A color composite technique for detecting root dynamics of barley (Hordeum vulgare L.) from minirhizotron images

Abstract

Quantification of root dynamics by destructive methods is confounded by high coefficients of variation and loss of fine roots. The minirhizotron technique is non-destructive and allows for sequential root observations to be made at the same depth in situ. Observations can be stored on video tape which facilitates data handling and computer-aided image processing. A color composite technique using digital image analyses was adapted in this study to detect barley root dynamics from sequential minirhizotron images. Plants were grown in the greenhouse in boxes (80 × 80 × 75 cm) containing soil from a surface horizon of a Typic Cryoboroll. A minirhizotron was installed at a 45 °C angle in each box. Roots intersecting the minirhizotron were observed and video-recorded at tillering, stem extension, heading, dough and ripening growth stages. The images from a particular depth were digitized from the analog video then registered to each other. Discrimination of roots from the soil matrix gave quantitative estimates of root appearance and disappearance. Changes in root appearance and disappearance were detected by assigning a separate primary color (red, green, blue) to selected growth stages, then overlaying the images to create red-green and red-green-blue color composites. The resulting composites allowed for a visual interpretation and quantification of barley root dynamics in situ.

Monitoring of root growth and redox conditions in paddy soil rhizotrons by redox electrodes and image analysis

“…Methodological imperfection such as over and under estimation of detected areas (RingroseVoase 1991; Pan et al 1998) or inclusion of background objects (Heeraman et al 1993) were minimized by the definition of suitable thresholds. Hence, the visualization and detection technique applied in this study allows an improved analysis of the oxidized and reduced areas of the soil in terms of their development in space and time (Fig.…”

Classification of rhizosphere components using visible–near infrared spectral images

“…Numerous nondestructive studies have been conducted using belowground rhizosphere images to examine root dynamics (e.g., Hendrick and Pregitzer 1992;Heeraman et al 1993;Majdi and Öhrvik 2004). For example, in the minirhizotron method (Hendrick and Pregitzer 1992), which is currently one of the most widely used methods in field studies, fine-root dynamics are observed through the repeated capture of images of roots growing on the sides of transparent tubes installed in the soil.…”

Root Methods

“…coring (Bragg et al 1983;Hansson and Andren 1987;McMichael and Taylor 1987;Hansson et al 1992;Andren et al 1993;Heeraman and Juma 1993;Wiesler and Horst 1994). Minirhizotrons have been widely used to estimate the rooting distribution in the surrounding soil.…”

“…Minirhizotrons have been widely used to estimate the rooting distribution in the surrounding soil. Various explanations have been given for this discrepancy in root data: (Upchurch and Ritchie 1983;Bragg et al 1984;Heeraman and Juma 1993), 3. coring (Bragg et al 1983;Hansson and Andren 1987;McMichael and Taylor 1987;Hansson et al 1992;Andren et al 1993;Heeraman and Juma 1993;Wiesler and Horst 1994).…”

“…There are several factors that may contribute to the poor quality of minirhizotron images. Low battery power can also contribute to photometric distortion due to poor illumination by the incandescent bulbs of the minirhizotron camera (Heeraman et al 1993). Non-perpendicular viewing or camera-tube non-linearity may lead to geometrically distorted images (Heeraman et al 1993).…”