Manganese nanoparticles synthesized from hemp biomass waste modulate metabolic responses in soybean

Synthesis of nanoparticles (NPs) from plant material is a sustainable alternative to chemical synthesis. Manganese-based NPs were synthesized from the waste of two subspecies of Cannabis sativa and using two different salts (sulfate and nitrate). Nanoparticles synthesized from Cannabis sativa spp. indica were more stable (ζ = - 26.31 ± 0.49 mV and - 38.07 ± 0.33 mV) than those from ssp. sativa (ζ = - 0.77 ± 0.04 mV and - 9.89 ± 0.24 mV). Additionally, nanoparticles synthesized using sulfate were larger, but more stable than those synthesized using nitrate. The NPs' elemental composition was also different, NPs synthesized from ssp. sativa contained ∼2x more sodium and less potassium than nanoparticles synthesized from ssp. indica. Nanoparticles synthesized from ssp. indica significantly increased soybean's chlorophylls content (by 120 % and 126 %, synthesized from nitrate and sulfate, respectively; compared to control) and content of antioxidants (134 % and 140 %, synthesized from nitrate and sulfate, respectively; compared to control). These increases were greater than those caused by nanoparticles synthesized from ssp. sativa (111 % and 119 % for chlorophylls and 114 % and 106 % for antioxidants, compared to the control). Nanoparticles synthesized using nitrate significantly increased polyphenols content (158 % (for nanoparticles synthesized from sativa) and 116 % (for nanoparticles synthesized from indica, compared to control) more than nanoparticles synthesized using sulfate (123 % (for nanoparticles synthesized from sativa) and 110 % (for nanoparticles synthesized from indica), compared to control). These findings can help develop the method for synthesis of manganese nanofertilizers from hemp waste by influencing selection of subspecies and salt.