Detecting and monitoring water stress states in maize crops using spectral ratios obtained in the photosynthetic domain

Abstract

, "Detecting and monitoring water stress states in maize crops using spectral ratios obtained in the photosynthetic domain," J. Appl. Remote Sens. 11(3), 036025 (2017), doi: 10.1117/1.JRS.11.036025. Abstract. The reliable detection and monitoring of changes in the water status of crops composed of plants like maize, a highly adaptable C4 species in large demand for both food and biofuel production, are longstanding remote sensing goals. Existing procedures employed to achieve these goals rely predominantly on the spectral signatures of plant leaves in the infrared domain where the light absorption within the foliar tissues is dominated by water. It has been suggested that such procedures could be implemented using subsurface reflectance to transmittance ratios obtained in the visible (photosynthetic) domain with the assistance of polarization devices. However, the experiments leading to this proposition were performed on detached maize leaves, which were not influenced by the whole (living) plant's adaptation mechanisms to water stress. In this work, we employ predictive simulations of light-leaf interactions in the photosynthetic domain to demonstrate that the living specimens' physiological responses to dehydration stress should be taken into account in this context. Our findings also indicate that a reflectance to transmittance ratio obtained in the photosynthetic domain at a lower angle of incidence without the use of polarization devices may represent a cost-effective alternative for the assessment of water stress states in maize crops. © The Authors. Published by SPIE under a Creative Commons Attribution 3.0 Unported License. Distribution or reproduction of this work in whole or in part requires full attribution of the original publication, including its DOI.

Chromatic and numerical approaches for the monitoring of corn plants under moderate water stress

“…1 to 4, we present the outcomes of our in silico experiments involving the reflective behaviour of the four selected specimens. As expected, 12,13 a moderate water stress led to a decrease in the specimens' reflectance (Figs. 1a, 2a, 3a and 4a).…”

“…Again, for conciseness, the complete description of the derivation of these parameters values, including supporting bibliographic sources, is provided elsewhere. 12,13 We remark that the corn leaves' chloroplasts usually remain arrayed along the mesophyll cell walls. 14,29 Accordingly, light can be propagated without encountering these organelles, a phenomenon known as the sieve effect [14][15][16]29 that decreases the probability of light absorption (in comparison with a homogeneous chlorophyll solution).…”

“…For conciseness, the complete description of the procedures employed to obtain the specimens' characterization data, including their bibliographic sources, is provided elsewhere. 12,13 The spectral curves computed for the specimens in their wilted state were obtained considering a 25% water reduction in their tissues. This reduction was accompanied by minor changes in their pigment contents as reported in the experiments by Maracci et al 10 involving corn leaves under in vivo moderate water stress.…”

“…14,29 Accordingly, light can be propagated without encountering these organelles, a phenomenon known as the sieve effect [14][15][16]29 that decreases the probability of light absorption (in comparison with a homogeneous chlorophyll solution). On the other hand, during moderate water stress under in vivo conditions, the mesophyll chloroplasts may adopt a more homogeneous intracellular distribution triggered by water deficit signals, 12,13 resulting in an intensification of light detour effects [14][15][16] that increase the probability of light absorption. 15,[17][18][19] To account for these phenomena, ABM-U adjusts the propagation (scattering) angle of the rays traversing the leaf's mesophyll tissue.…”

“…It has been proposed 12,13 that water deficit signals may trigger the migration of chloroplasts away from the corn leaves' mesophyll cell walls. This, in turn, may result in a more homogeneous distribution of these chlorophyll containing organelles.…”