Fig. 1: The leaf growth measuring system and example dynamics of local growth.

a A pot with a living plant is placed on the x–y stage of a profilometer. The stage and the lighting conditioned are controlled by a preset program, by which the leaf is automatically scanned (red line marks scanning beam) and then optically imaged, in constant time intervals for days. The camera is set at 200 cm distance from the leaf plane, in order to minimize optical artifacts due to vertical growth (Supplementary Note 1). b A typical leaf topography z(x,y) of a Tobacco wild-type leaf (after smoothing) as obtained by the profilometer. Scale bar: 1 mm. c An optical image of the leaf in b, after deleting the low spatial frequency data (black). the small-scale features (white) are used as tracers in the growth calculation algorithm. d An example of an area-growth field, (AG), measured within the time interval \(\Delta t = 15\,{\mathrm{min}}\). Spatial resolution: 250 × 250 micron. e A histogram of all area-growth values, during 90 intervals of \(\Delta t = 15\,{\mathrm{min}}\) during 2 days of measurement (∼70,000 growth events). The most probable value is ∼1% (dashed line). A Gaussian distribution with the same mean and std is depicted in a solid red line. f–h Principal growth measurements, taken from the same leaf area (marked with a rectangle in d) with different time intervals (indicated, all during light-time). At each point, the maximal and minimal growth vectors are depicted: The lines are oriented along the principal directions and their lengths indicate the relevant growth values (scaled by the same arbitrary factor in all panels). Blue lines represent positive growth, red lines represent shrinkage. Scale bar: 0.5 mm. More samples of such data, in Supplementary Fig. 3.