Emerging investigator series: linking nanoparticle infiltration and stomatal dynamics for plant nanobionics

Fluidic infiltration through the leaf lamina and the displayed stomata pores is a common method by which nanoparticles can be introduced into living plants for applications that include nanoscale sensors and genetic engineering approaches. The family of techniques that can augment or transform the functions of a living plant using nanoparticles have been labeled plant nanobionics. Yet studies of the controlled fluidic infiltration of nanoparticles are currently absent, mainly due to challenges associated with controlling the precision of the process. Herein, we develop an automated infiltration platform for living plants that enables precise control of the applied pressure and delivery volumes into the leaf mesophyll past the cuticle and the stomata. Using three orthogonal measurement techniques of microscopy, gas exchange quantification, and nanoparticle infiltration rates, we study the stomata dynamics and its effect on fluidic infiltration in spinach (Spinacia oleracea), cat palm (Chamaedorea cataractarum), and peace lily (Spathiphyllum) plants. We find that the infiltration efficiency changes throughout the day for spinach plants, while remaining constant for cat palms and peace lily. We conclude that stomata type and open fraction determine the pressure drop and the infiltration efficiency with spinach plants having the most active stomata: the estimated infiltration pressure changes from 115 kPa in the night to 16 kPa in the day due to 70% of stomata reaching the average aperture of 1.0 mu m. As an aid to the potential user, we discuss smartphone stomata detection to rapidly characterize the leaf surface and smartphone-based nanosensor detection for in-field applications of plant nanobionics. The discovered relationships reported herein and the new tools demonstrated promise optimal and automated incorporation of nanoparticles into living plants for a variety of emerging applications.