Coated Magnetite Nanoparticles and <i>Tillandsia usneoides</i> : More Friends Than Foes

Micronutrient delivery by nanotechnology is becoming an effective strategy in plant fortification and growth. Among element deficiencies, one of the most detrimental is Fe ion shortage, in that it may affect many physiological processes, including photosynthetic and respiratory pathways. Here, we used citrate-stabilized magnetite nanoparticles (FeCi) which were postengineered by coverage with polysaccharides of natural origin, to produce biocompatible iron carriers. Specifically, Aloe vera extracts (APS) and exopolysaccharides from Cyanospira capsulata (EPS) were chosen as capping agents for magnetite nanoparticles to facilitate the interaction with the model plant Tillandsia usneoides. The complex structure of these novel nanohybrids was elucidated by in-depth physicochemical characterization. In the plant specimens, treatment with FeCi complexed with APS by foliar spray improved the growth and photosynthetic activity. This was attributed to a 3–4 times increase in iron content. In turn, this evidenced a synergistic activity between the nanoparticles and the employed polysaccharides. These results open the way to new agricultural applications that may contribute to ameliorating both the yield and quality of crops.