The is the primary organ of photosynthesis. Its flattened blade optimizes surface area for light absorption. The leaf's anatomy is a masterpiece of physiological engineering: an upper and lower epidermis (with cuticle and stomata primarily on the lower surface) sandwiching the mesophyll, a photosynthetic ground tissue differentiated into palisade and spongy parenchyma. A network of veins (vascular bundles) provides both hydration and a means to export sugars.
The provides structural support and positions leaves optimally for light capture. Its anatomy shows an arrangement of vascular bundles embedded in ground tissue. In dicots, these bundles are arranged in a ring, allowing for secondary growth via the vascular cambium. In monocots, bundles are scattered throughout the ground tissue, which generally limits them to primary growth. The vascular cambium, a lateral meristem, produces secondary xylem (wood) to the inside and secondary phloem to the outside, leading to an increase in girth. plant anatomy
Connecting the other systems is the , a continuous transport network. It consists of two specialized conducting tissues: xylem and phloem. Xylem conducts water and dissolved minerals from roots to shoots. Its key conducting cells are tracheids and vessel elements, both dead at maturity with lignified walls. Vessel elements, found in angiosperms, align end-to-end to form continuous tubes, offering high efficiency. Phloem transports the products of photosynthesis (primarily sucrose) from source to sink organs. Its conducting cells, sieve-tube elements, remain living but lose their nuclei and are metabolically supported by adjacent companion cells. Phloem sap flows under hydrostatic pressure generated by osmosis. The is the primary organ of photosynthesis
