AUTOMATED MEASUREMENT OF ROOT LENGTH WITH A 3-DIMENSIONAL HIGH-RESOLUTION SCANNER AND IMAGE-ANALYSIS

For measuring the length of root samples, the use of a three-dimension al (3D) scanner is proposed to address the problem of a too low resolu tion. The scanner's high resolution (up to 354 pixels per cm) enables in the resulting grey-value image very thin roots (diameter 100 mu m) to be segmented from the background by a simple thresholding operation . After skeletonizing, total length of the roots is calculated by mult iplying the number of skeleton pixels by a correction factor. A compar ison with the modified Newman Line-Intersect Method showed a correlati on of r = 0.98. Besides its superior resolution, an advantage of this type of scanner is its focusing depth, which allows root samples to be recorded on the scanbed similarly to a camera-oriented system.