Evaluating the Contribution of Cx to Leaf Nitrogen Quantification using Fluspect and Airborne Imaging Spectroscopy in Almond Orchards

Among all essential nutrients, nitrogen (N) is required by plants in large quantities throughout the entire developmental process. This is due to its importance for plant growth and development and as a primary source of energy for photosynthesis. Previous research has demonstrated that solar-induced chlorophyll fluorescence (SIF) coupled with chlorophyll a+b content (C ab ) improved the estimation of leaf N, outperforming standard vegetation indices. The present study investigates the contribution of leaf C x , a measure of the de-epoxidation state of the xanthophyll cycle, for explaining leaf N variability, concluding that it ranks third after C ab and SIF consistently over two growing seasons. Among the rest of the biochemical constituents estimated by model inversion, C x contributed more than anthocyanins (Anth), the total carotenoid content (C car ), and crown-level structural traits.