UTTAR PRADESH JOURNAL OF ZOOLOGY

Chitosan is a biodegradable biopolymer with potential agricultural applications, but its concentration-dependent effects during early crop establishment require careful evaluation. In this study, chitosan was extracted from shrimp shell waste, characterised by Fourier-transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM), and assessed for its effects on mustard (Brassica juncea (L.) Czern) seed germination and early seedling growth under in vitro conditions. Seeds were exposed to 0, 25, 50, 75 and 100 mg L⁻¹ chitosan, and germination percentage, shoot length, root length, total seedling length, seed vigour index (SVI), relative root elongation (RRE), tolerance index (TI), phytotoxicity, biomass and moisture content were evaluated. FTIR analysis indicated characteristic functional groups of chitosan, including peaks at 3449 cm⁻¹ (O–H/N–H stretching), 3233–2888 cm⁻¹ (C–H stretching), 1560 cm⁻¹ (N–H bending), and 1399, 1280 and 1033 cm⁻¹ (C–N/C–O stretching). SEM showed a porous, rough and heterogeneous surface. The control recorded the highest shoot length (5.10 ± 0.41 cm), root length (5.70 ± 0.70 cm), germination percentage (86.15 ± 0.04%) and SVI (930.42). Increasing chitosan concentrations progressively reduced all growth parameters, with the greatest inhibition at 100 mg L⁻¹, where shoot length, root length and SVI declined to 1.16 ± 0.19 cm, 1.34 ± 0.36 cm and 129.22, respectively. Phytotoxicity increased from 24.27% at 25 mg L⁻¹ to 76.48% at 100 mg L⁻`¹, while moisture content remained comparatively stable (89.75–91.11%). Linear regression confirmed strong dose-response relationships (R² = 0.939–0.994), with estimated IC₅₀ values of approximately 56–70 mg L⁻¹. The findings indicate that shrimp shell-derived chitosan can inhibit mustard germination and early growth above a concentration-dependent threshold, supporting the need for dose optimisation before agricultural application.