Pb tolerance in Echinodorus grandiflorus through the maintenance of root growth, nutrient uptake, and changes in the root cortical anatomy

Abstract

Lead (Pb) is a toxic pollutant for plants and animals that has increased in abundance worldwide; and aquatic environments are among those sensitive to Pb contamination. This study aimed to evaluate the effects of Pb on nutrient uptake, growth, and root anatomy in Echinodorus grandiflorus. Experiments were established with E. grandiflorus plants exposed to 0, 0.75, 1.5, 3.0, and 9.0 μM Pb(NO₃)₂ in nutrient solution. The plants were kept under these conditions for 60 days. At the end of the experiment, the concentrations of lead, macro-, and micronutrients, plant growth, and changes in root anatomy were evaluated. E. grandiflorus absorbed Pb proportionally to the concentrations applied in the nutrient solution. The species also showed changes in the absorption of N, P, K, Mg, S, Ca, Cu, Mn, Zn, and Fe. However, at all Pb concentrations, the modified absorption of these nutrients was still adequate for the plant and did not demonstrate evident toxicity. Root growth was not significantly altered, and root anatomy analysis revealed increased proportions of aerenchyma in the cortex to the detriment of exodermis and even endodermis at higher Pb concentrations. Therefore, E. grandiflorus plants demonstrate the potential for remediating Pb-contaminated environments due to their ability to absorb Pb without nutritional disturbances or disruptions in root structure and growth.