforming it to H
2
O
2
and O
2
. It plays
an important role in protecting plant cells from reactive
oxygen species (ROS) and very commonly exists in
plants. Under the high concentration (0.25 g/mL), the
treatment of all extracts except
Melia azedarachn
leaves
caused the SOD activity increase of the soybean seedlings
leaves. The activity value induced by
Eucalyptus
leaves
extract was 2.26 times of the control group, whereas the
values of SOD activity, which were induced by
Sapium
sebiferum
leaves and
Melia azedarachn
leaves at a
concentration of 0.05 g/mL, respectively, were only 0.81
and 0.88 times of the control group (Figure 1).
POD plays an essential role in enzymatic system of
scavenging active oxygen of plants, namely, which
further decomposes H
2
O
2,
the dismutation product of
SOD, into H
2
O and O
2
. CAT was the other path to the
degradation of H
2
O
2
in plants, that is, CAT and SOD
Figure 1 Effects of three plant extracts on SOD activity in soybean
Note: There is no significant difference (p<0.05) among the
same letters
together clear away H
2
O
2
and O
-
2
in vivo
to minimize the
formation of hydroxyl radical. POD activity in soybean
leaves had changed under treatments of extracts of
Eucalyptus
leaves and
Melia azedarachn
leaves, which
obviously showed in the following two cases. POD
activity, treated by
Eucalyptus
leaves at 0.05 g/mL and
0.01 g/mL, were 2.28 times and 2.04 times respectively
of the control group. Treated
Melia azedarachn
leaves at
0.25 g/mL, 0.05 g/mL and 0.01 g/mL, the POD activity
increased to 2.0 times, 1.75 times and 1.48 times
respectively of the control group (Figure 2). Extracts of
Sapium sebiferum
leaves and
Melia azedarachn
bark had
no significant effect on POD activity of soybean seedlings
leaves. Comparing with POD, CAT activity was much
significantly affected by
Sapium sebiferum
leaves and
Melia azedarachn
bark extracts, whereas under
Eucalyptus
leaves extract treatment, the CAT activity was only
slightly higher than the control group (Figure 3).
Figure 2 Effects of three plant extracts on POD activity in soybean
Note: The same as figure 1