Chitosan Nanoparticles as a Biostimulant During In Vitro Multiplication of Vanilla Using Temporary Immersion Bioreactors.

This research aimed to assess the effect of chitosan nanoparticles (ChNPs) during in vitro shoot proliferation of vanilla using temporary immersion bioreactors (TIB). TIB culture is a biotechnological process that uses semiautomated containers for the production of explants exposed in liquid culture medium. Concentrations of control, 25, 50, 100, 200, and 400 mg/L ChNPs were evaluated in Murashige and Skoog culture medium. Morphological characterization of ChNPs was performed using scanning electron microscopy. At 60 days of culture, survival (%), development variables, photosynthetic pigment content, lipid peroxidation expressed in malondialdehyde, total phenolic content (TPC), hydrogen peroxide (H2O2) content, and total antioxidant capacity (TAC) expressed in trolox equivalents were evaluated. The data were analyzed with analysis of variance, with a Tukey test (p ≤ 0.05) using SPSS statistics software, version 29. The results revealed that the greatest survival (%) was obtained at concentrations of control, 25, and 50 mg/L ChNPs, while the lowest survival (%) was observed at concentrations of 400 mg/L ChNPs. Growth stimulation was found, as well as an increase in chlorophyll and β-carotene at concentrations of 25 and 50 mg/L ChNPs. The level of H2O2 increased at 25 and 50 mg/L ChNPs. Lipid peroxidation showed no differences among treatments. TPC increased at 100 and 200 mg/L ChNPs, while TAC increased at 200 and 400 mg/L ChNPs. In conclusion, the administration of ChNPs at low concentrations can stimulate growth, while at high concentrations they can inhibit it, a response known as hormesis or hormetic effect.