Eudicot leaf development and structure.

(a) Leaves develop from primordia produced at the sides of shoot apical meristems, as shown in this thinly sliced, stained shoot tip. (b) Mature leaves are typically thin and flat, and they show bilateral symmetry. (c) An internal view of a thinly sliced and stained leaf reveals top to bottom (adaxial to abaxial) tissue differentiation. A layer of palisade parenchyma lies just beneath the upper epidermis capped with waxy cuticle. Veins of conducting tissue (xylem and phloem) are embedded in the photosynthetic mesophyll. Spongy parenchyma lies above the lower epidermal leaf surface, which displays stomatal pores. These structural features of mature leaves facilitate photosynthesis.