Manganese-Integrated Carbon Nanobionic Agents for Accelerated Plant Growth and Enhanced Harvestable Yield

Abstract To meet escalating global food demands, plant nanobionics has emerged as a transformative strategy to modify the inherent spectral and metabolic inefficiencies of photosynthesis. This study reports the precursor-directed synthesis of two morphologically distinct manganese-integrated carbon nano-assemblies derived from quinine sulfate (Q-Mn) and tetrachloroterephthalonitrile (TCTPN-Mn). Precursor chemistry fundamentally dictated the resulting architectures, yielding 4.6 nm spherical nanoparticles for Q-Mn and extended 568 nm nanotubes for TCTPN-Mn. Benchtop time-domain nuclear magnetic resonance relaxometry revealed that the smaller dimensions of Q-Mn facilitated superior seed coat penetration and internal hydration (effective transverse relaxation time T2eff increased by 76%), driving accelerated early-stage vigor and a 73% increase in harvestable radish dry mass. Ex vivo Hill reaction assays confirmed that TCTPN-Mn nanotubes, which mainly integrated by wrapping around the isolated chloroplasts, yielded a 76% enhancement in electron transport rates. However, while TCTPN-Mn achieved substantial manganese accumulation (283% increase in root Mn), the high metallic load triggered a photoprotective stress response, characterized by a 25% reduction in total chlorophyll. In contrast, Q-Mn may have acted as a metabolic biostimulant. Untargeted metabolomics evidenced a significant upregulation of glutamic acid and ribose, providing the biochemical foundation for a 27% boost in chlorophyll biosynthesis and a 73% increase in harvestable yield. Our findings establish that a “less is more” benefit-to-risk ratio, governed by nanoparticle morphology and metallic loading, is essential for designing sustainable nanobionic interfaces that harmonize photonic capture with plant metabolic pathways.