Quick estimates of root length, using a video image analyzer

Abstract

A black and white video camera and an image analyzer were used to measure the length of oak roots from which soil had been washed. The image analyzer is an automated intersect counter which uses the same basis for length estimation as the modified line intersect method. The roots were arranged within a 13.5 × 19 cm rectangle on clear plastic sheets and photocopied (dry process), then the lengths of the photocopied root images were measured with the video system. Two measurements were made on each photocopy, with a 90° rotation of the photocopy made between the two measurements. The two measurements were summed to obtain an index of root length. The automated system tested had insufficient resolution to detect very fine roots (<0.3 mm); however, the video method was found to be linearly correlated (R 2 = 0.92) with the modified line intersect method. Other root samples may require enhanced system resolution to achieve adequate correlation between methods. Once the video method has been calibrated, length of root samples may be determined up to 8 times faster than by the line intersect method.