An
incomplete understanding of how agrochemical nanocarrier properties
affect their uptake and translocation in plants limits their application
for promoting sustainable agriculture. Herein, we investigated how
the nanocarrier aspect ratio and charge affect uptake and translocation
in monocot wheat (Triticum aestivum) and dicot tomato
(Solanum lycopersicum) after foliar application.
Leaf uptake and distribution to plant organs were quantified for polymer
nanocarriers with the same diameter (∼10 nm) but different
aspect ratios (low (L), medium (M), and high (H), 10–300 nm
long) and charges (−50 to +15 mV). In tomato, anionic nanocarrier
translocation (20.7 ± 6.7 wt %) was higher than for cationic
nanocarriers (13.3 ± 4.1 wt %). In wheat, only anionic nanocarriers
were transported (8.7 ± 3.8 wt %). Both low and high aspect ratio
polymers translocated in tomato, but the longest nanocarrier did not
translocate in wheat, suggesting a phloem transport size cutoff. Differences
in translocation correlated with leaf uptake and interactions with
mesophyll cells. The positive charge decreases nanocarrier penetration
through the leaf epidermis and promotes uptake into mesophyll cells,
decreasing apoplastic transport and phloem loading. These results
suggest design parameters to provide agrochemical nanocarriers with
rapid and complete leaf uptake and an ability to target agrochemicals
to specific plant organs, with the potential to lower agrochemical
use and the associated environmental impacts.