Translocation of Foliar-Applied Nanoparticles: A Critical Review From a Plant Science Perspective.

Recent advances in plant science have greatly enhanced agronomic practices involving the foliar application of agrochemicals such as fertilizers and pesticides. However, the limited phloem mobility of certain nutrients and nonsystemic pesticides reduces the effectiveness of these strategies. Nanoparticles (NPs) have emerged as promising carriers to improve nutrient use efficiency (NUE) and crop protection by enabling long-distance transport and targeted delivery of essential nutrients and active ingredients. While increasing evidence suggests that foliar-applied NPs can translocate within plants, a mechanistic understanding and agronomically relevant case studies remain scarce. As a result, the extent to which NP translocation can facilitate significant distribution and cargo release within plants is yet to be fully established. This review critically evaluates existing research on foliar NP translocation, emphasizing key findings within a plant science framework. Specifically, we examine how NP design can influence translocation and assess the existing quantitative data of NP remobilization within plants. Additionally, we explore how physiological processes affect NP transport and highlight alternative, often overlooked translocation pathways. Lastly, we assess current techniques used to study NP transport, discussing their applicability and limitations. This review identifies significant research gaps that must be addressed to advance nano-enabled plant nutrition as well as crop protection and can therefore be used to inspire future research.