| Waxy cuticle | A clear, non-cellular, protective layer covering the top and bottom of the leaf. | Waterproof to reduce water loss by evaporation; transparent to allow light to pass directly through to the photosynthetic cells below. |
| Upper epidermis | A single layer of tightly packed, thin cells at the top of the leaf containing no chloroplasts. | Protects inner tissues from mechanical damage; transparent to allow maximum light penetration into the palisade layer. |
| Palisade mesophyll | Column-shaped cells packed closely together vertically near the upper surface. | Contains the highest density of chloroplasts per cell; situated at the top of the leaf to absorb the maximum amount of sunlight. |
| Spongy mesophyll | Loosely packed, rounded cells situated below the palisade layer. Contains fewer chloroplasts. | Forms a network of large air spaces that allow gases (carbon dioxide and oxygen) to diffuse rapidly between the stomata and the palisade cells. |
| Air spaces | Large gaps between the cells of the spongy mesophyll layer. | Increases the internal suface area for efficient gas exchange and allows carbon dioxide to circulate freely. |
| Lower epidermis | The bottom layer of protective cells on the leaf. | Contains the majority of the guard cells and stomata to regulate gas exchange while minimizing water loss from the shaded underside. |
| Stomata (sg. stoma) | Tiny pores or openings found mostly in the lower epidermis. | Act as the entry and exit points for gases; allows carbon dioxide to diffuse into the leaf and oxygen (plus water vapour) to diffuse out. |
| Guard cells | Pairs of specialized epidermal cells surrounding each stoma. | Control the opening and closing of the stomata. They open during the day to allow carbon dioxide entry for photosynthesis and close at night (or during drought) to conserve water. |
| Vascular bundle | The transport system of the leaf, containing the xylem and phloem. | Provides structural support to keep the leaf blade flat and well-positioned to cattch sunlight, while containing the transport vessels. |
| Xylem | Thick-walled, dead vessels found in the upper part of the vascular bundle. | Transports water and dissolved mineral ions from the roots up to the leaf cells. Water is a direct raw material for photosynthesis. |
| Phloem | Living transport tissue found in the lower part of the vascular bundle. | Transports sucrose and amino acids made from the products of photosynthesis away from the leaf to growing regions or storage organs (translocation). |
| Chloroplasts | Organelles concentrated mainly within the mesophyll layers. | Contain chlorophyll to trap light energy and convert it into chemical energy for synthesizing carbohydrates. |
