Synergistic effects of low-concentration nanoparticles and Bacillus megaterium on the growth of roses and rhizosphere microbial communities

This study explores the interactions between SiO₂-NPs, ZnO-NPs, and Bacillus megaterium and their potential effects on the growth and rhizosphere microbial communities of roses with the development of nanotechnology applications in agriculture.

At concentrations of 10 ppm ZnO-NPs and 1 ppm SiO₂-NPs, favorable coexistence with Bacillus megaterium was observed. Therefore, six treatment groups were established: water control (CK), Bacillus megaterium (Bm), 10 ppm ZnO-NPs (ZnO-NPs10), 1 ppm SiO₂-NPs (SiO₂-NPs1), Bacillus megaterium & 10 ppm ZnO-NPs (BZ), and Bacillus megaterium & 1 ppm SiO₂-NPs (BS). These groups were studied to evaluate their effects on morphological growth, photosynthetic pigments, soluble sugars, soluble proteins, flavonoids, and soil enzyme activities in roses. Additionally, 16 S rRNA high-throughput sequencing was used to analyze changes in the rhizosphere microbial communities.

Different nanoparticle treatments and Bacillus megaterium promoted plant height, stem thickness, and root vitality in roses. The BZ treatment significantly enhanced photosynthetic pigments. However, total flavonoid content, soluble substances, and soil nitrate reductase (NR) activity did not significantly change across all treatments. ZnO-NPs10 treatment significantly increased soil nitrite reductase (NIR) and dehydrogenase (DHA) activities. Furthermore, there were no significant impacts on the rhizosphere microbial communities, as indicated by the Shannon and Chao indices, although some fluctuations were observed. Functional prediction of the rhizosphere communities indicated primary functions in cell cycle control, amino acid transport and metabolism and carbohydrate transport and metabolism.

This study demonstrated that the application of SiO₂-NPs, ZnO-NPs, and Bacillus megaterium at low concentrations positively influenced rose growth by enhancing plant height, stem thickness, biomass, and root vitality. While the impact on photosynthetic pigments, soil enzyme activity, and microbial community composition was limited, the absence of negative effects on soil microorganisms suggests the safety of these treatments. Future research should focus on long-term effects and explore the metabolic mechanisms underlying plant-soil interactions to further optimize sustainable agricultural practices.