Agriculture Reference
In-Depth Information
3.2 Higher plants
Plants, despite their structure and metabolic differences, can offer important information
about the cytotoxic, genotoxic and mutagenic potential of substances, even when exposed in
short term and offer some advantages such as low cost cultivation and easy maintenance,
comparatively, to mammals (Rodrigues et al., 1997). In studies with complex mixtures,
plants have also shown satisfactory results, indicating that plants are sensitive enough to
detect the adverse effects of environmental samples (Majer et al., 2005).
Plants can be directly exposed to the contaminant, without any dilution or filtration of the
sample (Steinkellner et al., 1999). Moreover, Grant (1994) cites other advantages of
employing higher plants: (1) higher plants are eukaryotes, thus, their structure and cellular
organization are similar to that of humans and it is possible to establish comparisons with
animals; (2) the techniques employed for the study are relatively simple and can be
performed with agility; (3) cultivation of the organisms has low cost and easy maintenance;
(4) the assays can be carried out under a wide range of environmental conditions, pH and
temperature; (5) higher plants can regenerate easily; (6) assays with higher plants can be
used to assess the genotoxic potential of simple substances or even complex mixtures; (7) it
can be used for
in situ
monitoring
;
(8) can be used for monitoring for several years and are
highly reliable; (9) studies have shown correlations with cytogenetic assays in mammals;
(10) can be used together with microbial assays to detect mutagenic metabolites (pro-
mutagens); (11) genotoxicity studies with plants are presenting high sensitivity in tests with
carcinogenic agents.
On the other hand, according to Majer et al. (2005), one of the limitations of using plants as
bioindicators is the lack of sensitivity for certain classes of pro-mutagens such as the
nitrosamines, heterocyclic amines and some classes of PAHs. In contrast, Ventura (2009)
showed that the
A. cepa
system is susceptible to nitro aminobenzene, while Mazzeo (2009)
observed the same effect for benzene, toluene, ethylbenzene and xilene (BTEX).
Among the higher plants, onion (
A. cepa
) is the most used plant to determine the cytotoxic,
genotoxic and mutagenic effects of many substances present in the soil. Its cellular kinetics
characteristic favours a rapid growth of the roots, due to the great number of cells in
division. Therefore, the record of the mitotic activity and abnormalities in the cell cycle of
the meristematic cells of its roots can be easily visualized (Grant, 1994). Leme and Marin-
Morales (2009) affirm that the
A. cepa
test is a fast and sensitive technique to detect genoxotic
and mutagenic substances dispersed in the environment.
The evaluation of genetic alteration can be also performed using different species of the
genus
Tradescantia
(figure 3) through the detection of mutations induced by agents present
in the air, soil and water by the analysis of micronuclei in the mother cell of the pollen grain
(Trad-MCN). The species
Tradescantia
are specially indicated for direct application in regions
and countries in development due to the advantages such as easy handling and relatively
low maintenance cost (Shima et al., 1997).
Vicia faba
is a popular material that has been widely used not only in cytological studies, but
also in physiological experiments (Kanaya et al., 1994). This organism was initially used in
radiobiological tests in investigation of mechanisms of formation of chromosomal
aberrations by ionizing radiation (Read, 1959). Later, Kihlman (1975) developed and
standardized the
V. faba
meristematic cell bioassay for analysis of chromosomal aberrations,
and since then has been widely used for genotoxicity studies for evaluation of sister
chromatid exchange (Kihlman & Kronborg, 1976; Kihlman & Andersson, 1984). This
technique is very similar to
A. cepa
test; the method does not require sterile conditions or
