Abstract
ABSTRACTThis study aims at investigate how exogenous glutathione (GSH, 1.0 mM) affects the oxidative stress and antioxidant defense in wheat seedlings under lead (Pb) stress [0.5 and 1.0 mM Pb(NO3)2]. Lead treatment decreased growth, leaf relative water content, and chlorophyll (chl) content whereas raised proline (Pro) level. Lead stress increased H2O2 content, generation rate, and membrane lipid peroxidation. Addition of Pb also disrupted antioxidant enzyme activities and status of endogenous ascorbate and GSH pool. The increase of methylglyoxal was evident under Pb stress. Glutathione supplementation under Pb stress increased antioxidant redox pool and augmented the activities of antioxidant enzymes, and decreased ROS production. Exogenous supplementation of GSH reverted the increase in the methylglyoxal level due to Pb stress due to increased activities of glyoxalase enzymes. Exogenous GSH also regulated Pro, well-maintained tissue water status and prevented chl degradation and increased plant growth and biomass. Abbreviations: AO- ascorbate oxidase; APX- ascorbate peroxidase; AsA- ascorbic acid (ascorbate); BSA- bovine serum albumin; CAT- catalase; CDNB-1-chloro-2, 4-dinitrobenzene; chl- chlorophyll; DHA- dehydroascorbate; DHAR- dehydroascorbate reductase; DTNB- 5,5′-dithio-bis (2-nitrobenzoic acid); EDTA- ethylenediaminetetraacetic acid; Gly I- glyoxalase I; Gly II- glyoxalase II; GR- glutathione reductase; GSH- reduced glutathione; GSSG- oxidized glutathione; GPX- glutathione peroxidase; GST- glutathione S-transferase; MDA- malondialdehyde; MDHA- monodehydroascorbate; MDHAR- monodehydroascorbate reductase; MG- methylglyoxal; NADPH- nicotinamide adenine dinucleotide phosphate; NBT- nitroblue tetrazolium chloride; Pb- lead; PEG- polyethylene glycol; Pro- proline, ROS- reactive oxygen species; RWC- relative water content; SLG- S-d-lactoylglutathione; SOD- superoxide dismutase; TBA- thiobarbituric acid; TCA- trichloroacetic acid.
Highlights
Lead (Pb) is highly persistent and naturally occurring toxic metal (Schreck et al 2012)
Exogenous GSH application in Pb-treated seedlings showed a lower amount of MDA, H2O2 and O†2 − in the tissue and on the leaf surface and compared to Pb alone (Figure 1(A–C))
Histochemical recognition of H2O2 and O†2− in leaf Hydrogen peroxide and O†2 − were detected in wheat leaves by histochemical staining of DAB and nitroblue tetrazolium chloride (NBT)
Summary
Lead (Pb) is highly persistent and naturally occurring toxic metal (Schreck et al 2012). Lead contamination has been noticed in drinking and irrigation water, even in the air. Permissible quantity of Pb is not more than 5 mg L–1 of irrigation water (Ayers and Westcot 1985) whereas in soil, the allowable range is in 10–30 μg g–1. Lead contamination can reach 30– 2,000 μg Pb g–1. High water and soil Pb content have become acute environmental hazards (Silva et al 2017). Lead is spread from the environment and enters into the human body through food ingestion, water and air (Piano et al 2008; Cai et al 2015)
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