Manual and digital line-intercept methods of measuring root length: a comparison.
1993
Farrell R.E. | Walley F.L. | Lukey A.P. | Germida J.J.
The manual line-intercept (MLI) method is widely accepted as the standard method of estimating root length. Recently, however, semiautomated systems employing a digital line-intercept (DLI) method have been developed. Although the DLI method is said to represent a significant time savings over the MLI method, comparisons between the two methods are relatively scarce. This study was conducted to determine and compare root length estimates obtained using manual and digital line-intercept methods and to evaluate different methods of preparing root subsamples for analysis. Roots were collected from spring wheat (Triticum aestivum L.) inoculated with three different plant growth-promoting rhizobacteria and a vesicular-arbuscular mycorrhizal fungus. Subsamples were cut from bulk root systems before or after they had been dried, and root lengths were estimated using both the MLI and DLI methods. Although the DLI and MLI methods yielded highly correlated results (r2 = 0.880*** (*** = significant at the 0.001 probability level)) when the subsamples were dried before being cut, the DLI method consistently underestimated root lengths and could not distinguish between inoculant effects. This was attributed to the inability of the imaging system to resolve small pieces of shattered root. When subsamples were prepared from fresh root material, the number of small root fragments was minimized; the two methods yielded highly correlated results (r2 = 0.943***) and both methods were equally adept at distinguishing significant differences between inoculant effects. Accurate root length estimates can be obtained using the DLI method with subsamples prepared from fresh roots in one- to two-thirds less time than can be achieved with the MLI method.
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