Root Length

General

One of the most common techniques for determining the length of a sample of roots is the line-intercept method introduced by E. I. Newman (1966).  Generally, this procedure involves laying a set of lines over a random assemblage of roots, scanning over the lines and counting the number of intersections between root fragments and the lines.  Without a computer this technique is quite laborious.  There have been numerous revisions of Newman's original formulation for this technique.  The calculations used here were taken from Harris and Campbell's (1989) work with a Delta-T Devices (Cambridge, UK) Image Analysis System.  I have done detailed calibrations of this technique.  I haven't gotten as reliable a set of measurements as Harris and Campbell, but they are fairly good.  In my tests the orientation correction factor was more important than the overlap and resolution correction factors (discussed below).  The worst coefficients of determination (r^2, between actual and estimated length) I had in any set of tests was 0.93.  

Processing Options

The options that can be modified for this module are as follows:

Process Sub-Array: allows you to select a sub-portion of image to be processed.  Convenient for decreasing the size of overly-large images and getting rid of garbage at the edge of images.

Non-Random Orientation: This option takes approximately two times as long as when it isn't selected.  With this option selected, BranChing! scans the image from two different orientations and corrects for any non-random orientation of the roots within the image.  I highly recommend you ALWAYS have this option enabled.

Overlap and Resolution: This option is available only when the Non-Random Orientation option is on.  This option increases the time it takes to process an image by 10-20 times.  It yields more reliable results than with just the Non-Random Orientation correction on - assuming you have properly estimated the effective resolution of the images being processed.

Minimum Resolution: This is the minimum number of pixels that can be resolved by the input device used.  This needs to be independently determined for each imaging system (at any given setting of camera height, contrast, resolution etc.).

Details

BranChing will prompt you for all actions necessary to properly load and analyze an image. When BranChing is done with an image, it will update the Result Window.  The output results are labeled as follows:

LH - Length from Horizontal Scans
LV - Length from Vertical Scans
LC - Length Corrected Non-Random Orientation
s  - Length Corrected for Non-Random Orientation and Overlap and Resolution

If any of the correction options were disabled, the corrected length field in Result Window will have a missing value entered (•).