Fig. 2

A 3D representation of the platform framework: a cuboid main frame (MF), a rhizobox frame (RF), an H-shaped linear-motion gantry for driving the RFs and the imaging device, an irrigation-circulation system and an integrated shading system. a An RF loaded with four rhizoboxs is fixed on the sliders of the linear guideway on the top of MF. The gantry is composed of one cross-beam in the center and two vertical beams on each side. It is mounted on two linear ballscrew-driven actuators on the bottom of the MF, and the top outer sides of two vertical beams are mounted with two linear-guideways which are fixed on the inner top sides of MF to stabilize the motion of the gantry. The cross-beam of the gantry is housed on the linear actuators of two vertical beams of the gantry for rise-and-fall motion. The imaging device is mounted on a linear actuator which is fixed on the cross-beam for left-and-right motion. The imaging device includes a camera mounted on a rotary table, a studio flash-lamp, and a reflector. The irrigation-circulation system comprises an irrigation subsystem and a circulation subsystem. The former includes a nutrient container, some irrigation tubes, a self-priming pump and some electromagnetic valves, and the latter includes a main-channel, some sub-channels, a temporary storage box and an immersible pump in the box. b The integrated shading system includes one top shading face and four vertical shading faces. Heat insulation open-cell ethylene propylene diene monomer (EPDM) is used to fill the inner gap between the two top beams of the RF. A long n-shaped flexible accordion shield is customized to connect neighboring RFs