Role of Sulfur in Increasing Guinea Grass Tolerance of Copper Phytotoxicity

Soil pollution with trace elements is a growing problem with serious environmental impacts and developing strategies to reduce those impacts is a high priority. The objectives of this study were to assess the role of sulfur (S) in reducing the phytotoxic effects of copper (Cu) and the appearance of oxidative stress due to excess Cu in the growth medium and to assess the potential of guinea grass for Cu phytoremediation. The experiment was carried out in a greenhouse, where the forage grass Panicum maximum cv. Tanzânia was grown with a nutrient solution containing combinations of three S concentrations (0.1, 2, and 4 mmol L⁻¹) and four Cu concentrations (0.3, 100, 500, and 1,000 μmol L⁻¹) using a 3 × 4 factorial design in complete randomized blocks with four replicates. The following variables were measured: shoot and root dry mass production, leaf and tiller number, S and Cu concentrations in diagnostic leaves and roots, H₂O₂, lipid peroxidation, and proline levels in the diagnostic leaves. Very high Cu availability (1,000 μmol L⁻¹) that resulted in Cu concentration higher than 60 mg kg⁻¹ in diagnostic leaves caused more than 50 % reduction in shoot and root dry mass production about 30–40 % in the number of leaves and tillers around 20 % increase in lipid peroxidation and more than 10 times increase in proline production. Plants properly fed with S showed mitigation to Cu toxicity. Guinea grass showed promise as an agent in the phytoremediation of Cu-polluted areas.