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Subject: Biochemistry × Author: Manne Hemanth Kumar × End date: 2023 × Start date: 2022 × Type: Thesis × Thesis Type: Ph.D ×
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    ThesisItemOpen Access
    Effect of exogenous sulphur in alleviating lead toxicity in Indian mustard [Brassica juncea (L.)]
    (CCSHAU, Hisar, 2023) Manne Hemanth Kumar; Nisha Kumari
    The Indian mustard [Brassica juncea (L.)] is one of the well-known plant for phytoextraction of heavy metals. The present study was designed to elucidate whether exogenously applied sulphur (S1; 100 ppm, S2; 200 ppm sulphur) alleviate lead (Pb)-induced (Pb1; 100 ppm, Pb2; 200 ppm and Pb3; 300 ppm Pb) stress in the leaves of Brassica juncea. Lead was applied in the form of lead nitrate five days prior to sampling and sulphur applied in the form of zinc sulphate at three days before sampling and samples were collected on 30, 60 and 90 DAS. Lead stress of 100, 200 and 300 ppm has considerably reduced plant growth as evidenced by increased H2O2 contents of 303.64, 317.39 and 238.89 % at 300 ppm of 30, 60 and 90 DAS, respectively, and they further caused the peroxidation of lipid membranes. This disruption increased more leakage of electrolytes, and created ionic imbalance. Further, alteration of chlorophyll pigment by replacing its central magnesium atom has reduced photosynthetic rate by 27.24 % at Pb3 stress, in respect to control. The redox status of the cell got altered by lead toxicity, depleting the AsA and GSH pool metabolites. Besides, GR, APX and POX antioxidative enzyme activities have shown highest increase under Pb3 stress by 51.97, 57.84 and 121.45 %, at 30, 60 and 90 DAS, respectively. In contrast, S application showed an increased AsA-GSH contents by 15.30, 9.40 and 7.89 % at S1 spray and 38.12, 23.44 and 33.40 %, respectively, at 30, 60 and 90 DAS at S2 spray. Sulphur-metabolites such as ATPS, OASTL and GST activities enhanced upon stress and resulted in further augmentation upon sulphur supplementation. Sulphur application to the Pb-stressed Brassica plants has reduced the oxidative stress by decreasing EL content by 11.69 % and MDA contents by 13.79 % at 90 DAS, respectively, in respect to Pb3-stressed plants. This decrease in oxidative stress biomarkers was due to an increase in AsA-GSH thiol pool and antioxidative enzyme enhancement under 100 and 200 ppm sulphur application to the Pb-stressed plants. Besides, S2 application to the Pb3+S2 stressed plants has increased phytochelatins by 522.47, 352.60 and 443.48 %, at 30, 60 and 90 DAS, respectively, in respect to Pb3 stress and called for PC-based detoxification of Pb. Furthermore, lead stress shown a decreased relative gene expression of BjSULT1.a gene and increased BjPb2.1, BjATPS1, BjOASTL2, BjABCC2 and BjGR1 gene expression. Moreover, S2 spray increased gene expression levels by 1.32, 1.49, 2.42 and 2.24 folds of BjSULT1.a, ABCC2, BjATPS1 and BjOASTL2, respectively, under Pb3 stress. Sulphur spray of S1 and S2 to the Pb-stressed Brassica juncea plants increased morpho-physiological parameters and yield and yield parameters. In the view of present findings, greater decrease of oxidative stress (H2O2, MDA and EL), increased enzymatic, non-enzymatic antioxidants, phytochelatins, enhanced relative gene expression levels and maximum seed yield was found under exogenous supplementation of 200 ppm sulphur and has ameliorated lead stress.