Nanosensorfor Fe(II) and Fe(III) Allowing SpatiotemporalSensing <i>in Planta</i>

Fluorescent nanosensors operating <i>in planta</i> have shown recent success toward informing basic plant biology and agricultural applications. We developed near-infrared (NIR) fluorescent nanosensors using the Corona Phase Molecular Recognition (CoPhMoRe) technique that distinguish Fe(II) and Fe(III) species with limit of detection as low as 10 nM. An anionic poly(p-phenyleneethynylene) (PPE) polyelectrolyte wrapped single-walled carbon nanotube (SWNT) shows up to 200% turn-on and 85% turn-off responses to Fe(II) and Fe(III), respectively, allowing spatial and temporal analysis of iron uptake in both foliar and root-to-shoot pathways. Our findings reveal species-dependent iron uptake efficiency, mobility, and utilization rates, which we show is primarily affected by the chelation status of iron source and by plant physiological conditions such as iron deficiency and treatment with the stress hormone, abscisic acid (ABA). The broad applicability of this sensor across important plant species highlights the potential of nanotechnology-enabled sensors to enable precise and sustainable nutrient management.