Mitigative effect of green tea extract against mercury(II) chloride toxicity in Allium cepa L. model

Abstract

Mercury (Hg) is a highly toxic heavy metal for all organisms. In the present study, the mitigative role of 190 mg/L and 380 mg/L doses of green tea extract (GTex) against mercury(II) chloride (HgCI 2 )-induced toxicity was evaluated in Allium cepa L. For this aim, selected physiological, genotoxicity, and biochemical parameters as well as meristematic cell injuries in the roots were investigated. Ratios of catechin and caffeine in GTex were determined by HPLC analysis. Also, free radical scavenging activity of GTex was tested against superoxide and hydrogen peroxide radicals. As a result of HgCI 2 application, germination percentage, root elongation, weight gain, and mitotic index (MI) declined, while the frequency of micronucleus (MN), chromosomal abnormalities (CAs), and meristematic cell damages increased. HgCI 2 administration also led to a significant increase in malondialdehyde content, superoxide dismutase, and catalase activities which are signs of oxidative stress. On contrary, applications of GTex together with HgCI 2 reduced HgCI 2 -induced adverse effects in all parameters in a dose-dependent manner. Antioxidant components in GTex were listed as caffeine, epigallocatechin gallate, epigallocatechin, epicatechin gallate, and catechin according to their abundance. GTex exhibited a strong scavenging ability in the presence of superoxide and hydrogen peroxide radicals. The present study revealed the strong protective capacity of GTex against HgCI 2 -induced toxicity in A. cepa owing to its high antioxidant content with a multifaceted perspective. With this study, a reliable starting point was established for future studies investigating the more common and diverse use of GTex against toxic substances.

Effect of Plant Growth-Promoting Bacteria on Biometrical Parameters and Antioxidant Enzymatic Activities of Lupinus albus var. Orden Dorado Under Mercury Stress

“…Another consequence of Hg exposure is the appearance of oxidative stress with the accumulation of reactive oxygen species (ROS) ( Çavuşoğlu et al, 2022 ) and an increase in the antioxidant enzymatic response ( Kim et al, 2017 ). When plants exceed the threshold of tolerance to heavy metals, their metabolism can be altered, cellular homeostasis is compromised, electron transport chains and the functioning of lipids and proteins are altered, DNA damage is produced and activates the antioxidant defense system ( Yang et al, 2018 ).…”

“…This should not be interpreted as a lack of activity per se , but rather the death of the seeds in the absence of PGPB treatment that neutralizes Hg toxicity, as occurs in treatments with PGPB 18, 23, 41, and 69I. The molecular mechanisms by which heavy metals induce ROS formation are not well described, although they have been shown to induce oxidative stress ( Cargnelutti et al, 2006 ; Ajitha et al, 2021 ; Çavuşoğlu et al, 2022 ). Traditionally, the accumulation of ROS has been considered a negative effect on plants, the prelude to the cell degradation process.…”

“…However, there is evidence that it can be a nuclear part of the cellular response system ( Flores-Cáceres, 2013 ), being able to act as secondary messengers that regulate growth and development functions ( Foyer and Noctor, 2005 ). Consequently, it is important for the plant to control the concentration of ROS, but not to eliminate them completely ( Çavuşoğlu et al, 2022 ). In this sense, Kim et al (2017) studied the role of GR in mitigating the toxicity of Hg (and other heavy metals) on the development of Arabidopsis thaliana .…”

“…Plant tolerance to abiotic stress depends, to a large extent, on the bacteria present in its rhizosphere to mitigate the harmful effects of pollutants ( Gontia-Mishra et al, 2016 ; Mariano et al, 2020 ; González et al, 2021a ). Additionally, these bacteria have been used to improve plant resistance to different abiotic stress situations, such as salinity or desiccation ( Ali et al, 2022 ), as well as the oxidative stress produced by Hg ( Ajitha et al, 2021 ; Çavuşoğlu et al, 2022 ). However, no references have been found verifying the potential of PGPB in reversing lethality resulting from exposure to high Hg concentrations.…”

Evaluation of the oxidative stress alleviation in Lupinus albus var. orden Dorado by the inoculation of four plant growth-promoting bacteria and their mixtures in mercury-polluted soils

“…The use of plant growth-promoting bacteria (PGPB) in soils contaminated with Hg has traditionally focused on the phytoextraction of this metal, as well as on the direct promotion of plant growth ( Gontia-Mishra et al, 2016 ; Mariano et al, 2020 ; González et al, 2021a ). These bacteria have also been used to improve the resistance of plants against different situations of abiotic stress such as salinity or desiccation ( Ansari et al, 2021 ; Ha-Tran et al, 2021 ; Khalilpour et al, 2021 ; Ali et al, 2022 ), as well as the oxidative stress produced by Hg ( Cho and Park, 2000 ; Cargnelutti et al, 2006 ; Ajitha et al, 2021 ; Quiñones et al, 2021 ; Çavuşoğlu et al, 2022 ). To alleviate the harmful effect of pollutants, plants rely heavily on bacteria present in their rhizospheres.…”