Fig. 1

Sample preparation. A Germinated Arabidopsis seedlings on agar plates immediately before dissection. B General dissection setup under stereoscope for a right-handed researcher. Seedlings can be dissected within the plate or moved to a glass slide to dissect off cotyledons. C Stereoscope image under 50 × magnification of sample post-dissection, 3 DAS (Days after sowing). Yellow scale bar = 2 mm. D Schematic of positions of coverslip (blue square), grease strips for cover-slip suspension (gray lines) and microscope objective (gray shape, not to scale). The leaf blade flattens along the affixed coverslip. E One plate with all samples dissected, below suspended coverslip and immersed in perfluorodecalin (PFD). F Schematic of leaf growth without a coverslip. The abaxial surface naturally curves perpendicularly out from the plate. Directions relative to the proximal–distal and medial–lateral axes indicated with purple or magenta arrows, respectively. Purple plane indicates the cross-section displayed on the right