Standardization of bulb and root sample sizes for the Allium cepa test

Abstract

Although the Allium cepa test has been widely used to identify potentially cytotoxic and genotoxic pollutants in aquatic environments, variable non-standardized choices have been made regarding the number of plant bulbs and roots analyzed. We propose numbers for bulbs and roots per bulb when comparing the frequencies of micronuclei, mitotic anomalies and mitotic index with this test. Roots that had been treated with aqueous solutions, such as water samples collected in August 2007 from the Paraíba do Sul River at the Brazilian cities of Tremembé and Aparecida; negative and positive controls were used for bioassays. The presence of pollutants in the river water had been presumed based on our previous cytological data and an official report by the São Paulo State Environmental Agency (Brazil) on presence of fecal contaminants (Tremembé and Aparecida) and elevated dissolved aluminium (Aparecida) in the water under study. The sampling of ten bulbs and five roots per bulb was found adequate for comparative studies to evaluate with the A. cepa test the potential damage inflicted by pollutants in aquatic environments. Furthermore, even one bulb and one root per bulb was sufficient in discerning this damage, thereby shortening the time required to attain a statistically confident comparative evaluation. However, to allow for the use of statistical programs based on the evaluation of average values, and to avoid criticism based on genetic variability, we propose that three bulbs and three roots per bulb be considered as standard sample sizes for the A. cepa test.

Potential cytotoxic effect of Anilofos by using Allium cepa assay

“…Higher plants such as A. cepa, V. faba and T. paludosa have large monocentric chromosomes in reduced numbers and are accepted as suitable test material for the study of environmental mutagenesis (Rank and Nielsen 1998;Grover and Kaur 1999;Patra and Sharma 2002;Sharma and Vig 2012). Allium cepa assay is one of the best and extensively used system for the determination of cytotoxic and genotoxic impacts of pollutants, due to its sensitivity (Barberio et al 2011). Also, A. cepa showed a good correlation with the results from other established test systems using eukaryotic as well prokaryotic cells (Fiskesjö 1985;Yıldız et al 2009).…”

Mutagenicity of two herbicides widely used on soybean crops by the Allium cepa test

“…It is known that anaphase bridges are formed during an unequal exchange of chromatids or by breakage and fusion of chromosomes and chromatids, and these bridges can cause structural chromosomal mutations (El-Ghamery et al 2000). Chromosome stickiness has generally been inflicted by highly toxic agents and could lead cells to death (Barbério et al 2011). Usually, chromosome bridges are found when A. cepa suffers from clastogenic damage.…”

Bioassays with Plants in the Monitoring of Water Quality

“…This parameter predicts the root growth behavior, which is conducted by the frequency of cellular division in the root tissue. This index has been clearly correlated to the root length in the A. cepa test, as for instance decreasing in value with increasing concentrations of toxic metals like chromium and cadmium [46].…”

“…The mitotic index is a parameter that allows to estimate the frequency of cells in cell division, reflects cell proliferation and is regarded as an important parameter when determining the rate of plant root growth. Therefore, a low mitotic index (mitodepressive effect) characterize a few dividing cells [45][46] and is more frequently reported in the literature. This parameter predicts the root growth behavior, which is conducted by the frequency of cellular division in the root tissue.…”

“…Chromosomal aberration types detected may depend on DNA lesions and the cell cycle phase that is considered [46]. The mitotic anomalies often detected by the Allium test are: chromosome stickiness, multipolar anaphase, anaphasic bridge, c-mitosis or c-metaphase, and micronuclei (Figure 2).…”