Identification of Signaling Transmitter to Activate Nitrate Reductase in Vegetable Leaves by Near-Infrared Hyperspectral Imaging System

A hyperspectral imaging system was developed to analyse nitrate metabolism in vegetables; this system involves visualising the spatial distribution of nitrate concentration in a leaf plane. The nitrate concentration at each pixel of a leaf was estimated by near-infrared spectroscopy. The estimation model demonstrated a correlation coefficient of 0.9216 between the measured and estimated nitrate concentration and a weighted mean standard error, which is the weighted mean of the standard error of calibration and that of validation, of 2140 mg/L. The nitrate concentration of a leaf was varied artificially by a pulse-chase method. The spatial distribution of nitrate concentration was measured by the hyperspectral imaging system while applying the pulse-chase method, and then transitions of the spatial distribution of nitrate concentration were recorded. The points at which the concentration was high or low were detected; future analysis of the activation level of the nitrate reductase at these points will clarify a signaling pathway for activating nitrate reductase.