changed by contribution factors. So all the sys- tems can be regarded as serial states of one sys-
tem. Perturbation
Value PV
is used
to quantitatively measure the differences between the
systems. PV can be obtained from any system no less than two systems only if each of them shares
the parameters induced by common contributing factors. The lower PV denotes fewer differences
among systems.
Perturbation analysis was conducted among the reference plants F
and the three generation plants of V. faba growing in the EF. MCN fre-
quency was exclusively used in calculation of the PV, based on background value, data obtained
from the treatment of NaN
3
and Cd
2 +
at differ- ent dose levels. Given F
m
m = 1, 2, 3 is the state of initial F
plants that have experienced metal pollution for different series of exposure years
m; contributing parameter set f for evaluating the difference of V. faba from four different gen-
erations included one group of background, six groups of data obtained from NaN
3
treatments with six different concentrations, and six groups
of data from Cd
2 +
treatments with six different concentrations. So we have 13 contributing
parameters i.e. f = f
1
, f
2
,... f
j
,... f
13
to calculate PV. PV can be determinated by the following
formula: PV
m
=
r j = 1
[12 × 1r + a
j
] ×
1 − MinP
f
j
, P
m
f
j
MaxP f
j
, P
m
f
j
n
where, PV
m
: relative value of PV of F
m
; r: total numbers of contributing factors r = 13; a
j
: desig- nated weighted coefficient of j contributing factor
Sa
j
= 1. As a rule, all weighted coefficients is
usually designated equal in biological studies be- cause it is hard to say which contributing factor
should be more important than any others; P
f
j
: parameter of F as to f
j
contributing fac- tors; P
m
f
j
parameter of F
m
as to f
j
contributing factors. In general, the lowest background value
and the largest increased dose-effects was set as optimum criteria for evaluation of the reliability
and efficiency of different generations of V. faba. As a result, the lower value of PV in this study
indicates the higher reliability and efficiency of V. faba to be used as sentinel plants for biomonitor-
ing mutagens.
Calculation for PV was performed with soft- ware programmed with FORTRAN 77 language.
3. Results
The background values of the MCN frequen- cies of different Vicia faba generation plants con-
tinuously growing in both the RS and the EF are given in Table 1.
There was no difference in the background values of MCN frequency of V. faba between the
generations that had been planted in the RS. However,
significantly different
background MCN frequencies were observed between F
and the other generation plants from the EF. Among
the different generation in EF, MCN frequency in F
was significantly lower than that in root tips of F
1
, F
2
and F
3
. With increasing generations of experiencing metal-contaminated soil, V. faba had
a decreased background MCN frequency. The sequence of background MCN frequency in the
plants obtained from EF was F
3
B F
2
B F
1
. According to these results, the root tips MCN
frequencies of V. faba growing in RS represented no differences between the generations. This fact
may indicate that background Vicia MCN fre- quency will be constant if the test Vicia plants
Table 1 Background MCN frequency in four generations of V. faba Continuously planted in RS and EF
a
F
2
F
3
F F
1
Generation 7.46 9 1.29
b
In the RS MCN 1000 cells
− 1
7.32 9 1.48
b
7.56 9 1.63
b
7.08 9 2.31
b
7.40 9 1.56
b
8.54 9 0.87
c
10.48 9 1.76
cd
12.71 9 3.74
d
In the EF MCN 1000 cells
− 1
a
Superscript letters indicate significant differences shown successive generation on each soil at PB0.05.
Fig. 1. Dose effect relationship between Cd
2 +
treatment and MCN frequency in the V. faba among different generation plants in EF bars indicate standard deviations
have not been exposed to chemicals. On the ba- sis of this observation, we may take the initial
F plants as the reference ones that have never
been experienced environmental mutagens in or- der to compare the others that have grown in
metal-contaminated soil for different years. If not specifically mentioned in the following text,
F
1
, F
2
and F
3
are referred, respectively to the F
1
, F
2
and F
3
generation that are obtained from metal-contaminated EF.
Dose – response curves in V. faba from differ- ent generations to Cd
2 +
treatments are given in Fig. 1. The dose-effect curve of F
was typical in toxicology, which increased MCN frequencies
with increasing Cd
2 +
level up to 20 mg l
− 1
, and decreased slightly when Cd
2 +
was over 20 mg l
− 1
. However, as shown in Fig. 1, the dose- effect curves for the following three generations
in response to Cd
2 +
treatment were obviously different, just representing increased MCN fre-
quencies with increased Cd
2 +
concentration, but at a lower incremental MCN level.
Regression analysis between Cd
2 +
dosage and MCN frequency in different generation plants
are given in Table 2. Because good linear regres- sions between Cd
2 +
concentrations and MCN values were observed in F
1
, F
2
and F
3
, even if the relationship in F
is not well linearly corre- lated, we may choose all the linear regression
slope to contrast with different generations in order to make these data sets comparable. In
general, the declined regression slope was ob- served in V. faba plants growing in the EF for
more generations. The slope values of F
, F
1
, F
2
and F
3
are respectively 0.069, 0.058, 0.048 and 0.034.
In response to NaN
3
treatment at different dose levels, MCN frequencies in root tips of Vi-
cia from different generations are illustrated in Fig. 2. For the same reason as stated above,
regression slopes are used to contrast relative increased MCN values RIV as to NaN
3
treat- ment between different generations even if F
1
and F
2
did not represent typical linear regres- sions between NaN
3
concentrations and MCN values. The regression equations between MCN
frequencies and NaN
3
treatments in different generations are listed in Table 2.
As shown in Fig. 2, the Vicia F plants, which
had never experienced contamination showed the lowest background value and constantly increas-
ing MCN value with increasing NaN
3
level. With regard to F
1
and F
2
generation, they shared a high background MCN value, keeping increase
with NaN
3
up to 20 and 10 mg l
− 1
, respectively. Judging from the regression slopes, F
plants kept the largest in RIV, and F
3
plants 0.23 had a lower RIV than F
’s 0.28; F
2
0.15 plants had a higher RIV than F
1
’s 0.14. Perturbation analysis results are given in Table
3. From Table 3, the sequence of perturbation value among generations was F
3
\ F
2
\ F
1.
Table 2 Regression between Vicia MCN frequency Y, MCN 1000 cells
− 1
and mutagenic treatment X, mg l
− 1
of Cd
2+
and NaN
3
in root tip of V. faba between different generations from EF
Vicia Cd
2+
NaN
3
Regression equation Correlation cooefficient
Regression equation Generation
Correlation cooefficient Y = 0.28X+9.69
0.931 F
Y = 0.069X+13.26 0.56
0.652 Y = 0.14X+14.68
0.86 F
1
Y = 0.058X+13.55 Y = 0.15X+12.83
0.557 F
2
Y = 0.048 X+10.93 0.99
0.90 Y = 0.034X+9.30
0.975 F
3
Y = 0.23X+8.21 PB0.05.
PB0.01.
Fig. 2. Dose effect relationship between NaN
3
treatment and MCN frequency in the V. faba among different generation plants in EF bars indicate standard deviations.
Table 3 Perturbation values in different generation plants of V. faba from EF
F Vicia generation
F
1
F
2
F
3
0.133 0.214
Perturbation value 0.303
0.102 Sensitivity to mutagens judging from perturbation value
F \
F
1
\ F
2
\ F
3
4. Discussion
