Leaves Arise on the Flanks of the Shoot Meristem

(A) Vegetative apex of Arabidopsis. The adaxial side of the leaf is adjacent to the central shoot apical meristem, whereas the opposite, abaxial, side of the leaf is farther from the shoot meristem. Dorsoventrality is established early in development and is clearly evident in the leaf on the left, which arches over the meristem due to differential growth on each side of the leaf. Scale bar is 50 μm.

(B) Developing vegetative leaf of Arabidopsis. Adaxial trichomes on the larger leaf are one marker distinguishing dorsoventrality. Scale bar is 250 μm.

(C) Diagrammatic representation of a leaf cross section with adaxial and abaxial outer epidermal and inner mesophyll marked.

(D) Cross section of leaf midvein with adaxial xylem and abaxial phloem cells marked.