Comparative Effects of Indigenous Exiguobacterium Isolates and Pigment‐Associated Fractions on Chickpea Seed Germination and Early Seedling Growth

Microbial seed biostimulants may improve crop establishment while reducing reliance on synthetic inputs, but the relative contributions of viable cells, extracellular metabolites, and pigment‐associated fractions remain unclear. Here, three pigment‐producing Exiguobacterium isolates from the Sundarbans mangrove ecosystem of Bangladesh, E. mexicanum , E. alkaliphilum , and E. aestuarii , were comparatively evaluated for effects on chickpea ( Cicer arietinum ) germination and early seedling growth. Whole‐cell bacterial suspensions, cell‐free culture supernatants, and crude pigment‐associated extracts were tested at 1, 2, and 3 mg L ⁻¹ , with Luria–Bertani broth as control. Germination and seedling growth were monitored for 96 h using triplicate biological replicates, and germination indices and seedling vigor index (SVI) were calculated. The isolates showed 16S rRNA gene sequence identities of 98.13%–99.25% with reference taxa. Crude fractions yielded 48.6–53.6 mg L ⁻¹ and showed UV–visible (UV–vis) absorption maxima at 210.44–220.08 nm; Fourier‐transform infrared (FTIR) profiles indicated chemically heterogeneous functional groups, with no distinct 400–500 nm maximum supporting definitive carotenoid assignment. Whole‐cell preparations produced greater responses. E. aestuarii at 2 mg L ⁻¹ produced the highest germination (93 ± 1.5%) and SVI (124.62). Root and shoot lengths were strongly correlated ( r  = 0.95). These findings support further seed‐biopriming evaluation while indicating that activity cannot be attributed to pigment‐associated fractions alone.