ALLEVIATION OF CADMIUM-TOXICITY BY APPLICATION OF ZINC AND ASCORBIC ACID IN BARLEY

ABSTRACT

Effect of cadmium (Cd) on biomass accumulation and physiological activity and alleviation of Cd-toxicity by application of zinc (Zn) and ascorbic acid in barley was studied, using semisolid medium culture including 15 treatments [four Cd concentration treatments: 0.1, 1, 5, 50 µmol L⁻¹, four treatments with addition of 300 µmol L⁻¹ Zn or 250 mg L⁻¹ ascorbic acid (ASA) based on these four Cd concentrations, respectively, and three controls: basic nutrient medium, and with Zn or ASA, respectively]. Cadmium addition to semisolid medium, at a concentration of 1, 5, and 50 µmol L⁻¹, inhibited biomass accumulation and increased malondialdehyde (MDA) content of barley plants, while the addition of 0.1 µmol L⁻¹ Cd increased slightly dry mass. There was a tendency to a decrease in Zn, copper (Cu) concentrations both in shoots and roots and iron (Fe) in shoots of barley plants exposed to 1 to 50 µmol L⁻¹ Cd. In addition, there were indications of a stress repose characterized by increased superoxide dismutase (SOD) and peroxidase (POD) activities relative to plants not subjected to Cd. The physiological changes caused by Cd toxicity could be alleviated to different extent by application of 300 µmol L⁻¹ Zn or 250 mg L⁻¹ ASA in Cd stressed plants. The most pronounced effects of adding Zn or ASA in Cd stressed medium were expressed in the decreased MDA and increased biomass accumulation, e.g., MDA contents were reduced (p≤0.01) by 4.8%–17.8% in shoots and 0.5%–19.7% in roots by adding 300 µmol L⁻¹ Zn, in 50 µmol L⁻¹ Cd stressed plants, and by 1.3%–7.4% in shoots and 2.6%–4.5% in roots by application of 250 µmol L⁻¹ ASA, respectively. However, ASA addition may enhance Cd translation from root to shoot, accordingly, ASA would be unsuitable for the edible crops grown in Cd contaminated soils to alleviate phytotoxicity of Cd.

Keywords:

• Barley (Hordeum vulgareL.)
• Cadmium (Cd)
• Biomass
• Physiological activity
• Stress mitigation

ACKNOWLEDGMENTS

This study was financially supported by higher education link program (SHA/992/310) of the British Council. High gratitude is expressed to the specialists Dr. Y-F. He and Dr. Q. Lin in the College of Environment and Resources for their technical assistance in the determining of heavy metal concentrations.