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This article in AJ

  1. Vol. 72 No. 5, p. 847-851
    Received: Nov 19, 1979

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Root Length Measurement with a Computer-Controlled Digital Scanning Microdensitometer1

  1. W. B. Voorhees,
  2. V. A. Carlson and
  3. E. A. Hallauer2



Root length measurements are often neglected in research because of the time and labor involved. A technique is described that greatly facilitates measuring root length using a computer-controlled digital scanning microdensiometer. This equipment systemically scans a photographic image of the roots and assigns numerical values to the light brightness from small areas of the image. These digitized light brightness values are used to determine the number of intersects between plant roots and a scanning line. The number of intersects is linearly related to root length. Resolutions of 1 µm can be obtained with photographic enlargement or microscopic lens. Calibration is obtained by scanning photographic images of known lengths of string, with a calibration regression coefficient for a linear fit > 0.98. A photographic image can be scanned three times in less than 5 sec and root length estimated with a coefficient of variation of < 5% among the three replicated scans. Computer programming, digitizer adjustment, and photographic modification can be used to adjust for different types of root systems.

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