The present study investigates ameliorative effect of silicon nanoparticles (SiNPs) and indole acetic acid (IAA) alone and in combination against hexavalent chromium (Cr^VI) toxicity in rice seedlings. The results of the study revealed protective effects of SiNPs and IAA against Cr^VI toxicity. The 100 μM of Cr^VI imposed toxic effects in rice seedlings at morphological, physiological and biochemical levels which coincided with increased level of intracellular Cr^VI and declined level of endogenous nitric oxide (NO). The Cr^VI enhanced levels of superoxide radicals (SOR) (59.51% and 50.1% in shoot and root, respectively) and H₂O₂ (19.5% and 23.69% in shoot and root, respectively). However, when SiNPs and IAA were applied to plants under Cr^VI stress, they enhanced tolerance and defence mechanisms as manifested in terms of increased biomass, endogenous NO, photosynthetic pigments, and antioxidants level. It was also noticed that Cr^VI arrested cell cycle at G2/M phase whereas growth was restored as compared to control when SiNPs and IAA were supplemented. Thus, the hypothesis that combined application of SiNPs and IAA will be effective in alleviating Cr^VI toxicity is validated from the results of this study. Moreover, in SiNPs and IAA-mediated mitigation of Cr^VI toxicity, endogenous NO has a positive role. The importance of the study will be that the combination of SiNPs and IAA can be utilized against heavy metal stress and even when supplied alone, they will enhance the crop productivity parameters with and without stress conditions.

本研究调查了硅纳米颗粒 (SiNPs) 和吲哚乙酸 (IAA) 单独和联合使用对水稻幼苗中六价铬 (Cr ^VI ) 毒性的改善作用。研究结果揭示了 SiNPs 和 IAA 对 Cr ^VI毒性的保护作用。100 μM C​​r ^VI在形态、生理和生化水平上对水稻幼苗产生毒性作用，这与细胞内 Cr ^VI水平增加和内源性一氧化氮 (NO) 水平下降相吻合。Cr ^VI提高了超氧自由基 (SOR)（在地上部和根中分别为 59.51% 和 50.1%）和 H ₂ O _{2 的水平}（分别在地上部和根中分别为 19.5% 和 23.69%）。然而，当 SiNPs 和 IAA 应用于 Cr ^VI胁迫下的植物时，它们增强了耐受性和防御机制，表现为增加的生物量、内源性 NO、光合色素和抗氧化剂水平。还注意到，当补充 SiNPs 和 IAA 时，Cr ^VI在 G2/M 期阻止细胞周期，而与对照相比，生长恢复。因此，假设，即SiNPs和IAA的联合应用将是有效地缓解铬^VI毒性从该研究的结果验证。此外，在 SiNPs 和 IAA 介导的 Cr ^VI毒性，内源性NO有积极作用。该研究的重要性在于，SiNPs 和 IAA 的组合可用于对抗重金属胁迫，即使单独供应，它们也会在有和无压力条件下提高作物生产力参数。