Figure 2.

Logic of custom software for measurement of length and segment angles of roots. A key feature of the software is its ability to identify the edges of the root based on a user-defined threshold luminous intensity and record that pixel location. Black and white arcs denote segment limits as determined by the search routine of the software. The size of each segment is selected by the user and input as a searching radius. Black arcs indicate the limits of odd-numbered segments (1, 3, 5, etc.) and white arcs indicate the limits of even-numbered segments (2, 4, 6, etc.). Segment angle was determined by first finding the line connecting the edge points of the root at a given search distance, then determining the angle of the line connecting the midpoints of the two limit lines relative to vertical. The overlapping process used to define segment limits increases the resolution of angle measurement. By definition the segments remain a fixed distance relative to the root tip as the root elongates. Total length of each edge is measured from the tip to a user-defined basal point in the mature region of the root.