Root Observations and Measurements at (Transparent) Interfaces with Soil

Abstract

Glass windows are often installed in rhizotron facilities to observe root growth. The same principle has been applied under field conditions, using “root windows” and “minirhizotrons” (transparent glass or plastic tubes pushed into the soil: Bates 1937), through which roots are observed non-destructively in situ at the interface between the glass and the soil. The possible observations include recording root growth and decay — processes which are difficult to measure otherwise — by still photography or videos, thereby providing time series that reveal the dynamics of root growth. Root researchers also use transparent interfaces when estimating the rooting characteristics of the surrounding bulk soil, such as root length intensity (Lv) and root mass per unit volume of soil (Wv), although this often necessitates a (cumbersome) conversion from 2-D to 3-D. All these methods and tools used to view roots are reviewed in this chapter.