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This article in AJ

  1. Vol. 70 No. 4, p. 675-677
     
    Received: Jan 30, 1978
    Published: July, 1978


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doi:10.2134/agronj1978.00021962007000040035x

Quantitative Estimation of Living Wheat-Root Lengths in Soil Cores1

  1. Kathy J. Ward,
  2. Betty Klepper,
  3. R. W. Rickman and
  4. R. R. Allmaras2

Abstract

Abstract

A rapid, efficient method for separating living wheat (Triticum aestivum L.) roots from dead roots in field soil samples is needed to understand the dynamic nature of wheat root development, because the proportion of living roots is highly variable and often may constitute less than 20% of the estimated length. A soil core, wrapped in a cloth “root bag” with a weave comparable to a 100-mesh screen (0.149 mm opening) was suspended in a container of water from a wrist-action shaker. Roots, organic residues, and sand remained in the bag, but fine sand, silt, and clay washed out. Roots and organic material were then decanted from the remaining sand. A 1% aqueous solution of congo red stained the living roots red; nonliving roots remained unstained or were stained a brownish pink. After flotation separation of the stained roots from debris, living root length was estimated. Newman's grid method was modified to measure root length with an accuracy of ±9% as determined with known lengths of string. With these combined techniques of separation, staining, and length measurement, we could determine rooting density with an accuracy of ±9%. When incubated at 15 C, severed living wheat roots could be stained for up to 1 week, but stainability dropped to less than 35% after 5 weeks. Most monocot roots stained more intensely than dicot roots, indicating that monocot-dicot root separation from the same root medium may faciliate studies of root competition.

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