Novel Manual and Automatic HD Minirhizotron Camera Systems to Facilitate MR use in Plant Sciences

Minirhizotron (MR) systems are a qualitative and quantitative observation tool to study root and hyphal growth, longevity and distribution in situ or mesocosms. MR systems are based on transparent tubes (MR-T) inserted tightly into the soil. Subsequently an MR imaging device is inserted into MR-T in order to record images; the images are named and processed by a control unit. A modular set of new MR camera systems is currently developed by cross-sectoral collaboration between academic and industrial partners to improve the image quality and ease of use of MR systems accessible to researchers while sustaining the reliability of well-established MR systems. Full-HD images can be captured manually or by (semi‑)automatic systems; partially two (bidirectional) cameras are available. High image resolutions are decisive for detailed root morphological (e.g. root hairs, colour change) and hyphae observations, automatic systems reduce workload and increase correct image labelling—especially in large experimental set-ups (e.g. “rhizolabs” featuring hundreds of MR-T). Realized image size depends on the diameter of MR-Ts but are in the range of 2×2 cm (stackable); the utilisation of “realistic” image sizes is decisive to limit the subsequent workload of (manual) image analysis. Novel features such as “automatic recognition of MR-T” and “remote-triggered image capturing” are implemented to reduce mislabelling of images while increasing imaging speed. Features of the novel MR camera systems will be discussed and feedback of researchers at ISRR 2018 conference will be utilized to further improve the usability of a new generation of MR camera systems as an important tool for root researchers worldwide.