Uptake and transport of montmorillonite particles by wheat

Elucidation of the interactions of crop plants with clay minerals is essential to understanding the roles of clay minerals in terrestrial ecosystems. The prevailing hypothesis suggests that the physiological barriers of plant roots prevent the direct uptake of these large-size particles. However, whether crops can directly take up clay mineral particles remains unknown. Montmorillonite is a ubiquitous and important clay mineral in soils. This study used covalent fluorescence labelling and microscopic techniques were used to investigate the uptake and transport of montmorillonite particles by wheat (Triticum aestivum L.) in hydroponic cultures, sand matrices, and sandy soils. Additionally, the surface attachments of montmorillonite particles in xylem sap were analyzed at the nanoscale level with transmission electron microscopy, and atomic force microscopy combined with infrared spectroscopy. Our results confirmed that micrometer-sized montmorillonite particles enter the root steles of wheat seedlings from lateral root emergence sites and are subsequently transported upward to the shoots and leaves through the vasculature via the transpiration stream. In this process, the surfaces of the montmorillonites adsorb inorganic mineral nutrients and are covered by a layer of biomolecular corona. This study reveals the potential for plant uptake of micrometer-sized particles and complements existing theories regarding the interactions of clay minerals with crops. Furthermore, the findings may lay a foundation for future studies on clay minerals interactions with plants in terrestrial ecosystems.