Diurnal Cycle Relationships between Passive Fluorescence, PRI and NPQ of Vegetation in a Controlled Stress Experiment
2017
Luis Alonso | Shari Van Wittenberghe | Julia Amorós-López | Joan Vila-Francés | Luis Gómez-Chova | Jose Moreno
In order to estimate vegetation photosynthesis from remote sensing observations: some critical parameters need to be quantified. From all absorbed light: the plant needs to release any excess that is not used for photosynthesis: by non-photochemical quenching: by fluorescence emission and unregulated thermal dissipation. Non-photochemical quenching (NPQ) processes are controlled photoprotective mechanisms which: once activated: strongly control the dynamics of photochemical efficiency. With illumination conditions increasing and decreasing during a diurnal cycle: photoprotection mechanisms needs to change accordingly. The goal of this work is to quantify dynamic NPQ: measured from active fluorescence measurements: based on passive proximal sensing leaf measurements. During a 22-day controlled light and water stress experiment on a tobacco (Nicotiana tabacum L.) leaf we measured the diurnal dynamics of passive fluorescence (Chl F): the Photochemical Reflectance Index (PRI): the Absorbed Photosynthetically Active Radiation (APAR) and leaf temperature in combination with the actively retrieved non-photochemical quenching (NPQ) parameter. Based on a bi-linear combination of diurnal APAR and PRI (plane fit model) we succeeded to estimate NPQ with a RMSE of 0.08. The simple plane fit model estimation represents well the diurnal NPQ dynamics: except for the high light stress phase: when additional reversible photoinhibition processes took place. The present works presents a way of determining NPQ from passive remote sensing measurements: as a necessary step towards estimating photosynthetic rate.
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