Biogenic synthesis of zinc oxide nanoparticles from flower extract of Viola odorata and zinc biofortification of rice using its effects on seed germination and growth

Background

Zinc is a crucial micronutrient for plant growth and metabolism, but its supplementation through chemical fertilizers poses environmental and health risks. This study introduces a novel, eco-friendly approach using Viola odorata flower extract for the green synthesis of zinc oxide nanoparticles (ZnO NPs), aimed at improving rice growth and zinc biofortification. The novelty of this research lies in the use of Viola odorata, a plant not previously reported for nanoparticle synthesis, and the application of its biogenic ZnO NPs to enhance the nutritional content and early development of rice seedlings.

Methods

ZnO NPs were synthesized using Viola odorata extract and characterized through UV–Vis spectroscopy, XRD, FT-IR spectroscopy, SEM, TEM, and EDX. The effects of varying ZnO NP concentrations were evaluated on rice seed germination, seedling growth, and zinc uptake.

Results

UV–Vis spectroscopy revealed a characteristic absorption peak at 375 nm, confirming ZnO NP formation. XRD indicated a cubic crystalline structure with an average size of 17.08 nm. FT-IR analysis confirmed functional groups involved in synthesis. SEM and TEM showed spherical particles ranging from 20 to 50 nm, while EDX confirmed the elemental composition of zinc and oxygen. Application of 10 mg/L ZnO NPs significantly enhanced germination rate, seedling biomass (4.5 g/L vs. 1.2 g/L in control), and seedling length (12.8 cm vs. 8.9 cm in control). Zinc content in rice seedlings increased to 0.71 mg/kg (at 20 mg/L) and 0.65 mg/kg (at 10 mg/L), compared to 0.42 mg/kg in the control group.

Conclusion

This study demonstrates that biogenic ZnO NPs synthesized using Viola odorata effectively enhance rice seedling growth and zinc biofortification. The findings highlight the potential of green nanotechnology in sustainable agriculture and suggest that such approaches can contribute meaningfully to crop nutrition and productivity. Further field-based studies across different crops are recommended to validate these results.