Improved photosynthetic performance induced by Fe 3O4 nanoparticles

Abstract

Interaction between 11 nm-sized magnetite nanoparticles and Cichorium intybus plants was studied in this work. In particular, the efect of these nanoparticles on the photosynthesis electron chain was carefully analysed. Magnetite nanoparticles were synthesised and physically characterised by Transmission electron microscopy (TEM), Scanning electron microscopy (SEM)), Energy-dispersive X-ray spectroscopy (EDS), Fourier transform infrared spectroscopy (FTIR), Magnetic hysteresis cycles and UV–visible spectroscopy. Suspensions of the obtained magnetite nanoparticles with diferent concentrations (10–1000 ppm) were sprayed over chicory leaves and their photosynthetic activity was evaluated using chlorophyll fuorescence techniques. The study was complemented with the determination of pigment concentration and spectral refectance indices. The whole set of results was compared to those obtained for control (non-treated) plants. Magnetite nanoparticles caused an increment in the content of Chlorophyll a (up to 36%) and Chlorophyll b (up to 41%). The ratio Chlorophyll/ Carotenoids signifcantly increased (up to 29%) and the quotient Chlorophyll a/b remained relatively constant, except for a sharp increase (19%) at 100 ppm. The refectance index that best manifested the improvement in chlorophyll content was the modifed Normalised Diference Vegetation Index (mNDI), with a maximum increase of about 35%. Electronic transport fuxes were favoured and the photosynthetic parameters derived from Kautsky’s kinetics were improved. An optimal concentration of nanoparticles (100 ppm) for the most benefcial efects on photosynthesis was identifed. For this dose, the probability by which a trapped electron in PSII was transferred up to PSI acceptors (ΦRE0) was doubled and the parameter that quantifes the energy conservation of photons absorbed by PSII up to the reduction of PSI acceptors (PIABS total), augmented fve times. The fraction of absorbed energy used for photosynthesis increased to 86% and the energy lost as heat by the non-photochemical quenching mechanism was reduced to 31%. Beyond 100 ppm, photosynthetic parameters declined but remained above the values of the control.