Stomata, stoma singular, are tiny pores which are the only interruptions in the epidermal barrier and are flanked by guard cells. They are usually more numerous on the bottom side of the leaf to minimize water loss. Guard cells allow gas exchange between the surrounding air and the internal photosynthetic cells. This is the major avenue for water loss in plants. There are two distinct regions on most dicots.
Air spaces are larger in the vicinity of the stomata.
Parenchyma cells are equipped with chloroplasts and specialized for photosynthesis. Veins bring xylem and phloem into close contact with photosynthetic tissue. Water and minerals are obtained from the xylem and sugars and other organic products are loaded into the phloem for shipment to other parts of the plant. Xylem is the tube-shaped, nonliving portion of the vascular system in plants that carries water and minerals from the roots to the rest of the system. Phloem is the portion of the vascular system in plants consisting of living cells arranged into elongated tubes that transport sugar and other organic nutrients throughout the plant.