期刊
ACS NANO
卷 13, 期 5, 页码 5291-5305出版社
AMER CHEMICAL SOC
DOI: 10.1021/acsnano.8b09781
关键词
foliar application of nanoparticles; uptake pathways; in planta translocation; root exudation; agriculture; enhanced dark-field microscopy coupled with hyperspectral imaging; X-ray fluorescence mapping
类别
资金
- U.S. Department of Energy (DOE) Science User facility [302315]
- National Science Foundation (NSF)
- Environmental Protection Agency (EPA) under NSF [EF-0830093, DBI-1266252]
- Center for the Environmental Implications of NanoTechnology (CEINT)
- [MCF-677785]
- [CBET-1530563]
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 (similar to 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 zeta 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.
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