DOI: 10.5281/zenodo.12800064
title: Leaf spectroscopy and active fluorescence datasets for early drought and nitrogen stress diagnosis in tomato
title: with spectral fitting results: fluorescence quantum efficiency and absorbance associated to regulated heat dissipation

description: The dataset contains different plant physiological parameters collected during a 14-day stress and recovery experiment on tomato (Solanum lycopersicum L. cv Moneymaker) plants, undergoing a nitrogen deficiency, drought or control treatment. 

A full description of the experiment, together with the scientific results, is published by Pescador-Dionisio et al. (2024), and can be found through: https://doi.org/10.1111/nph.20253.

The goal of the dataset collection was to obtain a non-invasive proximal sensing dataset at leaf level (reflectance, transmittance, upward and downward fluorescence), in parallel to gas exchange and active fluorescence measurements. The leaf spectroscopy dataset was further processed by a pigment spectral unmixing algorithm according to Van Wittenberghe et al. (2024), to calculate fluorescence quantum efficiency (FQE) and effective absorbance (A_eff) changes associated to the activation of regulated heat dissipation (A_eff_535_Xan). The latter absorption feature is linked to the xanthophyll ('Xan') absorption in the 500-600 nm range, which is modelled by the sum of three Gaussians. For a full description of this feature, see Van Wittenberghe et al. (2021).

Gas exchange and active fluorescence measurements were carried out with a LI-6400 portable photosysthesis system (LI-COR Biosciences, Lincoln, USA) equipped with a 6400-40 leaf chamber fluorometer. Steady-state measurements were done at 300 and 1000 μmol m−2 s−1 ('PAR300' and 'PAR1000'), i.e. growing light conditions and light saturating conditions. Light response curves were taken on different days. Common fluorescence parameters (e.g., Fv/Fm, Fo, Fm, NPQ, YNO, YNPQ) are provided together with 'sustained' and reversible' NPQ parameters calculated according Porcar-Castell (2011).

Leaf spectroscopy and active steady-state fluorescence measurements were performed on the same measuring days ('d0', 'd2', 'd4', 'd7', 'd14') and on the same leaf, both at 300 and 1000 μmol m−2 s−1 ('PAR300' and 'PAR1000'), taking into account an adaptation time. We used a LED light source and several filters, placed in front of a FluoWat leaf clip, which was connected to two high-performance VIS-NIR spectroradiometers (QEPRO, Ocean Insight Inc., Orlando, Florida, USA). The spectroscopy measurements are presented in the Matlab structures for each measuring day, e.g. "2023_d0_Leaf_Spec_Tomato_Stress.mat".

The outputs of the pigment spectral fitting code are presented by Matlab structures, e.g. "2023_d0_Leaf_Fitting_Tomato_Stress.mat", which contains the effective absorbance fitting (A_eff) of each pigment (Chl a, Chl b, Carotene-b, Anthocyanins, and Xanthophylls) for the wavelength range [500-780] nm, the absorbed photosynthetically active radiation by Chlorophyll a ('APAR_Chla') for the wavelength range [400-800] nm, and the fluorescence quantum efficiency, calculated as the ratio of the emitted fluorescence photons and the flux of photons absorbed by Chlorophyll a. 

Additional metadata from HPLC photosynthetic pigment analyses, xanthophyll-related enzyme expression, biomass and total content of elemental nitrogen are provided.

Please follow the README files for more detailed information.