Foliar application of nanoparticles: mechanisms of absorption, transfer, and multiple impacts†
Foliar spray of engineered nanoparticles (NPs) as nanofertilizers, nanopesticides, nanosensors, and nanocarriers is increasingly being employed in the agricultural industry. Foliar spraying of NPs improves the effectiveness of plant protection technologies compared to traditional soil–root application. Foliar-sprayed NPs mainly enter the leaves through stomata and are transported to different plant parts via apoplastic and symplastic pathways. Foliar NPs enhance defenses and resistance against pests and diseases and improve the yield and quality of crops. However, the mechanisms of damage caused by foliar NPs need further elucidation. Moreover, important factors limiting foliage uptake of NPs such as wax deposits on leaf surfaces, environmental factors (e.g., light, temperature, and humidity), and physical and chemical properties of NPs should be investigated to further improve this technology.