Correction of photochemical reflectance index (PRI) by optical indices to predict non-photochemical quenching (NPQ) across various species
Yukiko Nakamura, K. Tsujimoto, Tetsu Ogawa, Hibiki Noda, Kouki Hikosaka
Abstract
Photochemical reflectance index (PRI) is an optical index that reflects the de-epoxidation state of the xanthophyll cycle. It is strongly correlated with non-photochemical quenching (NPQ) and is expected to be a good indicator of plant stress status in remote sensing. However, PRI is also influenced by other factors, such as leaf pigment composition, and varies widely among plant species, which prevented its practical use in the past. Since the slope of the NPQ-PRI relationship is generally shared among leaves, NPQ can be correctly predicted if the PRI value of NPQ zero (PRI0) is known. Here we conducted the correlation analysis with PRI0 and 64,606,179 optical indices across leaves of 22 species from different functional types. Twelve indices were selected that were strongly correlated with PRI0 and were less sensitive to light intensity. PRI corrected with these 12 optical indices successfully predicted NPQ. Our pigment analysis suggested that PRI0 was not explained by the content of single pigment but was related to the relative contents of xanthophylls and chlorophylls. The indices proposed in this study are expected to be useful in predicting plant photosynthesis and stress status in remote sensing, contributing to future agriculture technology.