Drought has a direct impact on rice growth performance at various stages. Nevertheless, the impact of nanoparticles on the rice seedlings under drought stress remained limited. Thus, a laboratory experiment was conducted to investigate the effects of different concentrations (300, 600, and 900 mg/L) of silica nanoparticles (SiNPs) on morpho-histological and biochemical features of two rice varieties (UMT-R and MR219) under drought stress (15 % PEG). The findings indicated a substantial reduction due to drought stress in the growth, protein, and antioxidant enzymes, while increasing the proline, malondialdehyde (MDA), and hydrogen peroxide (H2O2) content, and negatively affecting the root histology. Results showed that SiNPs at 600 mg/L were managed to improve plant growth, root vigour, and enzymatic antioxidant levels. Under SiNPs treated plants, among UMT-R and MR219, the proline (1.947 and 1.748 in leaves, 2.010 and 1.890 U/mg protein in roots), peroxidase (POD) (2.850 and 3.512 in leaves, 2.521 and 2.952 U/mg protein in roots), superoxide dismutase (SOD) (3.958 and 4.558 in leaves, 4.296 and 4.606 U/mg protein in roots), and catalase (CAT) (2.171 and 2.289 in leaves, 1.897 and 2.050 U/mg protein in roots) were higher than the drought stress conditions. Meanwhile, the nonenzymatic antioxidant, MDA (0.974 and 0.812 in leaves, 0.842 and 0.778 U/mg Protein in roots), and H2O2 (1.378 and 1.229 in leaves, 1.280 and 1.054 U/mg Protein in roots) showed an opposite trend. SiNPs application noticeably enhanced the histological features of roots under drought conditions. The current findings suggested that SiNPs at 600 mg/L can mitigate the adverse impacts of drought stress and enhance the plant's resistance. Further study should be carried out on the reproductive stage and post-harvest performance of drought-stress rice treated with SiNPs.

Effects of silica nanoparticles on morpho-histological and antioxidant activities of rice seedlings under drought stress