MEASURING ROOT SURFACE-AREA AND MEAN ROOT DIAMETER OF PEACH SEEDLINGSBY DIGITAL IMAGE-ANALYSIS

Using area profile integration software and an image processing system , we reliably estimated total root surface area of intact peach [Prunu s persica (L.) Batsch.] seedlings by 1) producing high-quality monochr omatic video images under preset and constant conditions; 2) determini ng a threshold gray intensity value that differentiates the finest roo ts on the image; 3) producing a binary image where all pixels with gra y values above the threshold are black; 4) determining the proportion of black pixels on the 480 x 512-pixel matrix; and 5) multiplying this two-dimensional root surface value by pi to estimate total root surfa ce area. Normalized intensity (an average intensity weighted according to the proportion of the binary image in each gray scale class) was c alculated using software that superimposed the video image on the bina ry image and was used to estimate mean root diameter. Evidence of reli ability and examples of the use of both estimates are provided.