Root-TRAPR: a modular plant growth device to visualize root development and monitor growth parameters, as applied to an elicitor response of Cannabis sativa

Abstract

\n Background\n\nPlant growth devices, for example rhizoponics, rhizoboxes, and ecosystem fabrication (EcoFAB) have been developed to facilitate studies of plant root morphology and plant-microbe interactions in controlled laboratory settings. However, several of these designs are suitable only for studying small model plants such as Arabidopsis thaliana and Brachypodium distachyon, and therefore require modification to be extended to larger plant species like crop plants. In addition, specific tools and technical skills required for fabricating these devices may not be available to researchers. Hence, this study aimed to establish an alternative protocol to generate a larger, modular and reusable plant growth device based on differently available resources.\nResults\n\nRoot-TRAPR (Root-Transparent, Reusable, Affordable three-dimensional Printed Rhizo-hydroponic) system was successfully developed. It consists of two main parts, an internal root growth chamber and external structural frame. The internal root growth chamber is comprised of a polydimethylsiloxane (PDMS) gasket, microscope slide and acrylic sheet while the external frame is printed from a three-dimensional (3D) printer and secured with nylon screws. To test the efficiency and applicability of the system, industrial hemp (Cannabis sativa) was grown with or without exposure to chitosan, a well-known plant elicitor used for stimulating plant defense. Plant root morphology was clearly detected in the system and plant tissues were easily collected and processed to examine plant biological responses. Upon chitosan treatment, chitinase and peroxidase activities increased in root tissues (1.7- and 2.3-fold, respectively) and exudates (7.2- and 21.6-fold, respectively). Phytohormones related to plant growth and defense response were higher in root tissues as compared to the shoots. Additionally, within two weeks of observation, hemp plants exhibited dwarf growth in Root-TRAPR system, easing plant handling and allowing increased replication under limited growing space.\nConclusion\n\nThe Root-TRAPR system facilitates exploration of root morphology and root exudate of C. sativa under controlled conditions and at a smaller scale. The device is easy to fabricate and applicable for investigating plant responses toward elicitor challenge. This fabrication protocol is modifiable to suit other plants and can be adapted to study plant physiology in other biological contexts, such as plant responses against biotic and abiotic stresses.