Lemna minor and Allium cepa Bioassays as Tools for Toxicity Assessment of Effluent from the Textile Industry

Abstract

Textile effluent (TE) contains azo dyes and hazardous chemicals, including heavy metals, making their discharges into aquatic environments as an emerging environmental issue, particularly in developing countries. This study evaluated the ecotoxicological impacts of TE using Allium cepa and Lemna minor bioassays. The toxicity of TE on L. minor was assessed using multiple endpoints, including frond number, growth rate, fresh/dry biomass, and chlorophyll contents. Exposure to TE concentrations (0–100%) for seven days exhibited a dose-dependent inhibition in growth, with a complete suppression of frond development at concentrations ≥30%. Chlorophyll-a, Chlorophyll-b, and total chlorophyll content also declined significantly with an inhibition approaching 100% at higher concentrations. In the Allium cepa assay, root growth inhibition, mitotic index (MI), chromosomal aberrations (CAs), and nuclear abnormalities (NAs) were evaluated after 48 h exposure to TE concentrations ranging from 0% to 100%. Root growth was severely inhibited at concentrations ≥25%, with a complete inhibition observed at higher concentrations. The MI decreased markedly from 68.73% in the control to 4.6% at 100% TE, while chromosomal and nuclear abnormalities increased significantly, confirming strong cytotoxic and genotoxic effects. EC50 values for chlorophyll-a inhibition ranged from 22.76% to 41.30%, while EC50 for total chlorophyll inhibition ranged from 30.38% to 39.72%, across the three effluent types. Overall, TE exerted significant concentration-dependent phytotoxic and genotoxic effects, confirming the suitability of L. minor and A. cepa as reliable bioindicators for textile effluent toxicity assessment and highlight the need for effective TE treatment to protect aquatic ecosystems and human well-being.