Supporting Agricultural Products Development with Non-destructive Root Imaging

We describe a complete system for growing plants and non-destructively imaging their root systems in order to perform comparative evaluations of the effects of synthetic and biological products on root health and development. A grow room capable of growing one hundred and sixty-eight plants under controllable temperature, light levels and watering rates is presented. Plant containers one meter in depth are used with artificial growth media. The media is totally inert and is incapable of absorbing moisture or providing nutrients to the growing plants. Nutrients are provided via a recirculating drip irrigation system. The system is capable of independent temperature control of the root zone and the surrounding air temperature.

Periodically the plants are taken to an X-ray imaging chamber for root image acquisition. The X-ray chamber is designed to scan the one meter deep by 20 cm wide container in six minutes to 27 micron resolution. Once imaged the plants are returned to the grow room. Plants are typically scanned once a week for product evaluations. We have imaged the same root system as often as once every 6 hours for several days to capture important developmental phenomenon.

Maize and soybean are the most requested species for testing product performance. The system has also been used to evaluate product effects on tomato, cotton, canola, pepper, sunflower, broccoli, prairie grasses and some young trees (poplar, pine, and citrus).

Automated software will be described that has been developed to extract root features from the low energy x-ray images. This software segments root structure from background noise in the images. The segmented image is then analyzed to extract root diameters, cross sectional root area, total root length, projected 2D root area, and the number of root crossings at different depths. These features are determined independently and summarized for five root diameter ranges.