Abstract
Due to rising concerns for environmental and human health, many toxic compounds, such as auxin-based herbicides, have been tested in relation their toxicity effect. Especially cyto- and phytotoxic assays have been performed on a number monocot and eudicot plant species. In these approaches the toxicity level of the auxin is compared to a positive control – usually a commercial compound with known effects and chemical similarity to the target compound. However, many target compounds still lack an indication of an adequate positive control. Here, we evaluate the phytotoxic and cytotoxic effect of the auxins 2,4-dichlorophenoxyacetic acid, dicamba, and picloram in order test their potential use as positive controls. All tested auxinic herbicides showed clastogenic and aneugenic effect mechanisms. The results indicate 2,4-dichlorophenoxyacetic acid as the most phyto- and cytotoxic in the discontinuous method in Lactuca sativa L. and Allium cepa L., and also in the continuous method in A. cepa. Thus, we suggest 2,4-dichlorophenoxyacetic acid as a positive control for future mutagenesis studies involving new auxins. For studies with L. sativa in continuous method, we recommend the auxin picloram as positive control as this one was the only one which allowed the development of roots.
Highlights
The extensive and indiscriminate use of herbicides has provoked rising concerns about the environment and human health (Ribeiro & Lima 2011, Boccolini et al 2013, Fagundes et al 2015)
Phytotoxicity assays test the toxic effect of the target compound on germination and initial development of the seedlings, while cytotoxicity assays evaluate the damage in the cell cycle, in the chromatin and in the chromosome number (Andrade et al 2008, 2010, Fernandes et al 2009, Aragão et al 2017, Costa et al 2017, Silveira et al 2017)
Herbicides solutions The herbicides picloram (Sigma – Aldrich, ≥98%), dicamba (Sigma life Science, ≥98%) and 2,4-D (Sigma life Science, ≥98%) were used at 0.01% — the same concentration recommended for commercial glyphosate (N-(phosphonomethyl) glycine acid equivalent and inert ingredients), which we applied as positive control (PC)
Summary
The extensive and indiscriminate use of herbicides has provoked rising concerns about the environment and human health (Ribeiro & Lima 2011, Boccolini et al 2013, Fagundes et al 2015). Phytotoxicity assays test the toxic effect of the target compound on germination and initial development of the seedlings, while cytotoxicity assays evaluate the damage in the cell cycle (mitotic index, nuclear alterations), in the chromatin (structural aberrations) and in the chromosome number (eu- and/or aneuploidy) (Andrade et al 2008, 2010, Fernandes et al 2009, Aragão et al 2017, Costa et al 2017, Silveira et al 2017). These assays allow to classify the target compound according to its effect mechanism as clastogenic and/or aneugenic (Vidaković-Cifrek et al 2002)
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