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Book: Tomography of Soil-Water-Root Processes
Published by: Soil Science Society of America, American Society of Agronomy, and Crop Science Society of America

 

This chapter in TOMOGRAPHY OF SOIL-WATER-ROOT PROCESSES

  1.  p. 115-133
    SSSA Special Publication 36.
    Tomography of Soil-Water-Root Processes

    S. H. Anderson and J. W. Hopmans (ed.)

    ISBN: 978-0-89118-931-2

     

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doi:10.2136/sssaspecpub36.c10

Techniques and Approaches for Documenting Plant Root Development with X-Ray Computed Tomography

  1. E. W. Tollner,
  2. E. L. Ramseur and
  3. C. Murphy
  1. University of Georgia, Griffin, Georgia
    Westinghouse Savannah River Company, Aiken, South Carolina

Abstract

Quantification of root activity in terms of root growth and indirectly through water uptake is necessary for understanding plant growth dynamics. A greenhouse study of soil columns (Lakeland sand, thermic, coated Typic Quart zipsamment, bulk density 1.4 Mg m−3) planted with soybean [Glycine max (L.) Merr.], bahiagrass (Paspalum notatum Fluegge), and a control (not planted) was conducted in 1989. A Treflan based chemical barrier was placed in half of the soil columns. Columns were watered every other day except when being subjected to water stress tests at selected times. Columns were scanned using x-ray computer tomography (CT) once weekly and daily during the stress evaluation periods. X-ray CT enabled qualitative (images) as well as quantitative outputs (statistical moments derived from pixel absorption histograms). The mean x-ray absorption correlated with water content. Results suggested that root presence can also be indirectly inferred based on water content drawn down during planned stress events. Images and statistical moments (e.g., mean, standard deviation, or skewness) from the pixel absorption histogram yielded information related to plant rooting activity especially when roots are large enough to be clearly visible. Quantitative information was extracted from the images themselves using edge detection and binarization image analysis techniques. Image analysis procedures suggested a continuous development of porosity in upper layers that would be expected with root development. X-ray CT may be a valuable tool in plant root studies particularly when one can couple water extraction observations with statistical moment and image analysis results.

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