Typical MRI projection images of maize roots growing in mixed sands with different bulk densities (Groups Mix), textures (mixed sand of Group Mix_low and sandy loam of Group Loam_low with the same bulk densities) and structures (Group Bilayer with layered soil structure). The images are 2-D projections of 3-D data along the z–x plane (where z is the vertical axis, x and y are perpendicular planar axes). Four plants per pot can be seen, and their organs are indicated: (a) seed, (b) primary root, (c) shoot, (d) secondary and (e) seminal roots. The plants are 4 and 9 d old at Day 1 and Day 6 of the experiment, respectively. The perlite covering used to limit water evaporation is visible as a defuse layer on the top. The grey spots represent remaining soil water as well as some small weed plants that accidentally germinated in the soil during the experiments. The dashed line on the image of Group Bilayer represents the interface between the upper sandy loam layer, Group Bilayer_loam_top and the lower mixed sand layer, Group Bilayer_mix_bottom. The white bar represents 10 mm.