Nanoparticle Size and Coating Chemistry Control Foliar Uptake Pathways, Translocation, and Leaf-to-Rhizosphere Transport in Wheat

Abstract

Nanoenabled foliar-applied agrochemicals can potentially be safer and more efficient than conventional products. However, limited understanding about how nanoparticle properties influence their interactions with plant leaves, uptake, translocation through the mesophyll to the vasculature, and transport to the rest of the plant prevents rational design. This study used a combination of Au quantification and spatial analysis to investigate how size (3, 10, or 50 nm) and coating chemistry (PVP versus citrate) of gold nanoparticles (AuNPs) influence these processes. Following wheat foliar exposure to AuNPs suspensions (∼280 ng per plant), adhesion on the leaf surface was increased for smaller sizes, and PVP-AuNPs compared to citrate-AuNPs. After 2 weeks, there was incomplete uptake of citrate-AuNPs with some AuNPs remaining on the outside of the cuticle layer. However, the fraction of citrate-AuNPs that had entered the leaf was translocated efficiently to the plant vasculature. In contrast, for similar sizes, virtually all of the PVP-AuNPs crossed the cuticle layer after 2 weeks, but its transport through the mesophyll cells was lower. As a consequence of PVP-AuNP accumulation in the leaf mesophyll, wheat photosynthesis was impaired. Regardless of their coating and sizes, the majority of the transported AuNPs accumulated in younger shoots (10−30%) and in roots (10−25%), and 5−15% of the NPs <50 nm were exuded into the rhizosphere soil. A greater fraction of larger sizes AuNPs (presenting lower ζ potentials) was transported to the roots. The key hypotheses about the NPs physical−chemical and plant physiology parameters that may matter to predict leaf-to-rhizosphere transport are also discussed.

Reducing Nitrogen Dosage in Triticum durum Plants with Urea-Doped Nanofertilizers

“…For that reason, only species able to cross the cuticle or penetrate through stomata (lacking cuticle coat) can be internalized in the leaves. In agreement with previous reports [54,55], our results confirm that nanoparticle surface dissolution (and consequently nutrient release) is not necessarily a limiting step to allow nutrients uptake through the leaves. This opens the door to the future development of ACP functionalized with other active species (besides fertilizers) for foliar applications.…”

Foliar Application of Zn Phosphite and Zn EDTA in Soybean (Glycine max (L.) Merrill): In Vivo Investigations of Transport, Chemical Speciation, and Leaf Surface Changes

“…Stomata may take up water and solutes, and even small particles may penetrate leaves through stomata. The mechanisms behind this process are still not fully understood (Avellan et al 2019;. It is possible that the uptake occurs by diffusion through a liquid water film in the stomata walls, which are formed by increasing the wettability of the stomata pores (Burkhardt 2010;.…”

Nanoscale Drug Delivery Systems: From Medicine to Agriculture

“…They found that "regardless of their coating and sizes, the majority of the transported AuNPs accumulated in younger shoots (10-30%) and in roots (10-25%), and 5-15% of the NPs <50 nm were exuded into the rhizosphere soil. A greater fraction of larger sizes AuNPs (presenting lower ζ potentials) was transported to the roots" (Avellan et al, 2019).…”