Environmental and Experimental Botany 44 2000 83 – 92
Changes of reliability and efficiency of micronucleus bioassay in Vicia faba after exposure to metal
contamination for several generations
Changqun Duan
a,
, Bin Hu
a
, Tao Guo
a
, Mingbo Luo
a
, Xiaoyong Xu
a
, Xuexiu Chang
a
, Chuanhao Wen
a
, Ling Meng
a
, Liang Yang
b
, Huanxiao Wang
a
a
Department of Biological Sciences, Yunnan Uni6ersity,
52
N Greenlake St., Kunming, Yunnan
650091
, PR China
b
Yunnan Center for En6ironmental Monitoring, Yunnan
650232
, China Received 12 February 2000; received in revised form 18 February 2000; accepted 22 April 2000
Abstract
Mitotic root micronucleus MCN frequency in Vicia faba as a bioassay, is primarily based on the extent of the sentinel Vicia response in terms of cytogenetic damage quantitatively or qualitatively to indicate the presence of
mutagenic contaminants. This paper describes an investigation designed to assess changes in MCN frequencies of Vicia faba from three generation plants obtained, respectively from a reference site RS and a metal-contaminated
experimental field EF in the bioassay of mutagenic Cd
2 +
and NaN
3
. The background value, dose – response to Cd
2 +
and to NaN
3
in three generation F
1
, F
2
and F
3
plants of the EF and the initial F plants were determined
in terms of MCN frequencies. With more generations of growing Vicia plants in the EF, a higher background value of MCN frequency, a lower slope value in the regression equation, a smaller ratio of MCN frequency between the
control and treatment in the same generation and larger perturbation values were observed. This denotes that the decreased reliability and efficiency are represented in Vicia plants from the EF if the plants are used as sentinels in
the bioassay of mutagenic Cd
2 +
and NaN
3
. It was concluded that the Vicia MCN bioassay should be used as an endpoint biomarker acceptable in biomonitoring environmental mutagens when the sentinel plants were collected
from clean areas. Because no place is absolutely without pollutants, it is suggested that several seed stock centers should be established for providing sentinel Vicia if Vicia MCN bioassay is used as a biomarker to identify the global
environmental status. © 2000 Elsevier Science B.V. All rights reserved.
Keywords
:
Bioassay reliability; Environmental mutagens; Micronucleus test; Resistance; Vicia faba www.elsevier.comlocateenvexpbot
1. Introduction
The micronucleus MCN test in the root tip of Vicia faba has been widely used in biomonitoring
Corresponding author. Tel.: + 86-871-5032753; fax: + 86- 871-5153832.
E-mail address
:
chqduanynu.edu.cn C. Duan. S0098-847200 - see front matter © 2000 Elsevier Science B.V. All rights reserved.
PII: S 0 0 9 8 - 8 4 7 2 0 0 0 0 0 5 8 - 7
genotoxicity in water and soils. Some countries and international institutions, including China,
United States of America and United Nations Environmental Program UNEP have approved
this biomarker technique as a bioassay for the detection of environmental hazardous matter
Ma, 1982; CEPA, 1990; Ma et al., 1995. The Vicia MCN bioassay was improved by Ma et al.
1995 through scoring MCN frequency from the F
1
cells region of the root tip rather than from the meristematic region. Good reliability, short turn-
around time and low cost enable Vicia MCN test to have a promising future in biologically uncov-
ering the global environmental status, especially in the detection of environmental mutagens
Grant et al., 1992; Duan et al., 1994; Duan and Wang, 1995; Duan et al., 1999.
It has been well recognized that the mitotic root V. faba MCN bioassay as a biomarker, is the
measurement of cytogenetical damage that quan- titatively indicates the presence of mutagenic con-
taminants on the basis of the extent of the V. faba response to mutagens Ma, 1982; Ma and Harris,
1985; Grant et al., 1992; Butterworth, 1994; Grant, 1994; Duan and Wang, 1995. Thus, the
sensitivity to mutagens in V. faba, which is depen- dent on the response of test plants to mutagens in
term of MCN induction, is crucial to the reliabil- ity and efficiency of the Vicia MCN test applica-
ble to biomonitoring mutagens. Many researchers have revealed that a lot of plants have certain
potentials to evolve resistance sufficient not to present physiological or genetic damages after
they have experienced polluted environments for a certain time Ernst, 1976; Shaw and Albright,
1990; Dickinson et al., 1991, 1992; Prasad, 1995; Prus-Glowacki and Godzik, 1995; Duan, 1995,
1996. In another words, these plants may de- crease their sensitivities to mutagens if they have
been exposed. So we hypothesised: V. faba may become less sensitive to chemical mutagens after it
has been exposed to mutagen-stressed environ- ments, and the reliability and efficiency of Vicia
MCN test will be reduced if a bioassay is per- formed by use of such an already mutagen-ex-
posed sentinel V. faba.
To prove this, a 4-year field cultivation was conducted to obtain different generation plants
derived from the same variety of V. faba that had been successively planted in the experimental field
EF; three-generation seeds from the EF, to- gether with the seeds harvested from the reference
site RS, were used to determinate the back- ground values of MCN frequencies and the dose
effects between MCN frequencies and mutagenic chemical treatments; the reliability and efficiency
of Vicia MCN bioassay observed in the plants of the different generations were compared.
2. Materials and methods
