Evolution and Potential of the Mini-Horhizotron as an Apparatus for Teaching and Research Investigations in the Plant Sciences

The mini-Horhizotron was developed at North Carolina State University to study root growth of seeds, liners, and plugs planted into common greenhouse containers during their production cycle. The design of the mini-Horhizotron is comprised of a clear three-chamber configuration suitable for observing and measuring root growth by utilizing the clear walls. The mini-Horhizotrons have a substrate volume similar to a standard greenhouse container, and the height of the mini-Horhizotron (10.2 cm) is also similar to a 16.5 cm diameter container (11.8 cm), providing similar air and water profiles comparatively. However, the surface area of the mini-Horhizotron is almost three times larger than a container, allowing for an increase in potential viewing of roots as they explored the substrate. Possible root measurements in situ include; root length, speed of root growth, presence and quantity of root hairs, and root branching/architecture. In order to block sunlight from the rhizosphere, shade panels slide directly against the concave-shaped clear walls. In this original design, the shade panels had to be removed by pulling them up vertically which often was obstructed by (or damaged) the foliage of the plant growing in the apparatus. To prevent damage to the plants when removing the shade panels, a design modification was made to change the configuration of the shade panels such that they were set back away from the center (concave sides) of the apparatus, thus not interfering with the plant foliage when removed vertically. A second modification was made to the mini-Horhizotron to decrease the glare on the clear sides which previously caused problems when trying to photograph the roots. This was a big concern that potentially limited the usefulness of the mini-Horhizotron, as it is believed that advancements in digital imagery data collection will be the future of research and teaching activities. An anti-glare reflective coating sprayed on the clear sides was added to reduce the glare and improve the effectiveness and quality of digital images. These modifications have improved the utility of the mini-Horhizotron in ways that should increase their utilization as research and teaching tools.