Visualization of root growth in heterogeneously contaminated soil using neutron radiography

Abstract

We used neutron radiography (NR), a non-invasive and in situ technique, to study living plant roots in soil. Plant roots have a larger water content than their unsaturated surrounding media. As water strongly attenuates a neutron-beam, NR can identify root structures in detail. We investigated the use of NR to visualize the root growth of lupin in quartz sand and in a loamy sand field soil. Further experiments elucidated the root growth of lupin in the loamy sand heterogeneously contaminated with 10 and 20 mg kg À1 boron (B) and 100 mg kg À1 zinc (Zn). We obtained high-quality images of root growth dynamics in both media with a resolution range of 110-270 mm. The images with quartz sand revealed fine structures such as proteoid roots that are difficult to locate in situ by other methods without destruction of the soil. Though quartz sand provided excellent visibility of roots, it proved to be a poor medium for growing plants, probably because of its bulk density (1.8 Mg m À3 ). The images with field soil showed normal root growth with slightly less contrast than the quartz sand. The poorer contrast was due to the greater neutron interaction with soil water and soil organic matter. In the heterogeneously contaminated soil, root growth was significantly reduced in the contaminated part of the soil in all B and Zn treatments. This study shows that NR has potential as a non-invasive method to investigate root growth over time as well as the response of roots to various abiotic stress factors.

A simple three-dimensional macroscopic root water uptake model based on the hydraulic architecture approach

“…Yet, root architecture and hydraulic properties are more difficult to derive from in situ measurements of plant roots than rRLD. However, this type of information can be obtained from root growth models calibrated on root profile measurements (as done in this study) or from noninvasive methods like MRI (Pohlmeier et al, 2008), X-ray or neutron tomography (Menon et al, 2007). The sensitivity of SSF to the root architecture type should be characterised in the future.…”

Recovering Root System Traits Using Image Analysis Exemplified by Two-Dimensional Neutron Radiography Images of Lupine

“…Plants were grown in a climate chamber at a humidity of 60% with a 16-h/8-h day/night cycle with 21°C/16°C temperature. The root system was visualized with neutron radiography at 12, 19, and 26 d after germination (at the Paul Scherrer Institute in Villigen, Switzerland), which is highly suitable to visualize roots and water in soil (Menon et al, 2007;Moradi et al, 2009). The field of view was 18 3 18 cm with a nominal resolution of 0.176 mm; thus, four scans per plant container were needed to record the whole sample.…”

“…A major advantage of NR as well as magnetic resonance imaging is the possibility to monitor water distribution and roots simultaneously (Menon et al, 2007;Oswald et al, 2008;Moradi et al, 2009;Carminati et al, 2010;Stingaciu et al, 2013). This is especially useful as water is a crucial factor ruling root allocation in soil (Hodge, 2010).…”

Root Phenotyping Pipeline for Cereal Plants

“…Nonetheless, greenhouse-based assays of root phenotyping still remain time-consuming and labour-intensive when a soil substrate is applied for plant growth. Soil-based root phenotyping experiments are extremely limited by the difficulty of observing root growth and development without the disruption of the surrounding soil core (Menon et al 2007). Moreover, the rooting volume of plants growing in pots of varying sizes significantly influences the calculated root system volume (Poorter et al 2012).…”