The lower epidermis contains stomata cells that help prevent water loss and regulate the exchange of gases such as oxygen and carbon dioxide, enabling plants to survive. Other cells in the lower epidermis include a waxy cuticle to protect underlying layers, according to Education Portal. Transparency in epidermal cells allows sunlight to pass through to chloroplasts, which are involved in photosynthesis.
The stoma complex is a functional unit consisting of two chloroplast-containing guard cells enclosing the actual stoma and two to four subsidiary cells with no chloroplasts. Guard cells play a role in helping the plant conserve water. In wet conditions, guard cells absorb potassium ions from the intercellular space, thereby creating osmotic potential and causing water to flow into the cells. When guard cells are bloated, the stomata open and release water, according to Education Portal.
Photosynthesis enables plants to manufacture complex organic molecules by transforming carbon dioxide and sunlight into sugar molecules and oxygen. This process forms the nutritional foundation for life on Earth, according to Scitable. The waxy cuticle, in addition to offering protection, absorbs waste products such as resins and salt. In plants such as the tomato, the cuticle is pigmented with carotinoids that give it a characteristic color, as explained by Botany Online.