###### Abstract  
Vegetation indices (VIs) related to plant greenness have been studied extensively for the remote detection of foliar nitrogen content. Yet, the potential of chlorophyll fluorescence (ChlF) and photoproduction-based indices such as the photochemical reflectance index (PRI) or the chlorophyll/carotenoid index (CCI) for the detection of a wide range of nutrients remains elusive. We measured the dynamics of foliar macro- and micronutrient contents in potato plants as affected by fertilization and water stress, along with leaf and canopy level observations of spectral reflectance and ChlF (or solar-induced fluorescence). ChlF and photoproduction-related indices were more strongly related to a wide range of foliar nutrient contents compared to greenness-based indices. At the leaf level, relationships were largely mediated by foliar chlorophyll contents (Cab) and leaf morphology, which resulted in two contrasting groupings: a group dominated by macronutrients N, P, K, and Mg that decreased during canopy development and was positively correlated with Cab, and a group including Cu, Mn, Zn, and S that increased and was negatively related to Cab. At the canopy-level, spectral indices were additionally influenced by canopy structure, and so their capacity to detect foliar nutrient contents depends on the spatiotemporal covariation between foliar Cab, morphology, and canopy structure within the observations. ch chlorophyll fluorescence; potato (_Solanum tubreosum_ L.), SIF; PRI; UAV; canopy structure 2023152498. 12498.  
common plant growth-limiting macronutrient and an estimated 1-5% of above-ground plant dry matter is N, making it the second most needed element after carbon (C) [5]. In plants, N is used, for example, to produce chlorophyll, nucleic acids, and proteins, such as ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBisCO) [6], which is used by plants in carbon fixation. Other macronutrients include phosphorus (P), sulfur (S), calcium (Ca), magnesium (Mg), and potassium (K). Micronutrients, such as copper (Cu), iron (Fe), manganese (Mn), and zinc (Zn) play varying important roles in plant protein formation and plant stress response [5] (Table 1). Plants require a balanced amount of macro- and micronutrients to function optimally. A deficiency of mineral nutrients can lead to a decrease in the overall photosynthetic activity of foliage [7; 8] and reduced plant growth [9], affecting canopy development by reducing the leaf area index (LAI) of the canopy [10]. Accordingly, nutrient deficiencies are expected to express themselves through optical signatures both at the leaf, e.g., via pigment contents and radiation absorption, and at canopy levels, via structural effects such as a decrease in leaf area, offering opportunities for the remote detection of plant nutrient dynamics using optical remote sensing techniques. Vegetation indices (VIs) derived from leaf reflectance have been used in remote sensing since at least the 1960s, the most well-known of which is the normalized difference vegetation index (NDVI) [11], based on the red, which is absorbed by the vegetation, and near-infrared, which is strongly reflected by the vegetation, reflectance difference. Originally used for differentiating vegetated areas from non-vegetated areas in satellite data [12], it has since seen use in both commercial and scientific applications [4] and has been used to detect N from crops [13; 14]. It does, however, suffer from limitations due to saturation under high canopy cover conditions [12; 15; 16]. Additional vegetation greenness-based indices (henceforth referred to as greenness indices in this study together with NDVI) have been developed to refine the original NDVI formulation, such as the MERIS terrestrial chlorophyll index (MTCI) [17]. The MTCI is a proxy for the position of the red edge, which is the sharp increase in vegetation reflectance between the red and near-infrared that shifts towards longer wavelengths with increasing chlorophyll contents.