# Application of the _Aliium_ Test in Toxicity Studies of Lead and Copper: A Cytological Perspective
## 1 Introduction
\(Cu^{+2}\) is not only essential for the organism but is also widely used in agriculture; e.g., copper sulfate has proven to be an excellent fungicide against mildew [37] and other plants diseases [38]. The widespread use of copper in agriculture as a fungicide or fertilizer, as well as in the electrical industry and for water conduits, has highlighted the need for timely prevention of its toxic concentrations [39]. Although an essential metal, a \(Cu^{+2}\) intake of 10-20 mg/day can cause symptoms of toxicity, while very high doses exceeding 60 mg/day can lead to liver failure and in some cases, even death [39]. The legislative limits for copper across individual EU countries range from 75 to 1750 mg/kg DM (\(\equiv\)1.180 mM-27.539 mM) [35]. Taking into consideration the wide variability in limits across different countries regarding heavy metals, there is a need for an early warning system [34; 40; 41; 42; 43]. Utilizing bioindicators, such as the _Allium_ test, can serve as an effective tool for preventing soil contamination [44]. This approach enables the detection of concentrations of heavy metals and other chemicals that may not yet visibly affect plants but which could compromise their physiological processes, such as nutrient absorption and root system development [45]. The _Allium_ test was used as a bioindicator to monitor the genotoxicity of several heavy metals [46; 47; 48]. The advantages of using the _Allium_ test for cytological analyses are significant and make it appropriate as a bioindicator for heavy metals toxicology [49; 50; 51]. The _Allium_ test is a short-term test that offers the ability to monitor cellular processes such as mitotic activity and chromosomal aberrations, thereby evaluating DNA integrity under specific conditions or treatments [52]. It is widely used due to its cost-effective advantages for assessing potential risks of heavy metals in species like _Allium cpa_[53] but also in _Allium sativum_[54]. Another considerable advantage of the _Allium_ test is its high sensitivity, demonstrated through changes in the mitotic index rate or the occurrence of chromosomal aberrations [55; 56; 34; 57]. Furthermore, due to the large size of the cells and the easily observable chromosomal structures under a microscope, the test provides clear evidence of genotoxicity at specific concentrations of heavy metals [55; 34; 56]. Studies demonstrate that applying the _Allium_ test reveals modifications in mitotic division even at low concentrations, enabling the monitoring of various cellular abnormalities. These abnormalities include chromosomal bridges, lagging chromosomes, stickiness, binucleated cells, nuclear lesions, giant cells and c-mitosis [52]. In this study, we aimed to (i) investigate the cytological impact of lead (_Pb+_2) and copper (_Cu+_2) on the mitotic divisions of _Allium sativum_ L., focusing on parameters such as the mitotic index (MI) and the abnormalities index (AI), (ii) determine the concentration of lead and copper that inhibits the mitotic process by 50% (IC\({}_{50}\)), (iii) compare the different genotoxic effects of lead and copper, and to (iv) analyze the correlations between multiple cellular indices and parameters under exposure to heavy metals.