Activities of all enzymes except SOD were expressed in enzyme units per mg of protein,
where 1 enzyme unit is defined as a change of 0.01 absorbance min
− 1
caused by the enzyme sample. Protein sample content was determined using
bovine serum albumin as a standard Bradford, 1976.
2
.
3
. Statistics Three tests were performed for each plant, and
data for enzyme activity, biomass and germina- tion rate were generated in triplicate for each
treatment or control, thus n = 9. No observed effect concentration NOEC and lowest observed
effect concentration LOEC values were deter- mined using Williams’ test P 5 0.05 Williams,
1971 after checking homogeneity of variances with the Hartley test. The software TOXSTAT
3.0 University of Wyoming, Laramie, WY, USA was used for these different calculations. The
coefficient of variation is representative of re- peatability triplicates and of reproducibility
tests realized at three different times.
3. Results
The pH values of the soils were practically unaltered from 7.0 to 6.7 during the test period.
Tables 1, 2 and 3 show biological and biochemical data for oat A6ena sati6a, Chinese cabbage
Brassica campestris cv. chinensis and lettuce Lactuca sati6a exposed to TCA herbicide.
3
.
1
. Effects of TCA on germination rate and plant growth
Although no visible symptoms such as wilting or leaf coloring were caused by the lower TCA
concentrations, weak leaf chlorosis was observed in some plants of lettuce and Chinese cabbage
species at the highest TCA concentration. The biomass fresh weight and germination rate
Table 1 Biomass, germination rate and enzymatic activities measured in oat A6ena sati6a exposed to different treatments of TCA
a
Parameter 0.00
3.90 1.90
0.98 0.48
0.12 0.03
mg TCA kg dry soil
− 1
95.0 94.6
93.7 Germination
73.3 97.2
96.2 95.4
9 6.8
9 4.2
9 5.1
9 4.2
9 6.1
9 6.4
9 5.1
7.2 4.4
5.4 4.4
6.5 8.8
5.3 6.1
8.05 9.2
9.7 Biomass mg fresh weight per plant×10
− 2
9.6 9.3
9.3 9
0.7 9
0.5 9
0.5 9
0.3 9
0.7 9
0.5 9
0.9 7.2
5.4 9.6
7.5 5.2
5.6 4.4
Superoxide dismutase
b
5.78 5.83
5.57 5.39
5.28 5.53
4.65 9
0.6 9
0.6 9
0.4 9
0.8 9
0.5 9
0.6 9
0.3 6.4
10.5 9.4
7.7 10.7
10.6 14.5
17.1 18.1
19.2 Peroxidase
c
13.5 15.6
16.3 9
1.8 9
2.6 9
2.5 9
2.5 9
2.8 9
2.5 NR
13.3 16.5
15.0 14.8
15.5 12.9
Catalase
c
12.3 13.5
13.7 13.9
14.0 14.7
15.9 9
0.5 9
0.9 9
0.8 9
0.7 9
1.3 9
1.1 9
1.7 4.9
6.4 4.3
5.6 10.5
8.9 7.9
Glutathione reductase
c
23.6 22.1
22.1 21.5
19.8 16.9
9 4.6
9 2.4
9 2.8
9 0.7
9 0.6
NR 9
4.4 10.7
13.2 2.9
20.6 4.0
18.4
a
Data n = 9 are listed in the following order: mean, standard deviation and coefficient of variation; NR, not realized.
b
Asada units mg protein
− 1
×10
− 1
.
c
Enzymatic units mg protein
− 1
×10
− 2
. Statistically significant differences P50.05.
