Estimation of Leaf Area Index of Table Grapes Using a Digital Camera Equipped with Fisheye Lens and the Image Processing Software “Fiji-ImageJ”

Abstract

Using a digital camera equipped with a fisheye lens and the image processing free-software “Fiji-Image J”, we developed a new protocol for determination of the leaf area index (LAI) of table grapes with the same level of measurement accuracy as the plant canopy analyzer (PCA). A regression analysis between the leaf width (X) and single leaf area (Y) indicated highly significant values (Y = 0.5716X^2.0425, R² = 0.99**). A highly significant correlation was obtained between the actual LAI and the LAI measured by PCA (r = 0.964**). Regarding “Fiji-Image J”, we performed the following three-step image processing: (1) R-, G-, and B-separation of the original image taken, (2) correction of the three separated images by “Subtract background algorithm” and “Minimum” threshold treatment mode, (3) calculation of cumulative vegetation rate in the three images. As the range of LAI values was 1 to 4, a highly significant linear correlation was noted between the cumulative vegetation rate (X) and actual LAI (Y): Y = 0.0769X − 18.325, R² = 0.82**.