Minirhizotrons in Modern Root Studies

Abstract

In recent years, minirhizotrons have received increasing interest in field studies for characterising several biological processes, such as fine root production, root longevity, mycorrhization and parasitism, as collecting repeated video or digital images allows the fate of individual roots to be followed in time.This review summarises recent technical improvements in root observation and imaging, comparing results from various construction materials and installation angles. Both glass and transparent acrylic or polycarbonate tubes have shown a relatively low influence on root behaviour; tilted tubes are preferred to vertically oriented ones, in order to avoid artefacts, and to horizontal ones, which involve considerable soil disturbance during positioning in their surroundings in the open field. Precise camera positioning systems and new high-resolution (600 DPI and more) digital sensors are currently replacing external-tracked tubes and analog sensors, enhancing image capturing and quality. This allows for frequent root observation throughout the plant cycle and seasons, required for accurate estimation of root dynamics.Although manual and semi-automatic image analysis requires timing and tedious work, in the last few years minirhizotron systems have been increasingly used, thanks to fundamental advances in image analysis. The development of new algorithms for root detection and measurement in minirhizotron images has speeded up processing and research. The most interesting results in image analysis derive from the integration of luminance intensity-and geometry-based root vs. non-root classifiers. Discrepancies still remain between minirhizotron data and

Screening of Maize Genotypes for Drought Tolerance Related Trait Variability

“…Studying root architecture extensively under field condition is limited due to the expenditure of time and labor involved in destructive techniques like the core method, and the likelihood of under-estimation of root depth and density with alternative method like minirhizotron (Vamerali et al, 2012). To circumvent these constraints, we used a simple and inexpensive system including soil media that allowed root growth in order to identify a medium which supports the best maize root growth for our future studies and easy extraction of intact roots.…”

Root growth of maize as studied with minirhizotrons and monolith methods

“…Discrepancies in root quantity data have been reported by other researchers using similar methods. This could be attributable to the experimental conditions, the method for installing the minirhizotron, and the root parameter used in the comparisons (Upchurch & Ritchie 1983;McMichael & Taylor 1987;Jose et al 2001;Bernier & Robitaille 2004;Milchunas 2012;Vamerali et al 2012;Taylor et al 2014). Furthermore, a high correlation of RLD between MT and QMM meant that MT was a reliable method, and the fact that the correlation was lower using the number of roots from MT has important implications on root parameters measured using MT.…”

“…MT has improved our understanding of the root system (Rewald & Ephrath 2013), including the influence of nitrogen fertilizer on fine root growth, senescence, and death (Hendricks et al 2006;Yu et al 2009). Some indices of biomass, production, turnover, and longevity of fine roots have been constructed using MT (Smucker et al 1982(Smucker et al , 1987Cheng et al 1991;Bai et al 2005;Majdi et al 2005;Faget et al 2012;Vamerali et al 2012). Studies were conducted to compare MT with the soil-water-depletion, core, and monolith methods of quantifying plant root distribution (Majdi et al 1992;Heeraman & Juma 1993;Samson & Sinclair 1994;Kirkham et al 1998;Jose et al 2001;Liu et al 2009;Liao et al 2010;Milchunas 2012;Rytter & Rytter 2012;Taylor et al 2013;Liao et al 2014).…”

“…The minirhizotron can be used for monitoring of roots over multiple years. It is a preferred method, especially to study root dynamics (Smit et al 2000), and its use has increased as a result of advances in image analysis technology (Vamerali et al 2012). So the question is how accurate the minirhizotron observation of the maize root is.…”

“…hand, there are well-known discrepancies between MT and QMM for estimating RLD like the underestimation in upper soil layers and the overestimation at deeper soil depths (Jose et al 2001;Linsenmeier et al 2010;Milchunas 2012;Vamerali et al 2012). Although we found good correlation between the two RLD methods used here, others have shown variation when comparing these two methods based on soil depth, with maximum RLD seen between 20 and 40 cm (Upchurch & Ritchie 1983;McMichael & Taylor 1987) using MT and between 0 and 20 cm using QMM (Majdi et al 1992;Samson & Sinclair 1994;Jose et al 2001).…”