Nano-priming with calcium silicate nanoparticles (CaSiO3NPs) promotes germination, seedling growth, and antioxidant enzyme activity in Iraqi rice genotypes under drought stress

Drought is a major abiotic stress limiting rice (Oryza sativa L.) cultivation in Iraq.This study aimed to enhance germination, early seedling growth, biochemicals, and antioxidant enzymes activity in Iraqi rice genotypes under drought stress through nano-priming with calcium silicate nanoparticles (CaSiO₃NPs).Seeds of three rice genotypes: 'Amber', 'Furat', and 'Yasmine' were primed with CaSiO₃NPs at 0.01%, 0.02%, 0.03%, and 0.05%, alongside a non-primed control.Results showed that primed seeds significantly improved, though differed among rice genotypes.'Furat' showed the highest germination percentage (GP; 90%) and germination index (GI; 9.35 and 9.05) at 0.03%-0.05%,compared to control (GP 63.2% and GI 5.93).Shoot length increased in all genotypes, with 'Furat' showing more than a two-fold higher (8.78 cm and 9.08 cm) at 0.02%-0.03%compared to control (3.82 cm).'Yasmine' showed the highest root length and seedling length at 0.02% (8.68 cm-fourfold that control 1.92 cm) and at 0.02% (18.79 cm vs. 11.24cm in the control).Seed vigour was the highest in 'Furat' at 0.03%, showing 2.6-fold increase (12.0 vs. 4.6 in the control).Compared to control, total chlorophyll highest in 'Yasmine' (10.49mg mL -1 ) at 0.03%, total sugar in 'Furat' (74.56 mg mL -1 ) at 0.05% showed more than one-fold higher while total protein three-fold higher in 'Amber' (21.36 mg g -1 fwt) at 0.03%.Catalase activity increased nearly two-fold in 'Yasmine' (0.42 U g -1 FW) at 0.03%.The ascorbate peroxidase activity increased in 'Amber' (0.32 U g -1 FW) and 'Furat' (0.34 U g -1 FW) at 0.01%.In conclusion, CaSiO₃NPs nano-priming is a promising strategy to enhance rice cultivation in Iraq.