Role of Foliar Biointerface Properties and Nanomaterial Chemistry in Controlling Cu Transfer into Wild-Type and...

Seven Arabidopsis thaliana mutants with differences in cuticle thickness and stomatal density were foliar exposed to 50 mg L^-1 Cu₃(PO₄)₂ nanosheets (NS), CuO NS, CuO nanoparticles, and CuSO₄. Three separate fractions of Cu (surface-attached, cuticle, interior leaf) were isolated from the leaf at 0.25, 2, 4, and 8 h. Cu transfer from the surface through the cuticle and into the leaf varied with mutant and particle type. The Cu content on the surface decreased significantly over 8 h but increased in the cuticle. Cu derived from the ionic form had the greatest cuticle concentration, suggesting greater difficulty in moving across this barrier and into the leaf. Leaf Cu in the increased-stomatal mutants was 8.5-44.9% greater than the decreased stomatal mutants, and abscisic acid to close the stomata decreased Cu in the leaf. This demonstrates the importance of nanomaterial entry through the stomata and enables the optimization of materials for nanoenabled agriculture.