Synthesis of hydroxyapatite nanoparticles and its effect on Raphanus sativus seedlings

Abstract

The potential of nanofertilizers to increase crop yields has recently
been reported. Hydroxyapatite nanoparticles (nHAp) are applied as
fertilizers to plants due to their high content of P and Ca (Ca₁₀(PO₄)₆(OH)₂),
but there is little information in this regard. The objective of the work was to
produce synthetic nHAp, characterize it and evaluate its effect as a nutrient in
the development of seedlings of radish (Raphanus sativus) variety Champion.
The synthesis of nHAp was carried out using an aqueous solution of calcium
hydroxide [Ca(OH)₂] and orthophosphoric acid (H₃PO₄). To analyze its biological
effect, a bioassay was established with seven treatments on radish seeds with the
following concentrations: control (distilled water, T1); 25 (T2); 50 (T3); 100 (T4);
200 (T5); 500 (T6) and 1000 mg L^-1 (T7); the seedlings developed up to seven
days after sowing. The results show that a concentration of 1 000 mg L^-1 reduced
germination by 14.4% compared to the control treatment (0 mL^-1). While the vigor
of the seedlings was reduced 11.2% with 500 mg L^-1. The plumule and radicle
did not show significant differences by the treatments with respect to the control,
however, a statistical difference was observed with the doses of 25 and 200 mg
L^-1, when inhibiting and promoting the growth of the seedlings, respectively. High
concentrations of nHAp were found to have adverse effects on seeds. Finally, then HAp stimulated biomass production.