IMAGE-BASED ESTIMATION OF PPFD DISTRIBUTION ON THE CANOPY SURFACE IN A GREENHOUSE
In this study, a simple and useful method is provided to evaluate the light environment in a greenhouse. Light intensity distribution on the canopy surface was estimated as a photosynthetic photon flux density (PPFD) histogram using reflection images. Reflection images of the tomato canopy surface were acquired from three different directions using a digital camera through a blue-green band-pass filter. PPFD was measured at one point on the canopy by a quantum sensor simultaneously with imaging and was used for determining a regression model for calculating PPFD on leaves from image pixel values. The PPFD histograms estimated from the reflection images were compared with the histograms of actual PPFD determined by measuring all leaves in the target canopy surface using a quantum sensor. The histograms showed similar patterns, with the mean estimated values being close to the measured values. The pattern of the PPFD histograms estimated from the reflection images changed over time during the day. The changes in the mean values calculated from the estimated PPFD histograms corresponded to those in PPFD measured on the horizontal plane. These results suggest that reflection image-based estimation of PPFD distribution on a plant canopy surface can be used for simple evaluation of the light environment in a greenhouse.
Ibaraki, Y., Kishida , T. and Shigemoto, C. (2012). IMAGE-BASED ESTIMATION OF PPFD DISTRIBUTION ON THE CANOPY SURFACE IN A GREENHOUSE . Acta Hortic. 956, 577-582
digital camera, light control, light intensity distribution, reflection image, tomato canopy