Phyto-toxicological effect of fipronil to plant seedlings: Assessing germination attributes, root-tip morphology, oxidative stress, and cellular respiration indices

Abstract

Pesticides including insecticides are applied in agricultural practices to control insect pests. However, their excessive usage often poses a severe threat to the growth, physiology, and biochemistry of plants. Here, responses of chickpea and greengram seedlings exposed to three fipronil (FIP) concentrations i. e. 100 (1×), 200 (2×) and 300 (3×) μg mL⁻¹ was evaluated under in vitro. Among doses, 3× had a greater negative impact on germination attributes, root-shoot elongation, vigor indices, length ratios, and survival of seedlings. Besides, the morphological distortion in root tips, oxidative stress generation, and cellular death in fipronil-supplemented root seedlings were observed under scanning electron (SEM) and confocal laser scanning (CLSM), respectively. A significant (p ≤ 0.05) and pronounced upsurge in plant stressor metabolites such as proline, malondialdehyde (MDA), electrolyte leakage (EL), hydrogen peroxide (H₂O₂) content, and antioxidants enzymes in plant seedlings further confirmed the fipronil toxicity. In addition, a concentration-dependent decrease in respiration efficiency (RE) and ATP content in FIP-treated seedlings was observed. Reduced mitotic index (MI) and numerous chromosomal anomalies (CAs) in root meristematic cells of seedlings are a clear indication of insecticide-induced cytotoxicity. Furthermore, a dose-dependent increase in DNA damage in root meristematic cells of greengram revealed the genotoxic potential of fipronil. Conclusively, fipronil suggested phyto and cyto-genotoxic effects that emphasize their careful monitoring in soils before application and their optimum addition in soil-plant systems. It is high time to prepare both target-specific and slow-released agrochemical formulations for crop protection with concurrent safeguarding of the soil.