Polarization of light reflected from grain crops during the heading growth stage

A Multiband Polarimetric Imager for Field Crop Survey: ―Instrumentation and Preliminary Observations of Heading-stage Wheat Canopies―

“…However, the estimated DP values generally agreed with results obtained in previous studies using portable spectropolarimeters (Fitch et al, 1984;Ghosh et al, 1993;Shibayama and Watanabe, 2007). Mean DP values observed from erectophyll plant canopies, such as wheat, are expected to be relatively smaller than those obtained from planophyll plants, like the sweet potato, even if the directions of viewing and insolation are opposing (looking toward the sun).…”

“…This increased reflected light intensity may account for the relatively higher signal to noise ratio obtained for the 550 nm band. In addition, compared to observations conducted using a unifi ed-fi eldof-view radiometer (e.g., Fitch et al, 1984;Ghosh et al, 1993;Shibayama and Watanabe, 2007), the pixel-by-pixel estimations of DP values employed in this study for the image data may produce DP values with slightly different arithmetic means; however, this is just speculation and further research is required in order to clarify the contribution of differences in the morphological and physiological status on the spectral characteristics of DP values of crop and/or vegetation canopies. Consequently, due to the limited number of observations in this study, care should be taken when interpreting the results.…”

Remote Assessment of Wheat Canopies under Various Cultivation Conditions Using Polarized Reflectance

“…Theoretical and practical research revealed that it is possible to use the polarization of the refl ected light from canopies to detect the leaf inclination geometry of vegetation canopies (Egan, 1970;Curran, 1981;Fitch et al, 1984;Rondeaux and Herman, 1991;Nadal and Bréon, 1999;Shibayama, 2003;Shibayama, 2004). Previously, we reported the preliminary results of polarization measurement of crop canopies using a portable spectropolarimeter designed for fi eld use (Shibayama and Akita, 2002).…”

Testing Polarization Measurements with Adjusted View Zenith Angles in Varying Illumination Conditions for Detecting Leaf Orientation of Wheat Canopy

“…Because MTA is the mean inclination angle of the whole leaves that also distribute in the lower part of the leaf layer, it could not be the most appropriate indicator in explaining the responses of polarization. Actually, polarization may be affected not only by the MTA but also by other plant parameters such as the emergence of panicles above the canopy surface (Fitch et al, 1984). However, in this study there were no panicles above the canopy at the time of measurement.…”