Construction of the rhizoslides. A: Root slides consistent of a plexiglass sheet covered with germination paper and a transparent PE foil belt with PVC bars with watering channels. Tubes on the site serve as nutrient solution reservoir. B: Cross section of the rhizoslide, illustrating the seed placement and separation of embryonic and crown roots. The seed is placed between the germination paper and the space between the PVC bars is filled with a layer of Potassium polycarbonate and a granulate substrate. Me: Mesocotyl; Cr: Crown root; Se: Seminal root; Pr: Primary root. C: Schematic figure of the separation of the embryonic and shoot-born crown roots: Embryonic roots are growing hidden below the germination paper whereas crown roots are growing visible on the top of the germination paper. D: Images taken of one slide with front- or backlight. Front 1 and Back 1 (complementary Front 2 and Back 2) are images of the same side taken with either front or backlight. Front images show crown roots whereas the transmitted light allows detection of seminal roots as well.