Comprehensive toxicity screening of Pazarsuyu stream water containing heavy metals and protective role of lycopene

In this study, heavy metal pollution in the Pazarsuyu stream of Giresun province and the protective role of lycopene against the toxicity caused by this pollution were investigated using the Allium test. Germination percentage, root length and weight gain as physiological markers of toxicity; mitotic index (MI), micronucleus (MN) and chromosomal aberrations (CAs) as genetic markers of toxicity; malondialdehyde (MDA) level, superoxide dismutase (SOD) and catalase (CAT) activities as biochemical markers of toxicity, and meristematic cell damages were used as anatomical markers. For this aim Allium cepa L. bulbs were divided into six groups and germinated for 72 h with 215 mg/L and 430 mg/L doses of lycopene, tap water and stream water. Heavy metals pollution was analyzed with ICP-MS and Fe > Sr > Ba > Be > Mo > Li were determined according to the rate of presence in the water samples of Pazarsuyu. As a result, germination-related parameters and meristematic cell proliferation of bulbs germinated with Pazarsuyu water samples decreased significantly. Germination percentage, root length and weight gain of the group treated with Pazarsuyu water samples were decreased 50%, 73% and 68%, respectively compared to control. In addition, MN and CAs frequencies, indicating the genotoxic effects, were increased and significant abnormalities were detected in MDA, SOD and CAT levels, which indicate the deterioration of antioxidant/oxidant balance. CA observed with high frequency was also confirmed by DNA fragmentation determined by the Comet test. Stream water application promoted anatomical damages such as epidermis and cortex cell damage, accumulation of some substances in cortex cells, flattened cell nucleus and non-apparent appearance of conduction tissue in root tip meristem cells. All these abnormalities observed in A. cepa root tip cells were associated with the presence of heavy metals in the water samples. Simultaneous application of lycopene with stream water reduced the effects of heavy metals and resulted in a dose-dependent improvement in all parameters studied. Lycopene application showed a protective role by providing an increase in germination parameters and MI, decrease in MN and CAs frequencies, and improvements in MDA, SOD and CAT activities. As a result, heavy metals detected in the water samples of Pazarsuyu stream caused multiple toxicities in the bio-indicator plant, and lycopene reduced this toxicity and recorded a protective role.