The mesophyll is the inner tissue of a leaf, found between the upper and lower epidermis. It is made up mainly of chloroplast-containing cells, which makes it the primary site of photosynthesis in most plants.
The mesophyll is divided into two layers:
- Palisade mesophyll (upper layer): made of tightly packed, column-shaped cells rich in chloroplasts.
- Spongy mesophyll (lower layer): made of loosely arranged cells with many air spaces for gas exchange.
The importance of the mesophyll lies in its key roles in plant function:
1. Site of Photosynthesis
The mesophyll contains many chloroplasts, which capture sunlight and use it to convert carbon dioxide and water into glucose (food) and oxygen. This process provides energy for the plant and releases oxygen into the atmosphere.
2. Gas Exchange
The air spaces in the spongy mesophyll allow easy movement of gases — carbon dioxide, oxygen, and water vapor — between the cells and the stomata. This helps the plant maintain efficient photosynthesis and respiration.
3. Water and Nutrient Transport
The mesophyll is closely connected to the leaf veins (xylem and phloem), which bring water and minerals to the photosynthetic cells and carry away the sugars produced.
4. Storage of Food and Water
In some plants, mesophyll cells can also store starch, water, or other nutrients, helping the plant during periods of low light or drought.
In simple terms, the mesophyll is the working part of the leaf — it captures sunlight, produces food through photosynthesis, allows gas exchange, and connects with the plant’s transport system. Without the mesophyll, a leaf could not perform its main function of making food for the plant.