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<p>Among abiotic stressors, heavy metal contamination poses a serious challenge to global agricultural productivity. Cadmium (Cd), a highly toxic heavy metal, adversely affects crop plant health as well as yield. Melatonin (MT), a promising plant growth regulator and signaling molecule, has recently gained attention for its potential role in enhancing plant tolerance to abiotic stresses. This study explores the impact of exogenous application of MT (100 µM) on the growth and physio-biochemical attributes of barley (<i>Hordeum vulgare</i> L.) subjected to varying levels of cadmium stress (0, 0.1, 0.5, 1.0 and 1.5 mM).&#xa0;Many growth traits, photosynthetic pigment content, antioxidant enzyme activities, cellular viability and osmolyte accumulation were evaluated. The germinating tray was filled with coco-peat and four different CdCl<sub>2</sub> solutions were added, both with and without foliar spraying 100 µM MT. The experiment was conducted in a greenhouse. The growth and physio-biochemical characteristics were evaluated at 30 days of seedling.&#xa0;It has been reported that Cd markedly reduced the growth biomarkers, chlorophyll contents, nitrate reductase (NR) activity by 11% and carbonic anhydrase (CA) activity by 13%, nitrogen (N) by 9%, phosphorus (P) by 9% and potassium (K) contents by 15% and significantly raised the enzymatic antioxidants like superoxide dismutase (SOD) by 38%, catalase (CAT) by 41%, peroxides (POX) by 41%, ascorbate peroxidase (APX) by 11%, glutathione reductase (GR) by 20%, glutahione S-transferase (GST) by 42%, glutathione peroxidase <b>(</b>GPX) by 41%, enhanced non-enzymatic antioxidants such as ascorbate (AsA), phenolic, carotenoids, glycine betaine (GB) by 53%, proline by 67% and stress indicator hydrogen peroxide (H<sub>2</sub>O<sub>2</sub>) by 31%, malondialdehyde (MDA) by 52% content and electrolyte leakage (EL) by 41%. However, the foliar application of MT to both control and Cd-stressed plants showed significantly improved growth traits, chlorophyll contents, NR and CA activities, N, P and K contents and also augmented enzymatic and non-enzymatic antioxidants, whereas it decreased the H<sub>2</sub>O<sub>2</sub> by 8%, MDA content by 10% content and EL by 10%. Further, confocal microscopy confirmed that Cd stress causes damage to the lipoprotein membrane and DNA of the root cells of the tested seedlings. However, MT application reverses this toxic effect and improves the viability of the root cells.&#xa0;The present study concluded that MT spray application proved to be an effective strategy in reducing Cd stress effects maximally.</p>

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Melatonin Mediated Modulation of Antioxidant Defense Machinery, Nutrient Homeostasis and Cellular Viability in Hordeum vulgare L. Under Cadmium Stress

  • 期刊论文

  • 发表日期：

    2026年1月22日

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  • Sandeep Kumar Barwal,
  • Sajad Hussain Shah,
  • Md Atikur Rahman,
  • Yerramilli Vimala

摘要

Among abiotic stressors, heavy metal contamination poses a serious challenge to global agricultural productivity. Cadmium (Cd), a highly toxic heavy metal, adversely affects crop plant health as well as yield. Melatonin (MT), a promising plant growth regulator and signaling molecule, has recently gained attention for its potential role in enhancing plant tolerance to abiotic stresses. This study explores the impact of exogenous application of MT (100 µM) on the growth and physio-biochemical attributes of barley (Hordeum vulgare L.) subjected to varying levels of cadmium stress (0, 0.1, 0.5, 1.0 and 1.5 mM). Many growth traits, photosynthetic pigment content, antioxidant enzyme activities, cellular viability and osmolyte accumulation were evaluated. The germinating tray was filled with coco-peat and four different CdCl2 solutions were added, both with and without foliar spraying 100 µM MT. The experiment was conducted in a greenhouse. The growth and physio-biochemical characteristics were evaluated at 30 days of seedling. It has been reported that Cd markedly reduced the growth biomarkers, chlorophyll contents, nitrate reductase (NR) activity by 11% and carbonic anhydrase (CA) activity by 13%, nitrogen (N) by 9%, phosphorus (P) by 9% and potassium (K) contents by 15% and significantly raised the enzymatic antioxidants like superoxide dismutase (SOD) by 38%, catalase (CAT) by 41%, peroxides (POX) by 41%, ascorbate peroxidase (APX) by 11%, glutathione reductase (GR) by 20%, glutahione S-transferase (GST) by 42%, glutathione peroxidase (GPX) by 41%, enhanced non-enzymatic antioxidants such as ascorbate (AsA), phenolic, carotenoids, glycine betaine (GB) by 53%, proline by 67% and stress indicator hydrogen peroxide (H2O2) by 31%, malondialdehyde (MDA) by 52% content and electrolyte leakage (EL) by 41%. However, the foliar application of MT to both control and Cd-stressed plants showed significantly improved growth traits, chlorophyll contents, NR and CA activities, N, P and K contents and also augmented enzymatic and non-enzymatic antioxidants, whereas it decreased the H2O2 by 8%, MDA content by 10% content and EL by 10%. Further, confocal microscopy confirmed that Cd stress causes damage to the lipoprotein membrane and DNA of the root cells of the tested seedlings. However, MT application reverses this toxic effect and improves the viability of the root cells. The present study concluded that MT spray application proved to be an effective strategy in reducing Cd stress effects maximally.