Fluorescence, PRI and canopy temperature for water stress detection in cereal crops


Narrow-band multispectral remote sensing techniques and thermal imagery were investigated for water stress detection in cereal crops. Visible and near infrared AISA Eagle (Specim, Finland) and thermal AHS-160 (Sensytech Inc., USA) imageries were acquired with an airborne survey on a farm-level experimental site where maize (Zea mays L.) and sorghum (Sorghum bicolor L.) were grown with three different irrigation treatments. Vegetation biophysical and eco-physiological measurements were collected concurrently with the airborne campaign. Leaf fluorescence yield (ΔF/Fm’) resulted to be a good indirect measure of water stress. Therefore, ΔF/Fm’ measurements were compared against remotely sensed indicators: (i) the Photochemical Reflectance Index (PRI), (ii) the sun-induced chlorophyll fluorescence at 760 nm (F760), retrieved by the Fraunhofer line depth method and (iii) the canopy temperature (TC) calculated decoupling soil and vegetation contributions. TC was related to ΔF/Fm’ with the highest determination coefficient (R2 = 0.65), followed by PRI586 (reference band at 586 nm) (R2 = 0.51). The relationship with F760 was significant but weaker (R2 = 0.36). The coefficient of determination increased up to 0.54 when pigment concentration was considered by multiplying ΔF/Fm’ and chlorophyll content, confirming the close relationship between passive fluorescence signal, pigment content and light photosystem efficiency. PRI586, F760 and TC maps were produced in maize and sorghum plots. The differences in the average values of PRI586, F760 and TC extracted from the plots with different water treatments showed that water treatments were well discriminated in maize plots by the three remotely sensed indicators. This was confirmed by the visual observation of the PRI586, F760 and TC maps, while in sorghum plots, F760 and TC appeared more sensitive to water stress compared to PRI586. © 2014 Elsevier B.V.

International Journal of Applied Earth Observation and Geoinformation, (30), 1, pp. 167-178, https://doi.org/10.1016/j.jag.2014.02.002