Arsenic tolerance in Tagetes erecta L.: Phytoaccumulation, physicochemical and anatomical studies through electron microscopy

Arsenic (As), a toxic metalloid that is becoming more and more concentrated in the environment, poses risks to human health, plant production, and species at every trophic level through bioaccumulation and biomagnification. Finding tolerant and hyperaccumulative plant species that can be used in contaminated land is a potential eco-friendly strategy for As removal in terms of its mitigation. Tagetes erecta L. is an ornamental plant species chosen as phytoremediator plant for As removal. To assess the morphological and biochemical changes we conducted pot experiments with plants that were treated with different concentration of sodium arsenate (Na3AsO4) for up to 60 days. Atomic absorption spectrophotometer (AAS) was used to measure the amount of As absorbed in various tissues of the plant. Highest As accumulation was detected in root tissues (12.864 mg kg⁻¹), whereas shoot had least quantity of As (3.443 mg kg⁻¹). With increasing As concentrations, the maximum levels of proline and polyphenol were 14.743 µ mol g⁻¹ and 4.25 mg g⁻¹, respectively. At 60 days, antioxidant enzymes APX (6.952 mM mg⁻¹), CAT (2.143 mM mg⁻¹), and GR (76.631 mM mg⁻¹) were found to be increased. As transport and distribution were confirmed by anatomical analysis in root and shoot tissues by FESEM-EDX, TEM, and light microscopy. The results obtained after morpho-physiological and anatomical studies are in favor of high degree of tolerance of As concentration (25 mg kg⁻¹) by T. erecta suggesting that it could be a potential phytoremediator of As from polluted soil.