Figure 6

Leaf tissue expansion measured on two- and three-dimensional images. (a) Thickness and proportions of leaf thickness (average %, indicated inside bars) occupied by, from top to bottom, the adaxial epidermis, the palisade mesophyll, the spongy mesophyll and the abaxial epidermis, in the middle of leaf 6 of the Arabidopsis rosette as measured by histological sectioning (2D, left) and three-dimensional imaging (3D, right). (b) Transversal (xz) views of leaf 6 of the Arabidopsis rosette (19 days after initiation) obtained by histological sectioning (2D, left) and three-dimensional imaging (3D, right, scale bar of 50 μm for both images). (c) Paradermal (xy) and transversal (xz, yz) views of a leaf image stack illustrating the difficulty in the assessment of palisade and spongy mesophyll cell identity using transversal views only. The palisade mesophyll cells encircled in red could easily be mistaken for spongy mesophyll cells based on the xz-view only (bottom left). Their identity is clear in the xy-(top left) and yz-views (top right). True spongy mesophyll cells are shown for a comparison of cell shapes (xy, bottom right, scale bar of 50 μm).