Table 2 Biomass, germination rate and enzymatic activities measured in Chinese cabbage Brassica campestris cv. chinensis exposed to
different treatments of TCA
a
0.48 1.90
3.90 7.80
0.00 15.60
Parameter 31.20
62.50 mg TCA kg dry soil
− 1
96.1 96.2
94.9 95.2
94.7 91.8
85.7 Germination
95.8 9
5.0 9
3.9 9
5.0 9
0.5 9
5.0 9
3.9 9
4.8 9
5.8 5.2
4.0 5.2
6.0 4.1
5.2 5.2
6.8 7.8
7.7 7.8
7.7 7.5
Biomass mg fresh weight per 7.0
6.3 5.6
plant×10
− 2
9 0.3
9 0.3
9 0.5
9 0.5
9 0.5
9 0.4
9 0.4
9 0.4
4.1 4.2
6.4 5.9
5.8 6.0
6.8 7.4
Superoxide dismutase
b
2.07 2.29
2.29 2.35
2.22 2.24
2.26 2.30
9 0.1
9 0.3
9 0.2
9 0.1
9 0.2
9 0.2
9 0.2
9 0.3
9.3 4.3
15.3 9.0
6.9 11.2
7.6 1.9
15.2 Peroxidase
c
15.0 12.4
15.2 14.6
15.0 14.0
16.4 9
2.2 9
2.1 9
2.2 9
2.1 9
1.3 9
3.5 9
2.7 9
2.2 14.2
14.0 14.5
14.7 23.5
10.3 19.5
13.1 17.3
17.6 18.5
17.5 15.0
17.5 Catalase
c
17.6 9
1.1 9
1.6 9
3.1 9
2.9 9
1.6 9
2.0 9
1.9 NR
9.3 17.1
15.7 9.2
7.3 11.4
10.8 11.3
Glutathione reductase
c
13.9 13.9
14.1 13.2
13.2 12.2
13.1 9
1.5 9
0.7 9
1.9 9
1.6 9
1.6 9
2.8 9
1.6 9
1.8 10.9
13.9 11.4
12.0 21.2
12.8 6.3
13.7
a
Data n = 9 are listed in the following order: mean, standard deviation and coefficient of variation; NR, not realized.
b
Asada units mg protein
− 1
×10
− 1
.
c
Enzymatic units mg protein
− 1
×10
− 2
. Statistically significant differences P50.05.
clearly decreased with increasing TCA concentra- tions for the three plant species. Germination
rates decreased significantly with LOEC values of 3.9 mg TCA kg dry soil
− 1
for oat and lettuce and 62.5 mg TCA kg dry soil
− 1
for Chinese cabbage. The reproducibility of germination endpoint was
good, with coefficients of variation between 4.0 and 8.8.
Concerning biomass in species response, lettuce and oat showed the same sensitivity for TCA with
an LOEC value of 1.9 mg TCA kg dry soil
− 1
, both species being more sensitive than Chinese
cabbage which showed an LOEC value of 15.6 mg TCA kg dry soil
− 1
. For biomass endpoint, the reproducibility was similar to the germination
endpoint, with coefficients of variation between 4.1 and 9.6.
3
.
2
. Effects of TCA on enzyme acti6ities Activities of all enzymes were significantly dif-
ferent from plant controls at the lowest concentra- tion of TCA tested, i.e. 0.03 mg TCA kg dry
soil
− 1
for oat and lettuce and 0.48 mg TCA kg dry soil
− 1
for Chinese cabbage. As all test con- centrations produce significant effects, the LOEC
values found in this study were presumed to be less than the lowest concentration tested. For the
three plant species tested, the maximum level of increase in the activities of peroxidase 43 for
oat, 37 for lettuce, and 22 for Chinese cab- bage and glutathione reductase 40 for oat,
37 for lettuce, and 24 for Chinese cabbage were larger than that of catalase 20 for oat
and Chinese cabbage, and 29 for lettuce and
superoxide dismutase 30 for lettuce, 25 for oat, and 14 for Chinese cabbage.
The peroxidase showed a higher coefficient of variation, ranging from 10.3 to 23.5 mean
CV = 15.2, while catalase showed the lower coefficient of variation mean CV = 8.3.
At highest concentrations of TCA, severe biomass and germination rate diminution were
observed, as well strong reduction on enzyme activities results not shown.
4. Discussion
