Shedding light on the mechanisms of absorption and transport of ZnO nanoparticles by plants via in vivo X-ray spectroscopy

Several factors have contributed to bring pressure on agriculture. In this context, nanomaterial properties can be explored to design more efficient fertilizers and therefore increase productivity. In the present study, the roots of Phaseolus vulgaris were immersed in several nano ZnO dispersions for 48 h. The absorption and transport phenomena were in vivo monitored by X-ray fluorescence spectroscopy (XRF) and X-ray absorption spectroscopy (XAS). The nanoparticle size, concentration and coating with surfactants affected the rate of Zn release and therefore its uptake. In vivo X-ray absorption spectroscopy showed that Phaseolus vulgaris takes up Zn bound to both citrate and malate, while entire nanoparticles were only absorbed when roots were injured. X-ray fluorescence microanalysis unravelled that besides xylem bundles, root to shoot Zn transport can take place through the cortex.